Structural Features of Porphyry Copper Deposits and the Tectonic Evolution of Continents

CIM Bulletin, 1972

The petrology and mineralogy of porphyry copper deposits are thoroughly described in recent literature and cited as the definitive characteristics for this type of deposit. The magmatic-hydrothermal aspect of genesis is also dealt with in detail. However, descriptions of their internal structure and regional setting are not as rigorous, and the genesis of this structure is simply stated as the release of high fluid press ures in a cooling magma emplaced along large fault zones. Genetic relationships between internal structur.e, regional setting and the tectonic evolution of continents has been alluded to infrequently in the past, but can now be considered together within the developing concept of orogeny at the margins of drifting crustal plates. R. W. HODDER V. F. HOLLISTER R. W. HODDER is a graduate of Queen's University and The University of California at Berkeley. He worked as an exploration geologist in North and South America for twelve years before joinin~ the staff of the Department of Geology, The University of Western Ontario, in 1970. V. F. HOLLISTER is a graduate of The University of California at Berkeley. He has had more than twenty years' experience in exploration throughout the world, including extended periods in South America and the western United States. He has been with Duval Corporation for the past seven years. PAPER PRESENTED: at the 73rd Annual General Meeting of the CIM, Quebec City, April, 1971. KEYWORDS: Geology, Ore deposits, Structural geology, Porphyry copper deposits, Tectonics, Continents, Cordilleran Orogen, Eastern Fold Belt, Omenica Crystalline Belt, Coast Plutonic Complex, Interior Zone, Insular Fold Belt, Crustal evolution, Faulting. CIM TRANSACTIONS: Vol. LXXV, pp. 23-27, 1972. ( CIM) Bulletin for February, 1972 Tensional structures, on both local and regional scale, and a Triassic to Tertiary age are described for porphyry copper deposits. We contend that such structure and age are distinct and unifying characteristics for this type of deposit and are genetically related to major crustal movements. British Columbia has porphyry copper deposits contemporaneous with plutons 180 to 200 million years old and 40 to 60 million years old. The former age group correlates with early stages of the continent's westward drift, and the latter group with a change in tectonic style during late development of the Canadian Cordillera. Hence, one can in British Columbia reflect on the genesis of a deposit's structure in the broader context of tectonic evolution. Such consideration should lead to more definitive criteria for area selection in exploration.

Keywords: British Columbia, British Columbia, Mesozoic, plate tectonics, porphyry copper, CIM, Deposits, Evolution, Fault, Faults, Porphyry copper deposit, Porphyry copper deposits, Structure, Tectonics