The 5th International Symposium of the - CAGSigcp589.cags.ac.cn/5th Symposium/Abstract...

The 5th International Symposium of the

International Geoscience Programme (IGCP) Project 589

October 25-November 2, 2016

Function Hall, MES Building,

Yangon, Myanmar

Organized by

Myanmar Earthquake Committee

In collaboration with

Yangon University,

Ministry of Education

IGCP 589 Project Leaders

Dr. Xiaochi Jin, Institute of Geology, Chinese Academy of Geological Sciences, China

Dr. Katsumi Ueno, Fukuoka University, Japan

Dr. GracianoYumul Jr., Monte Oro Resources and Energy Inc., Philippines

Dr. Pol Chaodumrong, Bureau of Geological Survey, DMR, Thailand

Fifth Symposium Organizing Committee

Chairman: Hla Hla Aung (Senior Researcher & Patron of Myanmar Earthquake Committee,

Former Lecturer in Geology, Geology Department, University of Yangon)

Secretaries: Aung Kyaw Tun (Researcher and Former Assistant Lecturer, Geology

Department, University of Yangon)

Su Su Myint, Engineer, Myanmar Earthquake Committee

Dr. Sandy Chit Ko, Geology Department, Yangon University

Members:

Dr. Day Wa Aung Dr.Myat Thuza Soe

Dr.Than Htut Lwin Dr. ThanThan Oo

Dr. Cho Cho Aye Dr. Own Thwin

Dr.ThanThan Sint Dr.Htun Naing Zaw

Dr. Saw Thamu Lay Paw

Field trip Leaders: Pre-symposium (1): Aung Kyaw Tun & Dr. Saw Mu Tha Lay Paw

Post-symposium (2): Aung Kyaw Tun & Dr. Zaw Win

Sponsors of the Symposium

Preface

The International Geosience Programme (IGCP) Project 589 has served as a

platform for geoscience professionals and students to present their innovative

research. The breadth and depth of the technical sessions are international in

scope and span across multiple geosciences disciplines.

The 5th International Symposium of IGCP 589 2016 will be held at Function Hall,

MES Building, Hlaing University Campus, Yangon, Myanmar on October 27 - 28,

2016. The symposium will provide an opportunity for participants to present

their recent work and discuss complicated problems related to the development

of the Asian Tethyan Realm. In addition to technical sessions, the pre- and post-

symposium excursions– the Neo-Tethys suture zone (Accretionary History of the

Rakhine Western Ranges) and western part of Shan Plateau (A complete

Paleozoic and Mesozoic sequences of the Sibumasu Block) will be carried out.

The 5th IGCP 589 symposium is undoubtedly the place to explore, discuss, and

understand where our geosciences community will explore on interpretation of

the development of the Asian Tethyan Realm.

The most important aspects of this symposium is the opportunity it offers for the

exchange of views and perspectives in understanding the evolution of Tethyan

Ocean among researchers from all over the world. I strongly hope that with all of

your presence here, the symposium will be able to reach its objectives and bring

about fruitful outcomes and further collaboration in the future. I would like to

express my sincere appreciation to all of you for your kind participation in this

symposium, especially IGCP leaders and the support to run the symposium.

I wish you successful meeting and enjoyable field trips to Yakhine and Shan

States in Myanmar.

Hla Hla Aung

Chairman of Organizing Committee

October 2016

i

Contents

Page

1. Fourty years of the International Geoscience Programme (IGCP)

Shigeki HADA 1

2. Geochemistry and Petrogenesis of Proterozoic Eimodal Volcanic Rock of the

Betul Chhindwara Fold Belt, Central Indian Tectonic Zone (CITZ) Central India.

Ibrahim YOUSUF 2

3. Permian fusuline fauna from the Minwun Range, Central Myanmar

Katsumi UENO 6

4. The Tectono-Stratigraphy and the Upper Paleozoic Petroleum Systems of the

Khorat Plateau Basin in Onshore NE Thailand Tomonari MINEZAKI 7

5. Accretionary process of basaltic rocks into the Jurassic Chichibu accretionary

complex in the Kanto Mountains, central Japan Kohei TOMINAGA 12

6. Petrochemistry of volcanic rocks of Sisophon Area in Northwestern Cambodia:

Implication for tectonic setting Punya CHARUSIRI 13

7. Hydrodynamic adaptration of fusulinid foraminifera Yukun SHI 14

8. Permian oolitic carbonates from the Baoshan Block, China; ooid features,

stratigraphic distribution and paleogeographic indications Hao HUANG 15

9. Juxtaposed forearc sequences and structure evolution of North Luzon Trough

onshore and offshore eastern Taiwan: Processes for development of forearc Lichi

Mélange in Coastal Range Chi-Yue HAUNG 17

10. Geochemistry of Lower Paleozoic basalts from the Hida Gaien belt, SW Japan –

An evidence of Early Paleozoic subduction initiation at Gondwana margin

Kazuhiro TSUKADA 18

11. Ultramafic rocks outcropping largely in SW Yunnan and its significance

for revealing the Paleotethyan LIPs Qing SHI, Nianqiao FANG 19

12. The Manila subduction zone: Its structure, deformation and seismogenic potential

L.T. ARMADA 22

The 5th Symposium of the International Geoscience Programme (IGCP) 589

MES Building, Hlaing University Campus, Yangon, 27-28 October 2016

589 Yangon

ii

13. Petrological and geochemical characteristics of the ultramafic section of the

Samar Ophiolite: Implications on the origins of the ophiolites in Samar

and Leyte, Philipphines J.M.R. GUOTANA 25

14. Mineral Systems and Exploration Targeting in Southern Philippines:

Possible Clues from the Maco Gold Mine, Compostela Valley, Mindanao,

Phillippines G.P. YUMUL 31

15. History of fluvial-marine interaction in Pak Nam Pran, Pran Buri, Prachuap

Khiri Khan, southern Thailand: a preliminary report Wickanet SONGTHAM 34

16. Geochemical Characteristics, Petrogenesis and Tectonic Settings of Precambrian

Basement of I- and S-types Granitic Gneisses of Saghand Region, Central Iran

Monireh POSHTKOOHI 36

17. Sinistral subduction along the eastern margin of the Asian continent during

Albian to Cenomanian Tetsuya TOKIWA 37

18. Transitional Carbonate Facies between Cool and Warm Settings: A Permian Case

from the Baoshan Block in Western Yunnan, China. Xiaochi JIN, Hao HUANG 38

19. The Mid Cretaceous Biogeographic Revolution in the Pacific. Yasuhiro IBA 40

20. The Separated Twins: Sumatra and Myanmar in a Dynamic World John MILSOM 42

21. The Accretionary complexes Large-Scaly Juxtaposed by the Out-of-Sequence

Thrust in the Cretaceous Shimanto Belt of Southwest Japan: Yusuke SHIMURA 43

22. Sandstone Provenance and Detrial Zircon U-Pb ages from Permian-Triassic Forearc

Sediments within the Sukhothai Arc, Northern Thailand: Record of Volcanic-arc

Evolution in Response to Paleo-Tethys Subduction. Hidetoshi HARA 48

23. Coal – Forming Episodes in Vietnam, Cambodia and Lao PDR. Van Tri TRAN 50

24. New Age Constraints on the Evolution of the Naga Hills: Radiolarians and

Radiometric. Jonathan C. AITCHISON. 54

25. Meso-Tethys and Neo-Tethystectonic Evolution in Myanmar and its Adjacent

Areas Zhu WEN, Nianqiao FANG, Renchen XIN 55



589 Yangon

iii

26. Paleomagnetic Constraints for the Tectonic History of the South China Sea:

Post – Expedition Study of IODP Expending 349 Xixi ZHAO 56

27. Volcanogenic-sedimentary Deposits of the Alpine Orogenic System

(European Tethys) from SE Asian Prespective (Asian Tethys) Michal KROBICKI 58

28. Southwestern Aisan/Pacific Faunal Province in the MId-Cretaceous: A Possible Clue

to Revealing the Evolutionary History of Rudists and Other Carbonate Platform Biota

Shin-ichi SANO 61

29. Lithostratigraphy of Middle Triassic Siliceous Rocks Distributed in the Mae

Sariang Area, Northwestern Thailand Yoshihito KAMATA 64

30. Ultramafic Rocks of Nan Suture Zone in Northern Thailand and its Northward

Extension in Laos Ken-ichiro HISADA 65

31. Late Palaeozoic to Cretaceous Evolution and Lithofacies Paleogeography of the

Central Asian Tethyan Realm Lingyu LIU 66



589 Yangon

- 1 -



589 Yangon

Fourty years of the International Geoscience Programme (IGCP)

Shigeki Hada

Professor Emeritus of the Kobe University

Abstract

IGCP launched in 1972 is an outstanding and unique enterprise between UNESCO

and IUGS. For over forty years, IGCP has been mobilizing global cooperation in the

Earth Sciences and always built bridges between disciplines and between scientists with

aims of stimulating cutting-edge research and sharing scientific knowledge for the

benefit of all. IGCP is once referred to as the ‘International Geological Correlation

Programme’ and enhanced scientific exchange through the correlation of geological

strata and research data, focusing on basic geoscientific research and on making

connections between events throughout the Earth's history. In 2003, the Scientific Board

of IGCP decided that the Program should be renamed ‘International Geoscience

Programme’, encouraging more applied geological projects with clear societal relevance.

My career of IGCP began on Project No. 224, and Nos. 321, 411, 516 and 589 successor

to No. 224 all targeted at geological evolution of Asia and the Tethys and has been taken

over more than 30 years. I am proud a set of projects continuously submitted over years

showing high regard by the scientific community.

Recently, UNESCO approved the creation of the new International Geoscience and

Geoparks Programme (IGGP) that would reform the existing IGCP but also allow for

the creation of UNESCO Global Geoparks in order to more closely reflect the societal

challenges of Earth Science today. Geoparks are single, unified geographical areas

where sites and landscapes of international geological significance are managed with a

concept of protection, education and sustainable development. I believe the success of

IGGP by global collaboration of a research programme and an outreach programme is

essential to release the power of science for international collaboration.

Keywords: UNESCO, IUGS, IGGP, IGCP, Geoparks

- 2 -



589 Yangon

Geochemistry and Petrogenesis of Proterozoic Eimodal Volcanic Rock of the Betul

Chhindwara Fold Belt, Central Indian Tectonic Zone (CITZ), Central India.

Ibrahim Yousuf1, Talat Ahmad1,2, and D.V. Subba Rao3

1Department of Geology, University of Delhi, Delhi – 110007, India

2Jamia Millia Islamia, New Delhi 110025, India

3CSIR-National Geophysical Research Institute, Hyderabad – 500 007, India

E mail:[email protected]

Abstract

The Precambrian crust of Central India comprising Bundelkhand craton in the north and

Bastar craton in the south were accreted along the ENE-WSW trending Proterozoic Central

Indian tectonic zone (CITZ). The CITZ contains Proterozoic supracrustal belts of varied

metamorphic grades. Betul belt is one of the supracrustal belt sandwiched between

Mahakoshal belt in the north and Sausar belt in the south separated by faults. The betul

ultramafic-mafic complex emplaced into the supracrustal assemblages of bimodal volcano-

(mafic-felsic volcanics) sedimentary sequence (quartzite-phyllite-marble-BIF), which

represents the supracrustal lithology of the Betul belt (Ramachandra and Pal, 1992;

Chaturvedi, 2001; Mahakund and Raut, 2001; Roy and Prasad, 2003; Roy et al., 2004). The

betul belt comprises bimodal volcanics that include metabasalt, metagabbro, rhyolite, leuco

micro granite, quartzite, clastic sediment and ultramylonite. One of the syn-tectonic granitic

phases yielded a Rb-Sr age of ca. 1.5 Ga (quoted in Raut and Mahakud, 2002), which

constrains the upper age of the supracrustal sequence. Bimodal volcanics are intrusion in the

basement Tirodi gneiss. Mafic rocks have been metamorphosed from low to high grade

ambhibolite, epidote amphibolite which contain phenocrysts of hornblende and actinolite,

some of the amphibolites have been recrystallized. Rhyolites and leuco micro granites are

also deformed due to shear zones and includes quartz, plagioclase, muscovite, biotite, epidote

minerals. In some samples feldspar has been sericitized due to interaction with hydrothermal

fluids (Figure 1).

SiO2 shows a large compositional gap between the basic and acidic volcanics, depicting

their bimodal nature (the TAS diagram). In SiO2 vs K2O diagram felsic rocks belongs to the

high-K calc alkaline series. The negative covariances between Fe2O3, MgO, CaO and SiO2

imply the fractionation of olivine and clinopyroxene with little plagioclase during the magma

evolution. In the SiO2 vs Al2O3 and Sr variation diagram the basaltic samples display a weak

- 3 -



589 Yangon

positive correlation while a negative correlation for the felsic rocks, indicating either different

fractional trend between the two groups or different degree of the plagioclase fractionation.

Both mafic and felsic groups contain high concentration of LILEs especially for Ba but felsic

contains much higher (Fig. 3, 4). Sr is showing distinct behavior positive anomaly in mafic

samples and negative in felsic samples. Both the volcanics have distinct geochemical trends

but display some similarity in terms of enriched large ion lithophile element characteristics

with positive anomalies for U, Pb and Ba and negative anomalies for Nb and Ti. Felsic group

possess higher REE abundance with negative Eu anomaly implying lower degree of partial

melting. Whereas mafic group show slight positive Eu anamoly with low REE abundance

depicting high degree of partial melting. Th-Zr and Nd-La shows positive trend. Bimodal

volcanism leads to the intrusion of basic and felsic magma in the Tirodi basement

gneiss.Sericitization of feldspar indicates possibility of hydrothermal fluids intrusion.

Different anomalies of Sr for basic and felsic samples indicates different fractional trends.

Felsic samples are showing negative Eu anomaly indicating plagioclase fractionation where

as mafics are showing slight positive Eu anomaly. Positive trend of Th-Zr indicates crustal

contamination and positive trend of Nd-La signify primary magmatic characteristic. Positive

U, Pb and Ba with negative Nb and Ti anomalies indicate typical characteristics of

continental rift volcanism.

References

Chaturvedi, R.K. (2001) A review of the Geology, Tectonic features and tectono-

lithostratigraphy of Betul Belt, Geol. Surv. India Spec. Publ., no.64, pp.299-315.

Mahakud, S.P. and Raut, P.K. (2001) Sulphide Mineralization in the central part of Betul Belt

around Ghisi-Mauriya-Koparpani area, Betul District, Madhya Pradesh, Geol. Surv.

India Spec. Publ., no.64, pp.377-385.

Ramachandra, H.M. and Pal, R.N. (1992) Progress report on study of geology and

geochemistry and Cu-Pb-Zn mineralization in Kherli Area, Betul District, M.P., Geol.

Surv. India, Unpubld. Prog.Report, p.60.

Raut, P.K., Mahakud, S.P., 2002. Geology, geochemistry and tectonic setting of volcano-

sedimentary sequence of Betul belt, Madhya Pradesh and ore genesis of related Zinc and

Copper sulphide mineralization. Proceedings of the National Seminar on Mineral

Exploration and Resource Surveys, by Geological Survey of India, held at Jaipur.

- 4 -



589 Yangon

Roy, A. and Prasad, H.M., 2003. Tectonothermal events in Central Indian Tectonic Zone

(CITZ) and its implication in Rhodinian crustal assembly. Jour. Asian Earth Sci., v.22,

pp.115-129.

Roy, A., Chore, S.A., Viswakarma, L.L. and Chakraborty, K. (2004) Geology and

petrochemistry of Padhar mafic-ultramafic complex from Betul Belt: A study on arc type

magmatism in Central Indian Tectonic Zone, Geol. Surv. India. Spec. Publ., no.84,

pp.297-318.

Figure 1 Photomicrograph of deformed rhyolite showing laths of muscovite and biotite

and sericitized feldspar.

Figure 2 Photomicrograph of rhyolite showing sphene, opaque and biotite together

associated with vein.

- 5 -



589 Yangon

Figure 3 Primitive mantle-normalized multi-element pattern of felsic samples.

Figure 4 Primitive mantle-normalized multi-elementpattern of mafic samples.

