OCGS Seminar - Sarah Gleeson, HS Robinson Tour

2011-12 OCGC GEOSCIENCE SEMINARS

University of Ottawa, Department of Earth Sciences

Monday, March 12, 4:00pm, Marion Hall, Room 127

DR. SARAH A. GLEESON

2011-2012 Howard Street Robinson Lecturer

Geological Association of Canada

“The Genesis of the Carbonate Hosted Pb-Zn Deposits

of the Mackenzie Mountains”

 

The Mackenzie Mountains in northwestern Canada were formed during the Late-Cretaceous to Tertiary Laramide orogeny. Five main stratigraphic packages can be identified within the orogenic belt; the Mesoproterozoic Mackenzie Mountain Supergroup, the Neoproterozoic Windermere Supergroup, the Proterozoic-Cambrian succession, the Upper Cambrian-Silurian units and finally, the Devonianacrbonate platform successions that are the equivalent to the deep water clastic sediments preserved in the Selwyn Basin. The Neoproterozoic to Devonian carbonate sequences of the Mackenzie Mountains host over 200 Zn-Pb showings in an area of 70,000km3, including the Neoproterozoic-hosted Gayna River deposit.

The Gayna River deposit formed as the result of mixing of a hot (≈200°C) saline metal-bearing fluid with a cooler, more dilute fluid. This second fluid was carrying reduced S generated by thermochemical sulphate reduction of local evaporites. The geological setting suggests that the formation of Gayna River is related to Cordilleran compressional events and it is an example of an unusually hot Mississippi Valley type deposit. Geological, geochemical and isotopic studies have also been carried out on smaller regional showings. Fluid inclusion microthermometric data suggest that these mineralizing fluids originated as evaporated seawater and had a modal temperature of about 180°C and salinities that ranged from 10-30 wt%