The exhumed "Carlin-type" fossil oil reservoir at Yankee basin

The Carlin-type disseminated gold orebodies of Yankee basin in the southern part of the Alligator Ridge mining district in Nevada contain widespread o il as smears, open-space fillings, and fluid inclusions in syn- and pre-min eral calcite veins. These unusual oils are the relicts of an exhumed and de eply oxidized oil reservoir that encompasses the orebodies at the crest of a dissected, anticlinal trap. Results of fluid-inclusion microthermometry a nd organic geochemistry demonstrate that the oils experienced peak paleotem peratures of no more than about 150 degrees C, a temperature unusually low for Carlin-type mineralization, but ideal for the transport, entrapment, an d preservation of liquid hydrocarbon. Similar geothermal systems are active ly circulating at three of Nevada's producing oilfields-Grant Canyon, Bacon Flat, and Blackburn. Accordingly, concealed Carlin-type fossil hydrotherma l systems of this type even if subeconomic for gold, could contain commerci al concentrations of oil.