Dr Rian Dutch – Geological Survey of South Australia

A collaborative effort between:

LIFTING THE LID ON THE COOMPANA

PROVINCE

GEOLOGICAL SURVEY OF SOUTH AUSTRALIA

Geoscience for the Benefit of South Australians

• Part of the Mineral Resources Division of the South Australian

Department of the Premier and Cabinet.

• Our role is to undertake pre-competitive data acquisition and value-

add research to provide scientific information on the State's geology

and resource potential.

• Key role in investment attraction by reducing exploration risk and

creating a knowledge rich environment to increase the chance of

discovery.

The Coompana Province is a rare opportunity• Covers an area of approximately

200 000 km2, straddling the border

between South Australia and

Western Australia

• No known exposed basement rocks

of the Coompana Province, with the

region being extensively covered by

basin sediments

• No serious mineral exploration for

more than 30 years

• Existing datasets are dated and

coarse scale

COOMPANA PROVINCE: AN UNEXPLORED FRONTIER

Musgrave Province

Yilgarn Craton

Gawler Craton

Coompana Province

A WORKFLOW TO DISCOVERY

QUESTION – what are the key datasets and knowledge that will

provide a framework for discovery in this region

• Depth of cover

• Structural framework and fluid pathways

• Mapping basement under cover (distribution and rock properties)

• Tectonic and crustal evolution (geodynamic setting)

A WORKFLOW TO DISCOVERY

McCuaig & Hronsky, 2014.

Taking a mineral systems approach• Identify magmatic systems. These provide the

driving force for much of the worlds mineral

systems

• Identify crustal fertility and map out

architecture and pathways

• Identify the regional geodynamic setting of

events to assist explorers in applying the correct

exploration models and strategies

A WORKFLOW TO DISCOVERY

The second step – New pre-competitive data acquisition

To date ~$7.5M committed or expended PACE pre-competitive data collection

• $1.7M 13GA-EG1 seismic line

• $50K Pilot regional biogeochemistry

• $1.3M Coompana magnetics and radiometrics

• $500K AusLAMP ($240K from Geoscience Australia)

• $20K + collaborative funding Coompana cover geophysics

• $1.0M Coompana regional gravity

• $3M Coompana regional drilling

• $500K Regional soil geochemical survey

NEW DATA AQUISITIONEucla Gawler seismic and MT

NEW DATA AQUISITIONCoompana Regional Magnetic Survey

NEW DATA AQUISITIONAusLAMP Magnetotellurics

10 km 35 km

NEW DATA AQUISITIONCover geophysics

• Passive Seismic

• Reflection Seismic

• AMT

• Micro-gravity

70 65 60 55 50 45 40 35 30 25 20 15 10 5 -0

De

pth

(m)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230

Distance (m)

S-wave velocity cross-section : Line ID=CP04

(m/s)

S-wave velocity

10001100120013001400150016001700180019002000

Scale = 1/1000

NEW DATA AQUISITIONRegional Gravity - Previous

NEW DATA AQUISITIONRegional Gravity - New

NEW DATA AQUISITIONCoompana Drilling Program

• $3M collaborative program

Between GSSA and GA

• Up to 18 bores

• Targeting different

geophysical domains

• Boart Longyear selected

as drilling service provider

• Drilling commenced 9th

April 2017 for ~ 5 month

program

NEW DATA AQUISITIONCoompana Drilling Program

First look at

core from

CDP001

Basement at 346m

Currently 164m

HQ3 core

Mixture of foliated

dioritic gneiss and

undeformed

granitoids

A WORKFLOW TO DISCOVERY

QUESTION – what are the key datasets and knowledge that will

provide a framework for discovery in this region

• Depth of cover

• Structural framework and fluid pathways

• Mapping basement under cover (distribution and rock properties)

• Tectonic and crustal evolution (geodynamic setting)

DEPTH OF COVERDepth to magnetic source

• Work by Clive Foss

(CSIRO)

• Individual magnetic

depth estimates based

on multiple inversions

of individual anomalies

• Gridded data to produce

both a map and surface

DEPTH OF COVERDepth to magnetic sourceDepth to magnetic source

• Work by Clive Foss

(CSIRO)

• Individual magnetic

depth estimates based

on multiple inversions

of individual anomalies

• Gridded data to produce

both a map and surface

STRUCTURAL FRAMEWORK AND FLUID PATHWAYS

Based on known geology, potential field data and

seismic character a number of Domains and Seismic

Provinces have been identified

These domains are bound by a number of major shear

zones

• Jindarnga Shear Zone

• Palinar Shear Zone

• Border Shear Zone

• Mulyawara Shear Zone

• Mundrabilla Shear Zone

STRUCTURAL FRAMEWORK AND FLUID PATHWAYS

MAPPING BASEMENT UNDER COVER

Low magnetic Toolgana SS (~1600 Ma)

Non-magnetic intrusions – Undawidgi SS

(~1500Ma)

NNE and NE fabrics in Cook and Forrest

Domains and major structure reactivation

(1200 Ma?)

