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首页> 外文会议>Mizoram Science Congress >Geochemistry and nature of protolith of quartz sillimanite schist from Sonapahar area, West Khasi Hills district of Meghalaya
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Geochemistry and nature of protolith of quartz sillimanite schist from Sonapahar area, West Khasi Hills district of Meghalaya

机译：Meghalaya西Khasi Hills区Sonapahar地区石英Sillimanite Schist促果实的地球化学与性质

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The Precambrian terrain of the Sonapahar area is characterised by the presence of a thin, long, discontinuous band of quartz-sillimanite schist which hosts the massive sillimanite-corundum deposits. The quartz sillimanite schists are generally siliceous, SiO_2 (60.59-76.82 wt %) and are characterized by high Al_2O_3 content with average value (27.22 wt %), low P_2O_5, Fe_2O_3 and MgO, MnO Na_2O, K_2O and TiO_2. Average MgO, CaO, K_2O and Na_2O values are generally less than 0.15 wt %. TiO_2 values range from 0.13-0.35 wt %. Compared with the post-Archean metasediments, the Sonapahar schists are richer in SiO_2 and Al_2O_3 but depleted in other oxides. In Harkers variation diagram, SiO_2 shows a linear inverse correlation with Al_2O_3 and TiO_(2,) but there are no significant correlations observed with other oxides. In general, Al_2O_3 and SiO_2 constitute more than 97 wt % in most of the samples. Among trace elements, Zr, Hf and Pb are characterized by high concentration and low La/Th and Th/U. The schistose rocks are generally low in Sr/Ba ratios (<0.88%) and relatively high content of Rb in contrast to Ba. Chondrite normalize REE patterns of the schists reveals a strongly fractionated patterns with enriched LREE and low HREE values [(La/Yb)N = 27.38-43.98] with prominent negative Eu-anomaly. The concentration of V (10.28-51.49) shows the apparent mobility in these quartz sillimanite schists and the oxidizing conditions prevailed during weathering. Geochemical characteristics suggested that quartz sillimanite schists from Sonapahar area are derived from post-Archean recycled upper crust sources and the precursor sediments are possibly derived from felsic rocks and probably not mafic rocks.
机译：Sonapahar地区的前皮里亚格地区的特点是存在薄，长，不连续的石英 - 西巴尼岩分裂带，托管大量的Sillimanite-corundum沉积物。石英西乳酸米岩分类通常是硅质的，SiO_2（60.59-76.82wt％），其特征在于高Al_2O_3含量，具有平均值（27.22wt％），低p_2O_5，Fe_2O_3和MgO，MnO Na_2O，K_2O和TiO_2。平均MgO，CaO，K_2O和NA_2O值通常小于0.15wt％。 TiO_2值范围为0.13-0.35wt％。与前院后的MetaseDiment相比，Sonapahar Schists在SiO_2和Al_2O_3中更丰富，但在其他氧化物中耗尽。在Harkers变型图中，SiO_2显示了与Al_2O_3和TiO_（2，）的线性逆相关，但是与其他氧化物没有观察到的显着相关性。通常，在大多数样本中，Al_2O_3和SiO_2在大多数样本中构成超过97wt％。在痕量元素中，Zr，Hf和Pb的特征在于高浓度和低la / th和/ u。与BA相比，Schistose岩石通常在Sr / BA比率（<0.88％）和相对高的Rb含量下。 Chondrite正常化Schists的Ree图案揭示了富含富含欧盟异常的富集的LREE和低HREE值[（LA / YB）n = 27.38-43.98]的强烈分级的模式。 v的浓度（10.28-51.49）显示了这些石英西吡岩分离中的表观迁移率，并且在风化期间占氧化条件。地球化学特征表明，Sonapahar地区的石英Sillimanite Schists源自前甲基回收的上层壳体，前体沉积物可能来自猫科岩石，可能不是Mafic Rocks。

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