Dr.rer.nat. Arifudin IdrusDr.rer.nat. Arifudin IdrusAssociate Professor in Economic GeologyAssociate Professor in Economic Geology

Graduate Program of Geological Graduate Program of Geological EngineeringEngineering

Universitas Gadjah MadaUniversitas Gadjah Mada YogyakartaYogyakarta

COURSEAdvanced Geology of Ore Deposits

(2 SKS)

Stolberg, Germany, 2005

INTRODUCTIONMETALLOGENESIS

CLASSIFICATION OF MINERAL DEPOSITSMAGMATIC DEPOSITS

EPITHERMAL DEPOSITS

THE SCOPE OF DISCUSSIONTHE SCOPE OF DISCUSSION

IntroductionIntroduction MetalMetalllogenesis: ogenesis: the formation of ore deposits the formation of ore deposits Classification of ore mineral depositsClassification of ore mineral deposits Magmatic deposits (Chromite, Nickel and Magmatic deposits (Chromite, Nickel and

PGM)PGM) Hydrothermal deposits I: Epithermal and Hydrothermal deposits I: Epithermal and

PorphyryPorphyry Hydrothermal deposits Hydrothermal deposits II: II: Skarn and Skarn and

MesothermalMesothermal Volcanic hosted deposits (VMS)Volcanic hosted deposits (VMS) and SEDEX and SEDEX

(Sedimentary Exhalative)(Sedimentary Exhalative) Residual deposits Residual deposits ((chemical chemical weatheringweathering)) Sedimentary deposits Sedimentary deposits (placer)(placer) EvaluationEvaluation:: homeworkhomework and and testtest

BIBLIOGRAPHYBIBLIOGRAPHY

Evans, A.M., 1993. Ore geology and industrial minerals, an introduction, Blackwell Science, 389 p..

Edwards R., Atkinson K. (1986), Ore deposit geology and its influence on mineral exploration, Chapman and Hall, London, 466 p.

Robb, L. 2005, Introduction to Ore Forming Process...

International journals:1.Economic Geology2.Mineralium Deposita

INTRODUCTIONINTRODUCTION Ore is a metalliferous mineral, or anOre is a metalliferous mineral, or an aggregate ofaggregate of

metalliferous minerals, more or lessmetalliferous minerals, more or less mixed with gangue, mixed with gangue, which from the standpoint ofwhich from the standpoint of the miner can be won at a the miner can be won at a profit, or from theprofit, or from the standpoint of the metallurgist can be standpoint of the metallurgist can be treated at atreated at a profit. profit.

Ore minerals are defined as those from which metals are Ore minerals are defined as those from which metals are extracted, e.g., chalcopyrite and galena from which we extracted, e.g., chalcopyrite and galena from which we extract copper and lead.extract copper and lead.

““Opaque mineralsOpaque minerals” ” andand “ “metalliferous mineralsmetalliferous minerals” ” are are used as synonym of used as synonym of ore mineralsore minerals..

Economically mineable aggregates of ore minerals are Economically mineable aggregates of ore minerals are termed orebodies, oreshoots, ore deposits or ore reserves.termed orebodies, oreshoots, ore deposits or ore reserves.

MMetal Concentration in the crustetal Concentration in the crust

The average concentration of metal in the earth's crust, a The average concentration of metal in the earth's crust, a minimum concentration ofminimum concentration of economic value and enrichment through the economic value and enrichment through the processprocess of geological factors (geologicalof geological factors (geological enrichment factors)enrichment factors)..

OOre deposits can be dividere deposits can be dividedd into five groups into five groups (Evans, 1993):(Evans, 1993):

– Precious metals Precious metals : : gold gold (Au), (Au), silver silver (Ag), (Ag), platinum platinum (Pt)(Pt)

– Non-ferrous metals Non-ferrous metals : : coppercopper(Cu), (Cu), lead lead (Pb), (Pb), zinczinc (Zn), (Zn), tin tin (Sn), (Sn), and and aluminium (Al). the first four being commonly known aluminium (Al). the first four being commonly known asas base metals.base metals.

– Iron and ferroalloy metals Iron and ferroalloy metals :: iron iron (Fe), (Fe), mmangananganeseese (Mn), (Mn), ninicckel (Ni), kel (Ni), chchromromiumium (Cr), mol (Cr), molyybdenum (Mo), bdenum (Mo), tungsten tungsten (W), (W), vanadium (V), vanadium (V), cobaltcobalt (Co). (Co).

