Genesis of peculiarly zoned Co, Zn and Mn-rich chromian spinel in serpentinite of Bou-Azzer ophiolite, Anti-Atlas, Morocco
Genesis of peculiarly zoned Co, Zn and Mn-rich chromian spinel in serpentinite of Bou-Azzer ophiolite, Anti-Atlas, Morocco
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DOI：
10.2465/jmps.060212
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发表时间：
2007-04
影响因子：
0.7
通讯作者：
H. Gahlan;S. Arai
中科院分区：
文献类型：
--
作者：
H. Gahlan;S. Arai
特殊的富钴锌锰铬尖晶石赋存于摩洛哥元古界Bou-Azzer蛇绿岩地幔段的磁铁矿、蛇纹岩和铬铁矿中。尖晶石在光学或化学上具有复杂的分带，表现出异常高的MnO、ZnO和CoO含量(分别高达22wt%、7.5%和2wt%)。它有四个不同的光学带，特别是在磁铁矿矿脉中，在蛇纹岩中不太常见。这些元素中最高水平的元素，可能是二价元素，记录在铁铬矿带内和/或如果没有铁铬矿带，则记录在核心区内。这些元素以及铁沿晶界和蚀变尖晶石的断口显示出富集性。铁、锰、锌、钴很可能来自于蛇绿岩逆冲推覆过程中和之后严重的蛇纹岩作用后的橄榄石。Bou-Azzer铬尖晶石在锰、锌、钴中的富集主要受多种因素中流体/矿物(尖晶石)比和尖晶石与相关流体之间的分配系数的影响。富钴、富锌、富锰铬尖晶石可作为蛇纹石化橄榄岩伴生的钴镍锌铜硫化物矿化的找矿标志。
The peculiar Co, Zn and Mn-rich chromian spinels are hosted by magnetite veins, serpentinites and chromitites of the mantle section of the Proterozoic Bou-Azzer ophiolite, Morocco. The spinel is complexly zoned either optically or chemically, and exhibits anomalously high MnO, ZnO and CoO contents (up to 22, 7.5 and 2 wt%, respectively). It has four distinct optical zones particularly in the magnetite veins and less typically in serpentinites. The highest level of these elements, probably divalent, is recorded within the ferritchromite zone and/or within the core zone if the ferritchromite zone is absent. These elements as well as Fe exhibit enrichment along grain boundaries and fractures of the altered spinels. Fe, Mn, Zn and Co were most probably supplied from olivine upon severe serpentinization during and after obduction of the ophiolite. The enrichment of the Bou-Azzer chromian spinel in Mn, Zn and Co was governed mainly by the fluid/mineral (spinel) ratio and partition coefficient between spinel and the relevant fluid among many factors. The Co-, Zn- and Mn-rich chromian spinels can be used as an exploration guide for Co-Ni-Zn-Cu sulfide mineralization associated with serpentinized peridotites.