New Mössbauer measurements of Fe3+/ΣFe in chromites from the mantle section of the Oman ophiolite: evidence for the oxidation of the sub-oceanic mantle
New Mössbauer measurements of Fe3+/ΣFe in chromites from the mantle section of the Oman ophiolite: evidence for the oxidation of the sub-oceanic mantle
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DOI：
10.1180/minmag.2012.076.3.09
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发表时间：
2012-06
影响因子：
2.7
通讯作者：
H. Rollinson;J. Adetunji;A. Yousif;A. Gismelseed
中科院分区：
文献类型：
--
作者：
H. Rollinson;J. Adetunji;A. Yousif;A. Gismelseed
摘要室温穆斯堡尔谱和电子探针测量阿曼蛇绿岩地幔部分铬铁矿中的Fe 3 +/Fe 3 + Fe定义了两组样品：低Fe ~（3+）/Fe ~（2+）组（其中Fe 3 +/Cr Fe = 0.21-0.36）具有在0.49-0.75范围内的Cr# = Cr/（Cr + Al），而更小的、地理上更局部化的高Fe 3 +/Fe 3 + Fe组（Fe 3 +/Fe 3 + Fe = 0.71-0.78）具有0.72-0.75的更有限的Cr#比范围。低Fe ~（3+）/Fe ~（3+）铬铁矿的Fe ~（3+）/Fe ~（3+）比值变化很大。它们被认为是从与亏损地幔相互作用的熔体中结晶出来的，从而获得了它们可变的Fe 3 +/Fe 3 + Fe比。高Fe ~（3+）/Fe ~（3+）铬铁矿局限于地幔的一个小区域，其高氧化态被认为是岩浆期后的产物。它们要么是后期加热的产物，与熔体通量有关，要么是与后期氧化熔体相互作用的产物。氧逸度的差异之间的MORB亏损方辉橄榄岩主机，这是在石英-铁橄榄石-磁铁矿（QFM）的缓冲区和后来的含铬熔体（QFM + 2）意味着有一个真实的差异的氧化状态的MORB和弧岩浆源。
Abstract Room temperature Mössbauer and electron-probe measurements of Fe3+/ΣFe in chromite from the mantle section of the Oman ophiolite define two groups of samples: a low Fe3+/ΣFe group (with Fe3+/ΣFe = 0.21-0.36) have cr# = Cr/(Cr + Al) in the range 0.49-0.75, whereas a smaller more geographically localized high Fe3+/ΣFe group (with Fe3+/ΣFe = 0.71-0.78) have a more restricted range of cr# ratios of 0.72-0.75. The low Fe3+/ΣFe chromitites have very variable Fe3+/ΣFe ratios. They are thought to have crystallized from melts that have interacted with depleted mantle and thereby acquired their variable Fe3+/ΣFe ratio. The high Fe3+/ΣFe chromitites are restricted to one small area of the mantle and their high oxidation state is thought to be post magmatic. They are either the product of later heating, related to melt flux or interaction with a later oxidising melt. A difference in oxygen fugacity between the MORB-depleted harzburgite host, which is at the quartz-fayalite-magnetite (QFM) buffer and the later chromite-bearing melts (QFM + 2) implies that there is a real difference in the oxidation state of the MORB and arc-magma sources.