Abstract

Systematic temporal variations in the distribution of several important groups of metal deposits reflect the cyclic aggregation and breakup of large continents. In particular, metal deposits that form in continental basins or are associated with anorogenic magmatism were extraordinarily abundant in the Middle Proterozoic (2.0 to 1.4 Ga), corresponding to the assembly of the first large continents. It is important to note that peaks in the abundance of continental metal deposits also coincide with a postulated Late Proterozoic supercontinent (1.0 to 0.8 Ga) and the near maximum extent of Pangea. In contrast, metal deposits that form, or are preserved, in convergent-margin orogens were most abundant in the late Archean (2.9 to 2.6 Ga), corresponding to a period of high global heat flow and rapid stabilization of continental crust, and the past 200 m.y., which corresponds to the present tectonic cycle. Similar mineralization was also present, albeit less abundant, in Early Proterozoic orogens, as well as in Late Proterozoic and Phanerozoic orogens. Future metals exploration may benefit from the application of sequence stratigraphy, as used by the oil industry, to recognize such cycles, particularly in the Precambrian rock record.

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