0.01

0.1

1

10

100

1000

10000

Cs Rb Ba Th U Nb Ta La Ce Pb Pr Sr Nd Zr Hf Sm Eu Ti Gd Tb Dy Y Ho Er Tm Yb Lu

Ro

ck/P

rim

itiv

e M

antl

e

0.1

1.0

10.0

100.0

1000.0

Cs Rb Ba Th U Nb Ta La Ce Pb Pr Sr Nd Zr Hf Sm Eu Ti Gd Tb Dy Y Ho Er Tm Yb Lu

Ro

ck/P

rim

itiv

e M

antl

e

- 6 -



589 Yangon

Permian fusuline fauna from the Minwun Range, Central Myanmar

Katsumi Ueno1, Myint Thein2, Anthony J. Barber3

1 Department of Earth System Science, Fukuoka University, Fukuoka, 814-0180 Japan;

Departamento de Geología, Universidad de Oviedo, C/. Jesús Arias de Velasco s/n, 33005,

Oviedo, Spain

2 Geology Department, Mandalay University, Mandalay, Myanmar

3 Southeast Asia Research Group, Department of Earth Sciences, Royal Holloway University

of London, Egham, Surrey TW20 0EX, U.K.

Abstract

In the Minwun Range of Central Myanmar, there are several fault-bounded blocks of

Permian limestones within the Sagaing Fault Zone. Their fusuline fauna was first

documented by Myint Thein et al. (1983) and considered to be Middle Permian. This

information has been utilized for discussing the geotectonic affiliation of the West Burma

Block by later studies (Barber and Crow, 2009; Shi and Jin, 2015), but their discussion was

based only on illustrated specimens by Myint Thein et al. (1983) and the taxonomic

examination was not fully convincing. In our study we investigated some fusuline specimens

from the collection of Myint Thein et al. (1983) and also from additional samples in this area

to make clear their taxonomy, age, and paleobiogeographic characters.

The fusuline fauna from our samples consists of abundant Chalaroschwagerina, together

with Pseudofusulina, Levenella, Pamirina, Schubertella, Toriyamaia, Minojapanella, and

Pseudoreichelina. They indicate a late Yakhtashian (late Early Permian) age and clearly

show a Tethyan paleobiogeographic affinity. Myint Thein et al. (1983) illustrated two,

inflated schwagerinid specimens and identified them as Rugososchwagerina sp. This was

taken by Shi and Jin (2015) as conclusive evidence of the fauna to be of peri-Gondwanan

type. However, these specimens are suitable to be identified as other Early Permian inflated

genus, such as Sphaeroschwagerina, based on their basic morphology. Moreover,

Schwagerina specimens in Myint Thein et al. (1983), which were later reassigned to

Pseudofusulina postkraffti by Shi and Jin (2015), are better identified as late Early Permian

Pseudofusulina kraffti. Overall, the fusuline fauna from the Minwun Range consists of Early

Permian forms and clearly exhibits a Tethyan affinity. They are neither of Middle Permian

nor suggest peri-Gondwanan paleobiogeographic relation.

- 7 -



589 Yangon

The Tectono-Stratigraphy and the Upper Paleozoic Petroleum Systems of the Khorat

Plateau Basin in Onshore NE Thailand

Tomonari Minezaki1, Ken-ichiro Hisada2

1 Mitsui Oil Exploration Co., Ltd., Japan

2 University of Tsukuba, Japan

Abstract

The Khorat Plateau region and its surrounding of NE Thailand are underlain by Permian

carbonates. In particular, Permian carbonates occur in the Loei Pechabun fold belt to the west

of the Khorat Plateau. In the Khorat Plateau region, the thick Mesozoic red beds Khorat

Group overlies the Upper Paleozoic rocks. There are two commercial gas fields of Permian

carbonate reservoirs in the Khorat Plateau region. The stratigraphy of the Khorat Plateau is

composed of a complex set of basins, formed at five separate periods from late Carboniferous

to Cretaceous, and it is represented by unconformities related to several major orogenic

events. The intense deformed Carboniferous and Permian sections are recognized below

Indosinian I Event, which may be caused by the closure of back-arc basin between Sukhothai

arc and Indochina terrane at the end of Permian.

The Permian carbonates as hydrocarbon reservoirs are present worldwide in Middle East,

North America, China and also southern Thailand. The Permian gas bearing carbonate

reservoirs in the Khorat Plateau are composed of massive-thick bedded limestone and

fractured dolomite in the shallow marine environments. The main source rocks for natural

gases are thought to be lagoonal organic rich shales behind reef buildups.

Key words: Thailand, Khorat Plateau, Indochina terrane, Permian Carbonates, Petroleum

Systems

Introduction

The petroleum exploration for Thailand started in the Pattani Trough (Paleogene to Recent)

of Gulf of Thailand in late-1960s, and it was successful gas developments and commenced

large gas production from 1981. It has become a major contribution to economy and industry

of Thailand. Before exploration effort in Gulf of Thailand, Union Oil was granted exploration

license in early-1960s in the Khorat Plateau basin (Mid Paleozoic to Paleogene) of NE

Thailand. They drilled one exploration well, Kuchinarai-1 with only minor gas shows. The

- 8 -



589 Yangon

first gas discovery well in the Khorat Plateau was Nam Phong-1A which was drilled by Esso

in 1981. At present, two gas fields, Nam Phong and Phu Horm are producing commercial gas

from Permian carbonates. UNOCAL (former Union Oil) and Mitsui Oil Exploration Co., Ltd.

explored in northeastern Khorat region nearby Laos, and drilled four wells with some gas

shows from Triassic sandstones in early 1990s. The oil companies carried out seismic survey

for whole Khorat Plateau region and drilled more than 30 exploration wells to date. There are

available data with a certain amount of confidence in regard to the mapping and formation

correlation in the northern and central Khorat Plateau region.

Tectono-Stratigraphic Evolution in NE Thailand

NE Thailand comprises two main areas, the Loei-Petchabun Fold Belt and the Khorat

Plateau. The Loei-Petchabun Fold Belt is located to western part of NE Thailand. The N-S

trending mountain belt is mainly of folded Paleozoic rocks with some igneous rocks and

outliers hills of the Mesozoic Khorat group. The Khorat Plateau is a geographically relatively

flat plain, however, in the subsurface, it is a geologically complex region in which there is a

proven commercially gas producing hydrocarbon systems. It is underlain by a complex set of

basins, formed during five different periods from late Carboniferous to end of Cretaceous

time, and separated by unconformities related to several major orogenic events (Fig.1). The

complex geological features in the subsurface are intense deformed and thrust Carboniferous

and Permian sections under Indosinian I Event, and developed graben systems in Late

Triassic sections between Indosinian I and II Event. In contrast, almost entirely Jurassic to

early Cretaceous Khorat group red-bed which covers near the surface formed of gently long-

wave folded.

As for paleo-geography, the Khorat Plateau lies in the northwestern edge of Indochina

terrane. Collision and welding of the Sibumasu block to Indochina - East Malaysia, begun in

the latest Permian, continued in the Early-Middle Triassic and was completed by Late

Triassic times (Metcalfe, 2011). As described above, by the subsurface structural evidence,

the most intense thrust folded event is Carboniferous and Permian sections under Indosinian I

Event, therefore, it is thought to be corresponded with closed the back-arc basin between

Sukhothai arc and Indochina terrane at end of Permian.

Permian Carbonates in the NE Thailand

- 9 -



589 Yangon

The primary reservoir target in the Khorat Plateau Basin is the carbonates of Middle

Permian “Pha Nok Khao Formation”. The Permian carbonates crop out around the margin of

the Khorat Plateau, particularly toward to west in Loei-Petchabun Fold Belt. This formation

in Loei area consists chiefly of massive to thick-bedded limestones with nodular or layered

cherts on some levels (Ueno et al. 2011).

The Permian massive carbonates encountered also in the subsurface of Khorat Plateau

region as the Pha Nok Khao Formation. They are composed of massive-thick bedded

limestones and fractured dolomites in the shallow marine environments similar as outcrop. In

the subsurface on the seismic sections, there are in reality numerous, quite distinct and

separate, carbonate platforms which probably at different times (Booth et.al 2011).

Upper Paleozoic Petroleum Systems in the Khorat Plateau Basin

Sattayarak (2005) summarized the potential source rock horizons in the Khorat Plateau

region. The candidates of source rock for natural gases are 1) Shales for Permian and

Carboniferous, 2) Triassic lacustrine shales in the Kuchinarai Group, and 3) Mesozoic coals

in the Khorat Group. It will be needed more investigation in terms of petroleum geological

aspects, however, considering the seal position for hydrocarbons and depositional

environments, the main source rocks are thought to be lagoonal organic rich shales behind

reef buildups in Permian time. Nusara (2005) reported the gypsum-anhydrite deposits and

carbonates aging around Moscovian in Upper Carboniferous in the Loei-Wang Sapung, and

suggested a shallow marine deposition accumulated in a tidal flat to subtidal environments. It

is called “Si That Formation” of Late Carboniferous sediments in the Khorat Plateau basin

same as shallow marine and partly terrigenous deposits, which is also the candidate for

source rocks.

Conclusion

It was provided by many recent works for study of tectonic framework, Paleozoic and

Mesozoic geological evolution and paleo-geography of SE Asia and adjacent regions. Our

study continues integration of the recent geological findings and the subsurface data for

seismic sections and wells. It will be demonstrated tectonic evolution in the Khorat Plateau

basin with variation of tectonic regime around Indochina terrane by subduction and collision

in the Paleo-Tethys ocean.

- 10 -



589 Yangon

At present, it was summarized below.

1) Based on the subsurface structural evidence in the Khorat Plateau basin, the most intense

thrusting and folding deformations is the Carboniferous and Permian sections under

Indosinian I Event. It is probably corresponded closed the back-arc basin representing

Nan-Uttaradit suture between Sukhothai arc and Indochina terrane in latest Permian time

before completion of collision and welding of the Sibumasu block to Indochina terrane.

2) The source rocks for natural gases bearing in the Permian carbonates are thought to be

lagoonal organic rich shales behind reef buildups in Permian time. There is another

possibility for Upper Carboniferous shales in the carbonates - evaporites environments

and terrigenous colas lying beneath Middle Permian carbonates as candidate for source

rocks.

References

BOOTH J. & SATTAYARAK, N. 2011.Subsurface Carboniferous-Cretaceous geology of

NE Thailand, Chapter 9. In: RIDD, M.F., BABER, A. J. & CROW, M. J.The Geology of

Thailand. Geological Society, London, 185-222.

METCALFE, I. 2011. Paleozoic – Mesozoic history of SE Asia. In: HALL, R., COTTAM, M.

A. & WILSON, M. E. J. The SE Asian Gateway: History and Tectonics of Australia –

Asia Collision. Geological Society, London, Special Publications, 355, 7-35.

RIDD, M. F., BARBER, A. J., & CROW, M.J. 2011. Introduction to the geology of Thailand,

Chapter 1.In: RIDD, M.F., BABER, A. J. & CROW, M. J.The Geology of Thailand.

Geological Society, London, 1-17.

SURAKOTRA, N., PISUTHA-ARNOLD, VISUT & WARREN, JOHN K. 2005.Some

Characteristics of Gypsum-Anhydrite Deposit in the Loei-Wang Saphung, Northeast

Thailand.Thailand International Conference on Geology, Geotechnology and Mineral

Resources of Indochina (GEOINDO 2005). 28-30 November 2005, Khon Kaen,

Thailand, 422-430.

SATTAYARAK, N. 2005.Petroleum Potential of Northeast Thailand.Thailand International

Conference on Geology, Geotechnology and Mineral Resources of Indochina

(GEOINDO 2005). 28-30 November 2005, Khon Kaen, Thailand, 20-30.

- 11 -



589 Yangon

UENO, K. & CHAROENTITIRAT, T. 2011. Carboniferous and Permian, Chapter 6. In:

RIDD, M.F., BABER, A. J. & CROW, M. J.The Geology of Thailand. Geological

Society, London, 71-136.

- 12 -



589 Yangon

Accretionary process of basaltic rocks into the Jurassic Chichibu accretionary complex

in the Kanto Mountains, central Japan

Kohei Tominaga1, Ken–ichiro Hisada 2, Hidetsugu Taniguchi3, Shiki Machida4,

Kazutaka Yasukawa5, Yoshihiro Kato6

1Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai 1–

1–1, Tsukuba, Ibaraki, 305–8572 Japan, [email protected]

2Institute of Life and Environmental Sciences, University of Tsukuba

3Faculity of Science, Josai University

4Japan Agency for Marine–Earth Science and Technology

5Shool of Engineering, University of Tokyo

6Frontier Research Center for Energy and Resources, University of Tokyo

Abstract

Basaltic rocks are one of the important component in subduction related accretionary

complexes. They are interpreted to past oceanic crust or seamount accreted to a continental

margin, and provide valuable information about ancient ocean. However, accretionary

process of such basaltic rocks are not fully discussed. In this study, we investigated basaltic

rocks distributed in the Jurassic Northern Chichibu accretionary complex in the Kanto

Mountains, central Japan.

The Northern Chichibu accretionary complex in the study area is divided into “the main

part” and “the southernmost part”. Basaltic rocks are usually crop out as lenticular shaped

block, a few meters to some hundred meters in length. Chemical compositions of basaltic

rocks show both ocean island basalt (OIB) and mid ocean ridge basalt (MORB) are

distributed in the southernmost part while the main part contain only OIB. OIB type basaltic

tuff are associated with shallow marine limestone, indicating the basalt composed seamount

capped by atoll carbonate. In contrast, MORBs are pillow lava or hyaloclastite associated

with chert.

The distribution of OIB and MORB in the study area suggests that accretionary processes

of basaltic rocks are different between the southernmost part and the main part of the

Northern Chichibu accretionary complex: both ocean floor and oceanic seamount have

accreted in the southernmost part, while only OIB accretion have been occurred in the main

part.

- 13 -



589 Yangon

Petrochemistry of volcanic rocks of Sisophon Area in Northwestern Cambodia:

Implication for tectonic setting

Supachai Nildam, Apivut Veeravinantanakul, Sitichok Kumrangwat,

Apisit Salam, Punya Charusiri*

Department of Geology, Chulalongkorn University, Bangkok 10330 Thailand

* Email address: [email protected]

Abstract

Volcanic rocks of Sri Sophon area in northwestern Cambodia was investigated using

remote sensing information and field data. The aims of this investigation are to comprehend

more detailed geology and to interpret its tectonic setting. Therefore, sets of rock samples

have been collected for petrographic and geochemical analyses. Stratigraphically, limestones

with well-defined beds and local recrystallization are sitting onto the volcanic rocks. Our

filed investigation in the vicinity of Sri Sophon district show that the carbonate rocks are

exposed lying over the basalts. The contact shows no obvious contact metamorphism and is

irregular. Volcanic rock fragments are observed at the limestone base. Petrographic study

reveals that both fragments and volcanic bodies have the same lithology. Geochemical

analysis shows that the volcanic rocks are mainly basaltic in composition and they are

regarded as within – plate basalt. Age of the basalt is constrained based on the appearance of

index brachiopod fossils in the overlying limestone strata. Middle Permian age is therefore

assigned to these limestones. Our filed investigation in the vicinity of the low-lying to rolling

Sri Sophon district area show that these well-bedded carbonate rocks are always lying over

the basalts. Trace and REE data indicate that the basaltic rocks are quite similar to those of

the Mid-ocean ridge basalts from the Southern Central Indian Ridge of the India Ocean.

Therefore the studied basalts have formed on the sea-floor as submarine volcanos which in

turn give rise to development of the patchy or platform limestones. The basalt and limestone

association may have formed onto the oceanic crust situating between Shan – Thai and

Indochina continental terranes.

- 14 -



589 Yangon

Hydrodynamic adaptation of fusulinid foraminifera

Yukun Shi

School of Earth Sciences and Engineering, Nanjing University, China, [email protected]

Abstract

Fusulinid is one of the most important foraminifera in late Paleozoic, with respect to

biostratigraphy, paleoecology, and paleobiogeography. Compared with the biostratigraphic

and biogeographic significance, its paleoecological indication is much more controversy.

Different fusulinid taxa are always flourished in the environments with certain water energy

condition, and test shape was believed to be crucial to their hydrodynamic adaptation. This is

quite possible a misunderstanding when they are considered alike the sedimentary calcareous

grains of consistent density. The inner structure of fusulinid tests is exquisite and delicate,

and results in apparent density divergence between different taxa even when they have

identical test shape. Test density should significantly affect the settlement of fusulinids

although some of them may develop structures like pseudopodia or organic adhesive as the

fixing strategy. The influence of test shape might be overestimated and often mingled with

that of test density and size. The present study draws attention to the fusulinids from diverse

environments with different water turbulence, and explores their hydrodynamic preferences

and the biological cause.

