| Naturally acidic and metalliferous waters at unmined volcanogenic massive sulfide deposits in the Bonnifield mining district, Alaska Range, east-central Alaska |
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| 作者姓名： | Robert G. Eppinger Paul H. Briggs Cynthia Dusel-Bacon Stuart A. Giles Larry P. Gough Jane M.Hammarstrom Bernard E. Hubbard |
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| 作者单位： | [1]U.S. Geological Survey, Central Mineral Resources Team, Denver, Colorado, USA [2]U.S. Geological Survey, Western Mineral Resources Team, Menlo Park, California, USA [3]U.S. Geological Survey, Eastern Mineral Resources Team, Reston, Virginia, USA |
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| 摘 要： | The Bonnifield district hosts 26 tmmined volcanogenic massive sulfide （VMS） occurrences. Environmental geochemical samples of water and stream sediment were collected at several occurrences, concentrating on the two best-exposed and largest deposits, Red Mountain （RM） and Sheep Creek （SC）. Limited samples were also collected at the poorly exposed WTF deposit. The deposits are Late Devonian to Early Mississippian, and are hosted by felsic metavolcanic and carbonaceous schist members of the Totatlanika Schist or Keevy Peak Fm. Spring and stream waters at RM and SC have pH values commonly 〈3.5 （as low as 2.4 at RM and 2.5 at SC）, high conductivity （up to 11000 μS/cm）, and very high （Is to 100s mg/L） dissolved contents of Al, Cd, Co, Cu, Fe, Ni, and Pb. Waters at RM are characterized by extremely high REE contents （summed REE median 3200 μg/L, n=33）. At both RM and SC, pyrite oxidation and dissolution produce low pH waters that interact with and dissolve bedrock minerals, resulting in acidic, metal-laden, naturally degraded streams that are mostly devoid of aquatic life. Ferricrete is common. In contrast, WTF barely produces a surficial environmental footprint, mostly due to topography and relief. RM and SC are well exposed in the areas of relatively high relief, and both exhibit extensive areas of quartz-sericite-pyrite-alteration. While WTF shares many of the same deposit-and alteration characteristics, it is concealed by tundra in a large, nearly flat area. Surface water at WTF is absent and outcrops are sparse. Even though WTF is roughly the same size as Red Mountain （both around 3 million tonnes） and has similar base- and precious-metal grades, the surficial geochemical manifestation of WTF is minimal. However, exposure through mining of the altered, mineralized rock at WTF potentially could initiate the same processes of pyrite oxidation, acid generation, and mineral dissolution that are observed naturally at RM and SC.
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| 关 键 词： | 酸性排水 火山 堆积物 矿物 水文地球化学 |
Naturally acidic and metalliferous waters at unmined volcanogenic massive sulfide deposits in the Bonnifield mining district, Alaska Range, east-central Alaska |
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| Robert G. Eppinger Paul H. Briggs Cynthia Dusel-Bacon Stuart A. Giles Larry P. Gough Jane M.Hammarstrom Bernard E. Hubbard.Naturally acidic and metalliferous waters at unmined volcanogenic massive sulfide deposits in the Bonnifield mining district, Alaska Range, east-central Alaska[J].Chinese Journal of Geochemistry,2006,25(B08):232-232. |
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| Abstract: | |
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| Keywords: | acid rock drainage volcanogenic massive sulfide hydrogeochemistry tmrnined rare-earth element |
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