AUTHORS: Richard Goldfarb, David Groves, Robert Kerrich, David Leach
The temporal distribution of mineral deposits reflects both their position within the supercontinent cycle and the secular evolution of Earth processes. Thus many patterns for precious and base-metal deposit formation show a broad association with periods of supercontinent amalgamation or break-up. Superimposed on these patterns is the susceptibility of ore provinces to preservation or erosion, which itself is controlled by progressive cooling of Earth, the change from plume- to subduction-dominated tectonics, and ore formation depth. Orogenic gold and VMS deposits show episodic patterns correlating with the formation of Kenorland, Columbia, Gondwana, and Laurasia; the changing style of plate tectonics on a cooling planet explains a lack of Rodinian gold. Porphyry and epithermal deposits also formed in convergent margins, but at shallower crustal levels, thus having a low preservation potential over geologic time. A large post-Triassic, circum-Pacific gold endowment is supportive of Pangea break-up overlapping growth of a new supercontinent. Additional evidence of supercontinent growth is provided in foreland basins by unconformity uranium on Columbia and MVT deposits of Pangea. Periods and locations of supercontinent break-up are more difficult to define by a consistent ore deposit pattern. SEDEX deposits were associated with intracontinental rifting on Columbia, but younger deposits occur only along passive margin rifts. Giant magmatic Ni-Cu ores tend to show a temporal association with Columbia, Rodinia, and Pangea break-up. Secular trends of ore deposits clearly relate to changes in the supercontinent cycle, but there is no smoking gun from the ore deposits world that can consistently define supercontinent events.
KEYWORDS: metallogeny, tectonics, supercontinent, secular variation
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