Keywords: Fusulinid foraminifera, paleoecology, hydrodynamics, late Paleozoic

- 15 -



589 Yangon

Permian oolitic carbonates from the Baoshan Block, China: ooid features, stratigraphic

distribution and paleogeographic indications

Hao Huang, Xiaochi Jin

Institute of Geology, Chinese Academy of Geological Sciences

[email protected]

Marine carbonate ooids are environment-sensitive, and hence valuable for paleoclimatic

and paleogeographic reconstructions. Permian ooids from the Baoshan Block in western

Yunnan, China are described to offer a new means to refine the uncertain paleogeographic

details of this Gondwana-derived block. Four major types of ooids (micritic ooids, compound

ooids, leached ooids and half-moon ooids) are documented from the Hewanjie Formation in

the northern and the Shazipo Formation in the southern Baoshan Block. These ooids are

dated via biostratigraphic analysis to be Wordian–early Wuchiapingian and signify an

ameliorated shallow-marine temperature for the Guadalupian strata of the Baoshan Block.

Results of this study, coupled with literature data, reveal diachronous debut of Permian ooids

among the Gondwana-derived blocks (Fig. 1): mostly Sakmarian in Central Taurides of

Turkey, Central Iran, Central Pamir and Karakorum Block, versus Wordian–Capitanian in

Baoshan Block, Peninsular Thailand and South Qiangtang. In contrast, Asselian–Sakmarian

strata of Baoshan Block as well as Peninsular Thailand and South Qiantang are characterized

by glaciomarine diamictites. These observations suggest that the Baoshan Block was

probably situated at a considerably higher paleolatitude under distinct influence of Gondwana

glaciation during the Asselian–Sakmarian, than those blocks yielding Sakmarian ooids.

Moreover, marine ooids are virtually absent nearby the equator within the Permian Tethys,

similar to the modern situation. The Baoshan Block is accordingly interpreted to drift to

warm-water southern mid-latitudes during the Wordian–Capitanian, and remain to the south

of Central Iran, Karakorum Block and South China, which were equatorially located in the

Capitanian.

Acknowledgement: Financial support from National Science Foundation of China

(41102007, 41272043) and China Geological Survey (121201102000150009) are gratefully

acknowledged.

- 16 -



589 Yangon

Fig. 1 Distribution of ooids in different geological units

- 17 -



589 Yangon

Juxtaposed forearc sequences and structure evolution of North Luzon Trough

onshore and offshore eastern Taiwan: Processes for development of forearc Lichi

Mélange in Coastal Range

Chi-Yue Huang1,2 *, Shengxiong Yang3, Xuejie Li3

1Key Laboratory of Marginal Sea Geology, Guangzhou Institute ofGeochemistry, Chinese

Academy of Sciences, Guangzhou 510640, China

2Department of Earth Sciences, National Cheng Kung University, Tainan 701, Taiwan

3Guangzhou Marine Geological Survey, Guangzhou 51076, China

Abstract

The North Luzon Trough forearc basin in the oblique arc-continent collision zone offshore

SE Taiwan displays a bi-vergent thrusting to accommodate the space shortening by the active

collision. Westward thrusting occurs first along the arc-prism boundary in the west, and then

followed by eastward backthrusting along the arc backstop in the east. Bi-vergent thrusting

occurs simultaneously with forearc sedimentations. Syn-sedimentation deformations result in

a juxtaposition of three forearc sequences bounded by two unconformities. From east to west

across the forearc orogenic strike, forearc strata get older and structure deformations appear

intensive. Similar characteristics of the juxtaposed dynamic stratigraphy and structure

deformations are also recorded in the obducted forearc sequences onshore the Coastal Range

in eastern Taiwan. However, the forearc strata onshore the Coastal Range were further

deformed by west-propagating thrusting during the obduction in the last 1 Ma. Juxtaposition

of the dynamic forearc stratigraphy, multiple stages of thrusting with contrast structure

vergence and final emplacements of SSZ blocks during the obduction are the main

mechanisms responsible for the development of the forearc Lichi Mélange in the western

Coastal Range.

Keywords: juxtaposed forearc stratigraphy, syn-sedimentation deformations, arc-continent

collision, Coastal Range, eastern Taiwan

- 18 -



589 Yangon

Geochemistry of Lower Paleozoic basalts from the Hida Gaien belt, SW Japan: An

evidence of Early Paleozoic subduction initiation at Gondwana margin

Kazuhiro Tsukada

The Nagoya University Museum, Nagoya 464-8601, Japan

In placing Japanese tectonics in an Asian context, the Paleozoic geological environment is

a significant issue. This paper investigates the geochemistry of Lower Paleozoic basaltic

rocks in the Hida Gaien belt of SW Japan in order to determine its tectonic setting. The

basaltic rocks include the following two types in ascending order: (A) with intersertal texture,

and (B) with porphyritic texture. These basalts A and B are enriched in LILE and LREE as

opposed to MORB. The data of basalt A, high and uniform FeO*/MgO ratio (2.2 in avg.),

moderate TiO2 (1.3 wt.% in avg.), HFSE and REE concentrations nearly same as MORB, low

LREE/HREE ratio (1.0 in avg.), and flat chondrite-normalized REE pattern, point tholeiitic

arc basalt having somewhat MORB-like nature.This tendency is similar to that of “MORB-

like fore-arc tholeiitic basalt (FAB)” reported for example from Izu–Bonin–Mariana arc, and

high V concentration (412–456 ppm) and the low Ti/V ratio (18–21) in the basalt A also

support this view. On the other hand, basalt B, low FeO*/MgO ratio (1.2 in avg.), low TiO2

(0.6 wt.% in avg.), low V (281 ppm in avg.) and Ti/V ratio (12.9 in avg.), reducing-trend and

clear negative Nb anomaly in MORB-normalized multi-element concentrations diagram, and

moderately high LREE/HREE ratio (2.3 in avg.), is suggested as calk-alkaline basalt and

some of them have high-Mg basalt characteristics. It is generally known that FAB is erupted

at the earliest stage of arc-formation–namely initial stage of subduction, and subsequently

boninitic/tholeiitic/calc-alkaline volcanism occurs at supra-subduction zone (SSZ). Thus, the

pair of “basalt A (FAB) and overlying basalt B (high-Mg calk-alkaline rock)” likely evidence

the Early Paleozoic subduction initiation and arc-formation at a SSZ.

- 19 -



589 Yangon

Ultramafic rocks outcropping largely in SW Yunnan and its significance forrevealing

the Paleotethyan LIPs

Qing Shi, Nianqiao Fang *

*Correspondence author

Abstract

The Changning-Menglian orogenic belt in Western Yunnan is a main part of the

Paleotethyan Ocean (D1-T2), who developed to the largest scale during the Carboniferous

(Liu et al., 1993；Zhong and Wang, 1991; Fang and Feng, 1996). One of the evidences about

the above stateis that the seamounts and oceanic plateaus aged early Carboniferous is widely

distributed over the study area. The ultramafic accumulative and eruptive rocks and oceanic

island basalts outcropping at Manxin, which lies to the north of boundary tablet between

China and Myanmar, should be a typical suite constructing the base of those plateaus. Among

the ultramafic and mafic suite, the high-MgO (27%-30%) picrites have been paid attention by

some researchers (Fang and Niu, 2003). Our current work further divided these picrites into 3

types on the basis of some essentials such as their structure, the proportions of phenocrysts to

matrix, and the existence of feldspar minerals or not. We are confident that all picrites were

derived from the same magmatic process and tectonic background.

According to theFo of magmatic origin olivines in these picrites, the calculated average

liquidus temperature is 1336℃. Although it is lower than 1400±25℃, which was calculated

by Fang and Niu in 2003, it is still higher than the normal mid-ocean ridges liquidus

temperature 1250℃, thus prove the possible mantle plume origin. In addition, the new

discovered pyroxene peridotite outcrops near the picrites, they have similar Fo in their

olivines, and CaO content in olivines is higher than 0.1%, which indicates their magmatic

origin (Larsen & Pedersen, 2000), and makes a further proof about the activities of mantle

plume. The chondrite normalized REE patterns of picrites show patterns with light REE

enrichment, similar to the local OIB type basalts. According to the high field strength

elements in local basalts, most basalts plotted in the area of OIB in the Nb/Th - Zr/Nb graph

and Zr/Y-Nb/Y graph. Another evidence is about the Fe/Mn ratio. As the siderophile

elements concentrated in earth’s core, the high Fe/Mn ratio may indicates their deep source.

Picrites in this area have similar Fe/Mn ratio to the Hawaii OIB, or even higher, reflects the

deep source characteristics of mantle plume activities. Kerr et al. (2000) and Arndt (2002)

- 20 -



589 Yangon

have constructed petrologic models of Large Igneous Provinces and regarded the

hightemperature-genetic picrites (komatiite) as a necessary component in the model. The

various ultramafic rocks and OIB associations in the Mangxin area are very probably the

remains of the LIPs formed in the Paleotethyan ocean. It might be significantly a work to

further approach the associations both for clarifying the LIP's magmatic structure and

understanding the Paleotethy's evolution.

Beyond the Mangxin area, there is a large amount of ultramafic and mafic eruptive rocks

outcropping in the Shuangjiang and Gengma areas, mid Changning-Menglian Belt. Moreover,

the ocean-island carbonates sat upon those eruptive rocks are widely distributed over the

whole belt. The basalts discovered in Shuangjiang and Gengma have a MgO content about

7%-9%, which may reflect a higher melting setting. The frequent occurrence of high-

temperature melting strengthens a possibility of the LIPs in the Paleotethys.

The fossils from the carbonates and cherts intercalating the eruptive rocks indicate the

early Carboniferous was a main episode of the Large Igneous Province activities in SW

Yunnan. Contemporarily, the abyssal basin facies represented by thin-bedded radiolarian

cherts most developed in the Changning-Menglian belt, (Fang et al., 1998), which should

mean the Paleotethys reached its zenith at that epoch.

Reference

Arndt N., 2002, Oceanic plateaus as windows to the Earth's interior: An ODP success story,

in: Achievements and Opportunites of Scientific Ocean Drilling, A special issue of the

JOIDES, 28: 79-84.

Fang N, Feng Q, 1996.Devonian to Triassic Tethys in western Yunnan.Publishing House of

China University of Geosciences, Wuhan.

Fang N, Feng Q, Zhang S, et al. 1998. Paleo-Tethys evolution recorded in the Changning-

Menglian Belt, western Yunnan, China. Comptes Rendus de l'Académie des Sciences -

Series IIA - Earth and Planetary Science, 326(4):275-282.

- 21 -



589 Yangon

Fang N, Niu Y, 2003.Late Palaeozoic Ultramafic Lavas in Yunnan, SW China, and their

Geodynamic Significance [J]. Journal of Petrology, 44 (1): 141-157.

Larsen L M, Pedersen A K. 2000. Processes in high-Mg, high-T magmas:Evidence from

olivine, chromite and glass in Paleogene picrites from West Greenland[J]. Journal of

Petrology, 41: 1071-1098.

Liu B, Feng Q, Fang N, Jia J, He F, 1993. Tectonic evolution of Paleo-Tethys Poly-island-

ocean in Changning-Menglian and Lancangjiang Belts, south-western Yunnan, China.

Kerr A. C., Tarney J., Marriner G. F. et al., 2000. In: Large Igneous Provinces, Mahoney J. J.

& Coffin M. F. (eds.), 123-144.

Zhong D, Wang Y, 1991. Paleo Tethys tectonic evolution in western Yunnan, SW China.

Proceedings of 1st Inter. Symp. IGCP Project 321 Abstracts, Kunming, 280-285.

- 22 -



589 Yangon

The Manila subduction zone: Its structure, deformation and seismogenic potential

L.T. Armada1, S.-K. Hsu2, C.B. Dimalanta1, N.T. Ramos1, Y.-C.Yeh3, G.P. Yumul, Jr.4,

J.M.R. Guotana1, W.-B. Doo5

1 RWG Laboratory, National Institute of Geological Sciences, University of the Philippines,

Quezon City, Philippines 1101; (email: [email protected])

2Department of Earth Sciences, National Central University, Taoyuan County, Taiwan

3Taiwan Ocean Research Institute, National Applied Research Laboratories, Kaohsiung,

Taiwan

4Apex Mining Co. Inc., Ortigas Center, Pasig City, Philippines

5Center for Environmental Studies, National Central University, Taoyuan County, Taiwan

Abstract

Ongoing convergence between the Eurasian Plate and Philippine Sea Plate is being

accommodated by the subduction of the South China Sea crust beneath Luzon Island,

Philippines (Yumul et al., 2003). The present subduction in the Manila trench terminates into

arc-continent collision zones in the north (Taiwan) and south (Mindoro Island). Marked

heterogeneity is observed along its ~1000 km length.

In June-July 2014, a systematic geophysical survey of the Manila trench region was

conducted aboard Ocean Researcher 5. Collected high resolution multi-channel seismic

(MCS) reflection and bathymetric datasets provide detailed images of the latitudinal

variations in the crustal structures and deformation styles along the subduction zone.The

latitudinal variations in the subduction zone structure and deformation may reflect the

varying and evolving nature of the plate coupling in the convergent margin. Further, this

complex nature of the Manila trench region have implications on the mega-thrust earthquake

potentials of the subduction zone from north to south.

The MCS sections across the trench and fore-arc regions display distinct N-S changes in

the deformation patterns both in the mega-thrust/ subduction interface as well as the

overlying fore-arc regions. A distinct morphological and deformational boundary near 17°N

latitude is identified. Seafloor morphology also drastically varies along this boundary.

Differences in the nature of the subducting oceanic crust (i.e. seafloor relief related to

seamounts and ridges, sediment supply, reactivated features and faults associated with the

- 23 -



589 Yangon

SCS opening) cause variations in the deformation observed across this boundary in the

Manila trench and fore-arc region.

The nature of the subduction interface play a major role on the structural development of

the overlying fore-arc region (Vannucchi et al., 2003). The northern frontal wedge is

classified as an accretionary margin with prism widths ranging from ~50 km to >100 km near

southern Taiwan. The southern segment is mainly an erosive margin (with a narrow and steep

frontal wedge).Identified mass transport deposits (MTD) in the trench fill and associated

scarps in the southern segment (16.8°N, 16.5°N, and 15° N) point to extensive deformation

and erosion of the fore-arc region. This erosive margin also has a history of seamount

subduction and associated large submarine slope failures. Seamount subduction is associated

with distinct seafloor features that reflect the downward migration of the seamount and the

uplift and subsequent collapse of the overriding fore-arc crust (Harders et al., 2014). The

inferred ancient submarine mass wasting events may have caused tsunamis in adjacent areas.

Large scarps in the frontal wedge is consistent with morphologies associated with seamount

subduction. Widespread occurrence of gas hydrates in the frontal wedge of the subduction

may also contribute to slope failures in the Manila trench. Even small magnitude earthquakes

in the region may trigger instability in the slope materials and thus induce slope failures.

The 17°N latitude boundary also separates the fore-arc basin into the North Luzon Trough

(northern fore-arc basin) and the West Luzon Trough (southern fore-arc basin). The North

Luzon Trough is generally deeper than the West Luzon Trough. Sediment accumulation in

the fore-arc basin has implications on the strain energy loading in the mega-thrust (Fuller et

al., 2006). Abundant sediment deposition in the southern fore-arc basin and less sediments in

the northern fore-arc basin imply faster strain loading in the southern segment compared to

the northern segment of the subduction mega-thrust.

Seamounts in the subducting oceanic lithosphere may induce fracturing of the overlying

fore-arc crust as it progresses downward (Wang and Bilek, 2011). The fracture networks near

the subduction interface may then limit the rupture area of future mega-thrust earthquakes.

This make indicate a lower probability for great subduction earthquakes (Mw≥9) in the

southern segment of the Manila trench, although the occurrence of intermediate sized

earthquakes should not be discounted. Asperities associated with the rough subduction

interface in the southern Manila trench may also limit the rupture areas, thus smaller

earthquake magnitudes. The subduction interface to the north is relatively smooth and may be

conducive to large rupture areas (large magnitude earthquakes). In summary, the northern

- 24 -



589 Yangon

segment of the megathrust is inferred to be less coupled and is dominated by accretionary

wedge growth. The southern segment is the more coupled and is characterized by surface

erosion in the frontal wedge and a rough subduction interface.

References

Fuller, C. W., S. Willett, and M. T. Brandon, 2006. Formation of fore-arc basins and their

influence on subduction zone earthquakes, Geology, 34(2), 65 – 68, doi:10.1130/G21828.1.