– Minor metals and related non-metalsMinor metals and related non-metals: antimon: antimonyy (Sb), (Sb), arsenarsenicic (As), ber (As), beryylium (Belium (Be)), bismut, bismuthh (Bi), (Bi), CCadmium (Cd), admium (Cd), magnesium (Mg), magnesium (Mg), mercury mercury (Hg), REE, selenium (Se), tantalum (Hg), REE, selenium (Se), tantalum (Ta), tel(Ta), telllurium (Te), titanium (Ti), urium (Te), titanium (Ti), zzirircconium (Zr), onium (Zr), etcetc..

– Fissionable metalsFissionable metals: uranium (U), t: uranium (U), thhorium (Th), radium (Ra).orium (Th), radium (Ra).

CLASSIFICATION OF ORE DEPOSITSCLASSIFICATION OF ORE DEPOSITS(Pohl,….)(Pohl,….)

MMagmatic-hydrothermal depositsagmatic-hydrothermal deposits– Magmatic liquid deposits (Cr in ophiolite or banded intrusion with Magmatic liquid deposits (Cr in ophiolite or banded intrusion with

Pt, Fe/Ti and Ni by productPt, Fe/Ti and Ni by product))– PegmatitPegmatitee (Sn, Nb/Ta, Li, Be, etc). (Sn, Nb/Ta, Li, Be, etc).– Hydrothermal depositsHydrothermal deposits: : Cyprus-typeCyprus-type (VMS); skarn (W, Sn, Cu, etc), (VMS); skarn (W, Sn, Cu, etc),

porphyry porphyry (Cu, Mo, Sn, etc); (Cu, Mo, Sn, etc); veins veins (Sn, W, U); (Sn, W, U); epithermal epithermal Au-Ag; BIF Au-Ag; BIF ((Algoma typeAlgoma type))

Diagenetic hydrothermal depositsDiagenetic hydrothermal deposits– KupferschieferKupferschiefer type type (Cu, Pb, Zn) (Cu, Pb, Zn) SEDEX SEDEX– Mississippi Mississippi type type (MVT): Pb-Zn-Ba-F(MVT): Pb-Zn-Ba-F

Matamorphic-hydrothermal depositsMatamorphic-hydrothermal deposits– Quartz veins in the metamorphic rocks Quartz veins in the metamorphic rocks (Au) (Au) ororlode goldlode gold. .

Residual deposits Residual deposits ((ChemicalChemical))– residualresidual: bauksit dan Fe-laterit: bauksit dan Fe-laterit– supergenesupergene: Ni : Ni and and Au lateritAu lateritee; Mn, Fe, Cu, Ag; Mn, Fe, Cu, Ag enrichment enrichment

Sedimentary deposits Sedimentary deposits ((mechanicalmechanical))– Alluvial and sea placer deposits Alluvial and sea placer deposits (Au, Sn, Ti, REE)(Au, Sn, Ti, REE)

Pasific palte

Africa Plate Hindia-Australia Plate

Antartic Plate

Eurasia Plate

North America Plate

South America Plate

Plate Tectonic boundary

Nazca Plate

TETECCTONITONICSCS VS MINERALI VS MINERALIZATIONZATION

SOUTHWEST PACIFIC RIMSOUTHWEST PACIFIC RIM

INDONESIAINDONESIAN ISLAND ARCSN ISLAND ARCS

1a. MAGMATIC DEPOSITS

Ore minerals formed in the early phase Ore minerals formed in the early phase of magma differensiation, along with the of magma differensiation, along with the formation of olivine, pyroxene, Ca-formation of olivine, pyroxene, Ca-plagioclase suchplagioclase such as as magnetite, ilmenite, magnetite, ilmenite, chromite,chromite, sulfide nickel, PGM (Platinum sulfide nickel, PGM (Platinum Group Metals).Group Metals).

