2. Precious Metals Au-Ag

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GEOLOGI MINERAL LOGAM

INDRA SANJAYA

Precious Metals (Au – Ag)

China South Africa United States

Australia Indonesia Peru Russia Canada PNG Ghana

Gold (Tonnes) 276 272 255 251 171 167 153 93 67 63

276 272 255 251

171 167 153

93 67 63

TOP TENS GOLD PRODUCERS (2007) Source: USGS 2007 Mineral Year Book

China Australia United States

South Africa Russia Peru Indonesia Ghana Canada Uzbekistan

Gold (Tonnes) 341 266 240 190 190 170 120 100 90 90

375 341

266 240

190 190 170

120 100 90 90

TOP TENS GOLD PRODUCERS (2010) Source: Gold Mining Journal 2011

Total: 1,797 tonnes

Total: 1,768 tonnes

(Frimmel, 2008)

GOLD PRODUCTION BY DEPOSIT TYPE

GOLD OVERVIEW

GOLD BEARING MINERALS

KETERDAPATAN ENDAPAN EMAS

High‐, intermediate‐ and low‐sulphidation epithermal Au‐Ag

Porphyry & Skarn deposits Intrusion‐related base metal‐Au Intrusion‐related Au Carlin-type sediment hosted Au deposit Orogenic Deposits Placer

SISTEM HIDROTERMAL MAGMATIK

Corbett and Leach,1998)

lithosphere-scale environments for the formation of the principal gold deposit types ( Groves et al., 2005).

DEPOSIT MODEL (Corbett, 2005)

(Van Leuween, 2011)

Epthermal high sulphidation

KarakteristikMineralogi berupa enargit, pirit, kovelit, emas

murni, elektrum logam dasar sulfida, garam sulfat, dan telurid,

Logam yang dihasilkan berupa emas, perak dan tembaga,

Temperatur 200°-300°C,Salinitas 1-6 wt. % NaCl eg.,Didominasi oleh air magmatik.Kelompok argilik lanjut dicirikan oleh hadirnya

mineral alunit, kaolinit, pirofilit, belereng murni, diaspor, kuarsa, zunyit, dan barit (Sillitoe dan Bonham, 1990).Corbett and Leach,1998)

HS EPITHERMAL Au – Ag (Motomboto)

Motomboto can be classified as a structurally controlled system. Alteration and mineralization are apparently controlled by rift faults parallel to the Neogene arc (Kavalieris et al., 1992)

HS EPITHERMAL Au – Ag (Cabang Kiri)

Cabang Kiri can be classified as a porphyry related system. It shows progressive cooling and decrease in fluid pH away from the porphyry intrusion (Perello, 1994)

HS EPITHERMAL Au – Ag (Binabase-Bawone)

Binabase‐Bawone display aspects of both lithological and structural control (van Leuween, 2011)

HS EPITHERMAL Au – Ag (Binabase-Bawone)

Epthermal intermediate sulphidation

KarakteristikMineralization styles stockwork, disseminated, vein

and breccia‐hostedgold mineralizationcolloform banded quartz + adularia + carbonateMineralogy chalcopyrite-covellite‐galena sphalerite

and tetrahedrite-tennantite‐molybdenite (Einaudi et al., 2003)

Relationship with andesite to rhyodacite rocks

Epthermal intermediate sulphidation

KarakteristikMineralization styles stockwork, disseminated, vein

and breccia‐hostedgold mineralizationcolloform banded quartz + adularia + carbonateMineralogy chalcopyrite-covellite‐galena sphalerite

and tetrahedrite-tennantite‐molybdenite (Einaudi et al., 2003)

Relationship with andesite to rhyodacite rocks

IS EPITHERMAL Au – Ag (Doup)

A resource of about 12 Mt @ 2.09 g/t Au and 4.4 g/t Ag. The mineralization forms a pipe‐like body that extends to a depth of at least 200m, and is 100 by 200m in diameter elongated in a NW‐SE direction

Epthermal low sulphidation

KarakteristikBatuan induk terdiri dari andesit kalk-alkali, dasit,

riodasit atau riolit,Mineralogi berupa pirit, emas, hematit, tennantit,

molibdenum, dan tungsten,Alterasi yang terjadi yaitu kuarsa-adularia, karbonat,

dan serisit,Salinitas rendah (0-5 % NaCl),Asal larutan dari air meteorik dan air magmatik.

