The Geophysics of Cu-Au Porphyry Systems

Transcription

1 The Geophysics of Cu-Au Porphyry Systems Batu Hijau Elang Grasberg Wafi-Golpu Terry Hoschke Palembang November 2015

2 Physical Properties Magnetic Properties Remanent Magnetism Magnetic Susceptibility Electrical Properties Resistivity Chargeability Other Radiometrics Density Topography

3 Magnetic porphyry + magnetite-rich potassic zone 100nT Noisy magnetics from inhomogeneous volcanics Non-magnetic propylitic and phyllic zones 100nT Magnetic volcanics (k = 1000 µg/oe = S) Magnetic porphyry - (k = 1000 µg/oe = S) Non-magnetic porphyry

4 Poison Mountain N 500 m Dungate Creek 10 ms N Lowell and Guilbert (1970) > <5

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6 Resistivity Porphyry Deposits 109 in situ measurements

7 1990 Batu Hijau - indonesia Large porphyry Au-Cu situated in Sumbawa, ndonesia g/t Au & 0.53 % Cu 2007 Mineralisation associated with magnetic potassic zone P anomalies associated with potassic zone and pyrite halo

8 ???????? Batu Hijau - ndonesia E E Geology N Sulphides N Section 9080 N Young Tonalite ntermediate Tonalite Equigranular Quartz Diorite Porphyritic Quartz Diorite Porphyritic Andesite ntrusive Volcanic Lithic Breccia Fine Grained Volcaniclastics Bornite + Chalcopyrite Chalcopyrite Dominant Chalcopyrite > Pyrite Zone Pyrite > Chalcopyrite N N E E E Alteration Amplitude ~ 1000nT Magnetics N N Moderate to Strong Secondary Biotite Sericite Chlorite +/- Clay Feldspar Destroyed (Clay - Mica) Epidote Present RTP N

9 Porphyry Au-Cu Deposits Batu Hijau SBD m

10 Batu Hijau - ndonesia N N N N N N N N N N 1000m Au (ppm) Gold Calculated Magnetic Profile (TM) S N S Observed N Flight Path 600 RL 600 RL 400 RL 400 RL Cu (%) RL 200 RL Copper 0 RL 0 RL -200 RL -200 RL K=0.006 cgs -400 RL -400 RL -600 RL -600 RL -800 RL -800 RL Mag Sus (x10 S) Magnetic Susceptibility RL RL

11 Batu Hijau Magnetic Properties

12 Chalcopyrite >1.2% 0 (c) SO Om V\' E.,... ~ i ' T - rma. - ~.- 0.6% (b) -- >1.2% (a-) Pyrite.. _. """. Chargeability Section - S Assays

13 Elang - ndonesia Large porphyry Au-Cu in Sumbawa, ndonesia g/t Au & 0.33 % Cu (JORC compliant resource) Rugged topography Helicopter supported Discovered in 1991 using stream geochemistry

14 Elang Geology and Alteration Geology Alteration

15 Elang Geology and RTP Geology RTP ~700nT

16 Elang Geology and Potassium Geology Potassium ~700nT

17 ELANG GERBANG 500m ELANG GERBANG 500m

18 Elang Geology and Mineralisation ELANG GERBANG Cu % DLD % Cu & 0.82 g/t Au 0.3% Cu

19 Elang Geology and RTP Geology RTP

20 Elang Magnetic Susceptibility DLD027 Mag Sus Average in mineralised zone ~ S Au Cu

21 Elang Magnetic and Electrical Models Chargeability Red 60 ms N Resistivity Blue > 100 ohm-m

22 Elang Ground Magnetics (1991) 500nT 500m

23 Elang forward modelling and inversion results sosurface 0.05 S N

24 Elang Alteration & Magnetic nversion Model Section 3200 sosurface 0.05 S N N

25 Elang Magnetic nversion Models Red 2012 Exploratio n Drilling Green Model from ground magnetics Blue Model from 2012 airborne magnetics

26 Elang Pole-Dipole P Survey (200m Depth Slice) Chargeability Resistivity Red > 50 ms Blue < 15 ms Red > 100 Purple < 30 (ohm-metres)

27 500m GERBANG ELANG

28 ELANG GERBANG 500m ELANG GERBANG 500m

29 ELANG GERBANG 500m ELANG GERBANG 500m

30 Elang Resistivity (100m Depth Slice) Pole-dipole HoisTEM Red > 100 Purple < 30

31 Elang Soil Geochemistry Cu Mo RTP Au Zn Resistivity

32 Elang Resistivity NW 600 mrl Section NW 3000 Magnetic Body SE 600 mrl 500 mrl 400 mrl K-01 DLD-036 DLD-030A DLD-030B DLD mrl 400 mrl 300 mrl 0.48 % Cu, 0.36 g/t Au, 0.55 % Cu, 0.45 g/t Au) Td= 300m 182.6m 300 mrl 200 mrl 200 mrl 100 mrl 100 mrl 0 mrl 0.34 % Cu, 0.38 g/t Au 0.46 % Cu, 0.43 g/t Au) 0 mrl -100 mrl -100 mrl -200 mrl DLD-027 DLD % Cu, 0.52 g/t Au (ncl % Cu, 0.71 g/t Au) -200 mrl -300 mrl 838.5m 742.1m -300 mrl -400 mrl 0.46 % Cu, 0.59 g/t Au (ncl % Cu, 0.82 g/t Au) 865.1m 850.8m -400 mrl 913.2m

