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Mineralium Deposita

, Volume 42, Issue 6, pp 627–637 | Cite as

Three mechanisms of ore re-mobilisation during amphibolite facies metamorphism at the Montauban Zn–Pb–Au–Ag deposit

  • Andrew G. Tomkins
Article

Abstract

The relative importance of mechanical re-mobilisation, hydrothermal dissolution and re-precipitation, and sulphide melting in controlling redistribution of metals during concurrent metamorphism and deformation is evaluated at the middle amphibolite facies Montauban deposit in Canada. As at many other deposits, ductile deformation was important in driving mechanical re-mobilisation of massive sulphides from limb regions into hinge regions of large-scale folds and is thus the most important for controlling the economics of Pb and Zn distribution. Two possible stages of hydrothermally driven re-mobilisation are discussed, each of which produces characteristically different alteration assemblages. Prograde hydrothermal re-mobilisation is driven by pyrite de-sulphidation and concurrent chlorite dehydration and is thus an internally driven process. At Montauban, the H2S-rich fluid generated through this process allowed re-mobilisation of gold into the wall rock, where it was deposited in response to sulphidation of Fe Mg silicates. Retrograde hydrothermal re-mobilisation is an externally driven process, whereby large volumes of fluids from outside the deposit may dissolve and re-precipitate metals, and cause hydration of silicate minerals. This second hydrothermally driven process is not recognised at Montauban. Sulphide melting occurred as temperatures neared the peak metamorphic conditions. Melting initiated in the massive sulphides through arsenopyrite breakdown, and a small volume of melt was subsequently re-mobilised into the wall rock. Trace element partitioning and fractional crystallisation of this melt generated a precious metal-rich fractionate, which remained mobile until well after peak metamorphism. Thus, prograde hydrothermal re-mobilisation and sulphide melting were the most important mechanisms for controlling the distribution of Au and Ag.

Keywords

Mechanical re-mobilisation Hydrothermal re-mobilisation Ore metamorphism Sulphide melt Grenville province 

Notes

Acknowledgment

I would like to particularly thank David Pattison at the University of Calgary for both the opportunity to do a post-doctoral fellowship and the many enjoyable discussions. Brian Marshall and Michel Gauthier are thanked for their reviews and Associate Editor Pat Williams is thanked for his comments, which helped to improve this paper. Jean Bernard was very helpful in giving a tour of the Montauban deposit and assisting with selecting drill core samples. Funding for this project was provided by an Alberta Ingenuity Fellowship and a Monash University Fellowship to the author.

