AMIRA P765 ( ) Transitions and Zoning in Porphyry - Epithermal Districts: Indicators, Discriminators and Vectors

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1 Metal Dispersion around Porphyry Cu-Mo-Au Deposits: Implications for Fluid Flow and Exploration Cerro Casale porphyry Cu-Au deposit, Chile J. Bruce Gemmell AMIRA P765 ( ) Transitions and Zoning in Porphyry - Epithermal Districts: Indicators, Discriminators and Vectors 7 industry sponsors AMIRA P765A ( ) Geochemical and Geological Halos in Green Rocks and Lithocaps: The explorer s toolbox for porphyry and epithermal districts 18 industry sponsors AMIRA P1060 ( ) Enhanced Geochemical Targeting in Magmatic-Hydrothermal Systems 21 industry sponsors 1

2 From Holliday and Cooke (2007), with inspiration from Sillitoe and Thompson (2006) La Grande Rosario Ujina Epidote: basic field techniques Map epidote s distribution Largest deposits have the largest propylitic halos Epidote veins are more abundant close to the deposit centre Larger deposits have intensely developed epidote stockworks Monctezuma Alteration 1 km Potassic Epidote-Hematite Epidote-(Chlorite) Chlorite Skarn Sample Location Alteration map of the Collahuasi district, Chile Modified after Ireland (2010) Map mineral associations Epidote + actinolite higher temperature (proximal) Epidote + chlorite lower temperature (distal) Pyrite + epidote typically occurs close to mineralisation Watch for colour changes Pink high Mn epidote Orange high Pb epidote 2

3 Epidote Chemistry Epidote group minerals: A 2 B 3 (SiO 4 ) 3 (OH,F) A - Ca, Ce, Pb, Sr, Y B - Al, Fe, V, Mg, Mn + REE & other assorted metals Solid solution: Ca 2 Al 3 Si 3 O 12 (OH) clinozoisite Ca 2 Fe 3+ Al 2 Si 3 O 12 (OH) epidote to SBD m 2 cm Epidote Mineral Chemistry LA-ICPMS facility 3

4 Epidote LA-ICP-MS Analysis Counts per second * E07 1 * E06 1 * E05 10, , Sr Pb V La Sb Fe Mn Zn Ca As Time (seconds) Ca43 V51 Mn55 Fe57 Cu65 Zn66 Ga69 As75 Sr88 Y89 Zr90 Mo95 Sn118 Sb121 Te125 Ba137 La139 Ce140 Pr141 Nd146 Sm147 Eu153 Dy163 Yb172 Lu175 Au197 Tl205 Pb208 Bi209 Th232 Luzon Central Cordillera, Philippines 200 km Mankyan District 7.69 Mt Cu, 37 Moz Au Baguio District 2.7 Mt Cu, 35 Moz Au Cooke et al. (in review) 4

5 Baguio District, Philippines Black Mt Kennon: ~ 0.38% Cu, 0.35g/t Au & 0.01% Mo. Southeast: ~ 0.37% Cu & 0.26g/t Au. Nugget Hill Rock chip assays up to 1.17% Cu and 4.58g/t Au. Cooke et al. (in review) Concentration (ppm) 10,000 1, Epidote Mineral Chemistry Legend Whole rock mean Whole rock p. 75 Whole rock median Whole rock p. 25 Epidote mean Epidote p. 75 Epidote median Epidote p n (max) epidote = 3,521 n (max) whole rock = 985 Na Mg K Ti Ba Zr Zn Cu Ce Y Nd La Yb Mo Bi Cooke et al. (in review) 5

6 Epidote Mineral Chemistry 100,000 n (max) epidote = 3,521 n (max) whole rock = ,000 Concentration (ppm) 1, Legend Whole rock mean Whole rock p. 75 Whole rock median Whole rock p. 25 Epidote mean Epidote p. 75 Epidote median Epidote p. 25 Epidote is significantly enriched in As, Sb and Pb in the distal halo to porphyry deposits Al Fe Mn Sr V As Pb Sb Sn Eu Bi Cooke et al. (in review) Pyrite halo Potassic alteration SE SE SE SE Cooke et al.. (in review) 6

7 Cu_ppm Au_ppm BDL Cu_ppm to 0.18 Cu_ppm to 0.60 Cu_ppm to 1.36 BDL Au_ppm to 0.02 Au_ppm to 0.03 Au_ppm to 0.04 Au_ppm to 0.05 Cu_ppm to 4.00 Cu_ppm to Cu_ppm to SE SE Mo_ppm Sn_ppm BDL Mo_ppm to 0.07 Mo_ppm to 0.38 Mo_ppm to 0.76 Mo_ppm to 1.32 Sn_ppm to 0.41 Sn_ppm to 0.71 Sn_ppm to 1.36 Sn_ppm to 4.31 Sn_ppm to 5.94 Sn_ppm to SE SE Cooke et al.. (in review) SE SE SE SE Cooke et al.. (in review) 7