33 Elang Mag and Chargeability Model

34 Grasberg - ndonesia Situated in rian Jaya 2475 Mt 1.06 g/t Au 1.13% Cu >7% magnetite in the ore zone Samples with sulphide veining are electrically conductive nterpreted magnetic intrusion at depth

35 Section 15: A) Cu and Au grade shells and Au/Cu zonation SW Grasberg - ndonesia NE SW B) Simplified geology NE PT APRL 98 PT APRL m Level 3195m Level 2850m Level Meters Limit of model Au (ppm)/cu (%) > BLUE: 1% CuAu Equiv. GREEN: 1% Cu shell RED: 1ppm Au shell Trachyandesite lava Trachyandesite volcanic breccia Tertiary carbonate wallrocks NTRUSVE STAGES KAL GRASBERG DALAM Kali intrusive stage Freeport 1999

36 N Grasberg - ndonesia Magnetic Model S Red: 1ppm Au shell

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38 Wafi-Golpu Area RTP

39 SCHEMATC PLAN VEW () \ Miapilli '?> "'(\ i ~ \ \ \ \ Malaria Zone \ CJ)....g E 8 "', CD a ' ~ ~ : ' ~ 500 m - - i Wafi Local Gnd Western Diatreme \ \ \ \ \ \ \ 1 \, \ \ \ \ \, \,,, BZone A Zone, 20000mE ~ :;:, ~ ~ ~ :''OOOm~ Legend Wafi Diatreme Bx Golpu Porphyry Cu-Au Nambonga Porphyry Cu-Au Carb-BM Epithermal Au (Qtz-Rh-BM veins) High Sulphidation Epithermal Au ~ MOROBE M N NG WUt OOU'U MO.l'l.CT

40 w Wafi High Sulphidation Au 72 mill Oz Au E Nambonga Porphyry Cu-Au 7m1/ Oz Au, 0.1 Mt Cu ~ali \JJnk- ---'A lone l one Diatreme 'Golpu Porphyry Cu-Au 20.JmillOzAu, 9.0MtCu 500m Telescoped mineralisation events/systems Multiple Porphyry Cu-Au centres (Golpu, Nambonga) High Sulphidation epithermal overprint (Wafi (Au )) ntermediate sulfidation Carbonate-Base metal (Quartz-Rhodochrosite) veins Total resource inventory Wafi-Golpu to 28.3 Moz of Au and 9.06 Mt of copper or 73.SMoz of Au equivalent.

41 SCHEMATC PLAN VEW 0 -GJ - - ~ \ \ v ~\hli Zone of Potasslc Aheratlon K-feldspar 500m LEGEND ALTERATON Cl nner Potasslc C] Ph)-ilic D Outer Potasslc D Advanced Argllllc - Arglllk: C] Propylltlc - ntense silicification Hot spot of alteration is much larger than known intrusions ~ MOROBE M N N G WU GC>l.PU "'o.k.ct

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43 Heking conductor: carbonaceous shale

44 On western and upper parts of Golpu Locally exhibits Uni-directional Silica Textures (UST), indicative of transition between magmatic and hydrothermal conditions (Seedorff et al, 2005) ~ MOROBE MN NG WUt OOU'U "'OACT

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46 Yanacocha Alumbrera - Argentina -10 LMA Located in NW Argentina 402 Mt 0.64 g/t Au 0.54% Cu -20 Magnetic potassic ore zone Alumbrera Conductive potassic and phyllic zone SANTAGO

47 Alumbrera - Argentina Alteration RTP Magnetics Potassium Propylitic Phyllic Potassic 0 1 Kilometers Proffett 1996 Geology Resistivity Topography Porphyritic ntrusions into Andesitic Volcanics 0 1 Kilometers Proffett 1996

48 CHARGEABLTY SECTON RESSTVTY SECTON Colorado Norte ALTERATON + K-Feldspar + K-Feldspar 100m 0 100m - K-Feldspar Biotite Partial Biotite Epidote Chlorite Feldspar dest ruct ive Feldspar dest ruct ive Drillhole TH.PP02

49 Generalised Model of Porphyry and Epithermal System Geology Maryono, 2007 Magnetic Properties

50 Generalised Model of Porphyry and Epithermal System Geology Maryono, 2007 Electrical Properties

51 Geophysical Signatures Porphyry Gold Copper Mineralisation associated with magnetite Magnetite destructive alteration Conductive sulphide veins & clay alteration High chargeability due to sulphides Potassium response Alteration may influence topography