Vein distribution: eg. Kapitu prospect

Grade of Kapitu vein:

5.5m @ 4.4 g/t Au 1m @ 7.87 g/t Au 6m @ 8.77 g/t Au 1m @ 40.3 g/t Au 2m @ 5.59 g/t Au 1m @ 8.26 g/t Au

Low-sulphidation epithermal Au veins

Bonanza zone

Vein texturesBonanza zone

Kapitu veins

B. CU-AU PORPHYRY DEPOSITS

PERIPHERALC cp -G n-Sp-Au-Ag PERIPHERAL

C cp -G n-Sp-Au-Ag

LOW PYRITESHELLP y ~2%

Mag>Py

PYR ITES H E LLPy ~10%Ccp 0.1-3%Mo rare

M ag >Py& C cp

ORE SHELLPy 1 %C cp 1-3%M o 0 .03%

LOW GRADECORElow tota lCcp-Py-Mo

SAN M ANUEL FAU LT

KALAMAZOOSEGMENT

SAN M ANUELSEGMENT

Propylitic(Chl-Ep-Carb)

A dul-A b

ArgillicQ tz-K ln-C h l

PhyllicQ tz-S er-P y

PotassicQ tz-K fs-B t-+ S er+A n h

Q tz-S er-C h l-K fs

Chl-Ser-Ep-M ag

Cu-(Au) porphyry vein-veinlet system

a) Collahuasi/Chileb) Grasberg/Irian Jaya

Buladigun Cu-Au porphyry,North Sulawesi

Alteration styles

Carlin-type sediment hosted Au deposit

Karakteristik

1. Batuan pembawa berupa sedimen karbonat

2. Kandungan Au/Ag relatif tinggi

3. Pengkayaan unsur As, Sb, Hg yang tinggi

4. Invisible atau nosseum gold

5. Kandungan logam dasar yang rendah, dan kehadiran urat kuarsa dalam jumlah minimal

6. Batuan karbonat sebagai batuan pembawa mengandung karbon sebanyak 0.5 % berat.

Sumber: (Bagby & Berger, 1986); Ferdock (2002)

Carlin-style sediment hosted Au deposit

Mesel, Ratatotok(North

Sulawesi)

(Hendri & Farmer, 1997)

Carlin-style sediment hosted Au deposit

Yance-Leon Prospect, Mesel, Ratatotok (North Sulawesi)

Fresh limestone Silicified limestone

Argillic alterationRealgar, cinnabar (late stage)

Intrusion Related Au

Conceptual model for mineralization types in The Western Sulawesi Province (van Leuween, 2011)

Characteristics Orogenic belts, (collisional to postcollisonal)

convergent plate margin settings, extensional back-arc environments.

Presence of weakly reduced to moderately oxidised, intermediate to felsic magmatism.

Gold ± Bi, As, W, Mo, Sb, Te occurs in: single, planar, sheeted and stockwork quartz veins

Base metal contents are highly variable from almost absent to assemblages of Cu-Zn-Pb-As. Bi minerals may be well developed.

Alteration is variable in both style and intensity.

1. The gold is associated with sulphur‐poor, sodic‐rich fluids.

2. Albite‐pyrite‐silica±carbonate alteration associated with deformation and metamorphism in the older basement lithologies

3. Mineralization is typically hosted within a flysch sequence

4. Gold is usually associated with abundant quartz veining and silica‐albite‐pyrite alteration

(Gustavson, 2007)

AWAK MAS GOLD DEPOSITS

Querubin & Walters, 2011

POBOYA GOLD DEPOSIT(Wajdi dkk, 2011)

POBOYA GOLD DEPOSIT

(Wajdi dkk, 2011)

ENDAPAN Au MESOTERMAL Endapan mesotermal merupakan salah satu

tipe endapan hidrotermal yang terbentuk pada lingkungan batuan metamorfik,

Karakteristik endapan mesotermal:Urat emas–kuarsa yang terdapat di sekitar

batuan metamorfikEkstraksi Au dari batuan samping melalui air

kristal (H2O) dan CO2, oleh perubahan metamorfik antara fasies sekis hijau ke amfibolit pada T sekitar 400-600°C

Contohnya: greenstone belts → Homstake mine/S-Dakota, USA

DASAR TEORI

TINJAUAN PUSTAKA

Tatanan tektonik pembentukan endapan orogenik yang berada pada batas kontinen, zona akresi atau kolisi (Groves et al, 1998).

