Contribution of slab-derived fluid and sedimentary melt in the incipient arc magma with development of the paleo-arc related to the Oman Ophiolite
Contribution of slab-derived fluid and sedimentary melt in the incipient arc magma with development of the paleo-arc related to the Oman Ophiolite
复制标题
早期弧岩浆中板片衍生流体和沉积熔体对阿曼蛇绿岩相关古弧发育的贡献
DOI：
10.1016/j.chemgeo.2016.12.012
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Shoji ARAI
中科院分区：
文献类型：
--
作者：
Yuki KUSANO;Susumu UMINO;Ryuichi SHINJO;Anzu IKEI;Yoshiko ADACHI;Sumio MIYASHITA;Shoji ARAI
新鲜的火山玻璃的主元素和微量元素地球化学，和全岩Hf和Nd同位素组成的火山岩从阿曼蛇绿岩被用来了解在何种程度上板派生的流体和熔体参与岩浆生成在初始弧发展。扩张阶段（V1）样品具有类似洋中脊玄武岩的微量元素特征，Hf和Nd同位素组成的印度地幔域。初弧阶段（V2）火山玻璃的高场强元素（HFSEs）和中、重稀土元素（MREEs和HREEs）丰度较低，而大离子亲石元素（LILEs）丰度较高。B，铅，和LILE在V2阶段的玻璃与年龄的逐步增加表明，从早期弧拉斑玄武岩（LV 2）到后来的玻安岩（UV 2）的板状流体的贡献越来越大。LV 2是由角闪岩衍生流体的贡献产生的。UV2岩浆可分为低硅和高硅两类，前者SiO2、LILE含量较低，而Na2O、HFSE和REE含量较高。低硅UV 2岩浆是在高温板片流体的参与下形成的。与此相反，高硅UV2显示了勺形的微量元素模式和Hf和Nd同位素化学，表明在其岩浆成因的沉积物熔体的参与。随着年龄的增长，岩浆中的HFSE和HREE逐渐减少，表明在V2弧岩浆作用期间源地幔逐渐耗尽，这表明地幔楔中没有对流，这是由于年轻的热岩石圈下的热的浮力板俯冲造成的。
Major-element and trace-element geochemistry of fresh volcanic glass, and the whole-rock Hf and Nd isotopic compositions of volcanic rocks from the Oman Ophiolite were used to understand the extent to which slab-derived fluids and melts were involved in magma generation during incipient arc development. The spreading stage (V1) samples have trace-element characteristics similar to those of mid-ocean-ridge basalts, with Hf and Nd isotopic compositions of the Indian mantle domain. The incipient arc stage (V2) volcanic glasses have lower abundances of high field strength elements (HFSEs) and middle and heavy rare earth elements (MREEs and HREEs), and higher abundances of large ion lithophile elements (LILEs) than the V1 glasses. Progressive increases in B, Pb, and LILEs in the V2 stage glasses with age indicate an increasing contribution of slab-derived fluids from earlier arc tholeiite (LV2) to later boninite (UV2). The LV2 was generated by the contribution of amphibolite-derived fluid. The UV2 is subdivided into low-Si UV2 and high-Si UV2 magmas, with the former having lower SiO2, and LILE, and higher Na2O, HFSE and REE concentrations than the latter. The low-Si UV2 magma was generated with the involvement of high-temperature slab-derived fluid. In contrast, the high-Si UV2 shows a spoon-shaped trace-element pattern and Hf and Nd isotope chemistry, indicating the involvement of sediment melt in its magma genesis. Decreasing HFSEs and HREEs in the magmas with age indicate progressive depletion of the source mantle during the V2 arc magmatism, suggesting an absence of convection in the mantle wedge that resulted from subduction of a hot, buoyant slab beneath young, hot lithosphere.