Origin and Evolution of Ultramafic Rocks along the Sagaing Fault, Myanmar
Origin and Evolution of Ultramafic Rocks along the Sagaing Fault, Myanmar
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DOI：
10.1007/s12583-021-1435-x
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发表时间：
2023-02
影响因子：
3.3
通讯作者：
T. Morishita;Hnin Min Soe;H. Htay;Than Htut Lwin;J. Guotana;Akihiro Tamura;T. Mizukami;K. Zaw
中科院分区：
文献类型：
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作者：
T. Morishita;Hnin Min Soe;H. Htay;Than Htut Lwin;J. Guotana;Akihiro Tamura;T. Mizukami;K. Zaw
缅甸的活动实皆市断层界定了印度板块和欧亚板块之间的边界，并在缅甸的主要城市造成地震破坏。少量蛇纹岩沿着断层分布。我们首次调查了沿着实皆市断层的Sheinmagar地区和Yega Inn地区的高度剪切蛇纹岩体。广泛剪切/角砾化的蛇纹岩和相关岩石，如含滑石和/或绿泥石的岩石含有蛇纹岩的小岩石碎片。蛇纹岩的结构和矿物化学特征表明，蛇纹岩的原岩以方辉橄榄岩为主，含少量纯橄榄岩，部分被辉长岩脉切割。叶蛇纹石不存在择形取向，表明蛇纹岩化作用发生在相对静态的条件下。原岩和蛇纹岩矿物与实皆市断层北部（玉石矿带）含硬玉岩蛇纹岩相似。研究区尖晶石的化学成分变化处于弧前橄榄岩和附近蛇绿岩地幔部分的成分范围内。在静态条件下形成叶蛇纹石蛇纹岩后，这些蛇纹岩随后发生局部变形，可能是由于实皆市断层的活动，导致蛇纹岩片岩/角砾岩的形成。剪切角砾化带中存在变形较小的叶蛇纹石蛇纹岩，表明应变主要沿着周围的蛇纹-滑石（±滑石）片岩局部化，可能是蛇纹岩与围岩反应形成的。需要进一步的研究来更好地了解蛇纹化橄榄岩的分布是否导致实皆市断层活动性的变化。
The active Sagaing fault in Myanmar defines the boundary between the Indian Plate and the Eurasian Plate and causes seismic damage in the major cities of Myanmar. Small bodies of serpentinite occur along the fault. We for the first time investigated the highly sheared serpentinite bodies in the Sheinmagar area and Yega Inn area along the Sagaing fault. Extensively sheared/brecciated serpentinites and related rocks, such as talc and/or chlorite-bearing rocks contains small rock fragments of serpentinites. Serpentine texture and mineral chemistry indicate that the protolith of these serpentinites were mainly harzburgite with minor amounts of dunite, some of which are cut by gabbroic veins. No shape-preferred orientation of the antigorite is present, indicating that the serpentinization was occurred under relatively static conditions. Protolith and serpentine minerals are similar to those of the jadeitite-bearing serpentinites in the north of the Sagaing fault (the Jade Mine belt). Chemical variations of spinels in the studied area are within the compositional range of forearc peridotites and those in the mantle section of nearby ophiolites. After the formation of antigorite serpentinite under static conditions, these serpentinites were subsequently, but locally deformed, probably due to the activity of the Sagaing fault, resulting in the formation of serpentinite schist/brecciated rock. The presence of the less-deformed antigorite serpentinite in the sheared/brecciated zone indicates the strain localization mainly along the surrounding serpentine-talc (±chlorite) schistose rocks, which is probably formed by the reaction between serpentinite and country rocks. Further studies are needed to better understand whether the distribution of serpentinized peridotites cause variations in the activity of the Sagaing fault.