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Book Chapter

Mass Change Profiles in the Footwall of the Kidd Creek Orebody

By
E. M. Marnie Muirhead
E. M. Marnie Muirhead
Newmont Exploration Limited, P.O. Box 388, Valmy, Nevada 89438
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R. W. Hutchinson
R. W. Hutchinson
Department of Geology and Geological Engineering, Colorado School of Mines, Golden, Colorado 80401
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Published:
January 01, 1999

Abstract

The footwall to the Kidd Creek orebody comprises dominantly rhyolite volcaniclastic rocks of lapilli- to block-sized fragments and massive rhyolite flows. The deposit overlies a broad, conformable zone of alteration characterized by laterally extensive sericite and Mg-rich chlorite alteration, and locally, by strong silicification and Fe-rich chlorite alteration. Pervasive silicification of the footwall rhyolites has largely converted these rocks to fine-grained quartz. Sericite and chlorite have replaced the fine-grained, tuffa-ceous matrix of the fragmental rocks and occur as fracture fillings in the brecciated massive rhyolite flows. Mass change calculations employing the method of immobile elements delineate two broadly conformable zones of alteration: one immediately beneath the massive sulfide lenses (zone I), and the other a zone of weaker alteration 50 to 100 m stratigraphically below the lenses (zone II). Zone I is characterized by moderate to strong concentrations of SiO2 and FeO and a decrease in K2O. Zone II is characterized by concentrations of MgO and K2O. Both zones are strongly depleted in Na2O and CaO. Distinct trends of Fe increase adjacent to the ore lenses (zone I) and Mg increase at depth (zone II) are interpreted to reflect zones of high- and low-temperature fluid flow beneath the massive sulfide lenses. These zones follow the orebodies downplunge for more than 2 km and define a narrow corridor of focused hy-drothermal fluid flow along the original axis of the Kidd Creek graben.

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Contents

Economic Geology Monograph Series

The Giant Kidd Creek Volcanogenic Massive Sulfide Deposit, Western Abitibi Subprovince, Canada

Mark D. Hannington
Mark D. Hannington
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C. Tucker Barrie
C. Tucker Barrie
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Society of Economic Geologists
Volume
10
ISBN electronic:
9781629490052
Publication date:
January 01, 1999

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