Lithospheric Fertilization and Mineralization by Arc Magmas: Genetic Links and Secular Differences Between Porphyry Copper ± Molybdenum ± Gold and Magmatic-Hydrothermal Iron Oxide Copper-Gold Deposits
Published:January 01, 2013
Jeremy P. Richards, A. Hamid Mumin, 2013. "Lithospheric Fertilization and Mineralization by Arc Magmas: Genetic Links and Secular Differences Between Porphyry Copper ± Molybdenum ± Gold and Magmatic-Hydrothermal Iron Oxide Copper-Gold Deposits", Tectonics, Metallogeny, and Discovery: The North American Cordillera and Similar Accretionary Settings, M. Colpron, T. Bissig, B. G. Rusk, J. F. H. Thompson
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Porphyry Cu ± Mo ± Au deposits (porphyry) and iron oxide copper-gold deposits formed by magmatic-hydrothermal systems (MH-IOCG) share many features, most notably enrichments in Fe, Cu, and Au, as well as an association with calc-alkaline to mildly alkaline magmas generated in orogenic (subduction to collision) and postorogenic tectonic settings. Differences include the predominance of Fe-sulfide minerals and widespread late-stage acidic alteration in porphyry deposits, compared with Fe-oxide minerals and more extensive near-neutral pH alteration in MH-IOCG deposits. They are also separated by temporal distribution, with MH-IOCG deposits predominantly forming in the Precambrian era and porphyry deposits predominantly forming...
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Tectonics, Metallogeny, and Discovery: The North American Cordillera and Similar Accretionary Settings
The northern Pacific Rim—for the purposes of this contribution—comprises the Mesozoic and Cenozoic magmatic-arc and associated terranes of eastern China, Korea, Japan, the Russian Far East, Alaska, Yukon, British Columbia, the western United States, and Mexico. This ~1,800-km-long segment of the Pacific Rim is marked by a broad spectrum of metallogenic environments and mining jurisdictions, which combine to dictate where and how exploration is conducted and the overriding character of any resulting discoveries.
This summary report commences with a brief metallogenic overview of the northern Pacific Rim, with particular attention paid to the world-class Mesozoic and Cenozoic ore deposits that define the region’s premier metallogenic provinces. This is followed by a summary of the relative attractiveness of the region’s various mining jurisdictions, as recorded by recent exploration activity. The major discoveries made along the northern Pacific Rim, particularly during the past half century, are then placed in this metallogenic and regulatory context as a basis for determining the successful exploration methodologies employed. This discovery track record is then used to predict what the future of exploration in this vast and varied region may hold.
Much of the northern Pacific Rim, from eastern China and the Russian Far East in the northwest through Alaska to western parts of Canada, the United States, and Mexico in the southeast (Fig. 1), is characterized by a complex array of oceanic, accretionary prism, magmatic arc, and back-arc basin terranes and associated microcontinental blocks accreted to the North China, Siberian, Hyperborean, and North American cratons, mainly during Mesozoic times (Coney et al., 1980; Campa and Coney, 1983; Kojima, 1989; Nokleberg et al., 2005; Yakubchuk, 2009). The metallogeny of these tectonic collages is dictated by various combinations of pre-, syn-, and postaccretion ore-forming events, the last of which are generally preeminent, except in British Columbia (Nokleberg et al., 2005; Nelson and Colpron, 2007).
Although the Meso-Cenozoic metallogeny of the northwestern and northeastern Pacific quadrants displays some similarities, it is the contrasts that are most marked. The main contrasts stem from the preeminence of tin, tungsten, and antimony in eastern China, Korea, Japan, and the Russian Far East and of copper and silver in Western Canada, the conterminous United States, and Mexico. Nonetheless, both the northwestern and northeastern Pacific quadrants are exceptionally well endowed with gold and molybdenum deposits. The northeasternmost Russian Far East, Alaska, and Yukon Territory display elements of both northwestern and northeastern Pacific metallogeny (Fig. 1). These metallogenic contrasts between the northwestern and northeastern quadrants result in China being the world’s leading producer of tungsten, tin, bismuth, and antimony, mostly from its eastern Mesozoic metallogenic province.