Magmatic Processes

MAGMATIC PROCESSES

Crystallization process Crystallization process ((disseminateddisseminated), ), diamond diamond (C ) (C ) in Kimberlitein Kimberlite

Segregation process (cumulate, Segregation process (cumulate, gravity settling): gravity settling): chromite chromite (Cr), magnetit(Cr), magnetitee (Fe), platinum (Pt) (Fe), platinum (Pt)

Liquid immiscibility : NiLiquid immiscibility : Ni PegmatiPegmatitete : Fe, Sn : Fe, Sn

1a. 1a. Magmatic depositsMagmatic deposits

1.1. ChromiteChromite::

(1) (1) Stratiform typeStratiform type ( (layered mafic layered mafic intrusionsintrusions or or Bushveld-TypeBushveld-Type), ),

(2) (2) Podiform typePodiform type ( (Ophiolite-boundOphiolite-bound or or Alpine-TypeAlpine-Type))

2.2. NiNicckel (Nickel sulfide)kel (Nickel sulfide)

3.3. PGM/E (Platinum Group PGM/E (Platinum Group Metals/Elements)Metals/Elements)

ChromiteChromite-Ni-Nicckel-PGMkel-PGM depositsdeposits

Chromitite is a layer (seam), composed of 50-95&% fine Chromitite is a layer (seam), composed of 50-95&% fine size chromite cumulus (~0,2 mm), interstitial with olivine, size chromite cumulus (~0,2 mm), interstitial with olivine, orthopyroxene, plagioclase, clinopyroxene or its alteration orthopyroxene, plagioclase, clinopyroxene or its alteration products. products.

Primary chromite deposits are asociated with primary nickel Primary chromite deposits are asociated with primary nickel as as Ni-sulphidesNi-sulphides, , such as such as pentlanditpentlanditee (Ni,Fe) (Ni,Fe)99SS99, millerit, milleritee (NiS) (NiS) andand gersdorffit (NiAsS). gersdorffit (NiAsS).

Ni-sulphide minerals are also asociated with other sulphides Ni-sulphide minerals are also asociated with other sulphides such as chalcopyrite, pyrrhotite. such as chalcopyrite, pyrrhotite.

Can be formed together wiht PGE (Platinum Group Elemets) Can be formed together wiht PGE (Platinum Group Elemets) including including Os, Ir, Ru, Rh, Pt dan Pd. Os, Ir, Ru, Rh, Pt dan Pd. This This PGEPGE is is ususally ususally attachedattached in the stucture of those sulphide minerals. in the stucture of those sulphide minerals.

NickelNickel

Nickel deposit classification:Nickel deposit classification:– Nickel sulphides depositNickel sulphides deposit– Nickel Silicates ~ lateritic nickel depositNickel Silicates ~ lateritic nickel deposit

Nickel SulphidesNickel Sulphides Early magmatic deposit Early magmatic deposit magmatic magmatic

segregationsegregation Classification of Nickel Sulphides OreClassification of Nickel Sulphides Ore

– Dunite – Peridotite ClassDunite – Peridotite Class Intrusive Dunite AssociationIntrusive Dunite Association Volcanic – peridotite AssosiationVolcanic – peridotite Assosiation

– Gabbroic ClassGabbroic Class Intrusive mafic/Ultramafic ComplexesIntrusive mafic/Ultramafic Complexes Large Layered Intrusions, e.g. Bushveld Large Layered Intrusions, e.g. Bushveld

Complex, RSA; Great Dyke & Complex, RSA; Great Dyke & Sudbury, CanadaSudbury, Canada

Nickel sulphides depositNickel sulphides deposit

Segregation causes the deposition of heavy sulphides (nickel Segregation causes the deposition of heavy sulphides (nickel sulphides) on the bottom and separated from rock-forming sulphides) on the bottom and separated from rock-forming minerals.minerals.

Geology of Bushveld complex, Geology of Bushveld complex, RSARSA

Chromite layers of Bushveld Chromite layers of Bushveld complexcomplex

Bushveld Bushveld complex layered complex layered seriesseries

Subdivision of the Layered Series of the Bushveld Complex. MR. Merensky Reef, SC, Stcelpoort chromite (from Duke 1983, after Verrnaak, C. F. and von Gruenewaldt, G. (1981) The Bushveld Complex Excursion Guide, Geocongress

PGM associated with Bushveld PGM associated with Bushveld complexcomplex

1b. 1b. Hydrothermal depositsHydrothermal deposits

Focus of discussionFocus of discussion::

1.1. Epithermal Epithermal Au-AgAu-Ag deposits deposits

2.2. Pophyry Pophyry Cu-AuCu-Au deposits deposits

3.3. Skarn Skarn Cu-(Au)Cu-(Au) deposits deposits

4.4. MMesotesothhermalermal deposits deposits ( (quartz-Au quartz-Au lode)lode)

Magmatisme-hydrothermal Magmatisme-hydrothermal processprocess

Sub-volcanic Sub-volcanic hydrothermal systemhydrothermal system

epithermal depositsepithermal deposits

Characteristics:Characteristics:

