AURIFEROUS VOLCANOGENIC MASSIVE SULPHIDE, A NEW TYPE OF GOLD DEPOSIT IN THE GUIANA SHIELD?

Guiraud James1, Alain Tremblay1, Michel Jebrak1, Pierre-Simon Ross2 and Lefrançois Rock3, (1)University of Quebec at Montreal, Earth Sciences, Montreal, QC, Canada, (2)Institut national de la recherche scientifique, Centre Eau Terre Environnement, Quebec City, QC, Canada, (3)Columbus Gold Corp., Longueuil, QC, Canada

Contact First Author: Guiraud James; guiraud.james@courrier.uqam.ca

Abstract ID#: 34542

 

English Abstract:
In French Guiana, the “Montagne d’Or” gold mineralization (4.3 Moz Au at 1 g/t), property of Columbus Gold Corp., is hosted by the northern branch of the Proterozoic Paramaca Greenstone Belt (PGB). The PGB represents the remnant of a volcanic island-arc sequence formed between 2.18 to 2.13 Ga, during the Transamazonian orogeny. The main tectonic event has structured the two branches of the PGB, merging together along an E-W orientation, which there are surrounded by diverse intrusions and metamorphic complexes. The geological characteristics of the “Montagne d’Or” deposit contrast with those of other gold deposits of the area which comprise clastic-hosted, porphyry systems, shear zones, and lateritic enrichments.

The “Montagne d’Or” deposit is hosted by a bimodal volcanic and volcaniclastic sequence bounded to the south by a major E-W shear zone. These volcanic rocks are affected by a penetrative E-W trending and south-dipping regional schistosity. The rock sequence is facing south and is dominated by calc-alkaline felsic lithologies interbedded and interdigitated with tholeiitic mafic rocks cross-cut by transitional to calc-alkaline intrusives. Some mafic flows are pillowed and few graded felsic volcaniclastic sequences were found, indicating a submarine environment. The Au mineralization is associated with pyrite, pyrrhotite and chalcopyrite with minor sphalerite, magnetite and arsenopyrite. The sulphides show three distinct aspects, (1) stratiform disseminations, (2) stockworks or veinlets, and (3) structurally-transposed layers of semi-massive sulphides. Visible gold occurs within chlorite-sericite-rich zones and is spatially related to sulphides.

Based on these characteristics, the “Montagne d’Or” mineralization is thought to have a syn-genetic origin and is currently interpreted as the first occurrence of auriferous VMS in the PGB. However, remobilisation of sulphides may have occurred during metamorphism and tectonic deformation.

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