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Great Bear magmatic zone; epithermal; quartz veins; fluid inclusions
Abstract:
The Great Bear magmatic zone, Northwest Territories, hosts numerous giant quartz veins and stockwork zones. These zones can be up to 100 m wide and up to 10 km long, with two or more generations of quartz. A few of the giant quartz vein zones host base-metal +/- uranium mineralization, and many are proximal to mineralization, although some appear barren. Scanning electron microscope cathodoluminescence imaging shows the quartz veins have complex growth zones and a LA-ICP-MS trace element study shows that these zones are the result of Al and Li substitution in the quartz lattice. Oxygen isotopes (delta(18)O(qtz)) of the quartz veins vary within a single zone and between vein zones, but generally fall between +8 to +14.6 parts per thousand. (VSMOVV). Fluid inclusion homogenization temperatures and salinity data are also variable between zones, with the biggest difference between mineralized and non-mineralized zones. In total, fluid inclusions have homogenization temperatures ranging from 100 to 375 degrees C, with variable salinity. The fluids that created the giant quartz veins are epithermal in nature, and likely are a result of multiple fluid pulses and re-fracturing events.
