An amagmatic origin of carlin-type gold deposits

Geochemistry of the sediment-hosted disseminated gold deposits in Southwestern Guizhou Province, China /

“…The general geological characteristics of a number of SHDG deposits in U.S.A. have been tabulated by Tooker (1985), Bagby and Berger (1985), and Ilchik and Barton (1997).…”

“…The SHDG and MVT deposits are similar in that they are both hosted mainly in sedimentary rocks, and, in many cases, igneous rocks (contemporaneous with ore deposition) are absent. Data from SHDG deposits of Nevada suggests that the Pb in the ores was derived from the mixing of isotopically distinct sources (Arehart et al, 1993a;Arehart, 1996;Groff and others, 1997;Ilchik and Barton, 1997;Tosdal et al, 1998). Similar Pb isotopic variation may exist in the SHDG deposits in the study area; however, because of the paucity of Pb data it is not possible to make this kind of universal correlation.…”

“…3) Ore-forming element assemblages consisting of Au, As, Hg, Tl, Sb, and a greater than 1 Au/Ag ratio in the ores; 4) Alteration including silicification, sulfidation, argillic alteration of primary silicate minerals, and décalcification (carbonate dissolution); 5) Amagmatic origin for most if not all of the deposits (Yang and Dong, 1994;Ilchik and Barton, 1997). Some of the deposits are associated with intrusive rocks spatially but not temporally and genetically.…”

“…Different models regarding the gold source have been proposed: (1) The source bed hypothesis suggests that gold derived mainly from the gold-rich strata during deep circulation of meteoric water. The water was driven either by elevated geothermal gradients during regional extension and accompanying magmatism (Liu and Geng, 1985;Wang et al, 1992;Hofstra, 1995;Ilchik and Barton, 1997), or as a result of regional metamorphism and dehydration of these same metasedimentary rocks (Philips and Powell, 14 1993;Keuhn and Rose, 1995). Some researchers have proposed that the gold, heat and fluid (formation water) all come from the host rocks (He et al, 1993;He, 1996).…”

“…In models appealing to amagmatic origin, gold is thought to have been derived from sedimentary rocks during deep circulation of meteoric water driven by elevated geothermal gradients during extension (Hofstra, 1995(Hofstra, , 1997Ilchik and Barton, 1997). By systematically bringing hotter, more deeply buried rocks toward the surface, crustal thinning raises the geothermal gradient.…”