School of Geosciences, University of Edinburgh, Grant Institute, Edinburgh, UK.
Science. 2011 Jun 24;332(6037):1548-51. doi: 10.1126/science.1202924.
The iron isotope composition of sedimentary pyrite has been proposed as a potential proxy to trace microbial metabolism and the redox evolution of the oceans. We demonstrate that Fe isotope fractionation accompanies abiotic pyrite formation in the absence of Fe(II) redox change. Combined fractionation factors between Fe(II)(aq), mackinawite, and pyrite permit the generation of pyrite with Fe isotope signatures that nearly encapsulate the full range of sedimentary δ(56)Fe(pyrite) recorded in Archean to modern sediments. We propose that Archean negative Fe isotope excursions reflect partial Fe(II)(aq) utilization during abiotic pyrite formation rather than microbial dissimilatory Fe(III) reduction. Late Proterozoic to modern sediments may reflect greater Fe(II)(aq) utilization and variations in source composition.
已提出利用沉积黄铁矿中的铁同位素组成来追踪微生物代谢和海洋氧化还原演变。本研究证明，在没有 Fe(II)氧化还原变化的情况下，生物成因黄铁矿形成过程伴随着铁同位素分馏。Fe(II)(aq)、磁黄铁矿和黄铁矿之间的组合分馏因子允许生成的黄铁矿具有铁同位素特征，几乎包含太古宙至现代沉积物中记录的整个沉积 δ(56)Fe(pyrite)范围。本研究提出，太古宙时期的负铁同位素偏移反映了在生物成因黄铁矿形成过程中部分利用了 Fe(II)(aq)，而不是微生物异化还原 Fe(III)。晚元古代至现代沉积物可能反映了更多的 Fe(II)(aq)利用和源组成的变化。
