کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5783409 1637951 2017 40 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS
چکیده انگلیسی
Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth's history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes-many containing organic ligands-we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H2S(aq)] < 11 µM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO3, MoOxS4−x2− (intermediate thiomolybdates), and [MoOx(cat)4−x]2− (cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS42− (tetrathiomolybdate).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geochimica et Cosmochimica Acta - Volume 206, 1 June 2017, Pages 18-29
نویسندگان
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