Ore Deposit Research Produces New Model for Formation of World-Class Gold District in Northern Nevada

In the February 2011 issue of Nature Geoscience, Geoscience Professor Jean Cline and colleagues John Muntean (Nevada Bureau of Mines and Geology and University of Nevada Reno) and Adam Simon and Anthony Longo (UNLV) present a new comprehensive model for the formation of a district of gold deposits in northern Nevada, that are unique in the world, and that have produced more than $225B worth of gold.  The deposits are known as Carlin deposits, and are named after the small northern Nevada town located close to the 1961 discovery site.  The new model calls upon magmas generated at great depth as heat from asthenosphere impinged on the base of the Earth’s crust.  This heat initiated magmatic and hydrothermal processes that concentrated gold and passed it upwards through magmas and eventually exsolved hydrothermal fluids to the upper crust.  These processes were facilitated by deep, high angle crustal-scale structures that formed in the Neoproterozoic during continental rifting.  The structures were reopened in the Late Eocene as the plate tectonic stress field in northern Nevada shifted from compression to incipient tension, providing the tectonic trigger for deposit formation.  Ore fluids carrying gold traveled up the structures and reacted with ideal silty limestone host rocks in northern Nevada to form the mineral pyrite, which contains the vast resource of submicroscopic gold.  The published research provides insights that may be applied to other regions in the world that may be prospective for similar deposits.  It also provides suggestions – the intersection of generally common geologic processes with a unique crustal architecture – as to why Nevada is the only currently known location for these unique deposits and their vast gold resource.

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