Major regional factors favouring large size, high hypogene grade, elevated gold content and supergene oxidation and enrichment of porphyry copper deposits
by
Richard H Sillitoe, Consultant Geologist., 27 West Hill Park, Highgate Village, London, N6 6ND, UK.
in Porter, T.M. (Ed), 1998 - Porphyry and Hydrothermal Copper and Gold Deposits: A Global Perspective; PGC Publishing, Adelaide, pp 21-34.
ABSTRACT
Porphyry copper deposits occur in volcano-plutonic arcs worldwide: however, superior orebodies, whether due to large size and high hypogene grade, elevated gold content or well developed supergene oxidation and/or enrichment, are confined to restricted arc segments. regional factors are believed to be the fundamental controls on the location of these superior porphyry copper deposits. Large, high grade hypogene deposits develop in arcs built on continental crust that undergoes compressive tectonism and high rates of uplift and exhumation during intrusion and mineralisation. Gold rich deposits are generated in arc segments or individual districts where highly oxidised magma is emplaced. Oxidation and enrichment are optimised where uplift of deposits takes place under semi-arid climatic conditions, with several million years being required for the development of mature supergene profiles.
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