کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6441699 1639110 2013 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Inorganic and biogenic As-sulfide precipitation at seafloor hydrothermal fields
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Inorganic and biogenic As-sulfide precipitation at seafloor hydrothermal fields
چکیده انگلیسی
We investigated As-sulfides (orpiment, As2S3 and realgar, As4S4) from four seafloor hydrothermal fields: three from back-arc and one from mid-ocean ridge settings. Our studies suggest two different modes of As-sulfide precipitation at the seafloor hydrothermal sites: inorganic and biogenic. The Eh-pH modeling shows that the most stable As-sulfide at low-temperature (T < 100 °C) seafloor hydrothermal conditions is orpiment, whereas realgar appears as a stable As-sulfide phase at T = 25 °C and under a narrow range of Eh-pH values. Inorganically precipitated realgar forms euhedral crystals whereas the orpiment is mostly colloform. The biogenic type of orpiment (no realgar of this type was found) represents completely mineralized fungal hyphae. The proposed scenario of biogenic orpiment formation assumes that crack-dwelling fungal filaments in the sub-seafloor were killed by an As-rich hydrothermal fluid moving along the same crack network. The fungal organic matter served as a geochemical trap for hydrothermal As which reacted with S (leached from the basement or reduced from seawater sulfate) and mineralized the fungal hyphae as As2S3. This process of fungal orpiment precipitation is a mechanism of bio-sequestration of hydrothermal As and another mode of soft-tissue fossilization not described so far.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Marine Geology - Volume 342, 1 August 2013, Pages 28-38
نویسندگان
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