– T relatively low (50 – 250T relatively low (50 – 250°°C) with variable C) with variable salinities (0 – 5 wt.% NaCl equivalent)salinities (0 – 5 wt.% NaCl equivalent)

– Formed in shallow depth (~1 km)Formed in shallow depth (~1 km)– Fluid type: meteoric water and low magmatic fluidFluid type: meteoric water and low magmatic fluid

Classification:Classification:

– High sulfidation (acid sulfate type)High sulfidation (acid sulfate type)– Low sulfidation (adularia-sericite type)Low sulfidation (adularia-sericite type)

Disseminated (e.g., in epithermal Ag-(Sn-Pb-Zn))Disseminated (e.g., in epithermal Ag-(Sn-Pb-Zn))

Epithermal deposits Epithermal deposits (high sulfidation)(high sulfidation)

Endapan Au (ton) UmurYanacocha/Peru 820 M/PPueblo Viejo 680 CretPascua 640 M/PPienina/Peru 250 M/PLepanto 210 QuatEl Indio 190 M/PChinquashih 150 QuatSummitville 20 M/PRodalquilar 10 N/P

Epithermal deposits Epithermal deposits (low sulfidation)(low sulfidation)

Endapan Au (ton) UmurLihir 924 QuatPorgera 600 M/PRound Mountain 443 M/PBaguio District 300 QuatHishikari 250 QuatKelian 180 M/PGunung Pongkor 175 M/PDukat 150 CretCerro Korikollo 147 M/PCerro Vanguardia 100 Jura

PongkorHishikariHishikari

Hishikari Gold Ore - Photomicrograph

Epithermal high sulfidationEpithermal high sulfidation

Two stage model for the formation of high-sulfidation epithermal deposits (after Arribas et al., 1995). (a) Initial stage where a dominantly magmatic vapor phase is responsible for leaching of the country rock and development of an advanced argillic alteration halo around the main fumarolic conduit. (b1) Ore deposition stage, in this case where gold is transported as a chloride complex, and (b2) ore deposition stage where gold is transported as a bisulfide complex.

Kind of Kind of open-space fillingopen-space filling

Kind and geometry of Kind and geometry of epithermal deposits that epithermal deposits that describing the hydrothermal describing the hydrothermal structure and lithology structure and lithology controlling permeability controlling permeability scematically.scematically.

Hydrothermal alterationsHydrothermal alterations

Au-Ag-CuAu-Ag-Cu deposits deposits

– SiliSiliccifiificationcation

– AAdvancedvancedd argillic argillic

– SericitizatioSericitizationn

– PotassicPotassic

NoteNote:: the absence of silicification is not too important to the absence of silicification is not too important to characterize an epithermal deposits, for example: Keliancharacterize an epithermal deposits, for example: Kelian

Alteration ZoneAlteration Zone LateralLateral: : residual silica – qtz-alu – residual silica – qtz-alu –

qtz-kao – kao-ill – ill/smeqtz-kao – kao-ill – ill/sme

VerticalVertical::– Residual silica – py – enResidual silica – py – en

– Qtz – alu – pyroph – kao – pyQtz – alu – pyroph – kao – py

– Qtz – kao – ser, py, ccpQtz – kao – ser, py, ccp

– Qtz – ser – py, ccpQtz – ser – py, ccp

– Bio, or, cpy, bn, magBio, or, cpy, bn, mag

Depth

Depth

Hydrothermal Hydrothermal AlterationAlteration

Alteration, metals & texture zoning model

CHcCHb

CHm

CCh

CCx

Xas

Xc

Epithermal gold Epithermal gold vein/modelvein/model

Paulingan epithermal Paulingan epithermal vein, North Sulawesivein, North Sulawesi

Vein Vein modeling: modeling: An An

exampleexample

Vein Vein modelinmodelin

g: g: An An ExampleExample

ReserveReservess from ore from ore modelmodelllinging

Tonnage = Tonnage = reservereserve = Volume x BJ= Volume x BJ

= 693.190 m3 x 2,7 g/t= 693.190 m3 x 2,7 g/t= 1.871.613 ton bijih= 1.871.613 ton bijih

NO Vein Volume Z MinimumZ MaximumKedalamanm³ meter meter meter

1 Kapitu_Vein 98854 -41.687 243.5 285.1872 Paulingan1_vein 71236 13.924 219.842 205.9183 Paulingan2_vein 36490 45.703 234.275 188.5724 Prospek Samoy (blok sakong) 486610 100.58 222.576 121.997

Total 693190