2 PHASE SYNTECTONIC GOLD MINERALIZATION AND BARITE REMOBILIZATION WITHIN THE MAIN ORE-BODY OF THE GOLDEN-GIANT MINE, HEMLO, ONTARIO, CANADA

Structural analysis of the central part of the Hemlo gold deposit in t he Hemlo-Heron Bay greenstone belt has revealed four generations of de formation structures (D1-D4). The second (D2) and fourth (D4) deformat ions significantly influenced the orebody and controlled the localizat ion of gold mineralization. Development of D3 dextral shearing during retrogressive conditions resulted in strain partitioning around the fe ldspathic orebody, such that this deposit appears to be controlled by the Hemlo Shear Zone. However, the orebody dominantly preserves vertic al D2 parasitic folds rather than D3 structures. The earliest occurren ce of gold is with molybdenite as S1 inclusion trails in vanadium-musc ovite grains that grew during D2. This suggests that the gold deposit was emplaced by at least early D2. Syngenetic banded barite was partia lly dissolved, transported and redeposited during each deformation eve nt, and in particular in association with brittle deformation that occ urred during D4. Microstructural relationships indicate two distinct g enerations of gold: the first generation is associated with molybdenit e and potassic alteration and was deposited before or early in D2 duri ng progressive amphibolite-facies metamorphism. The second generation formed by redistribution and concentration of gold, together with stib nite in ductile-brittle D4 structures after peak metamorphic condition s.