Isotope Mapping Around the Kidd Creek Deposit, Ontario: Application to Exploration and Comparison with Other Geochemical Indicator

Exploration & Mining Geology, Vol. 4, No. 3, 1995
DAVID L. HUSTON, BRUCE E. TAYLOR, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada, WOUTER BLEEKER*, Falconbridge Ltd., P.O. Box 1140, Timmins, Ontario P4N 7H9, Canada, BOB STEWART, Falconbridge Ltd., P.O. Box 40, Falconbridge, Ontario P0M 1S0, Canada, RON COOK, Falconbridge Ltd., Kidd Creek Division, P.O. Bag 2002, Timmins, Ontario P4N 7K1, Canada, ELIZABETH R. KOOPMAN, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
Abstract Detailed oxygen isotope mapping of rhyolites in and around the Kidd Creek mine indicates that the orebodies are associated with relatively low (<12‰) whole rock values that extend up to 200 m laterally from ore. The zone of low d 18 O values is overlain stratigraphically by a carapace
of higher (>13‰) values that extends up to 1.5 km laterally from and 300 m to 500 m above ore.
Immediately above the stratigraphically highest orebody this carapace is cut by a zone of lower d 18 O values extending from the ore zone. Zones of higher d 18 O values also occur in massive rhyolite bodies that occur in the footwall of the orebodies. The zone of low d 18 O values partly coincides with a Na2O depletion anomaly associated with hydrothermal alteration, except that the Na2O depletion anomaly has a greater lateral extent, and the low d 18 O anomaly extends farther into the stratigraphic hanging wall. These data suggest that d 18 O mapping may detect hanging wall alteration above massive sul?de bodies more effectively than conventional lithogeochemistry. Zones of high d 18 O values, which de?ne zones through which large quantities of low-temperature hydrothermal ?uids have passed, may also have usefulness in exploration.
Oxygen isotope variations at Kidd Creek record three stages of a hydrothermal system that evolved in temperature with time, as follows: (1) an early, low-temperature event that produced rocks with high d 18 O values, (2) a high-temperature event that produced rocks with lower d 18 O values, and (3) a later, low-temperature event that also produced rocks with high d 18 O values. The high d 18 O signature of the massive rhyolite was recorded during early-stage, low temperature (<200°C) alteration, and was probably preserved owing to decreases in permeability associated with low-temperature silici?cation. The low d 18 O signature of cherty breccia and chloritite was recorded during the thermal peak at >300°C. High d 18 O values in the carapace above the deposit were recorded as the hydrothermal system waned.
Keywords: Kidd Creek Mine, Isotope mapping, Exploration, Geochemistry, Stratisgraphy, Oxygen isotope
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