Abstract

Quartz diorite dikes in the footwall of the 1.85 Ga Sudbury impact structure were emplaced within fractures formed during hypervelocity impact. The anisotropy of magnetic susceptibility of the radial Copper Cliff dike reveals a steeply dipping foliation that is counterclockwise oblique along both the eastern and western sides of the dike, and a steeply northwest plunging lineation. The data suggest that the Copper Cliff dike acted as a melt-filled dextral transfer fault during collapse of the inner rim of the central peak ring of the impact crater to accommodate ultrahigh-strain-rate displacements. Peak-ring rim collapse may have caused sulfide-rich melts to be injected into the Copper Cliff dike, leading to the formation of large Cu–Ni–platinum group element deposits.

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