Long-timescale variation in bulk and clay mineral composition of Indian continental margin sediments in the Bay of Bengal, Arabian Sea, and Andaman Sea
Long-timescale variation in bulk and clay mineral composition of Indian continental margin sediments in the Bay of Bengal, Arabian Sea, and Andaman Sea
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DOI：
10.1016/j.marpetgeo.2014.06.018
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发表时间：
2014-12
影响因子：
4.2
通讯作者：
S. Phillips;Joel E. Johnson;M. Underwood;J. Guo;L. Giosan;K. Rose
中科院分区：
文献类型：
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作者：
S. Phillips;Joel E. Johnson;M. Underwood;J. Guo;L. Giosan;K. Rose
本研究记录了X射线衍射结果，从散装粉末和定向粘土大小的聚集体使用的样品从现场钻孔和取芯在印度国家天然气水合物远征01（NGHP 01）。这些地点位于Krishna-Godavari盆地、Mahanadi盆地和孟加拉湾的安达曼增生楔以及阿拉伯海的Kerala-Konkan盆地。安达曼海和喀拉拉-康坎盆地的中上层地区的方解石含量更丰富，这与之前对生物生产力和岩源流入稀释的研究一致。克里希纳-戈达瓦里盆地和马哈纳迪盆地的半远洋沉积物主要分别由富含蒙脱石和伊利石的粘土矿物组合组成。我们将这些差异归因于德干玄武岩（蒙皂石来源）和东高止山脉带前寒武纪岩石之间碎屑来源的差异;这些来源在整个沉积历史（0-9 Ma）中保持一致。Mahanadi盆地中较高的石英含量和Krishna-Godavari盆地中较高的长石含量强化了这些碎屑物源的解释。蒙皂石是安达曼海沉积物中最丰富的粘土矿物，可能是由于沿着巽他弧火山源的风化作用。从喀拉拉邦Konkan盆地的地层显示在23马从蒙皂石-高岭石粘土矿物组合越来越伊利石丰富的组合的转变。我们还看到，在30万年的记录中，高岭石稳步减少，而高岭土和石英增加，这表明来自物理风化的物质的影响越来越大。在克里希纳-戈达瓦里盆地中，完全水化的蒙皂石丰度较高，在任何给定的泥岩孔隙度或孔隙比值下，其渗透率都较高，因此在天然气水合物形成中可能发挥较小的作用。
This study documents X-ray diffraction results from bulk powders and oriented clay-size aggregates using samples from sites drilled and cored during the Indian National Gas Hydrate Expedition 01 (NGHP01). These sites are located in the Krishna–Godavari Basin, Mahanadi Basin, and Andaman accretionary wedge of the Bay of Bengal, and the Kerala-Konkan Basin of the Arabian Sea. Calcite is more abundant at the pelagic sites of the Andaman Sea and Kerala-Konkan Basin, which is consistent with previous studies of biological productivity and dilution by lithogenous influx. Hemipelagic sediments in the Krishna–Godavari Basin and Mahanadi Basin are comprised primarily of smectite-rich and illite-rich clay mineral assemblages, respectively. We attribute those contrasts to differences in detrital sources between the Deccan basalts (smectite sources) and Precambrian rocks of the Eastern Ghats Belt; those sources remained consistent over the entire history of sedimentation (0–9 Ma). Higher quartz content in the Mahanadi Basin and higher feldspar content at the Krishna–Godavari Basin reinforce these interpretations of detrital provenance. Smectite is the most abundant clay mineral in the Andaman Sea sediments likely due to weathering of volcanic sources along the Sunda Arc. Strata from the Kerala-Konkan Basin show a shift at 23 Ma from a smectite–kaolinite clay mineral assemblage to an increasingly illite-rich assemblage. We also see steady decreases in kaolinite and increases in chlorite and quartz over the 30-Myr record, which indicates increasing influences of material derived from physical weathering. The higher abundance of fully hydrated smectite in the Krishna–Godavari Basin may play a minor role in gas hydrate formation by sustaining higher permeabilities at any given value of mudstone porosity or void ratio.