Harders, R., Cesar R. Ranero, and Wilhelm Weinrebe, 2014. Characterization of Submarine

Landslide Complexes Offshore Costa Rica: An Evolutionary Model Related to Seamount

Subduction in Submarine Mass Movements and Their Consequences edited by Sebastian

Krastel, Jan-Hinrich Behrmann, David Völker, Michael Stipp, Christian Berndt, Roger

Urgeles, Jason Chaytor, Katrin Huhn, Michael Strasser, Carl Bonnevie Harbitz, doi:

10.1007/978-3-319-00972-8.

Vannucchi, P., C. R. Ranero, S. Galeotti, S. M. Straub, D. W. Scholl, and K. McDougall-Ried,

2003. Fast rates of subduction erosion along the Costa Rica Pacific margin: Implications

for nonsteady rates of crustal recycling at subduction zones, Journal of Geophysical

Research, 108(B11), 2511, doi: 10.1029/2002JB002207.

Wang, K. and Bilek, S. L., 2011. Do subducting seamounts generate or stop large

earthquakes? Geology 39, 819–822.

Yumul, G. P. Jr., Dimalanta C. B., Tamayo R. A. and Maury R. A., 2003. Collision,

subduction and accretion events in the Philippines: A synthesis. Island Arc 12, 77-91.

- 25 -



589 Yangon

Petrological and geochemical characteristics of the ultramafic section of the Samar

Ophiolite: Implications on the origins of the ophiolites in Samar and Leyte, Philippines

J.M.R. Guotana1, B.D. Payot1, C.B. Dimalanta1, N.T. Ramos1, D.V. Faustino-

Eslava2,K.L. Queaño3, G.P. Yumul, Jr.3

1 Rushurgent Working Group, National Institute of Geological Sciences, College of Science,

University of the Philippines, Diliman, Quezon City, Philippines

2 Earth Systems Research Team (EaRT), School of Environmental Science and Management,

University of the Philippines - Los Baños, Laguna, Philippines

3Apex Mining Company Inc., Ortigas Center, Pasig City, Philippines

Abstract

The late Early to early Late Cretaceous Samar Ophiolite forms part of the Cretaceous belt

of ophiolites and ophiolitic complexes along eastern Philippines. Recent geologic surveys

revealed the presence of peridotites, gabbros and massive flow and pillow lavas at the

southern portion of Samar Island which represent the mantle and crustal sections of the

Samar Ophiolite. Several ophiolites are also exposed in Leyte Island which is located west of

Samar Island. These are the Tacloban Ophiolite Complex (TOC) and Malitbog Ophiolite

Complex (MOC). Mineral chemistry data of the ultramafic rocks from the three ophiolites

show distinct differences in their geochemical signatures. The ultramafic rocks of the TOC

and MOC show strong affinity with abyssal peridotites whereas those of the Samar Ophiolite

are more comparable to supra-subduction zone (SSZ) peridotites. Given the close proximity

of these ophiolites and ophiolitic complexes, these contrasting characteristics warrant the

reevaluation of the origin of these ophiolites. We propose that the Samar Ophiolite, and the

TOC and MOC are possible remnants of a subduction initiation event which led to the

preservation of different geochemical signatures.

Introduction

Ophiolites are distinctive assemblages of mafic and ultramafic rocks that represent

fragments of oceanic crust and upper mantle that were uplifted and emplaced on continental

margins, accretionary prisms and island arcs (e.g. Dewey and Bird, 1971; Robinson et al.,

2008; Dilek and Furnes, 2011). Identifying the tectonic setting in which ophiolites are formed

- 26 -



589 Yangon

remains to be a contentious issue. On the basis of geochemical characteristics, several

workers established that ophiolites could have been generated in mid-oceanic ridges (MOR)

or in supra-subduction zones (SSZ) (e.g. Miyashiro, 1973; Pearce et al., 1981). SSZ

ophiolites are further classified into forearc and backarc ophiolites based on key geochemical

distinctions. Ophiolites formed in backarc basins are characterized by low degree of partial

melting (~10-15%) and oxygen fugacities (Δlog fO2=-2-1) similar to MOR ophiolites. This is

in contrast with the high degrees of partial melting experienced by forearc ophiolites and high

oxygen fugacities (e.g. Parkinson and Pearce, 1998; Yaliniz, 2008; Dare et al., 2009; Pagé et

al., 2009). The distinction between MOR and SSZ ophiolites is therefore an essential

component in reconstructing the tectonic processes which led to the emplacement of

ophiolites.

The eastern margin of the Philippines is composed of Early to Late Cretaceous ophiolites

and ophiolitic complexes which exhibit subduction zone imprints (Yumul et al., 1997;

Tamayo et al., 2004). Several ophiolites and ophiolitic complexes occur in Samar and Leyte

Islands which form part of this ophiolitic belt. The Samar Ophiolite is located in the

southernmost portion of Samar Island. The TOC and MOC are exposed in the northeastern

and southwestern ends of Leyte Island, respectively (e.g. Tamayo et al., 2004).

Geology

The Samar Ophiolite is composed of harzburgites and dunites, gabbros, massive and

pillow lavas. Harzburgites cut by concordant and discordant dunites are exposed in Manicani

Island. Gabbros are in thrust fault contact with the serpentinized dunites in the interiors of

Balangiga. The volcanic section is composed of a lower massive flow with diabasic texture.

The upper section consists of massive and pillowed lava flows (Guotana et al., 2016). The

TOC is exposed in the northeastern portion of Leyte Island and is made up of harzburgites,

layered to isotropic gabbros, sheeted diabase, basalt dike complex, and pillowed and massive

basaltic flow (Suerte et al., 2005). Exposures of the MOC are recognized in southwestern

Leyte. The MOC is composed of harzburgites and lherzolites with minor exposures of dunites.

The crustal section consists of isotropic gabbros, diabase dike swarms and pillow lava

deposits. Interbedded chert, mudstone, sandstone and limestone cap the MOC (Dimalanta et

al., 2006).

- 27 -



589 Yangon

Methodology

Petrographic analysis and point counting of a minimum of 2000 grains of main mineral

phases per thin section were carried out to characterize and classify the peridotites. Mineral

chemistry data of the utramafic rocks from the Samar Ophiolite were obtained using a JEOL

JXA-8230 electron probe microanalyzer at the National Institute of Geological Sciences in

the University of the Philippines. The analysis was carried out using an accelerating voltage

of 15kV and a beam current of 50 nA. Selected clinopyroxenes were analyzed for rare earth

element (REE) concentrations using an Agilent 7500s inductively coupled plasma mass-

spectrometry with MicroLas GeoLas Q-plus 193 nm ArF excimer laser system (LA-ICP-MS)

at Kanazawa University, Japan.

Results and Discussion

The harzburgites of the Samar Ophiolite exhibit porphyroclastic texture and are comprised

of olivine, orthopyroxene and chromian spinel. Very minor amounts of interstitial

clinopyroxene and amphibole are also present. The dunites consist mainly of olivine and

minor orthopyroxene, chromian spinel and clinopyroxene. Mineral chemistry data show that

the forsterite content (Fo=Mg/Mg+Fe2+x100) of the olivines in the harzburgites and dunites

ranges from 90-91. The spinels have Cr# (=Cr/Cr+Al) of 0.62-0.72 for the harzburgites and

0.54-0.79 for the dunites. The values obtained suggest that they are residual mantle

peridotites (Arai, 1994). Spinel Al2O3 wt% versus TiO2 wt% classifies the peridotites as

supra-subduction zone (SSZ) peridotites (Kamenetsky et al., 2001). The chondrite-

normalized trace element concentrations of the clinopyroxenes show depletion of the light

rare earth elements (LREEs) and a relatively flat pattern for middle to heavy rare earth

elements (MREEs-HREEs).

The Cr# of the spinel in the TOClherzolites (0.10-0.27) and harzburgites (0.19-0.67) are

lower than those in Samar Ophiolite mantle peridotites. The low range of spinel Cr# is also

observed in the MOC lherzolites (0.11-0.40) and harzburgites (0.12-0.54). These values are

comparable to those in abyssal peridotites (Dick and Bullen, 1984). The TOC and MOC

ultramafic rocks straddle between the MOR and SSZ ophiolites fields in the spinel Al2O3

wt% versus TiO2 wt%.

Conclusions

The geochemical characteristics of the Samar Ophiolite peridotites are similar to supra-

subduction zone peridotites. This is in contrast with the abyssal peridotite signatures of the

- 28 -



589 Yangon

TOC and MOC peridotites. We propose that the Samar Ophiolite, and the TOC and MOC are

possible remnants of a subduction initiation event which led to the preservation of different

geochemical signatures.The TOC and MOC represent the early stages of proto-forearc

spreading yielding mantle and crustal sequences with MOR-like geochemical signature. The

Samar Ophiolite represents the stage wherein slab-derived fluids interact with the ophiolite

producing a strong SSZ-signature.

References

Arai, S., 1994. Characterization of spinel peridotites by olivine-spinel compositional

relationships: review and interpretation. Chemical Geology 113, 191-204.

Dare, S.A.S., Pearce, J.A., McDonald, I. and Styles, M. T., 2009. Tectonic discrimination of

peridotites using fO2-Cr# and Ga-Ti-FeIII systematics in chrome-spinel. Chemical

Geology 26, 199-216. http://doi.org/10.1016/j.chemgeo.2008.08.002.

Dewey, J.F. and Bird, J.M., 1971. The origin and emplacement of the ophiolite suite:

Appalachian ophiolites in Newfoundland. Journal of Geophysical Research 76, 3179-3206.

Dick, H.J.B. and Bullen, T., 1984.Chromian spinel as a petrogenetic indicator in abyssal and

alpine-type peridotites and spatially associated lavas. Contributions to Mineralogy and

Petrology 86, 54-76.

Dilek, Y. and Furnes, H., 2011. Ophiolite genesis and global tectonics: geochemical and

tectonic fingerprinting of ancient oceanic lithosphere. Geological Society of America

Bulletin 123, 387-411.

Dimalanta, C.B., Suerte, L.O., Yumul Jr., G.P., Tamayo Jr., R.A. and Ramos, E.G.L., 2006.

A Cretaceous supra-subduction oceanic basin source for Central Philippine ophiolitic

basement complexes: Geological and geophysical constraints. Geosciences Journal 10,

305-320.

Guotana, J.M.R., Payot, B.D., Dimalanta, C.B., Ramos, N.T., Faustino-Eslava, D.V., Queaño,

K.L. and Yumul Jr., G.P., 2016. Arc and backarc geochemical signatures of the proto-

Philippine Sea Plate: Insights from the petrography and geochemistry of the Samar

Ophiolite volcanic section. Journal of Asian Earth Sciences.

http://doi.org/10.1016/j.jseaes.2016.07.031.

- 29 -



589 Yangon

Kamenetsky, V.S., Crawford, A.J. and Meffre, S., 2001. Factors controlling chemistry of

magmatic spinel: An empirical study of associated olivine, Cr-spinel and melt inclusions

from primitive rocks. Journal of Petrology 42, 655-671.

http://doi.org/10.1093/petrology/42.4.655.

Miyashiro, A., 1973. The Troodos ophiolitic complex was probably formed in an island arc.

Earth and Planetary Science Letters 19, 218-224.

Pagé, P., Bedard, J.H. and Tremblay, A., 2009. Geochemical variations in a depleted fore-arc

mantle: The Ordovician Thetford Mines Ophiolite. Lithos 113, 21-47.

Parkinson, I.J. and Pearce, J.A., 1998. Peridotites from the Izu-Bonin-Mariana forearc (ODP

Leg 125): evidence for mantle melting and melt- mantle interaction in a supra-subduction

zone setting. Journal of Petrology 39, 1577-1618.

Pearce, J.A., Alabaster, T., Shelton, A.W. and Searle, M., 1981. The Oman ophiolite as a

Cretaceous arc-basin complex: evidence and implications. Philosophical Transactions of

the Royal Society of London 300, 299-317.

Robinson, T., Malpas, J., Dilek, Y. and Zhou, M., 2008.The significance of sheeted dike

complexes in ophiolites. GSA Today 18, 4-10.

Stern, R. J., Reagan, M. K., Ishizuka, O., Ohara, Y. and Whattam, S. A., 2012. To understand

subduction initiation, study forearc crust: To understand forearc crust, study ophiolites.

Lithosphere 4, 469-483. http://doi.org/10.1130/L183.1.

Suerte, L.O., Yumul Jr., G.P., Tamayo Jr., R.A., Dimalanta, C.B., Zhou, M.-F., Maury, R.C.,

Polve, M. and Balce, C.L., 2005. Geology, geochemistry and U-Pb SHRIMP age of the

Tacloban Ophiolite Complex, Leyte Island (Central Philippines): Implications for the

existence and extent of the proto-Philippine Sea Plate. Resource Geology 55, 205-214.

Tamayo Jr., R.A., Maury, R.C., Yumul Jr., G.P., Polve, M., Cotton, J., Dimalanta, C.B. and

Olaguera, F.O., 2004. Subduction-related magmatic imprint of most Philippine ophiolites:

Implications on the early geodynamic evolution of the Philippine archipelago. Bulletin de

la Societe Geologique de France 175, 443-60.

- 30 -



589 Yangon

Yaliniz, K.M., 2008. A geochemical attempt to distinguish forearc and back arc ophiolites

from the "supra-subduction" Central ophiolites (Turkey) by comparison with modern

oceanic analogues.Ofioliti 33, 119-129.

Yumul Jr., G.P., Balce, G.R., Dimalanta, C.B. and Datuin, R.T., 1997. Distribution,

geochemistry and mineralization potentials of Philippine ophiolite and ophiolitic

sequences. Ofioliti 22, 47-56.

https://www.researchgate.net/journal/0391-2612_Ofioliti

- 31 -



589 Yangon

MINERAL SYSTEMS AND EXPLORATION TARGETING IN SOUTHERN

PHILIPPINES: POSSIBLE CLUES FROM THE MACO GOLD MINE,

COMPOSTELA VALLEY, MINDANAO, PHILIPPINES

G.P. Yumul, Jr.1, W.W. Brown1, C.B. Dimalanta2, L.T. Armada2, J.M.R. Guotana2, P.C.

Manalo2

1 Apex Mining Company Inc., Ortigas, Pasig City, Metro Manila, PHILIPPINES

2 Rushurgent Working Group, National Institute of Geological Sciences, College of Science,

University of the Philippines, Diliman, Quezon City, PHILIPPINES

Abstract

The Maco Gold Mine in the province of Compostela Valley in southern Mindanao,

Philippines is an early to late Miocene low to intermediate sulfidation deposit. Gold is

associated with silver, copper, lead and zinc with underground mine extraction ranging from

conventional to mechanized, trackless mining methods. Quartz, quartz-carbonate to sulfide

veins characterize the vein systems which range from a few centimeters to two to three

meters in width. Fluid is basically neutral ph, highly saline, oxidizing with chloride

complexing as the major ligand. In the field, the vein systems are dominantly NW-SE

trending with associated E-W trending and NE-SW trending veins. Telescoping is present as

the potassic zone of a porphyry copper deposit is exposed and juxtaposed with the

dominantly gold-bearing quartz veins. Several controls have been proposed to account for the

observed mineralization in the Maco area similar to what has been noted in other parts of the

Philippines and the world. These include a.) Its location within the sphere of influence of the

NW-trending sinistral Philippine Fault Zone with the E-W veins being interpreted as

extensional relays between the various strands of the fault zone (e.g. Mitchell & Leach 1991;

Vearncombe & Zelic 2015); b.) Existence of adakitic rocks in the area (e.g. Chiaradia et al.

2012); c.)Its proximity to the active Lake Leonard geothermal system (e.g. Suerte et al.

2007); and d.) Having thicker crust which enhances fractionation and, to a certain extent,

mineralization potential (Dimalanta & Yumul 2008).

Looking at the regional setting of eastern Mindanao would indeed show that there appears

to be a geographic correlation between the distribution of the different precious-base metals

in the island and the Philippine Fault Zone. However, the Philippine Fault Zone as it is now is

coupled with the Pliocene to present-day Philippine Trench. Significant mineralization and

ore deposits along eastern Mindanao have been dated Oligocene to Late Miocene (e.g. Co-O,

- 32 -



589 Yangon

Kingking, Maco) which is older than the Pliocene to present-day Philippine Fault. The

petrology and geochemistry of the rocks from the different mines and prospects show that not

all are hosted or even related to adakitic rocks. As recognized before, adakitic rocks on a

regional to district level can be used as an exploration marker but not at the mine level

(Yumul et al. 2016). The Lake Leonard geothermal system is a young system (1800 ybp –

Delfin et al. 1999) that could not account for the older hydrothermal systems. A look at the

crustal thickness maps generated from geophysical and geochemical parameters would also

show that crustal thickness could not be a major control on mineralization (e.g. Dimalanta &

Yumul 2008).