8 As_ppm As_ppm to 3.06 As_ppm to 5.63 Sb_ppm Sb_ppm to 0.20 Sb_ppm to 0.88 As_ppm to Sb_ppm to 2.06 As_ppm to Sb_ppm to 5.04 As_ppm to Sb_ppm to As_ppm to Sb_ppm to SE SE Pb_ppm Zn_ppm Pb_ppm to 0.83 Pb_ppm to 4.67 Zn_ppm to 1.42 Zn_ppm to 5.71 Pb_ppm to Zn_ppm to Pb_ppm to Zn_ppm to Pb_ppm to Zn_ppm to Pb_ppm to Zn_ppm to SE SE Cooke et al.. (in review) Sn (ppm) ppm A Mexico Black Mt Nugget Hill Mexico Creek transect Pyrite halo B' C Liw-Liw Creek transect Pyrite halo Potassic alteration distance replacement epidote vein epidote skarn epidote whole rock Cooke et al. (in review) 8

9 As (ppm) A Mexico Mexico Creek transect Black Mt Nugget Hill B' C Liw-Liw Creek transect Pyrite halo ppm Potassic alteration distance replacement epidote vein epidote skarn epidote whole rock Cooke et al., (in review) Metal enrichment in epidote: lateral fluid migration and depletion of H 2 S chalcopyrite pyrite epidote Cooke et al. (in review) Potassic zone (H 2 S, SO 2-4 available) High T (> 450 C): Deposition of Cu-sulfides and Au Most other metals too soluble to precipitate High aqueous sulfate contents causes Ca deposition as anhydrite Epidote not stable Pyrite halo (H 2 S abundant) Moderate T (<450 C): Deposition of pyrite, minor chalcopyrite As, Sb, Pb scavenged by pyrite Epidote enriched in Y and REEs Epidote also incorporates Zr, minor Sn, trace Cu, Mo Green rock halo (H 2 S exhausted) Moderate - low T ( C) As, Sb and Pb substitute into epidote when sulfides are no longer being deposited Mn substitutes into epidote due to the similar ionic radius to Fe 3+ The most highly productive porphyries flux the most metals 9

10 Epidote chemistry (non-productive porphyry): Zn elevated Sn, Pb, As, Y, La depleted Epidote chemistry (outside pyrite halo of productive porphyry): Pb, As, Sb, La, Y, Zr elevated Cu, Zn, Sn, Mo depleted Epidote chemistry (inside pyrite halo of productive porphyry): Cu, Sn, Mo, Bi, Zn elevated Lithocap Py halo Vein + replacement epidote Replacement epidote only K-silicate halo Coalescing epidote alteration halos Replacement epidote only Weakly mineralised porphyry (e.g., Mexico) Strongly mineralised porphyry (e.g., Nugget Hill) Cooke et al. (in review) Concealed porphyry From Holliday and Cooke (2007), with inspiration from Sillitoe and Thompson (2006) 10

11 1) Acidic magmatic condensates cause AA alteration 2) Introduction of metalliferous metals Alteration 2 ORE 1 N.C. White, unpublished magmatic liquids rock saturated with groundwater Lithocap Mineralogy alunite,and quartz propylitic (chlorite) illite and smectite (montmorillonite) alunite, quartz and kaolinite vuggy quartz vuggy quartz Steven & Ratté,

12 AA Alteration Mineralogy Quartz SiO 2 Alunite KAl 3 (SO 4 ) 2 (OH) 6 Kaolinite Al 2 Si 2 O 5 (OH) 4 Halloysite Al 2 Si 2 O 5 (OH) 4 Dickite Al 2 Si 2 O 5 (OH) 4 Pyrophyllite Al 2 Si 4 O 10 (OH) 2 Diaspore AlO(OH) Topaz Al 2 SiO 4 (F,OH) 2 Zunyite Al 13 Si 5 O 20 (OH,F) 18 Cl Dumortierite Al BO 3 (SiO 4 ) 3 (O,OH) 3 Corundum Al 2 O 3 Andalusite Al 2 SiO 5 Cordierite Mg 2 Al 4 Si 5 O 18 Cathedral Peal lithocap with quartz alunite ledges, Cerro Casale, Chile Filter WR Geochemistry use samples with < 0.1% Cu, < 0.1ppm Au and contain alunite Mineralization at a later stage Vuggy quartz and alunite, Mankayan Chang et al. (2011) 12