MINERALISASI

CASE: BOMBANA

Mineralisasi :•cinnabar (HgS) •stibnit (Sb2S3). •pirit (FeS2)•kalkopirit (CuFeS2) •Goetit (FeO(OH))

ALTERASI HIDROTERMAL

CASE: BOMBANA

Urat kuarsa

Argilitisasi

ArgilitisasiSilisifikasi

Klorit-karbonat

karbonat

klorit

Karbonisasi.

CASE: BOMBANA

SIFAT FISIK-KIMIA FLUIDA ENDAPAN

CO2-rich fluid

Zona keberadaan endapan emas orogenik bombana dengan beberapa endapan orogenik yang terdapat di Western Australia berdasarkan korelasi nilai temperature pembentukan (modifikasi dari Goldfarb, 2005)

Perkiraan zona keberadaan endapan emas orogenik yang ada di Bombana pada model endapan orogenik (modifikasi dari Gebre-Mariam et al., 1995).

CASE: BOMBANA

South African fossil placers (gold-bearing conglomerates)

D. ENDAPAN EMAS PLACER

PLACER GOLD DEPOSIT

2. Perak (Ag)Ditemukan dalam bentuk - Native silver (sebagian besar)- Ag-sulphides.

Native silver di temukan dalam 2 bentuk utama: (1) Zona teroksidasi dari suatu endapan bijih.(2) Endapan larutan hidrotermal (primer).

Ag-sulphides, mineral utamanya: Acanthit (Ag2S) dan aguilarit (Ag4SSe) pada endapan

hidrotermal (low sulphidation epitermal) serta argentit (Ag2S) pada temperatur lebih tinggi.

Ag-sulphides sering bersama-sama ruby silvers seperti pyrargyrit (Ag3SbS3) dan proustit (Ag3AsS3). Juga sebagai inklusi dalam galena argentiferous galena.

Mineragrafi bijih perak dari endapan epitermal Pongkor, Indonesia

Acanthit (Ag2S) sebagai mineral perak minor berasosiasi dengan emas pada endapan sulfida rendah Pongkor, Jawa Barat (Warmada, 2003).

Notes: Gn = galena, Po = Pyrrhotit, Sp = Sphalerit, Uy = Uytenbogaardtit (Ag3AuS2), Mck = Mckinstryit (Ag,Cu)2S, Smy = stromeyerit (AgCuS) and El = Au-Ag alloy ((Au,Ag).

Analisis kimia mineral dari sulfida perak dari Pongkor, Indonesia

MAGMATIC-METEORIC

MAGMATIC

Textures: restricted Textures: diverse, modest Textures: diverse, spectacular

LOW SULFIDATIONHIGH SULFIDATION

Au-Ag-Cu Au-Ag

INTERMEDIATE SULFIDATION

METEORIC

Au-Ag, As, Cu, Sb, Bi

Stockwork, Golden Cross

Vein, Golden CrossVein, Hishikari

Vein, La Guitarra

SULFIDATIO

Chinkuashih La Coipa

Akeshi Sulfide vein, El Indio

SULFIDATIO

Characteristic Textures

Neutral-pH, meteoricLow-Sulfidation

banded veins

breccia veins

drusy cavities

crustification

lattice texture

Acid-pH, magmaticHigh-Sulfidation

‘vuggy quartz’

massive quartz

massive sulfide veins

crudely banded veins

White and Hedenquist, 1995

La Guitarra Golden Cross

SULFIDATIO

TEXTURES Dealul Crucii, Baia Mare Aginsky

2. Precious Metals Au-Ag

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