With these realities, it is important to understand what triggers the formation and

accumulation of deposits in the context of a mineral system (Wyman et al., 2016).

Exploration targeting will be more effective and efficient if the processes responsible for

mineralization, which are related in space and time to tectonic triggers, is understood (e.g.

Hronsky et al. 2012). Based on available information, a succession of compressive to

extensional regime related to subduction followed by large-scale faulting may account for the

rapid release of energy that can lead to mineral deposition and accumulation (e.g. Yumul et al.

2003). Collision of an oceanic bathymetric high with an overriding plate may not necessarily

result to any significant mineralization.

References:

Chiaradia M., Ulianov A., Kouzmanov K. and Beate B., 2012. Why large porphyry Cu

deposits like high Sr/Y magmas. Scientific Reports 2: 685, 1-5.

Delfin F.G., Jr., Newhall C.G. et al. 1999. 14C ages of some Quaternary explosive eruptions

in southern Philippines. GEOCON 1999 Abstract Volume, Manila, Philippines.

Dimalanta C.B. and Yumul G.P.Jr. 2008. Crustal thickness and adakite occurrence in the

Philippines: Is there a relationship? Island Arc 17, 421-431.

Hronsky J.M., Groves D.I., Loucks R.R. and Begg G.C. 2012.A unified model for gold

mineralization in accretionary orogens and implications for regional-scale exploration

targeting methods. Mineralium Deposita 47, 339-358.

Mitchell A.H.G. and Leach T.M. 1991. Epithermal gold in the Philippines. Island arc

metallogenesis, geothermal systems and geology: London, Academic Press Geology

Series 457p.

- 33 -



589 Yangon

Suerte L.O., Nishihara S., Imai A., Watanabe K., Yumul G.P.Jr. and Maglambayan V.B.

2007. The occurrences of ore minerals and fluid inclusion study on the Kingking porphyry

copper-gold deposit, eastern Mindanao, Philippines. Resource Geology 57, 219-229.

Vearncombe J. and Zelic M. 2015. Structural paradigms for gold: Do they help us find mine?

Applied Earth Science 124, 2-19.

Wyman D.A., Cassidy K.F. and Hollings P. 2016. Orogenic gold and the mineral systems

approach: Resolving fact, fiction and fantasy. Ore Geology Reviews 78, 322-335.

Yumul G.P.Jr., Brown W.W., Dimalanta C.B. et al. 2016. Adakitic rocks in the Masara gold-

silver mine, Compostela Valley, Mindanao, Philippines: Different places, varying

mechanisms? Journal of Asian Earth Sciences. Doi:

http://dx.doi.org/10.1016/j.jseaes.2016.06.005.

Yumul G.P.Jr., Dimalanta C.B., Tamayo R.A. and Maury R.A. 2003. Collision, subduction

and accretion events in the Philippines: A synthesis. Island Arc 12, 77-91.

Figure 1. Location of Maco gold-silver mine operated by Apex Mining Company Inc.

Location of a Quaternary volcano, Lake Leonard, is shown. CO2 emanations shown as

bubbles in water.

- 34 -



589 Yangon

History of fluvial-marine interaction in Pak Nam Pran, Pran Buri, Prachuap Khiri

Khan, southern Thailand: a preliminary report

Wickanet Songtham1, Poramita Phanwong2, Parichat Kruainok1

1 Northeastern Research Institute of Petrified Wood and Mineral Resources, Nakhon

Ratchasima Rajabhat University, Nakhon Ratchasima 30000, Thailand

2Faculty of Environment and Resource Studies, Mahidol University, Salaya, Nakhon Pathom

73170, Thailand

Abstract

Pak Nam Pran is a coastal area covering a river mount, Pran Buri River, Pran Buri,

Prachuap Khiri Khan, on the western coast of the Gulf of Thailand. It is characterized as a

small basin surrounded by lower gneissic hills to the north, west, and south and the Gulf of

Thailand to the east. The basin is where the Pran Buri River flowing from the west through

the basin and drained out into the Gulf of Thailand to the east. The basin is about 2

kilometers wide in N-S direction and about 4 kilometers long in E-W direction. The Pran

Buri River is from the west passing through a narrow water gap recharging into the basin in

form of a meandering river system with a trace of oxbow lake. The basin area is covered by

the meandering river with its floodplain area affected by seawater flooded during the high

tides. Vegetation in the area is dominated by mangrove along the riverbanks as well as the

low-lying areas in the basin.

A corer was used to collect soil samples, totally 3.7 m depth, beneath the mid of an oxbow

lake. Each core sample was collected 50 cm long and was cut into space intervals of 10 cm

for soil descriptions, pH testings, age determinations, XRF and palynological analyses. The

soil samples are mostly clay with little variation in color from pale grey to dark grey with

some thin layers of yellowish brown soils. The soil deep from the surface down to 25 cm is

slightly acid and turned into neutral between 25 and 50 cm deep. Soil at deep over 50 cm

down to 370 cm is dominated by alkalinity ranging from slightly alkaline to strongly alkaline

with some thin layers of neutral pH.

Five soil samples were dated by AMS carbon fourteen isotope at the depth 40-50, 120-

130, 160-170, 240-240 and 320-330 cm with the results of 99±27, 566±28, 577±28, 1,125±32

and 992±25 years B.P. respectively. Twelve soil samples were analyzed by XRF to get the

- 35 -



589 Yangon

percentages of MgO, Al2O3, SiO2, SO3, Cl, Ar, K2O, CaO, TiO2, Cr2O3, MnO2, Fe2O3, NiO,

Cu, ZnO, Br2O, Rb2O, SrO, ZrO2, Ta2O5 and PbO for each soil sample. Palynological

analysis is a combinational information to get understanding the depositional environments of

the 370 cm-thick soil deposit across one thousand years to the modern environment. The

research would provide good information on the changes of depositional environments,

vegetation and climates and probably regarding in term of human settlements.

- 36 -



589 Yangon

Geochemical Characteristics, Petrogenesis and Tectonic Settings of Precambrian

Basement of I- and S-types Granitic Gneisses of Saghand Region, Central Iran

Monireh Poshtkoohi1, Talat Ahmad2

1 Geological Survey of Iran

2 Currently VC of Jamia Millia Islamia University, New Delhi, India

Abstract

I- and S-types granitic gneisses of the Saghand region depict calc–alkalic characteristics.

The S–type gneisses/or paragneisses are strongly peraluminous, and the I–type gneisses/or

orthogneisses, with relatively medium to low FeOt, TiO2, and CaO/Na2O, Al2O3/TiO2, and

Rb/Sr values. The S–type gneisses/or paragneisses show strongly negative Sr, Nb and

positive Th and Pb anomalies in the primitive mantle–normalized spider diagram. The REE

in the basement S–type gneisses are moderate to strongly fractionated with (La/Lu)N = 11 to

128, which indicates heterogeneity in the sources for investigated rocks and display small to

significant negative Eu anomalies (Eu/Eu* = 0.02–0.11) in the rocks, which is attributed to

fractionation of plagioclase. The lesser to moderate fractionated REE patterns (La/Lu)N =

1.43 to 29.02 of I–type gneisses indicate that they derived from varying degrees of partial

melting of a tonalite–granodiorite source.Enriched LREE, Y and Yb are attributed to free

garnet in the residue, indicating a shallow source for the plutons. The S-type gneisses samples

indicate syn–collision and volcanic arc granite (VAG), whereas I-type gneisses are categorized

mostly as syn–collision and late–orogenic granites, and as related to post–collision uplift (post–

COLG). The calc–alkaline nature of these rocks suggests that these rocks plot in the fields of island

arc and rocks were generated in a thicker crust, probably shortly after the continental margin arc.

Keywords: I- and S-types gneiss, calc–alkaline, syn–collision, continental margin arc

- 37 -



589 Yangon

Sinistral subduction along the eastern margin of the Asian continent during Albian to

Cenomanian

Tetsuya Tokiwa1*, Akari Ota2, Yusuke Shimura3, Hiroshi Mori1

1 Faculty of Science, Shinshu University, 3-1-1, Asahi, Matsumoto 390-8621, Japan

2 Graduate School of Environmental Studies, Nagoya University, Chikusa, Nagoya 464-8601,

Japan

3 Graduate School of Science and Technology, Shinshu University, 3-1-1, Asahi, Matsumoto

390-8621, Japan

*Corresponding author: [email protected]

Abstract

Paleomagnetic studies and hotspot track analyses show that the Izanagi Plate existed as an

independent plate until about 85 Ma and moved with a dominant sinistral sense of obliquity

with respect to the East Asian margin where the proto-Japan arc was situated. Shear

directions deduced from tectonic mélanges in the accretionary complex provide important

information in examining accretion kinematics and estimating ancient plate motions.

However, geological evidence for sinistral subduction of the Izanagi Plate has not been

reported from the accretionary complex. Therefore, we carried out structural analysis of the

mélange in the Yukawa Accretionary Complex (Albian to Cenomanian) in the Shimanto Belt

of the southwest Japan. The results indicate that mélange fabrics show a sinistral sense of

shear both at outcrop and microscopic scales. In addition, restored shear directions in the

mélange indicate sinistral oblique subduction of an oceanic plate. This indicates that the

Izanagi Plate subducted sinistrally along the eastern margin of Asia during Albian to

Cenomanian in age. Combinations with other published kinematic constraints suggest that

southwest Japan experienced a change from sinistral to dextral shear at about 90 Ma. This

history is compatible with global scale plate reconstructions and places good constraints on

the timing of plate boundary interaction with the Cretaceous East Asian margin.

Key words: Izanagi Plate, mélange, accretionary complex, Cretaceous, Shimanto Belt

mailto:[email protected]

- 38 -



589 Yangon

Transitional carbonate facies between cool and warm settings: A Permian case from the

Baoshan Block in western Yunnan, China

Xiaochi Jin, Hao Huang

Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China

Abstract

The discrimination of cool-water carbonates from the warm-water ones significantly

updated the paleoclimatic meanings of ancient limestones since the 1980s. The Baoshan

Block in western Yunnan, China offers an opportunity to observe a unique carbonate facies

which is transitional between these two groups of carbonates. In this block, Early Permian

limestones in the top of the Dingjiazhai Formation demonstrate a mixture of both cool-water

and warm-water features. They are dominated by bryozoans, echinoderms and brachiopods

and also contain abundant fusulinids, but are essentially devoid of any non-skeletal grains

(Fig. 1). One remarkable feature of these limestones is the fitted fabric: many grain contacts

are characterized by microstylolites. This probably results from compaction and pressure

solution, due to scanty early cements and micritic matrix. These features, except the presence

of fusulinids, collectively suggest cool-water environment for carbonate deposition. On the

other hand, the associated fusulinids, although with rather low diversity, is distinct from

typical cool-water carbonates, and to certain degree signify warm-water condition. In the

stratigraphic framework, these limestones are sandwiched between Early Permian glacio-

marine diamictites and Mid-Permian warm-water photozoan carbonates (e.g. Oolites and

neoschwagerinids and verbeekinids of fusulinids). Inasmuch as these facts, we interpret the

limestones on the top of the Dingjiazhai Formation as a warm-temperate facies type. This

unique facies represents a transition between cool- and water-water conditions, thus is of

general significance for fulfilling the spectrum of carbonate facies types.

- 39 -



589 Yangon

Figure 1 Facies photomicrographs of carbonates in the top of the Dingjiazhai Formation

from the Baoshan Block in western Yunnan, China. (Scale bar=1mm)

- 40 -



589 Yangon

The mid Cretaceous biogeographic revolution in the Pacific

Yasuhiro Iba1, Shin-ichi Sano2

1Department of Earth and Planetary Sciences Hokkaido University, Sapporo, 060-0810,

Japan, Japan

2Fukui Prefectural Dinosaur Museum, Fukui 911-8601, Japan

Abstract

The present study sheds new light on the long-term biogeographic changes of marine

Cretaceous faunas in the Pacific and their underlying causes, changes in the oceanic gateway

configuration. In the Late Cretaceous the North Pacific hosted abundant endemic faunas, thus

giving way to an independent “North Pacific Realm”. Despite the importance of the North

Pacific Cretaceous biota for the understanding of global scale biogeographic patterns, little

research has been done on the geographic distribution patterns of marine floras and faunas in

this region. The purpose of the current study is to reveal the biogeography of the Pacific

throughout the Cretaceous, with special emphasis on the biogeographic relationship of the

North Pacific elements with those of the Tethyan and Boreal Realms. The spatiotemporal

changes of the following taxa were analyzed on the basis of extensive field survey in the

circum Pacific region: A) Mesogean reference key taxa (e.g., rudists), B) Mesogean

indicators (e.g., orbitolinids), C) nerineacean gastropods, D) Tethyan non-rudist bivalves, E)

warm-water bivalves Plicatula, F) belemnites, and G) hoplitid ammonites (northern

elements). These taxa are important for the Cretaceous marine biogeography as they

characterize the Tethyan and/or Boreal Realms.

Separation from the Tethyan Realm in the Albian: The following trends in the temporal

changes of Tethyan biota were recognized in the equatorial–North Pacific. 1) A continuous

distribution of the marine Tethyan biota during the Early Cretaceous, 2) a step-wise demise

of these faunas during the Albian and their disappearance in the latest Albian, and 3) a long-

term scarcity of Tethyan biota throughout the Late Cretaceous. These changes clearly

indicate that the Pacific became gradually independant from the Tethyan Realm during the

Albian. Similar biotic trends are unknown from other regions of the world’s oceans, they

contradict the general held view of a mid-Cretaceous global warming. This large-scale

biogeographic turnover is, however, consistent with simulated global changes in the ocean

- 41 -



589 Yangon

current system and ocean heat transport, triggered by the opening of South Atlantic and an

increase in atmospheric CO2 during the mid Cretaceous.

Separation from Arctic–North Atlantic and the closure of Bering Straight in the Albian:

Belemnites occurred continuously from the Jurassic–Lower Cretaceous in the North Pacific.

In the Albian, however, a demise of belemnites and their subsequent long-term absence

throughout the Late Cretaceous has been recognized in the North Pacific. This clearly

indicates a faunal isolation of the Pacific from the Boreal Realm, because belemnites show a

bipolar distribution in the Late Cretaceous with their center of diversification lying in the

Boreal. This interpretation is supported by the absence of Boreal-type ammonites in the Late

Cretaceous of the North Pacific. This mid-Cretaceous termination of a faunal interchange

between the Arctic-Boreal and the Pacific was presumably triggered by the closure of the

Bering Straight.

Following the demise of the Tethyan and Boreal biotas, marine molluscs became endemic

to the Pacific in the early Late Cretaceous. The Albian demise event is clearly distinguishable

from the world-wide extinction event. It is therefore defined as “vicariance event”, which was

caused by the separation of the Pacific from the Tethyan and Boreal Seas. This biogeographic

isolation triggered the evolution of new marine faunas, changes of the ecosystem, and finally

gave way to a new biotic realm in the Pacific. These processes, which were caused by the

opening of the Atlantic and the closure of the Bering Straight, can be seen as a good example

for the relationship of evolutionary dynamics of marine biota and the tectonic evolution of the

continents.

- 42 -



589 Yangon

The separated twins: Sumatra and Myanmar in a dynamic world

John Milsom

Department of Earth Sciences, University of Hong Kong, Pok Fu Lam Road, Hong Kong,

China

For much of their long geological histories, Sumatra and Myanmar occupied adjacent

positions at the active southern margin of the Asian continent. The impact of India on the

margin rotated them by different amounts and opened a gap that is now occupied by the

Andaman Sea. Continuity has, however, been preserved between the Sumatra forearc and the

Rakhine Yoma via the Andaman-Nicobar ridge, and elements of subduction-related tectonics

can still be observed in Myanmar despite its present orientation, which is almost parallel to

the India-Asia convergence vector.

Comparatively little has been written about the comparative geologies of the two areas.

Indeed, in the case of Myanmar rather more attention has been paid to analogies with Central

California. Myanmar is also poorly provided with regional geophysical data. Although it is

included in gravity and magnetic global grids, the information upon which the grid values are

based is very slight. Sumatra, on the other hand, has been exceptionally well covered by

gravity surveys and much of the data are in the public domain.

