Two marked periods of continental rifting can be identified in the geologic record. The younger of these led to the breakup of Pangea and has been attributed to subcontinental hot-spot activity. There is widespread evidence of an older late Proterozoic period of continental rifting that may have led to the breakup of a postulated proto-Pangea. These events appear to overlap in time with the assembly of continents into superconti-nents and can be explained in terms of heat dissipation from the mantle in situations where spreading centers are geographically remote from the central portions of supercontinents. The model provides an explanation for the shortlived nature of supercontinental assemblies and a conceptual framework within which the remarkable similarities of the late Proterozoic rock record—including major stratiform copper deposits—on various continents can be understood.

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