Electron microscopy study on the formation of ferromanganese crusts, western Pacific Magellan Seamounts
Electron microscopy study on the formation of ferromanganese crusts, western Pacific Magellan Seamounts
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DOI：
10.1016/j.margeo.2019.01.001
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发表时间：
2019-04
期刊：
影响因子：
2.9
通讯作者：
Kiho Yang;Hanbeom Park;S. Son;H. Baik;K. Park;Jonguk Kim;Junbeom Yoon;Chan-Hong Park;Jin-wook Kim
中科院分区：
文献类型：
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作者：
Kiho Yang;Hanbeom Park;S. Son;H. Baik;K. Park;Jonguk Kim;Junbeom Yoon;Chan-Hong Park;Jin-wook Kim
当铁锰结壳层形成时，矿物学和化学成分、层结构、Fe和Mn的氧化还原状态以及微生物多样性的变化与地球化学过程密切相关。从西太平洋麦哲伦海山（OSM 11）采集的样本，从上到下（L1-5）分为五个明确的层。与L1和L3中的碎屑石英、长石、针铁矿和赤铁矿以及L4-5中的碳酸盐氟磷灰石（CFA）相比，铁水钠石出现在所有层中。L4-5中Ca和P的相对高浓度以及L1和L3中Fe、Co和Si的相对高浓度对应于地壳层中的矿物学变化。沿着凸起生长线沿着的细长空隙的消失可能是由于L4-5中CFA的空隙填充沉淀，导致空隙减少（31.6至6.0%）。通过电子能量损失谱（EELS）测量的Fe-水铝石中Fe的氧化态范围为Fe 3 +/Fetot的36 - 63%，并且出现CFA的层（L4）含有更多还原形式的Fe（Fe 3 +/Fetot= 36-48%）。Fe-（coxC）和Mn-氧化基因（cumA）的存在，特别是在L2-3中表现出强的coxC PCR条带，表明为显性氧化条件。铁和锰氧化物沉淀与各种氧化还原条件下的微生物活性的直接证据被确定在聚焦离子束切片微体化石。特别是，光谱图像显示更还原形式的铁周围的空隙以前被微生物占据，强烈支持微生物在氧化还原反应中的地壳的生长中发挥重要作用。
Variations in mineralogy and chemical composition, layer structures, redox states of Fe and Mn, and microbial diversity are closely linked to the biogeochemical process when a ferromanganese crust layer forms. A sample collected from the Magellan Seamount (OSM11), in the western Pacific, was characterized in five well-defined layers, top to bottom (L1–5). Fe-vernadite occurs in all layers, compared to detritus quartz, feldspar, goethite, and hematite in L1 and L3, and carbonate fluorapatite (CFA) in L4–5. The relatively high concentrations of Ca and P in L4–5, and Fe, Co, and Si in L1 and L3 correspond to the mineralogical variations in the crust layer. Disappearance of elongated voids along the convex growth line is likely due to void filling precipitation of CFA in L4–5, resulting in the void reduction (31.6 to 6.0%). The oxidation states of Fe in Fe-vernadite measured by electron energy loss spectroscopy (EELS) ranges from 36 to 63% of Fe3+/Fetot, and a layer where CFA appeared (L4) contains a more reductive form of Fe (Fe3+/Fetot= 36–48%). Presence of Fe- (coxC) and Mn-oxidizing gene (cumA), particularly displaying a strong PCR band ofcoxCin L2–3, indicates a dominant oxidizing condition. Direct evidence of microbial activity in Fe - and Mn-oxide precipitation with various redox conditions was identified in the focused ion beam-sectioned microfossil. Particularly, a spectrum image displaying a more reducing form of Fe around the voids previously occupied by microorganisms, strongly supports that microorganisms play an important role in the redox reaction in the growth of a crust.