Both areas have long histories of oil exploration, and hydrocarbons continue to be

important factors in their economies, despite low oil prices. There is, however, a major

difference. In Sumatra significant hydrocarbons are produced only to the north and east of the

volcanic line, and in Myanmar only to its west. These differences suggest the possible

existence of under-evaluated exploration plays in both areas.

- 43 -



589 Yangon

The accretionary complexes large-scaly juxtaposed by the out-of-sequence thrust in the

Cretaceous Shimanto Belt of southwest Japan

Yusuke Shimura1*, Tetsuya Tokiwa2, Makoto Takeuchi3, Akari Ota3, Koshi Yamamoto3

1Graduate School of Science and Technology, Shinshu University.

2 Faculty of Science, Shinshu University.

3 Graduate School of Environmental Studies, Nagoya University.

* Corresponding author: [email protected]

1. Introduction

In recent years, the accretionary complexes large-scaly juxtaposed by activity of the out-

of-sequence thrust (OST) is coming to be recognized (e.g., Underwood et al., 1992; Awan &

Kimura, 1996), and its existence is reported in the Shimanto Belt, southwest Japan. The

Cretaceous Shimanto Belt in the Kii Peninsula is divided into the Kouyasan Sub-belt and the

Hidakagawa Sub-belt bounded by OST (Yamato Omine Research Group, 1998). The

depositional ages of these sub-belts have been studied by radiolarian fossils (e.g., Yamato

Omine Reserch Group, 1998; Kishu Shimanto Reserch Group, 2012; Yamamoto & Suzuki,

2012). According to these studies, the depositional ages of several strata in the Hidakagawa

Sub-belt correspond to those in the Kouyasan Sub-belt, and therefore it is possible that the

Cretaceous accretionary complex of the Hidakagawa Sub-belt is juxtaposed by OST as

Kouyasan Sub-belt. However, it is difficult to determine the depositional ages of several

strata in the Kouyasan Sub-belt by radiolarian fossils, because the strata have suffered low-

grade-metamorphism, especially the Mugitani Formation. Thus, in order to clarify the

depositional ages, we carried out the U-Pb dating on detrital zircons obtained from

sandstones of the Mugitani Formation (age-unknown strata) in the Kouyasan Sub-belt and

those of the Yukawa Formation (Albian to Cenomanian indicated by radiolarian fossils) in

the Hidakagawa Sub-belt. The both formations are located in the structurally uppermost part

in the sub-belts, respectively.

2. Methods of zircon U-Pb dating

The zircon U-Pb dating was carried out using LA-ICP-MS (ESI NWR-213+Agilent

7700x) at Nagoya University according to the methods of Kouchi et al. (2015). Based on the

judgement of discordance showed by the many previous studies (e.g., Gehrels et al., 2003;

- 44 -



589 Yangon

Tang et al., 2014; Wang et al., 2016), the zircon U-Pb ages with discordances of ≥ 10% were

rejected in data interpretation in this paper. Age calculations were performed using Isoplot/Ex

4.15 (Ludwing, 2008).

3. Result of zircon U-Pb dating

3.1 Mugitani Formation

Sandstone samples for the dating were obtained from three sites (Site Mg-1, Site Mg-2 and

Site Mg-3 from north to south) in the Mugitani Formation.

Site Mg-1; 200 spots on 195 zircon grains were analyzed and 128 spots (discordances of <

10%) were selected for statistical interpretations. The zircon U-Pb ages consist

mainly of three age groups; 100-140 Ma (5%), 160-300 Ma (47%) and 1400-

2500 Ma (46%). The youngest age is 104.6±5.1 Ma, and the weighted mean age

of the youngest cluster indicates 107.1±3.2 Ma (MSWD=1.1, n=3).




2500 Ma (42%). The youngest age is 108.8±2.6 Ma.






The zircon U-Pb ages of all sites are composed of three groups (100-140 Ma, 160-300 Ma

and 1400-2500 Ma), and indicate that weighted mean ages of the youngest cluster and/or the

youngest ages are 106-108 Ma. These results indicate a depositional age of the Mugitani

Formation after Albian.

3.2 Yukawa Formation

Sandstone samples for the dating were obtained from four sites (Site Yu-1, Site Yu-2, Site

Yu-3 and Site Yu-4 from north to south) in the Yukawa Formation.

- 45 -



589 Yangon

Site Yu-1; 218 spots on 218 zircon grains were analyzed and 152 spots (discordances of <








2500 Ma (31%). The youngest age is 98.8±2.5 Ma.











The zircon U-Pb ages of all sites are composed of three groups (100-140 Ma, 160-300 Ma

and 1400-2500 Ma), and indicate that weighted mean ages of the youngest cluster and/or the

youngest ages are 98-112 Ma. These results indicate a depositional age of the Yukawa

Formation after Albian to Cenomanian.

4. Discussion

In the Yukawa Formation, radiolarian fossils indicate that the depositional age is

Albian to Cenomanian (Kishu Shimanto Research Group, 2012) (93.9 to 113.1 Ma; Ogg et al.,

2016), and the radiolarian age is good agreement with the youngest zircon ages and the

youngest cluster ages of this study. Although radiolarian fossils have not been reported in the

Mugitani Formation, the youngest zircon ages, the youngest cluster ages and the composition

of zircon ages correspond to that of the Yukawa Formation. Thus, it is highly possible that

depositional age of the Mugitani Formation is Albian to Cenomanian.

- 46 -



589 Yangon

These results and previous radiolarian studies indicate that the Kouyasan Sub-belt is

composed of Albian to Campanian strata and the strata become younger as tectono-

stratigraphically downward between this period, and their characteristics correspond to the

Hidakagawa Sub-belt. Furthermore, illite crystallinity and metamorphic minerals show that

the Kouyasan Sub-belt had been accreted at the deep part of the subduction zone (Awan &

Kimura, 1996; Takeuchi, 1996). Therefore, it is possible that the deeper facies of the

accretionary complex of the Hidakagawa Sub-belt is juxtaposed with the Hidakagawa Sub-

belt as the Kouyasan Sub-belt by activity of OST.

Key words: accretionary complex, detrital zircon, OST, Shimanto Belt, U-Pb age

References

Awan, M. A. and Kimura, K., 1996, Thermal structure and uplift of the Cretaceous Shimanti

Belt, Kii Peninsula, Southwest Japan: An illite crystallinity and Mite b0, lattice spacing

study. Island Arc, 5, 69-88.

Gehrels, G. E., Yin, A. and Wang, X.-F., 2003, Detrital-zircon geochronology of the

northeastern Tibetan plateau. Geological Society of America Bulletin, 115, 881-896.

Kishu Shimanto Research Group, 2012, Proposal of the Yukawa Accretionary Complex-

Albian to Cenomanian accretionary prism-. Assoc. Geol. Collab. Japan, Monograph, 59,

25-34.

Kouchi, Y., Orihashi, Y., Obara, H., Fujimoto, T., Haruta, Y. and Yamamoto, K., 2015,

Zircon U-Pb dating by 213 nm Nd: YAG laser ablation inductively coupled plasma mass

spectrometry: Optimization of the analytical condition to use NIST SRM 610 for Pb/U

fractionation correction. Chikyukagaku, 49, 1-17.

Ludwig, K. R., 2008, Isoplot 3.70: Geochronological Toolkit for Microsoft Excel. Berkeley

Geochronology Center Special Publication, 4, 77.

Ogg, J. G., Ogg, G. and Gradstein, F. M., 2016, A Concise Geologic Time Scale: 2016.

Elsevier.

- 47 -



589 Yangon

Takeuchi, M., 1996, Geology of the Sanbagawa, Chichibu and Shimanto Belts in the Kii

Peninsula: Yoshino area in Nara prefecture and Kushidagawa area in Mie prefecture. Bull.

Geol. Suev. Japan, 47, 223-244.

Tang, W., Zhang, Z., Li, J., Li, K., Chen, Y. and Guo, Z., 2014, Late Paleozoic to Jurassic

tectonic evolution of the Bogda area (northwest China): Evidence from detrital zircon U–

Pb geochronology. Tectonophysics, 626, 144-156.

Underwood, M. B., Laughland, M. M., Byrne, T., Hibbard, J. P. and DiTullio, L., 1992,

Thermal evolution of the Tertiary Shimanto Belt, Muroto Peninsula, Shikoku, Japan.

Island Arc, 1, 116-132.

Yamamoto, T. and Suzuki, H, 2012, Hanazono Accretionary Complex in the northern margin

of the Shimanto Belt in the Kii Peninsula, Southwest Japan. Assoc. Geol. Collab. Japan,

Monograph, 59, 1-14.

Yamato Omine Research Group, 1998, Mesozoic and Paleozoic Systems in the central area

of the Kii Mountains, Southwest Japan (Part Ⅵ) -Mesozoic of the Tsujido area in Nara

Prefecture-. Earth Science (Chikyu Kagaku), 52, 275-291.

Wang, W., Liu, X., Zhao, Y., Zheng, G. and Chen, L., 2016, U–Pb zircon ages and Hf

isotopic compositions of metasedimentary rocks from the Grove Subglacial Highlands,

East Antarctica: Constraints on the provenance of protoliths and timing of sedimentation

and metamorphism. Precambrian Research, 275, 135-150.

- 48 -



589 Yangon

Sandstone provenance and detrital zircon U–Pb ages from Permian–Triassic forearc

sediments within the Sukhothai Arc, northern Thailand: Record of volcanic-arc

evolution in response to Paleo-Tethys subduction

Hidetoshi Hara1, Miyuki Kunii2, Ken-ichiro Hisada2, Yoshihito Kamata2, Katsumi

Ueno3, San Assavapatchara4, Anuwat Treerotchananon4,Thasinee Charoentitirat5,

Punya Charusiri5

1Geological Survey of Japan, AIST, 2Graduate School of Life and Environmental Sciences,

University of Tsukuba, 3Department of Earth System Science, Fukuoka University,

4Department of Mineral Resources, Thailand, 5Department of Geology, Faculty of Science,

Chulalongkorn University

Provenance analyses using sandstone petrography and geochemistry, detrital zircon U–Pb

dating were performed on Permian–Triassic forearc sediments from the Sukhothai Arc in

northern Thailand, to clarify evolution of missing arc system associated with the Paleo-

Tethys subduction. We focus on turbidite-dominant formations within Permian–Triassic

forearc sediments, which are composed of the Permian Ngao (Kiu Lom, Pha Huat, and Huai

Thak formations), Early to earliest Late Triassic Lampang (Phra That and Hong Hoi

formations), Late Triassic Song groups (Pha Daeng and Wang Chin formations). Based on

sandstone petrography and geochemistry, sandstones are subdivided into quartzose-type

sandstone for the Ngao Group and the Wang Chin Formation, and lithic-type sandstone for

the Lampang Group and the Pha Daeng Formation. The quartzose-type sandstones are

characterized by abundant contents of felsic volcanic and plutonic rocks, whereas lithic-type

sandstones include dominant basaltic to felsic volcanic rocks. In the present study of detrital

zircon U–Pb dating, the youngest single grain zircon U–Pb ages (YSG) that approximate or

are slightly younger than the depositional age. Youngest cluster U–Pb ages (YC1) is

estimated as a clear and single peak from all formations, presenting peak age of some igneous

activity on provenance. Combining geochemical signature and YC1 U–Pb ages from

sandstone, and direct geological evidences has enable to reconstruct the Sukhothai arc

evolution during the Permian–Triassic. The initial Sukhothai Arc during Late Carboniferous

to Early Permian was developed as a continental island arc with volcanic activity.

Subsequently, the Sukhothai Arc was a period of magmatic quiescence with undeveloped

- 49 -



589 Yangon

volcanic arc, minor magmatism bearing I-type granitoids during the Middle Permian. During

latest Permian to early Late Triassic, the Sukhothai Arc was intensively developed in tandem

with the Early to Middle Triassic I-type granitoids intrusion, the Middle to Late Triassic

volcanics, evolution of accretionary complex, abundant sediment supply from intensive

volcanics to trench through forearc basin. Subsequence to intensive igneous activity, the

Sukhothai Arc was a period of magmatic quiescence toward to the Paleo-Tethys closure after

Late Triassic. In conclusion, provenance information recorded in forearc sediments is very

useful to understanding of volcanic arc evolution.

- 50 -



589 Yangon

Coal –forming Episodes in Vietnam, Cambodia and Lao PDR

Tran Van Tri1,3, Do Canh Duong1,2,3, Dang Quoc Lich3,

Quach Duc Tin1,2,3, Nguyen Van Huynh3

1Vietnam National Committee for IGCP

2General Department of Geology and Minerals of Vietnam

3Vietnam Union of Geological Sciences

Based on geological investigation, exploration and mining activities, coal-forming

episodes in the region have been distinguished: Middle – Late Devonian, Early Carboniferous,

Late Permian, Late Triassic, Early Jurassic, Tertiary and Quaternary. Coals in this region

rank from anthracite, lignite and peat deposits. However, these coal basins occur widely, so

only the Early Carboniferous, Late Triassic and Tertiary coals are economically important.

1. Middle – Late Devonian: coal deposits

Coal – bearing sediments in this episode of the Dong Tho Formation with a thickness of

1050 m are distributed in North Trung Bo, Vietnam. This Formation consists mainly of

terrigeno-calcareous sediments anthracite and coaly shale containing flora fossils:

Protopteridium sp., Lepidodendropsis sp., brachiopods: Emanuellatumida, Chonetes sp.,

Undispiriferrudiferus etc. Coal seams are represented by two layers of 0.6 and 1.0 m thick, 5

km long. The reserve is small, not much economic value and for local use only (Dovjikov.

1965., Tong Duy Thanh, Vu Khuc 2006., Tran Van Tri, Vu Khuc et al 2011).

2. Early Carboniferous coal deposits

The coal-bearing sediments of terrestrial swamp epicontinental facies were formed in the

Salavan, Attapu, NW Vientiane Lao PDR (United Nations, 1900. Vol.7), Sisophon, Kratie,

Peam Pros, Bos Dambang, Kampot, Cambodia (United Nations, 1993. Vol.10; Fontain and

Workman, 1978) La Khe North Trung Bo, Vietnam. In the Salavan deposit, the sediment has

a thickness of up to 600-1500 m including basal conglomerate, sandstone, black-grey

calcareous siltstone containing plant debris, anthracite seams that grades upwards into thin

bedded limestone (Pham Xuan, 1985; Ha Xuan Binh, 2009 communications). They yield

abundant plant – fossil Stigmaria rugulosa, Pecopterisaspera, Calamites cf. sukowi,

Lepidophillumtrigeminum etc. and bivalves: Aviculopecten cf. dupontesi, Astartellalutungini

etc. (Hoffet, 1933); The 6 to 8 anthracite seams and/or lenses ranging in thickness from 0.8 to

7.7 metres with the inferred reserves are put at about 40 million tons (United Nations. 1990,

Vol.7, Lao PDR).

- 51 -



589 Yangon

The Early Carboniferous – Middle Permian sequence has been unconformably deposited

on the Devonian formations.

3. Late Permian coal deposits

Late Permian anthracites are scattered accumulations distributed throughout North

Vietnam, NW Lao, SW Cambodia. These deposits occur in the carbonaceous shale anthracite

seams, limestone, coaly shale containing leaf imprints of Gigantopterisnicotinaefoloia,

Lobatannularia multifolia, Pecopterris anderssom, Taenipteris multinervis etc. and Late

Permian brachiopods Leptodus sp., Oldhamina cf. decipiens, Neophricodothyris cf. asiatica

etc. of the Yen Duyet Formation N. Vietnam (Phan Cu Tien, 1991) which rests conformably

upon the Changhsingian volcano-sedimentary beds with isotopic ages of 250-260 Ma (Tran

Van Tri and Vu Khuc, 2011).

Futher to the south-west in the NW Lao, NE Cambodia of middle Mekong River Basin,

Late Permian coal occurs in the form of thin lesis, 0.4-7m thick, which have no economic

value (United Nations, 1900. Vol.7; 1993, Vol.10; Fontain, Workman, 1978).

