PALEOHYDROGEOLOGY OF THE CANADIAN ROCKIES AND ORIGINS OF BRINES, PB-ZN DEPOSITS AND DOLOMITIZATION IN THE WESTERN CANADA SEDIMENTARY BASIN

Results of stable isotopic and fluid-inclusion studies of Cambrian car bonate units in the southern Canadian Rockies indicate that, during th e Late Devonian or Early Mississippian, a warm brine migrated from mio geoclinal shales in the western part of the Western Canada Sedimentary Basin into the eastern carbonate sequences. This fluid had a temperat ure of 150 +/- 25-degrees-C, salinity values of 20 to 25 equivalent wt % NaCl, and isotopic values of deltaO-18 = -7 parts per thousand to 0 parts per thousand, delta-C-13 = -1 parts per thousand +/- -2 parts pe r thousand deltaD = -70 parts per thousand +/- 19 parts per thousand, and Sr-87/Sr-86 >0.710. The fluids formed large bodies of coarse, spar ry dolomite, as well as Pb-Zn, magnesite and talc mineralizations in t he Cambrian units. It is probable that this event was also responsible for the development of Pb-Zn mineralization (specifically Pine Point) in the Devonian units, as well as a compoent of the present-day basin al brines in the basin.