Abstract

Roof pendants of a late Aphebian (~1800 m.y.) volcano–sedimentary complex, within Hudsonian granites, outcrop on the eastern shore of Great Bear Lake. The volcano–sedimentary complex is similar to, and may be correlated with, the Echo Bay Group which outcrops farther to the north.The volcanic rocks are interbedded with immature volcanoclastic sedimentary rocks and with thinner units of calcargillite and dolomite. A unit of conglomerate, tuff, and siltstone, previously correlated with the Cameron Bay Group, is assigned to the 'Balachey Unit', until its relationships with other groups in the area are more clearly understood.Hudsonian granitic stocks and batholiths (~ 1750 m.y.) intruded the complex. Sharp contacts and narrow aureoles characterize these as high level intrusions. Zones of sulfide replacement are common in the aureoles. Porphyry dikes and stocks of similar age to the granites and rare, pegmatitic magnetite–apatite–actinolite bodies, also intrude the volcano–sedimentary complex.Three sets of diabase intrusions are identified, and related to three distinct fault directions. Giant quartz veins and mineralization of the U–Ag–Ni, Co arsenide – Bi type are found in zones of northeast-striking dextral faults.The volcano–sedimentary complex is interpreted as the molasse phase of the rising orogen of the Coronation Geosyncline, and is related to earlier deposits (the Snare and Epworth Groups) closer to the craton in the eastern part of the geosyncline.

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