Special Paper: Major Gold Deposits and Belts of the North and South American Cordillera: Distribution, Tectonomagmatic Settings, and Metallogenic Considerations

Abstract

A compilation of economically viable gold concentrations containing ≥10 Moz in the North and South American Cordillera reveals the existence of 22 discrete belts in addition to five major isolated deposits, most formed over the last 150 m.y. The gold concentrations are attributed to eight widely recognized deposit types, of which porphyry, sediment-hosted, and high-sulfidation epithermal are economically the most important. Individual gold belts are typically several tens to hundreds of kilometers long, dominated by single deposit types, and metallogenically active for relatively brief periods (<5-20 m.y.).Many of the gold belts and major isolated deposits were generated under extensional or transtensional tectonic conditions in either arc or back-arc settings. Nevertheless, the two main high-sulfidation epithermal gold belts were generated in thickening or already-thickened crust during low-angle subduction. Eight other gold belts or districts also accompanied compression or transpression, with two of them, the main orogenic gold belts, occupying fore-arc sites. There is a strong suggestion that the preeminent Cordilleran gold concentrations formed either during or immediately following prolonged contraction. The major gold deposits and belts occur along the craton edge as well as in adjoining accreted terranes, but almost all are of postaccretionary timing. Many of the gold belts and isolated deposits were localized by crustal-scale faults or lineaments, which may be either parallel or transverse to the Cordilleran margin.The gold concentrations accumulated during active subduction, commonly in close spatial and temporal association with intermediate to felsic, medium-to high-K calc-alkaline igneous rocks. By contrast, the lowsulfidation epithermal gold deposits accompany bimodal volcanic pulses of calc-alkaline, tholeiitic, or alkaline affinity. However, a gold-alkaline rock association is uncommon. A genetic link between gold mineralization and coeval magmatism is widely accepted for most of the deposit types, the exceptions being the sedimenthosted and orogenic gold deposits.Notwithstanding the small cumulative extent of the gold concentrations relative to the entire Cordilleran margin, there is a marked tendency for two or more belts or isolated deposits of different ages and genetic types to occur in close proximity within relatively restricted arc (including fore-and back-arc) segments. In the case of the western United States, for example, six belts and four isolated major deposits make up a particularly prominent cluster. If fortuity is discounted, this clustering or pairing of gold concentrations must imply a predisposition of certain arc segments to gold mineralization. An analogous situation is evident for other metals, particularly copper and tin. The reason for the recurrent generation of major deposits and belts dominated by one or more metals remains uncertain, although heterogeneously distributed metal preconcentrations, favorable redox conditions, or other parameters somewhere above the subduct...

Triggers for the formation of porphyry ore deposits in magmatic arcs

“…Although melt reduction is a viable mechanism for enhancing metal partitioning into hydrothermal fluids, in particular for gold, assimilation and reduction at depth could have the alternative effect of triggering sulfide saturation 87 (Box 2). At present, there appears to be no systematic correlation between more reduced porphyry melts and deposit metal endowment, although an association with gold enrichment does appear to exist for the allied family of reduced, pluton-related gold deposits 80 .…”

“…The proposal for the generation of a predisposition to form ore in crustal magma chambers as an explanation for large porphyry ore deposits remains speculative, although similar conclusions have been drawn for the development of major hydrothermal gold deposits 80 . It is hoped that the synthesis of research ideas from many authors summarized here provides some pointers to where further work will help us to better understand the heterogeneous distribution of porphyry and their associated epithermal ore deposits in time and space.…”

Geology and mineral resources of the North-Central Montana Sagebrush Focal Area: Chapter D in <em>Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming</em>

“…Epithermal deposits form within 1 km of the surface of the Earth, and they typically occur in volcanic arcs at convergent plate margins in continental and oceanic settings, in continental-margin back arcs, in rifts, and in intraplate environments (Hedenquist and Lowenstern, 1994;Sillitoe and Hedenquist, 2003;Sillitoe, 2008). Epithermal deposits form vein, stockwork, disseminated, and replacement deposits that are principally mined for gold and silver.…”

Contrôles structuraux de la minéralisation aurifère de la veine Consuelo, Pataz, La Libertad, Pérou /

“…gisements épizonaux de Gebre-Mariam et al 1995) qu'à des profondeurs de 10 km (Groves et Goldfarb 2007). L'absence de consensus quant au modèle génétique du gisement de Pataz démontre non seulement le caractère unique du district mais démontre bien la difficulté de classifier et différencier certains types de gisements aurifères filoniens, particulièrement les gisements orogéniques et les gisements orthomagmatiques (Groves et al 2003;Sillitoe 2008). En ce sens, les gisements de la ceinture de Pataz-Parcoy partagent plusieurs similarités avec la ceinture aurifère de Charters Towers dans la partie septentrionale du Queensland australien (Kreuzer 2005).…”

“…Bien que le cadre tectonique régional attribué à la ceinture de Pataz-Parcoy ait été décrit comme un régime en compression (Haeberlin et al 2003;Sillitoe 2008) …”