Composition and origin of authigenic carbonates in the Krishna-Godavari and Mahanadi Basins, eastern continental margin of India
Composition and origin of authigenic carbonates in the Krishna-Godavari and Mahanadi Basins, eastern continental margin of India
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DOI：
10.1016/j.marpetgeo.2014.08.023
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发表时间：
2014-12
影响因子：
4.2
通讯作者：
B. Teichert;Joel E. Johnson;E. Solomon;L. Giosan;K. Rose;M. Kocherla;E. Connolly;M. Torres
中科院分区：
文献类型：
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作者：
B. Teichert;Joel E. Johnson;E. Solomon;L. Giosan;K. Rose;M. Kocherla;E. Connolly;M. Torres
来自Krishna-Godavari（KG）和Mahanadi盆地的自生碳酸盐的矿物学和稳定同位素组成提供了对孟加拉湾印度东部大陆边缘沉积物中诱导碳酸盐形成的过程的更深入了解。自生碳酸盐胶结物，（微）结核，生物扰动铸件和管道从12个核心位置钻在印度国家天然气水合物计划（NGHP）远征01进行了研究。自生碳酸盐沉淀过程主要有三个过程：有机硫酸盐还原、甲烷厌氧氧化和甲烷生成。在7号、10号、12号（KG盆地）和19号（Mahanadi盆地）地点回收的碳酸盐中显示出甲烷大量渗漏的证据。这些甲烷衍生的碳酸盐显示出典型的共生碳酸盐矿物学（文石、MgCO 3>15 Mol%的高镁方解石、富钙白云石）。甲烷衍生碳酸盐的两个单独的层位在4个钻孔之间（相距达1.16 km）进行了对比。上部地层的年代测定为14 C（40，100 - 51，600 a BP 1950），清楚地表明甲烷渗漏在过去要强烈得多，这可能是由于较低的海平面对整个边缘的天然气水合物稳定带的影响。
The mineralogical and stable isotopic composition of authigenic carbonates from the Krishna–Godavari (KG) and Mahanadi Basin provide a deeper insight into the processes inducing carbonate formation in the sediments of the eastern continental margin of India in the Bay of Bengal. Authigenic carbonate cements, (micro) nodules, bioturbation casts and tubes from 12 core locations drilled during the Indian National Gas Hydrate Program (NGHP) Expedition 01 were investigated for this study. Three main processes responsible for authigenic carbonate precipitation are identified: organoclastic sulfate reduction, anaerobic oxidation of methane and methanogenesis. Evidence of vigorous methane seepage is indicated in carbonates recovered at Sites 7, 10, 12 (KG Basin) and 19 (Mahanadi Basin). These methane-derived carbonates display typical paragenetic carbonate mineralogies (aragonite, high-Mg calcite with >15 Mol% MgCO3, Ca-rich dolomite). Two separate horizons of methane derived-carbonates are correlated between 4 drill holes (up to ∼16 km apart). The upper horizon has been dated with14C (40,100–51,600 a BP 1950) and clearly indicates that methane seepage has been much more vigorous in the past, possibly due to the effect of lower sea level on the gas hydrate stability zone across the margin.