References

  1. Alcock FJ, (1930) Zinc and lead deposits of Canada. Geol Surv Canada, Economic Geology Series 8Google Scholar
  2. Barnes RG (1987) Multi-stage mobilization and remobilization of mineralization in the Broken Hill Block, Australia. Ore Geol Rev 2:247–267CrossRefGoogle Scholar
  3. Bernier L, Pouliot G, MacLean WH (1987) Geology and metamorphism of the North Montauban Gold Zone: a metamorphosed polymetallic exhalative deposit, Grenville Province, Quebec. Econ Geol 82:2076–2090Google Scholar
  4. Bryndzia LT, Kleppa OJ (1988) High-temperature reaction calorimetry of solid and liquid phases in the quasi-binary system Ag2S–Sb2S3. Geochim Cosmochim Acta 52:167–176CrossRefGoogle Scholar
  5. Connolly JAD, Cesare B (1993) C–O–H–S fluid composition and oxygen fugacity in graphitic metapelites. J Met Geol 11:379–388CrossRefGoogle Scholar
  6. Franklin JM, Gibson HL, Jonasson IR, Galley AG (2005) Volcanogenic massive sulfide deposits. In: Hedenquist JW, Thompson JFH, Goldfarb RJ, Richards JP (eds) Economic Geology, 100th anniversary volume, 1905–2005. pp 523–560Google Scholar
  7. Friesen RG, Pierce GA, Weeks RM (1982) Geology of the Geco base metal deposit. In: Hutchinson RW, Spence CD, Franklin JM (eds) Precambrian sulfide deposits. Geololgical Association of Canada, Special Paper 25, pp 343–363Google Scholar
  8. Gammons CH, Barnes HL (1989) The solubility of Ag2S in near-neutral aqueous sulfide solutions at 25 to 300°C. Geochim Cosmochim Acta 53:279–290CrossRefGoogle Scholar
  9. Gower CF, Krogh TE (2002) A U–Pb geochronological review of the Proterozoic history of the Eastern Grenville Province. Can J Earth Sci 39:795–829CrossRefGoogle Scholar
  10. Hemley JJ, Cygan GL, Fein JB, Robinson GR, d’Angelo WM (1992) Hydrothermal ore-forming processes in the light of studies in rock-buffered systems: I. Iron–copper–zinc–lead sulfide solubility relations. Econ Geol 87:1–22Google Scholar
  11. Hofstra AH, Leventhal JS, Northrop HR, Landis GP, Rye RO, Birak DJ, Dahl AR (1991) Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: chemical-reaction-path modeling of ore-depositional processes documented in the Jerritt Canyon district, Nevada. Geology 19:36–40CrossRefGoogle Scholar
  12. Jourdain V (1993) Geologie des amas sulfures auriferes de la Province de Grenville. Unpublished Ph.D. thesis. Universite du Quebec a Montreal, p 139Google Scholar
  13. Jourdain V, Roy DW, Simard J-M (1987) Stratigraphy and structural analysis of the north gold zone at Montauban-les-mines, Quebec. Can Inst Min Bull 80:61–66Google Scholar
  14. Larson L, Webber RR (1977) Chemical and petrographic variations in rhyolitic zones of the Noranda area, Quebec. Can Inst Min Metall Bull 70:80–93Google Scholar
  15. Loucks RR, Mavrogenes JA (1999) Gold solubility in supercritical hydrothermal brines measured in synthetic fluid inclusions. Science 284:2159–2163CrossRefGoogle Scholar
  16. Marshall B, Gilligan LB (1993) Remobilization, syn-tectonic processes and massive sulfide deposits. Ore Geol Rev 8:39–64CrossRefGoogle Scholar
  17. Marshall B, Vokes FM, Larocque ACL (2000) Regional metamorphic remobilization: upgrading and formation of ore deposits. In: Spry PG, Marshall B, Vokes FM (eds) Metamorphosed and metamorphogenic ore deposits. Rev Econ Geol 16:19–38Google Scholar
  18. Mountain BW, Seward TM (2003) Hydrosulfide/sulfide complexes of copper(I): Experimental confirmation of the stoichiometry and stability of Cu(HS)2− to elevated temperatures. Geochim Cosmochim Acta 67:3005–3014CrossRefGoogle Scholar
  19. Neall FB, Phillips NG (1987) Fluid-rock interaction in an Archean hydrothermal gold deposit: a thermodynamic model for the Hunt mine, Kambalda. Econ Geol 82:1679–1694Google Scholar
  20. Newberry SP, Carswell JT, Allnutt SL, Mutton AJ (1993) The Dugald River zinc–lead–silver deposit; an example of a tectonised Proterozoic stratabound sulphide deposit. In: Matthew IG (ed) World Zinc ‘93; Proceedings of the International Symposium on Zinc. Aust Inst Min Met, pp 7–21Google Scholar
  21. Okamoto H, Massalski TB (1986) Ag–Au (silver–gold). In: Massalski TB, Murray JL, Bennet LH, Baker H, (eds) Binary Alloy Phase Diagrams, vol 1. American Society for Metals, Ohio, p 7Google Scholar
  22. Osborne FF (1939) The Montauban mineralized zone. Econ Geol 34:712–726Google Scholar
  23. Sangster DF (1972) Precambrian volcanogenic massive sulfide deposits in Canada: a review. Geol Surv Can Paper 72–22, 44 pagesGoogle Scholar
  24. Sparks HA, Mavrogenes JA (2005) Sulfide melt inclusions as evidence for the existence of a sulfide partial melt at Broken Hill, Australia. Econ Geol 100:773–779CrossRefGoogle Scholar
  25. Spear FS (1993) Metamorphic phase equilibria and pressure–temperature–time paths. Mineralogical society of America, Washington, DC, p 799Google Scholar
  26. Stamatelopoulou-Seymour K, MacLean WH (1977) The geochemistry of possible metavolcanic rocks and their relationships to mineralization at Montauban-les-Mines, Quebec. Can J Earth Sci 14:2440–2452Google Scholar
  27. Stamatelopoulou-Seymour K, MacLean WH (1984) Metamorphosed volcanogenic ores at Montauban, Grenville Province, Quebec. Can Miner 22:595–604Google Scholar
  28. Tomkins AG, Mavrogenes JA (2002) Mobilization of gold as a polymetallic melt during pelite anatexis at the Challenger gold deposit, South Australia: a metamorphosed Archean deposit. Econ Geol 97:1249–1271CrossRefGoogle Scholar
  29. Tomkins AG, Pattison DRM, Zaleski E (2004) The Hemlo gold deposit, Ontario: an example of melting and mobilization of a precious metal–sulfosalt assemblage during amphibolite facies metamorphism and deformation. Econ Geol 99:1063–1084CrossRefGoogle Scholar
  30. Tomkins AG, Frost BR, Pattison DRM (2006) Arsenopyrite melting during metamorphism of sulfide ore deposits. Can Miner 44:1025–1042Google Scholar
  31. Tomkins AG, Pattison DRM, Frost BR (2007) On the initiation of metamorphic sulfide anatexis. J Pet 48:511–535CrossRefGoogle Scholar
  32. Toulmin P, Barton PB (1964) A thermodynamic study of pyrite and pyrrhotite. Geochim Cosmochim Acta 56:227–243Google Scholar
  33. Tracy RJ, Robinson P (1988) Silicate–sulfide–oxide–fluid reactions in granulite-grade pelitic rocks, central Massachusetts. Am J Sci 288A:45–74Google Scholar
  34. Vokes FM (1971) Some aspects of the regional metamorphic mobilization of pre-existing sulfide deposits. Miner Depos 6:122–129CrossRefGoogle Scholar
  35. Williams PJ (1990a) The gold deposit at Calumet, Quebec (Grenville Province): an example of the problem of metamorphic versus metamorphosed ore. In: Spry PG, Bryndzia LT (eds) Regional Metamorphism of Ore Deposits. Coronet Books, Utrecht, Netherlands, p 1–25Google Scholar
  36. Williams PJ (1990b) Evidence for a late metamorphic origin of disseminated gold mineralization in Grenville gneisses at Calumet, Quebec. Econ Geol 85:164–171CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of Geology and GeophysicsUniversity of CalgaryCalgaryCanada
  2. 2.School of GeosciencesMonash UniversityMelbourneAustralia

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