Geology, geochemistry, and origin of the gold deposits of the Yellowknife District, Northwest Territories

Abstract
The geology and mineralogy of the gold-quartz deposits of the Yellowknife district are described together with an exhaustive study of the geochemistry of the country rocks and alteration zones and the geochemistry and origin of the ore and gangue minerals, and underground waters. The deposits occur as quartz lenses in extensive chlorite schist zones (shear zones) cutting Precambrian greenstones, and as quartz lenses developed along structures in highly folded and contorted Precambrian sedimentary rocks. Those in the greenstones represent concentrations of silica, carbon dioxide, sulphur, arsenic, antimony, gold, silver and numerous other metallic elements. Those in the sediments are mainly concentrations of silica, sulphur, boron, iron, lead, zinc, gold and silver. Chemical evidence is presented to show that during metamorphism some of the carbon dioxide, water, sulphur, arsenic, gold, silver and other metallic elements in the greenstones were mobilized and migrated by diffusion into the shear-zone systems. In the shear zones, water and carbon dioxide reacted with the amphibolite rock producing extensive widths of chlorite and chloritecarbonate- sericite schist. Silica, iron, potassium and other elements and compounds were mobilized and migrated into dilatant zones in the shear zones where they were precipitated to form the mineralized gold-quartz lenses and veins. In the sediments, silica, boron, sulphur and various metallic elements were mobilized during metamorphism and migrated into, and were precipitated in, dilatant zones in faults, fractures, and drag-folds.

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