Large Igneous Provinces (LIPs) and Metallogeny
Published:January 01, 2013
Richard E. Ernst, Simon M. Jowitt, 2013. "Large Igneous Provinces (LIPs) and Metallogeny", 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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Large igneous provinces (LIPs) represent significant reservoirs of energy and metals that can either drive or contribute to a variety of metallogenic systems. The relationships between LIPs and these various systems can be divided into four distinct although partially overlapping classifications: (1) LIPs form the primary source of commodities within mineral deposits (e.g., orthomagmatic Ni-Cu-PGE sulfides, or Nb-Ta-REE and diamonds for often LIP-related carbonatites and kimberlites, respectively); (2) LIPs either provide the energy to drive hydrothermal systems or can act as source rocks for hydrothermal ore deposits (e.g., volcanogenic massive sulfide (VMS) deposits)—in some cases LIP rocks can also act as barriers to fluid flow and/or reaction zones causing mineralization (e.g., orogenic Au); (3) weathering can concentrate elements such as Al and Ni-Co within laterites that develop from exposed LIP mafic-ultramafic rocks in tropical climates, and for Nb, Ta, and REE in laterites from associated carbonatites; and (4) indirect links exist between LIPs and ore deposits; here we consider two of these types of links, the first of which involves LIP events that are linked to attempted or successful continental breakup where the LIP barcode record can be used as a correlation tool for reconstructing Precambrian supercontinents and therefore enable the tracing of metallogenic belts between presently separated, but formerly contiguous crustal blocks. A second, more speculative, indirect link is provided by the fact that major continental breakup (linked to LIPs) is associated with distal compression and transpression in the plate tectonic circuit (and the formation of orogenic deposits, such as Au).
We discuss the role of LIPs (be it major or contributory) in each of these classifications for the generation of this wide variety of differing mineral deposit types and potential implications of this link between LIPs and metallogenesis for exploration strategies. This review shows how our understanding of LIPs, and the processes that affect LIP magmas and rocks, have direct consequences for mineral exploration and economic geology.
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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.