Geochemical Characterization of the Oman Crust-Mantle Transition Zone, OmanDP Holes CM1A and CM2B
Geochemical Characterization of the Oman Crust-Mantle Transition Zone, OmanDP Holes CM1A and CM2B
复制标题
阿曼壳幔过渡带、OmanDP 孔 CM1A 和 CM2B 的地球化学特征
DOI：
10.1029/2021jb022694
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发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Kourim F
中科院分区：
文献类型：
--
作者：
Kourim F
在国际大陆科学钻探计划阿曼钻探项目的第二阶段（2017年11月至2018年1月）期间，在CM 1A和CM 2B孔（Wadi Tayin Baghaff）钻探了从辉长岩洋壳到阿曼蛇绿岩残留地幔方辉橄榄岩的过渡。为了揭示Wadi Tayin Bagraf壳幔过渡带和大洋扩张中心下地幔深部超镁铁质岩的形成过程，我们对这些超镁铁质岩（56块纯橄榄岩和49块方辉橄榄岩）的全岩常量和微量元素组成（以及CO2和H2O浓度）进行了研究。尽管有广泛的蛇纹石化和一些碳酸盐化作用，但大多数微量元素含量（REE，HFSE，Ti，Th，U）记录了高温，岩浆过程相关的特征。Th与U、Nb、LREE和（B）重REE、Ti、Hf具有良好的相关性。我们将第一种趋势解释为晚期熔体/橄榄岩相互作用的签名，因为LREE已知被这些过程（“岩石圈过程”）动员，第二种趋势解释为初始地幔部分熔融（“软流圈过程”）的签名，几乎没有或没有来自熔体/岩石反应事件的叠加。
The transition from the gabbroic oceanic crust to the residual mantle harzburgites of the Oman ophiolite has been drilled at Holes CM1A and CM2B (Wadi Tayin massif) during Phase 2 of the International Continental Scientific Drilling Program Oman Drilling Project (November 2017–January 2018). In order to unravel the formation processes of ultramafic rocks in the Wadi Tayin massif crust‐mantle transition zone and deeper in the mantle sections beneath oceanic spreading centers, our study focuses on the whole rock major and trace element compositions (together with CO2and H2O concentrations) of these ultramafic rocks (56 dunites and 49 harzburgites). Despite extensive serpentinization and some carbonation, most of the trace element contents (REE, HFSE, Ti, Th, U) record high temperature, magmatic process‐related signatures. Two major trends are observed, with good correlations between (a) Th and U, Nb and LREE on one hand, and between (b) heavy REE, Ti and Hf on the other hand. We interpret the first trend as the signature of late melt/peridotite interactions as LREE are known to be mobilized by such processes (‘‘lithospheric process’’) and the second trend as the signature of the initial mantle partial melting (‘‘asthenospheric process’’), with little or no overprint from melt/rock reaction events.