Study of the third dimension in the Thunder Bay silver veins : fluid inclusion and stable isotope results

Abstract

"Historic drill core from the Shuniah Mine and more recent drill core from the Keystone and Porcupine Mines have provided the basis for a study of these past silver-producing veins as a function of depth. Precipitation was initiated from a boiling fluid at temperatures in excess of 370 deg.C. Cooling of the fluid and precipitation of calcite and sulfides followed generally at 100 deg. C. Several episodes of deposition separated by fracturing events are evidenced. From fluid boiling temperatures the depth of emplacement for the veins is 1 km with the pressure regime alternating between hydrostatic and lithostatic. The ore-depositing solutions appear, therefore, to have arisen from depth and deposited their ores in proximity to diabase sills, which cap the various vein systems, in response to hydrologic factors." -- from abstract.