1. G EOL 5320 A DVANCED I GNEOUS AND M ETAMORPHIC P ETROLOGY Modeling the Petrology and PGE Reef Mineralization of the Sonju Lake Intrusion December 7, 2009

2. Sonju Lake Intrusion

3. TheSonjuLakeIntrusion From MGS Map M-71 (Miller et al., 1989)

4. Leucogranite Quartz ferromonzonite Apatitic olivine ferromonzodiorite Apatite olivine ferrodiorite Ol-bearing oxide gabbro Ol-bearing gabbro Troctolite- augite troctolite Dunite Melatroctolite PCFOAg PCFOAh PCFoi PC(O)fi POcfi O OP Modal Rock Names Cumulus Code Cumulus Mineral Mode Modal Variations Modal Variation and Cumulus Texture

5. Cryptic Variation

6. 1 km >20 km >10 km Sheet-like Geometry of the Sonju Lake Intrusion Estimation of Bulk Composition Becomes a 1-dimensional problem

7. SiO247.6 TiO22.28 Al2O314.0 FeOt14.7 MnO0.21 MgO8.3 CaO9.4 Na2O2.47 K2O0.55 P2O50.30 Volatiles0.20 Total100.0 mg# 50.2 Sc34 V192 Cr111 Co75 Ni185 Rb20 Sr233 Ba171 Y20 Zr114 Nb17 Hf3.1 La14.7 Ce33.4 Sm 4.1 Eu1.6 Tb0.8 Yb2.1 Lu.32 Bulk Intrusion Composition = Parent Magma = moderately evolved olivine tholeiitic basalt From Miller and Chandler (1998) and Miller and Ripley (1997) Liquid Line of Descent Calculated by summing composition of rock column above a specific horizon

8. Fractional Crystallization Modelling CHAOS 2 (NIELSEN, 1990) Model Parameters : fO2 = -2 log QFM; trapped liquid = 20%

10. 0 100 200 300 400 500 600 Cu (ppm) Discovery of Stratiform PGE Mineralization Skaergaard Intrusion Feb. 1999

11. PGEReef Outcrop Sampling

12. From Miller (1999) SLI Chemostratigraphy

14. Evolution of Sulfide in the Sonju Lake Intrusion

15. Exploration Drilling by FranconiaMinerals July 2002

16. 1 cm Core Logging and Sampling Sampling Regime Phase 1 – 1’ sample every 10’ Phase 1- continuous 1’ across PMZ 423 Total Whole Rock Analyses Plagioclase 65-73%

17. Detailed Geochemical Profiling of the PMZ

18. SL02-1 Cu-Pd Ratios Precious Metals Zone (PMZ) Meters above Cu-Au break SL02-1 Pd (ppb) Cu/Pd after Barnes et al. (1993)

19. PMZ Metallogenesis What was the PGE mineralizing agent? Cu-Fe Sulfide - close physical association of PGM and “cumulus” chalcopyrite Why the paucity of sulfide in the PMZ? Sulfide dissolution by deuteric and low-T hydrothermal fluids – dissolution and replacement textures in sulfide associated with silicate alteration; secondary pyrite above PMZ Are the stratigraphic variations in grade primary? Yes for Pd & Pt, not for Cu and Au – Pd and Pt concentrations correlate to subtle silicate layering; textural evidence of unreactive PGM; experimental evidence of Au and Cu mobility in oxidizing fluids

20. PGE Mineralizing Agent? Cu-Fe Sulfide? Fe-Ti Oxide??? Data from SL02-1 PMZ 0 to 105m below Cu-Au Break

21. Meters above Cu-Au break Precious Metals Zone (PMZ) “Cumulus” Sulfide in the PMZ SL02-1 SL02-2 SL02-3 100 um Bn Cp

22. Paucity of Sulfide in PMZ? Uralitized Augite PGM Chl-ActUralite

23. Mobility of Sulfide

24. Desulfurization and Oxidation of Cu Sulfide

25. Are Metal Offsets Primary? Kinetic Model Preservation of variable degrees of disequilibrium during sulfide liquation Controls on Equilibrium Sulf/Sil distribution coefficient Diffusivity of metals in silicate melt Nucleation density of sulfide droplet Size/Growth rates of sulfide droplets Settling rate of sulfide (strain rate of silicate melt)

26. Relationship of PGE to Modal Variations in the PMZ Plagioclase Augite Fe-Ti Oxide

27. From Andersen et al. (1998) Correlation of Leucocratic Gabbro to Skaergaard Platinova Reefs

28. Restite PGM / Resorbed Sulfide Chlorite- Actinolite Cp Augite Pd-Sb 50 um Plagioclase Pd-Sb Cp Actinolite Augite 50 um Cp Pt-Pd-As 50 um

29. Correlation by Secondary Pd Peaks

30. Mineralization Model Mineralization Model “Downer” Stage Upgrading sulfide in intercumulus magma Initial sulfide saturation PGE scavenging of magma column complete

31. D sulf/sil ~10 4 -10 8 Rapid Diffusion D sulf/sil ~10 2 Slow Diffusion

32. Mineralization Model Mineralization Model “Upper” Stage

33. ClassicOffsetSkaergaard-type Meters above sulfide increase Comparing the SLI to other PGE reefs

34. IF ONLY.....

35. PGE reefs

36. PELE – MELTS-based Modeling Program developed by Alan Boudreau

37. MH - magnetite-hematite 4 Fe 3 O 4 + O 2 = 6 Fe 2 O 3 NiNiO nickel-nickel oxide 2 Ni + O 2 = 2 NiO FMQ fayalite-magnetite-qtz 3 Fe 2 SiO 4 +O 2 = 2 Fe 3 O 4 + 3 SiO 2 WM wustite -magnetite 3 Fe 1-x O + O 2 ~ Fe 3 O 4 IW iron - wustite 2(1-x) Fe + O 2 = 2 Fe 1-x O QIF quartz-iron-fayalite 2 Fe + SiO 2 + O 2 = Fe 2 SiO 4 Common fO2 range for magmatic conditions arc non-arc Oxygen Buffers