4. Late Triassic (Novian – Rhaetion) coal deposits

Coal – bearing sediments were largely distributed in Vietnam, Lao PDR and Cambodia

and occur in two different facies both in lithology and organic matter [Fontain, Workman,

1978; United Nations, 1900. Vol.7; 1993, Vol.10; Tran Duc Luong, Nguyen Xuan Bao

(Eds).1988.]. The continental facies were formed in the intracontinental narrow graben – type

and/or rift basins and paralic facies were distributed largely basins: these sediments contain

abundant plant-fossils of Clathropteris meniscioides, Cycadites saladini, Taeniopteris jourdyi,

Podozamites lanceolatus, Glossopteris indica, Pterophyllum tietzei, Pedopteris tonquinensis,

Otozamites Obtusus etc. were known long ago under the name “Hon Gai Flora” [Zeiller 1903,

Vu Khuc et al., 2000; Nguyen Chi Huong, 1983, Nghiem Nhat Mai, 1986] and yield such

marine bivalves as Bakewellia cf. magnissima, Gervillia cf. inflata, halobia distincta,

Burmesialirata etc Discotropitesnoricus, Juavites magnus (anmmonite) etc.

The Late Triassic sediment rests unconformably upon the Early-Middle Triassic and

Paleozoic formations and it underlies also uncomformably the Jurassic sediments [Dovjikov

A.E. (Ed.) 1965.]

In some coalfields, the seams numbers are as many as 61, such as the Mao Khe, Hon Gai

graben of Quang Ninh, basin, NE Vietnam and the thickness of some single seams reaches

92m. The total forecast of coal resources of Quang Ninh basin to the depth of -1,500m are

- 52 -



589 Yangon

15,000 million tons of high quality and are mostly ranked as anthracite (United Nations,

1990. Vol. 6, Vietnam, Tran Van Tri (Ed).2005; Tran Van Tri, Vu Khuc, etc. 2011).

5. Early Jurrasic coal deposits

The coal-bearing sequence of this episode belongs to the continental faces which is

scattered accumulation in some places of North Vietnam, Lao PDR, and Cambodia. The

middle part of the sequence contains the flora fossils Coniopteris sp., Podozamites sp; and

Phyllopodsamussia sp., Bairdestheria sp., etc. (Vu Khuc et al; 2000). The coal fields occur

the in form of small and thin lenses and they have no economic value.

6. Tertiary coal deposits

The coal-bearing sediments of this episode are mainly distributed along the NW-SE

narrow grabens throughout Vietnam, Cambodia, Lao PDR and extensional-intracontinential

rifting basins are largely deposited in the East Vietnam sea, gulf of Thailand with the

thickness of 5-14 km, providing important targets for energy resoucres development.

Specially in which, the Red River delta of Hanoi depression is mainly of fluvio-lacustrine,

neritic-litoral facies with a thickness from 3,000 to 7,000 m, containing about 100 seams or

lenses of lignite-subbituminous with the forecasted resources under – 1,700 m with more than

100 billions tons (United Nation 1990, Vol. 6, Vietnam; Tran Van Tri, Vu Khuc et al., 2011).

These deposits yield the fresh water bivalves, mollusk, flora, spores and poleens and

forams of Oligocene-Neogene in ages.

7. Quarternary peat deposits

The peat deposits are scatterly distributed in the swamps, estuaries and mangrove areas

along the coastal line, inter-moutain plains, especially in the Mekong delta and Red River

delta basins. The largest peat deposit is located in the U Minh forest mangrove area, South

Vietnam with a thickness of up to 10 m was formed in a moderate decomposition of the

wooden trunks (United Nation 1990, Vol. 6, Vietnam; Tran Van Tri, Vu Khuc et al., 2011).

The numerous indications of peat deposits are known, but no immediately exploitable

fields have been discovered.

- 53 -



589 Yangon

References

Dovjikov A.E. (Ed.) 1965 Geologia Severnogo Vietnama. Gen.Dept.of.Geology. Hanoi,

668pp (in Russian);

Fontain H., Workman D.R., 1978. Review of the geology and mineral resources of

Kampuchea, Laos and Vietnam. in Proc.3rd GEOSEA, 541-603 pp. Bangkok;

Nghiem Nhat Mai, 1986. The Hongai flora and its stratigraphic significance – Pros. of 1st

Conference on Geology of Indochina 1; 127-136 pp. Ho Chi Minh city: General

Department of Geology Vietnam;

Nguyen Chi Huong, Dang Tran Huyen, 1990 Paleontological and stratigraphic materials of

Quang Ninh coal basin. Geology and Mineral resources 3, 167-180 Hanoi: Research

Institute of Geology and Mineral;

Pham Cu Tieu (Ed.) 1991 Geological Map of Kampuchea, Laos and Vietnam. Scale

1:1,000,000. Geological Survey of Vietnam, Hanoi;

Thongphath Inthavong, 2001. Mining and mineral resources development in the Lao PDR. In

Mineral Resources assessment development and Management series. Vol.6. United

Nations New York. 341-352 pp;

Tong Duy Thanh, Vu Khuc (Eds.) 2006. Stratigraphic units of Vietnam National University.

Publ. Hanoi.526 pp;

Tran Duc Luong, Nguyen Xuan Bao (Eds).1988. Geological Map of Vietnam. Scale

1:500.000, General Department of Mine and Geology;

Tran Van Tri (Ed.) 2005., Mineral Resources Map of Vietnam. Scale 1:1,000,000. Dept. of

Geology and Minerals of Vietnam, Hanoi;

Tran Van Tri and Vu Khuc (Eds.), 2011. Geology and Earth Resources of Vietnam.Publ.

House for Science and Technology, Hanoi, 646 pp;

United Nations 1993. Atlas of Mineral resources of the ESCAP region Vol.10. Cambodia.

87pp;

United Nations, 1990. Atlas of Mineral resources of the ESCAP region Vol.7. Lao PDR.

19pp;

United Nations, 1990. Atlas of Mineral resources of the ESCAP region Vol.6, Vietnam, 124

pp;

Vu Khuc (Ed.), 2000. Lexicon of geological units of Vietnam. Dept. of Geology and

Minerals of Vietnam, Hanoi. 430 pp.

- 54 -



589 Yangon

New age constraints on the evolution of the Naga Hills: radiolarians and radiometric

Jonathan C Aitchison1, Geoffrey L Clarke2, Trevor R Ireland3, Kapesa Lokho4, Ali Ao5,

Santanu K Bhowmik5, Tara Roeder2, Denis Stojanovic1, Sarah Kachovich1

1University of Queensland, St Lucia, Australia

2University of Sydney, School of Geosciences, Sydney, Australia

3Australian NationalUniversity, Research School of Earth Sciences, Canberra, Australia

4 Wadia Institute of HimalayanGeology, Dehradun, India

5 Indian Institute of Technology, Kharagpur, Department of Geology & Geophysics,

Kharagpur, India,

Abstract

Recent Australia-India Strategic Research Fund (AISRF07021) supported expeditions

have supported examination of previously little studied regions along the border between

Nagaland and Manipur in India and Myanmar. The Myanmar microplate clearly did not

originate where it presently lies and has been translated over 480 km northwards along the

Sagaing Fault. The Indo-Myanmar ranges include the Naga Hills, which are dominated by

Cenozoic sediments. They structurally overlie an Indian passive-margin sequence. Near the

Indo-Myanmar border this giant imbricate thrust stack also contains sheets of ophiolitic

mélange. The ophiolite is heavily disrupted and overlain by Eocene shallow marine shelf

sediments of the Phokphur Formation. Further east high-grade metamorphic units are also

thrust westwards over the ophiolite. Well-preserved Jurassic, Cretaceous and

Paleocene/Eocene radiolarians together with U/Pb SHRIMP data from ophiolitic and

metamorphic units provide important new age constraints.While superficially it appears that

rocks in this area can be correlated with units known from the Himalaya in fact this is

problematic. As oceans to the north and west of Australia have opened, grown and been

recycled through subduction various continental fragments that originated as part of

Gondwana have departed and, with time, transferred to Asia. The study area lies east of the

Namche Barwa syntaxis and reconstructions indicate it has not directly participated in

continent-continent collision. Indeed, stratigraphic and structural architecture differ from

classic Himalayan transects. New detrital zircon U/Pb studies suggest derivation of some

units from Sibumasu rather than the Lhasa or Qiangtang terranes.

- 55 -



589 Yangon

Meso-Tethys and Neo-Tethys tectonic evolution in Myanmar and adjacent areas

Zhu Wen, Nianqiao Fang, Renchen Xin

School of Marine Science, China University of Geosciences (Beijing), P.R.China

[email protected]

Abstract

The Tethyan evolution is essential to thegeological history of Southeast Asia. And

Myanmar and its adjacent areas are the southern continuation of the Meso-Tethys and Neo-

Tethyssutures in the Tibetan Plateau.On the basis of the data available, regional comparative

analysis of magmatic-sedimentary formation characteristics, and the extension trends of

tectonic belts and their interrelations, the authors divided the study area into 5 third grade

structural units, i.e., eastern edge of Indian continent, Indio-Burma Rangesuture, West

Burmablock, Taguang-Myitkyina suture,and Sibumasublock. The relationship between the

two sutures and the sutures in the Tibetan Plateau is controversial. Thus, study on the tectonic

evolution in Myanmar and its adjacent areas according to the problem is essential toour

understanding of opening and closure of theTethys Ocean that played a key role in

globalplate tectonics during the Mesozoic. The results show that (1) The ophiolite in

theTaguang-Myitkyina suturewas formed during the Middle Jurassic, which is coeval with

Meso-Tethyan ophiolites along the Bangong-Nujiang suture. Thus, the Taguang-Myitkyina

sutureis the southern continuation of theMeso-TethyanBangong-Nujiang suture in the Tibetan

Plateau. During the Middle Triassic-Early Jurassic, the Taguang-Myitkyina Meso-Tethys was

subducted eastward under the Sibumasu block, and the collision between the West

Burmablock and Sibumasu block resulted in the formation of the Taguang-Myitkyina suture

during the Middle Jurassic-Middle Cretaceous; (2) The ophiolite in the Indio-Burma Range

suturewas formed during the Early Cretaceous, which is coeval with Neo-Tethyan ophiolites

along the Yarlung-Tsangpo suture. Thus, the Indio-Burma Range sutureis the southern

continuation of theNeo-Tethyan Yarlung-Tsangpo suture in the Tibetan Plateau. Late

Jurassic-Early Cretaceous, the Indio-Burma RangeNeo-Tethys was subducted eastward under

the West Burmablock, and theclosure of the Indio-Burma Range Ocean occurred during the

Late Cretaceous-Tertiary, which resulted in the formation of the Indio-Burma Range suture.

The formation, development and closure of these ocean basins constituted the basic

framework of the Meso-Cenozoic tectonic evolution in the study areas.

Keywords: Myanmar; Meso-Tethys; Neo-Tethys; tectonic evolution

- 56 -



589 Yangon

Paleomagnetic Constraints for the Tectonic History of the South China Sea: Post-

Expedition Study of IODP Expedition 349

Xixi Zhao1, Qingsong Liu2, Zongqi Duan2, Congcong Gai2, Weiwei Chen1, Wei Yuan1

1 State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, China

2Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China

Corresponding author: Xixi Zhao ([email protected])

Abstract

International Ocean Discovery Program (IODP) Expedition 349 investigated the tectonic

and oceanographic evolution of the South China Sea (SCS). The SCS is a marginal sea of the

western Pacific and has undergone a near complete Wilson cycle from continental breakup to

seafloor spreading to subduction along the Manila Trench. Two of the primary objectives of

Expedition 349 are to determine the initiation and termination age of seafloor spreading

through direct sampling of oceanic crust and to elucidate the cause of differences in seafloor

magnetic anomalies between the East and Southwest Subbasins. Expedition 349 drilled five

sites in the deep basin of the SCS. Sites U1431, U1433, and U1434 recovered oceanic

basement and overlying sediments near fossil spreading centers, and Sites U1432 and U1435

recovered materials near or at the northern continent/ocean boundary. Paleomagnetic results

show that sediments and basement rocks from the sites drilled by Expedition 349 contain

both reversely and normally magnetized samples. Our post-expedition paleomagnetic study

revealed that stable characteristic remanent magnetization (ChRM) components are observed

throughout the studied cores. Anisotropy of magnetic susceptibility (AMS) results for Sites

U1431 and U1433 indicate that most of thestudied sediments display a normal sedimentary

fabric, suggesting the ChRM and magnetic susceptibility records can be used to construct

magnetostratigraphy for dating sediments. The similarity in crustal age between sites suggests

a similar age for the cessation of spreading in both the East and Southwest Subbasins. This

observation is at odd with some of the tectonic models for the opening of the SCS in which

the Southwest Subbasin was older than the East Subbasin. At Site U1435, core description,

biostratigraphy and magnetostratigraphy revealed a sharp discontinuity at about 33 Ma, with

shallow-water sandstones and mudstones of unknown age below the disconformity and deep-

water marine deposits above. We infer that this represents the transition from breakup to the

beginning of oceanic spreading. The oceanic seafloor spreading in the SCS, from 33 to ~16-

- 57 -



589 Yangon

18 Ma, is thus coeval with a large part of the left-lateral motion along the Ailao Shan-Red

River Fault Zone (dated 34 to 17 Ma). Studies of the growth of the Tibetan plateau and

opening of Asian marginal seas are beginning to reveal the geodynamic linkage between

them and our new magnetostratigraphic work helps to refine the ages of sedimentation events

and tectonic activities within and beyond the South China Sea basin.

- 58 -



589 Yangon

Volcanogenic-sedimentary deposits of the Alpine orogenic system (European Tethys)

from SE Asian perspective (Asian Tethys)

Michał Krobicki1,2, Anna Feldman-Olszewska3, Jolanta Iwańczuk3, Oleh Hnylko4,

Andrea Di Capua5, Jan Malec6

1Polish Geological Institute – National Research Institute, Carpathian Branch, Skrzatów 1,

31-560 Kraków, Poland

2AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland

3Polish Geological Institute – National Research Institute, Rakowiecka 4, 00-975 Warszawa,

Poland

4National Academy of Science of Ukraine, Naukova 3a, 79060 Lviv, Ukraine

5CNR-Istituto per la Dinamica dei Processi Ambientali, 34, Via Mangiagalli, 20133, Milano,

Italy

6Polish Geological Institute – National Research Institute, Holy Cross Mts Branch, Zgoda 21,

25-953 Kielce, Poland

Abstract

The geological record of the Alpine belt preserves the whole Permian-Mesozoic history of

the western part of the Tethys Ocean and constitutes the base for palaeogeographic-

geodynamic reconstruction of this ocean. Pre-orogenic period of the Jurassic-Cretaceous

deposits in the Carpathian part of the Alpine arc (Ukrainian-Romanian transborder zone) and

Permian-Mesozoic deposits in the Dolomite Mts document perfectly a long oceanic history of

the northern and central part of the Western Tethys. In the Carpathians the earliest Cretaceous

volcanogenic-sedimentary units occur, including basaltic pillow lavas together with syn- and

post-volcanic submarine flows. On the other hand, the Triassic units in Dolomite Mts which

are tripartite (from Werfen-type clastic-carbonate Early Triassic units, through Mid-Triassic

carbonate platforms with volcano-sedimentary deposits up to Late Triassic with carbonate

platforms) have the most characteristic Middle Triassic volcanogenic sequences.

The Ukrainian/Romanian Carpathians form a connecting link between the West and East

Carpathians. Accumulation of the ancient accretionary prism, which turned into the Flysch

Carpathian nappes – was caused by the subduction of the Carpathian Flysch Basin basement

beneath both the ALCAPA (ALpine-CArpathian-PAnnonian area) and Tisza-Dacia terranes.

Volcano-sedimentary complex oftheso-called Kamyanyi Potik Unit (ChyvchynianMountains

- 59 -



589 Yangon

in Ukrainian side)(= Black Flysch in Maramures Mts in Romanian side), which were

developed in the frontal part of the Crystalline Marmarosh Massif of the Central East

Carpathians, is represented by: basaltic pillow lavas, volcano-sedimentary debris-flows

breccias (witholistoliths ofthecorallimestonesand basalts) within

volcanic/tuffiticmatrixandcoarse/fine-grained calcareouspyroclastic turbidites (flysch) along

almost 100 km long belt in the eastern Carpathians. These associationswere formed in the

Early Cretaceous (Berriasian – documented by calpionellids) times generating several

different parts of the Carpathian basins. The present stage of investigations provide

arguments that the volcanogenic formation of the Chyvchynian Mts (Ukraine)/Maramures

Mts (Romania) was formed on the presumable oceanic crust and can be attributed to one of

thesuture zone in Carpathians.

On the other hand, the Late Anisian–Ladinian Magmatic Cycle in the Dolomite Mts (Italy),

which produced large amounts of volcano-sedimentary sequences, is a very well documented

geodynamic event in the Mid-Triassic history of the Western Tethys/Alps. This event is

represented by syn-volcanic subaqueous deposits: pillow lavas, pyroclastic density current

deposits, lahar deposits, volcaniclastic mass flow deposits, which indicate syn-rift

geodynamic regimes during this times in wider palaeogeographical reconstruction of the

Western Tethys Ocean.