13 Alunite Mineral Chemistry KAl 3 (SO 4 ) 2 (OH) 6 Alunite, Mankayan Al > Fe Fe > Al alunite KAl 3 (SO 4 ) 2 (OH) 6 jarosite KFe 3 (SO 4 ) 2 (OH) 6 natroalunite NaAl 3 (SO 4 ) 2 (OH) 6 natrojarosite NaFe 3 (SO4) 2 (OH) 6 minamiite (Na,K,Ca) 2 Al 6 (SO 4 ) 4 (OH) 12 hydronium jarosite (H 3 O)Fe 3 (SO4) 2 (OH) 6 huangite Ca 2 Al 6 (SO 4 ) 4 (OH) 12 argentojarosite AgFe 3 (SO 4 ) 2 (OH) 6 walthierite BaAl 6 (SO 4 ) 4 (OH) 12 beaverite Pb(Fe,Cu) 3 Fe 3 (SO 4 ) 2 (OH,H 2 O) 6 ammonioalunite 4 Al 3 (SO 4 ) 2 (OH) 6 ammoniojarosite ( 4 )Fe 3 (SO 4 ) 2 (OH) 6 schlossmacherite (H 3 O,Ca)Al 3 (SO 4 ) 2 (OH) 6 plumbojarosite PbFe 6 (SO 4 ) 4 (OH) 12 Variations in K, Na and trace element contents (e.g., Pb, La, etc.) Alunite 1480nm Spectral (SWIR) Feature Na/(Na+K) ratio (mole) Mankayan Baguio Cocanes Kuruga Casale samples 554 microprobe analyses Correlation coefficient = Higher Na/(Na+K) ratio indicates higher formation temperature (Stoffregen and Cygan, 1990) 13

14 Trace Elements in Alunite K, Na, Ag, Tl, 4, H 3 O, Ca, Ba, Pb, Hg, Sr, Zn, Cu, Rb, Ag, Th, Bi, REE S 6+, As 5+, Cr 6+, Sb, P 5+ Sn 4+, Al, As 3+, Fe 3+, Cr 3+, V 3+, Ga, Mg, Mn, Cu 2+ DG 3 (TO 4 ) 2 (OH,H 2 O,F) 6 Cr-rich Fe-Mn-rich canmin.geoscienceworld.org Ca-rich Zn-rich K-rich mineralatlas.com Jambor, 1999 Mankayan Linked porphyry and lithocap parts of system; lithocap hosts HS ore Lepanto HS: >0.9 Mt Cu & 102 t Au Production FSE porphyry: % Cu & 1.3 g/t Au resource 1.2 to 0.9 Ma Mineralisation 1.4 Ma 2.2 to 1.8 Ma Victoria veins, g/t Au + Ag-Cu-Pb-Zn 13 to 12 Ma Cretaceous to Miocene Chang et al. (2011) 14

15 Porphyry, lithocap and HS mineralization Dickite ± kaolinite Quartz-alunite Dickite ± kaolinite 1 km Genetic relationship between porphyry and lithocap established (lateral flow to NW): alteration, dating, fluid inclusion, isotope geochemistry study Arribas et al. (1995), Mancano and Campbell (1995), Hedenquist et al. (1998) Chang et al. (2011) Alunite absorption peak at ~1480 nm shifts to higher values closer to intrusive centre Chang et al. (2011) 15

16 Alunite composition (LA-ICPMS) Sr Chang et al. (2011) Alunite composition (LA-ICPMS) Pb Chang et al. (2011) 16

17 4 km long Lithocap Decrease: Alunite Pb, Ag/Au Whole-rock (alunite-bearing only): Pb, Ag, Ag/Au, Hg, Te, As/Zn All whole rock: Te, As/Zn Increase: Alunite 1480 pk position Alunite La, La/Pb, Sr, Sr/Pb Enargite: Au, Te, Ba, Th, As/Sb Whole-rock (alunite-bearing only): La/Pb, Sr/Pb, Cu/Hg Mankayan lithocap and ore deposits - schematic cross section Chang et al. (2011) Innovation and Exploration Lithocaps Fluid Flow: vapour vs brine transport into lithocap Exploration: alunite 1480nm peak position, alunite geochemistry and filtered whole rock geochemistry vector to intrusion (heat source) and potential sites for HS/porphyry ore Green Rock Fluid Flow: metal dispersion related to H 2 S availability Exploration: epidote geochemsitry can detect productive porphyry deposits several km beyond the limits of conventional lithogeochemical sampling (outside pyrite halo) epidote texture and chemistry as vectoring tools fertility assessment tool Bingham Canyon, Utah 17

18 District, camp and deposit scale Footprints Geological, mineralogical and geochemical VHMS SEDEX Sediment-hosted Cu Sediment-hosted Au (poster) Epithermal Au-Ag Porphyry Cu-Au-Mo Gemmell (2007) 18