Great Barrier Island silver-gold deposits, Hauraki Province, New Zealand

Geology and mineralisation of the former Broken Hills gold mine, Hikuai, Coromandel, New Zealand

“…Similar compositional variations for electrum grains from several mining areas in the Western U.S.A. have been described by Desborough et al (1971). At Broken Hills, the variations in composition clearly have not resulted from postdepositional processes such as those postulated by Desborough (1970) for certain placer deposits, and Ramsay & Kobe (1974) for the occurrence of zoned e1ectrum from the Iona quarry at Great Barrier Island. Rather, such compositional variations ale interpreted as changes 345 in composition of the fluids from which the grains originally grew, causing gold-silver alloys of different composition to form contiguous growth zones with time (Czamanske et al, 1973).…”

“…Ramsay & Kobe (1974) have described the occurrence of aguilarite and naurnannite from the Sunbeam and Barrier reefs region of Great Barrier Island. Here these minerals occur in quartz gangue and are associated with electrum, silver sulphosalts, pyrite, selenium-argyrodite, and minor stihnite, arsenopyrite, chalcopyrite, galena, and tetrahedrite.…”

Au-Se Paragenesis in Cambrian Stratabound Gold Deposits, Western Qinling Mountains, China

“…The occurrence of selenides has been reported from four major types of hydrothermal deposits: "telethermal" selenide vein-type deposits, unconformity-related deposits, sandstone-hosted uranium deposits, and epithermal Au-Ag deposits in subaerial volcanic environments (Simon et al, 1997). As reported in the literature worldwide, hydrothermal gold deposits containing selenides are mostly restricted to epithermal Au-Ag deposits that are genetically related to continental volcanism, for instance, the Koryu (Shimizu et al, 1998), Kushikino (Mukaiyama and Izawa, 1964;Shikazono et al, 1990), Hishkari (Izawa et al, 1990;Shikazono et al, 1990), Chitose, and Yatani mines (Shikazono et al, 1990) of Japan; the Sleeper (Saunders et al, 1988;Saunders, 1993) and Jarbridge mines (Hewitt, 1968) of Nevada, the Silver City mine Ramdohr, 1980) of Idaho, and the Republic mine (Full and Grantham, 1968) of Washington, all in the United States; the Torquay mine (Paar et al, 1998) of England; the Great Barrier Island (Ramsay and Kobe, 1974) and Camoola mines (Main et al, 1972) of New Zealand; the Salida (Kieft and Oen, 1973) and Redzhang Lebong (Sindeeva, 1964) mines of Indonesia; the Guanajuato mine of Mexico; the Providencia mine (Paniuga, 1995) of Spain; as well as many Au-Ag deposits in the Circum-Pacific and Mediterranean metallogenic belts, such as the Prasolovskoye, Kunashir Island, and Kuril Island deposits (Nekrasov and Lunin, 1987;So et al, 1995), all of which can be taken as the typical examples. Nevertheless, those ore depos its bear no Se-rich mineralized bodies, although the concentrations of Se are somewhat elevated.…”

Geologic characteristics of sediment- and volcanic-hosted disseminated gold deposits - Search for an occurrence model

“…The Borealis deposit, Nev., probably formed within 100 m of the paleosurface, although sinter is absent. Deposits for which a subaerial hot-spring environment can be inferred for at least part of the precious-metal mineralization are the Great Barrier Island deposits, North Island, New Zealand (Ramsay and Kobe, 1974), and the Haile deposit, S.C. (Worthington and others, 1980). The McLaughlin deposit in the old Knoxville mercury district, Napa County, Calif., is localized in Quaternary volcanic rocks and in Franciscan rocks of Mesozoic age at the site of the old Manhattan mercury mine.…”