Our comparative studies between Carpathians and Dolomites indicate very similar, almost

identical, volcanogenic-sedimentary sequences. Such comparative studies, the most probably

of syn-rift in origin sequences, analyzed in different, independent both in space and time

selected parts of the Western Tethys, could help to understand similar

geodynamic/geotectonic regimes in separated parts of the Tethys Ocean.

From the Asian, and especially SE Asian perspective such sequences could be similar to

the Late Triassic flysch deposits with basaltic pillow lavas in NE Myanmar area. The

Triassic-Jurassic sequence in neighboring region (e.g., the Mae Sot area in northern Thailand),

belongs to the Shan-Thai terrane. This block is subdivided into several zones from the west to

east, including Mae Sariang zone, where the Mae Sot area is located. This zone contains

rocks of Triassic cherts (=radiolarites), carbonates and flysch (turbiditic) facies, which

indicate both pelagic condition and synorogenic deposits. From palaeogeographical point of

view the Shan-Thai block was a remnant of Palaeotethys Ocean, which occupied wide realm

between Cimmerian Continent and Eurasian plate during Late Paleozoic-Early Mesozoic

times. The Late Triassic Indosinian orogenic event has been connected with docking and

- 60 -



589 Yangon

amalgamation of Indoburma, Shan-Thai (Sibumasu) and Indochina terranes, which constitute

recently the main part of SE Asia. This Late Triassic volcanogenic-sedimentary event in

Myanmar correlate presumable with such syn-orogenic processes.

Finally, we can compare these Mesozoic Alpine/Indosinian volcanogenic units, both from

sedimentological and geodynamical point of view, with some Caledonian examples from

Europe (e.g., southern Poland – Sudety Mts and Holy Cross Mts). In the Sudety Mts whole

Early and Middle Cambrian history of the so-called Stronie basin indicate wide range of

similarities between these orogenic systems, although all rocks of this formation were

strongly metamorphosed [they are represented now by: amphibolites with marbles (as

olistoliths?), mica schists/metapelites, mafic metavolcanogenic rocks, metabasaltic pillow

lavas etc]. On the other hand, the Late Silurian (Ludlovian) pyroclastic and greywacke

flysch-type deposits in the Holy Cross Mts indicate strong volcanic activity in this part of the

Iapetus Ocean as well, during syn-orogenic episode of this ocean history.

In conclusion, we would like to suggest, that such type of volcanogenic and sedimentary

consortium usually occur together in several oceans independently in space and time, both in

such old as Palaeozoic and younger as Mesozoic ones, but geotectonic/geodynamic regimes

have probably been very similar.

- 61 -



589 Yangon

Southwestern Asian/Pacific faunal province in the mid-Cretaceous: a possible clue to

revealing the evolutionary history of rudists and other carbonate platform biota

Shin-ichi Sano1, Xin Rao2, Peter W. Skelton3, Yasuhiro Iba4

1Fukui Prefectural Dinosaur Museum, Katsuyama, Fukui 911-8601, Japan;

2State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and

Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China;

3School of Environment, Earth and Ecosystem Sciences, The Open University, Milton

Keynes MK7 6AA, UK;

4Department of Natural History Sciences, Hokkaido University, N10 W8, Sapporo, Hokkaido

060-0810, Japan

Abstract

Rudists are an extinct group of bivalves that flourished in the Tethyan Realm from the

mid-Oxfordian to the end of the Cretaceous. Since they are usually considered as a main

constituent of the Cretaceous carbonate platform biota, spatio-temporal change in the

distribution of rudists provides the important information for the reconstruction of the

palaeobiogeographical and paleoclimatic history of the Cretaceous oceans.

Recent studies of mid-Cretaceous rudist faunas in the western Pacific and Tibet of China

reveal the distinct similarity between those of southwestern Asia and western Pacific (Skelton

et al., 2013; Rao et al., 2015). An primitive radiolitid Auroradiolites, characterized by the

presence of outer shell layer composed of compact shell structure only, has been known from

the northern margin of the Tethys in southwestern Asia, such as Iran, central Afghanistan,

northern Pakistan, northern India, Tibet of China, and also Japan in the western Pacific (e.g.,

Masse and Gallo Maresca, 1997; Sano and Masse, 2013; Rao et al., 2015).

A new polycontid Magallanesia, having simple canals in the posterior and ventral parts of

the left valve, were established based on the material from the Cebu Island, the Philippines

(Sano et al., 2014), and its advanced form were later describedfrom the Lhasa Terrane, Tibet

(Rao et al., 2015). Magallanesia is probably derived from the non-canaliculate polyconitid

genus Praecaprotina, which has been known only from Japan and the Daiichi-Kashima

Guyot in northwestern Pacific. The Late Cretaceous canaliculate rudist family, the

- 62 -



589 Yangon

Plagioptychidae is probably derived from Magallanesia or related form. Thus the early

evolution of the plagioptychid rudists can be supposed to occur in the Pacific.Furthermore,

four advanced polyconitid genera are recognized in Japan, the Cebu Island and the Japanese

Seamounts in northwestern Pacific (Skelton et al., 2013). Among them, three genera are

endemic to the Pacific, suggesting the strong endemism in this region in the Aptian–Albian.

It should be noted that the possible endemic taxa of orbitolinid larger foraminifers have

been described from the Aptian–Albian limestones in Myanmar and Tibet (Sahni, 1937;

Cherchi and Schoreder, 1980), in addition to many cosmopolitan species (Rao et al., 2015).

Mesorbitolina birmanica, which is characterized by its plano-convex protoconch, has been

recognized in Myanmar, Tibet, northern India, Iran, and possibly Tunisia (Schlagintweit and

Wilmsen, 2014). Palorbitolinoides is considered as the direct descendant of cosmopolitan

Palorbitolonalenticularis of the Late Barremian–Early Aptian age. Although the earlier

(latest Early Aptian) species of this genus: P. orbiculata has been recorded from the southern

margin of the Tethys (Apulian and Adriatic platform, and southwestern Iran) and Tibet

(Cherchi and Schroeder, 2013), its type species P. hedini of the Albian age has been known

only from Tibet and northern India (Cherchi and Schoreder, 1980; Juyal, 2006). Thus

Palorbitolina lineage possibly survived mid-Aptian crisis in southwestern Asia.

Recent studies clearly show the importance of the mid-Cretaceous rudist records in the

Pacific and southwestern Asia for the discussion of the rudist palaeobiogeography and the

early evolution of the Late Cretaceous rudist family. The presence of the distinct

palaeobiogeographical province: Southwestern Asian/Pacific faunal province was suggested.

The interesting orbitolinid records are possibly recognized there. Further studies of the fossil

records in the Southwestern Asian/Pacific faunal province probably provide the clues to

revealing the evolutionary history of the carbonate platform biota in the mid-Cretaceous.

References

Cherchi, A., and R. Schroeder. 1980. Palorbitolinoides hedini n. gen. n. sp., grand

foraminifère du Crétacé inférieur du Tibet méridional. Comptes rendus de l’Académie des

Sciences Paris, ser. D, 291, 385–388.

Cherchi, A., and R. Schroeder. 2013. The Praeorbitolina/Palorbitolinoides Association: an

Aptian biostratigraphic key-interval at the southern margin of the Neo-Tethys. Cretaceous

Research, 39, 70–77.

- 63 -



589 Yangon

Juyal, K. P. 2006. Foraminiferal biostratigraphy of the Early Cretaceous Hundiri Formation,

lower Shyok area, eastern Karakoram, India. Current Science, 91, 1096–1101.

Masse, J.P., and M. Gallo Maresca. 1997. Late Aptian Radiolitidae (rudist bivalves) from the

Mediterranean and Southwest Asiatic regions: taxonomic, biostratigraphic and

palaeobiogeographic aspects. Palaeogeography, Palaeoclimatology, Palaeoecology, 128,

101–110.

Rao, X., P. W. Skelton, J. Sha, H. Cai and Y. Iba. 2015. Mid-Cretaceous rudists (Bivalvia:

Hippuritida) from the Langshan Formation, Lhasa block, Tibet. Papers in Palaeontology,

1, 401–424.

Sahni, M. R.1937. Discovery of Orbitolina-bearing rocks in Burma, with a description of

Orbitolina birmanica sp. nov. Records of the Geological Survey of India, 71, 360–375,

pls. 29–30.

Sano, S., and J.-P.Masse. 2013. First record of a primitive radiolitid rudist from Japan.

Paleontological Research, 17, 317–324.

Sano, S., Y. Iba, P. W. Skelton, J.-P.Masse, Y. M. Aguilar and T. Kase. 2014. The evolution

of canaliculated rudists in the light of a new canaliculate polyconitid rudist from the

Albian of the Central Pacific. Palaeontology, 57, 951–962.

Schlagintweit, F., and M. Wilmsen. 2014. Orbitolinid biostratigraphy of the top Taft

Formation (Lower Cretaceous of the Yazd Block, Central Iran). Cretaceous Research, 49,

125–133.

Skelton, P. W., S. Sano and J.-P.Masse. 2013. Rudist bivalves and the Pacific in the Late

Jurassic and Early Cretaceous. Journal of the Geological Society, 170, 513–526.

- 64 -



589 Yangon

Lithostratigraphy of Middle Triassic siliceous rocks distributed in the Mae Sariang area,

Northwestern Thailand.

Yoshihito Kamata1, Rikiya Yamamoto1, Katsumi Ueno2, Hidetoshi Hara3, Ken-ichiro

Hisada1, Thasinee Charoentitirat4, Punya Charusiri4, Apsorn Sardsud5

1Institute of Geosciences, University of Tsukuba, Ibaraki 305-8572, Japan

2Department of Earth System Science, Fukuoka University, Fukuoka 8140-0180, Japan

3Geological Survey of Japan, AIST, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan

4Department of Geology, Chulalongkorn University, Bangkok 10330, Thailand

5Bureau of Geological Survey, DMR, Bangkok 10400, Thailand

Abstract:

The Sibumasu Block has been recognized as one of principal continental basements of

mainland SE Asia and occupies the peninsular and western parts in Thailand. Tectonic setting

of the western margin of the Sibumasu Block has been basically understood as a passive

continental margin. However, detailed stratigraphy of the Paleozoic and Mesozoic has not

been well-documented, particularly in the northwestern part of mainland Thailand, due to a

poverty of index fossil for age determination. Recently, radiolaria-bearing Permian and

Triassic fine-grained siliceous sediments such as chert and siliceous shale have been reported

in the northwestern mainland Thailand. These sediments should be an important key to

construct a regional lithostratigraphy for the reconstruction of a concrete and detailed tectonic

setting of these areas just before the closure of the Paleo-Tethys and the consequentcollision

of continental blocks. In this presentation, we report the lithostratigraphy of radiolaria-

bearing Triassic succession and accompanied calcareous and clastic strata based mainly on

data obtained from field investigation. We discovered thin-bedded black radiolarian cherts

(less than 10 mthick) at several localities in the Mae Sariang area. They are underlain by

Permian anmmonoid-bearing siltstones and overlain by dark-gray bedded micritic limenstone

layers with pale-green calcareous mudstone. These lithstratigraphic characters of the Triassic

cherts are in contrast to coevalonesdistributed in the Inthanon Zone of Northern Thailand,

where Paleo-Tethyan pelagic successions of late Paleozoic radiolarian cherts and sea-mount

type carbonates are observed.

- 65 -



589 Yangon

Ultramafic rocks of Nan Suture Zone in northern Thailand and its northward extension

in Laos

Ken-ichiro Hisada1, Shoji Arai2, Katsumi Ueno3, Yoshihito Kamata1, Hidetoshi Hara4,

Thasinee Charoentitirat5, Punya Charusiri5, Hongthong Chanthavongsa6

1Institute of Geosciences, University of Tsukuba, Ibaraki 305-8572, Japan

2Department of Earth Sciences, Kanazawa University, Kanazawa 920-1192, Japan

3Department of Earth System Science, Fukuoka University, Fukuoka 8140-0180, Japan

4Geological Survey of Japan, AIST, 1-1-1 Higashi,Tsukuba, Ibaraki 305-8567, Japan

5Department of Geology, Chulalongkorn University, Bangkok 10330, Thailand

6Department of Geology and Minerals, Vientiane, Lao P.D.R.

Abstract:

The Nan Suture Zone was regarded as marking the site of collision of the Shan Thai

(Sibumasu) and Indochina continents. More recently it has become generally accepted that

the oceanic materials within the suture zone represent the floor of a marginal basin rather

than an open ocean, this is, named Nan Back-arc Basin (Ueno & Charoentitirat, 2011).

Although the Nan Suture Zone is one of major sutures in Southeast Asia, its northern

extension in Laos has been long unsettled. Recently, the northern extension of aultramafic

belt was confirmed near Pakbeng, northern Laos. The chemistry of chromian spinels from the

Pakbeng serpentinite is characterized by high Cr# (0.6-0.8) and very low TiO2 wt%(<0.5, but

almost <0.1). Also the schistose rocks are accompanied with serpentinite bodies. These

occurrences are much similar to those of the Nan ultramafic rocks. The Na Noi, Mae Charim,

and Sirikit Dam serpentinite bodies of the Nan Suture Zone are represented by dunite-

harzburgite, though they has been subject to metamorphism more or less and changed to

metaperidotite. In addition, partially hydrated gabbro (or granulite) is associated with these

rocks. Therefore, it is concluded that the Pakbeng serepentinite corresponds to the northern

extension of the Nan Suture Zone. Also these suggest strongly that ultramafic rocks were

derived from a supra-subduction zone. Thus, the Nan Back-arc Basin might be finally

terminated with closure due to succeeding subduction within a back-arc.

- 66 -



589 Yangon

Late Palaeozoic to Cretaceous evolution and lithofacies paleogeography of the Central

Asian Tethyan Realm

Lingyu Liu, Renchen Xin

School of Marine Science, China University of Geosciences (Beijing), P.R.China

[email protected]

Abstract

The formation and evolution of Central Asia closely relate to the history of two oceanic

domains, Paleo-Tethys and Neo-Tethys. The region we survey mainly in Turan platform and

south Kazakhstan (TSK), where is constituted by Cratons, micro-continents, oceanic crusts

and island arc fragments. These blocks began to converge since Early Carboniferous and

completely joined together in Early Permian. The formation of Turan platform is a sign of the

subductive elimination of Palaeo-Tethys. Affected by the successively subduction toward the

north between Paleo-Tethys and Neo-Tethys, from the Since Late Permian to the Eocene, the

subsidence associated with extension have dominated the TSK. And during the Mesozoic,

two compressional events of regional occurred significantly in continental blocks at the

southern margin of Eurasia. The first one, happened at the end of the Triassic, which has led

to strong selective inversion of basins over the Turan. The second one, took place at the Late

Jurassic-Early Cretaceous. Based on the tectonics and basin evolution of Central Asia and its

adjacent region, combined with the previous studies, we used the ArcGIS geographic

information software to analysis the lithofacies paleogeography of TSK. (1) From the Latest

Early Permian (Kungurian) to the Triassic (Norian). Strong subsidence occurred on the Turan

domain, sedimentation was mainly continental and terrigenous during the Late Permian,

becoming marine and terrigenous in the main depocenters during the Triassic. Sediments of

the Mangyshlak were deposited in an environment of alluvial volcaniclastic fans. (2) In the

Late Triassic, compressional deformation caused regional uplift and erosion. (3)In the

Jurassic (Hettangian to Kimmeridgian), sediments are mainly continental terrigenous and

fluvio-deltaic. (4)In the Late Jurassic to Early Cretaceous. Collision of the Helmend block in

Afghanistan with the southern margin of Eurasia resulted in a significant regional regression.

Most of the basins appeare carbonate deposits at the end of the Jurassic, with widespread salt

deposits on the southeastern part of the Turan. (5) The Late Cretaceous was a period of

widespread transgression over the TSK. Shallow-marine limestones and clays covered most

of the Turan. On the south Kazakhstan, continental terrigenous sediments accumulated on

high areas formed during Cimmerian events.

Keywords: Turan platform; south Kazakhstan; evolution; lithofacies paleogeography

The 5th International Symposium of the - CAGSigcp589.cags.ac.cn/5th Symposium/Abstract...

Documents

Transcript of The 5th International Symposium of the - CAGSigcp589.cags.ac.cn/5th Symposium/Abstract...