Intrusions of the ~1200 – 1140 Ma Moodini

SS

Intrusion of remnant magnetic bodies

intrusion of NNW trending dykes

Extension and deposition of Officer Basin

Intrusion of NW trending dykes?

MAPPING BASEMENT UNDER COVER

Coompana Drilling

Program designed to

ground-truth geophysical

interpretations and assist

in building a basement

geology map.

TECTONIC AND CRUSTAL EVOLUTION

Current available data provide

evidence for a number of events that

have affected the region

• Western Gawler events

• Inferred oceanic crust development in the

Coompana Province

• Magmatic-arc magmatism – Toolgana

Supersuite

• Within plate magmatism - Undawidgi Supersuite

(extension)

• A-type magmatism during the Maralinga Event –

Moodini Supersuite

TECTONIC AND CRUSTAL EVOLUTION

Toolgana Supersuite (~1620 – 1600 Ma)

Geochemical signature of subduction modified crust,

magmatic-arc related intrusions

Constrained by geochronology of magmatic rocks in the

Deakin Domain

Interpreted to be more widespread – inheritance,

geochemical signature in Hughes and Forrest domains

Correlated with similar units in the eastern Musgrave

Province and St Peter Suite

TECTONIC AND CRUSTAL EVOLUTIONToolgana Supersuite (~1620 – 1600 Ma)

• High K, calc-alkaline, magnesian

• LILE and LREE enriched, HFSE depleted

Chemistry typical of volcanic-arc setting

1540

1590

1640

1690

R20

125

49

R20

149

59

R19

613

88

R20

125

73

R19

614

32

R16

756

06

R16

756

07

R19

614

23

R19

613

34

R18

422

62

R10

391

40

R10

391

61

R10

391

53

R18

507

75

R21

348

56

R21

360

78

R21

360

69

R21

348

39

R21

360

59

R21

360

91

21

62

76

21

38

22

19

25

94

21

62

61

21

52

08

2

East Birksgate, St Peter Suite & Coompana Geochronology

TECTONIC AND CRUSTAL EVOLUTIONAn Evolving Arc System

St Peter arc complex - ~1650–1600 Ma

• Juvenile oceanic magmatic arc built on ~2000–1900 Ma

oceanic crust outboard of the Mawson/North Australian

Craton

Birksgate arc complex - ~1590–1540 Ma

Loongana arc - ~1415–1389 Ma

Wankanki arc complex - ~1350–1300 Ma

Progressively younging sequence of magmatic-arc

rocks as subduction retreats away from Gawler

Craton margin

TECTONIC AND CRUSTAL EVOLUTION

Undawidgi Supersuite (~1500 Ma)

• Apparently constrained to the Forrest Domain and one

occurrence in Mallabie 1

• Geochemical characteristics of rift related magmatism

• Associated with extensional structures in the Forrest

Domain

TECTONIC AND CRUSTAL EVOLUTIONMaralinga Event ~1220-1120 Ma

Seems to be major event recorded throughout the region

Associated with significant volumes of A type felsic and mafic magmatism

throughout the region – Including Shoshonitic Magmatism

Moodini Supersuite magmatism is syn- to late deformation

Associated with extensional fabric in the lower and mid crust which overprint

earlier fabrics, and crustal thinning

Magnetotelluric data seems to record the late effects of the Maralinga Event

and associated magmatism

IMPLICATIONS FOR MINERAL SYSTEMS• Geologically complex region

• A number of crustal scale structures identified, some coincident with MT conductors

• Recognition of a potential contiguous magmatic arc system out-board of the North

Australian/Gawler Craton begining at 1650–1600 Ma demonstrates a subduction

driven Mesoproterozoic evolution of southern Australia.

• Links between Provinces may allow us to map out these systems beneath cover –

potentially map where you are in the system in space and time

• western Gawler/GRV – backarc setting?

• Coompana

• Porphyrys/epithermal systems (crustal level?)

• Backarc orogenic/intrusion related

• Post-subduction magmatism - 1200 Ma

• Shoshonites – re-melting of subduction modified crust

A WORK IN PROGRESS

The work of the GSSA and our collaborators represents a significant

boost to the understanding of the geological history of western SA and

more broadly for Proterozoic Australia

By undertaking a consistent workflow from gap analysis to

comprehensive data and sample acquisition to synthesis, the GSSA

will provide arguably the greatest step-change in our geological

understanding of a region in modern times

And there’s still more to come………

DisclaimerThe information contained in this presentation has been compiled by the Department of the Premier

and Cabinet (DPC)and originates from a variety of sources. Although all reasonable care has been

taken in the preparation and compilation of the information, it has been provided in good faith for

general information only and does not purport to be professional advice. No warranty, express or

implied, is given as to the completeness, correctness, accuracy, reliability or currency of the

materials.

DPC and the Crown in the right of the State of South Australia does not accept responsibility for and

will not be held liable to any recipient of the information for any loss or damage however caused

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time at its discretion.