Coupled C–S–Fe geochemistry in a rapidly accumulating marine sedimentary system: Diagenetic and depositional implications
Coupled C–S–Fe geochemistry in a rapidly accumulating marine sedimentary system: Diagenetic and depositional implications
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DOI：
10.1002/2015gc005754
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发表时间：
2015-09
期刊：
影响因子：
3.7
通讯作者：
A. Peketi;A. Mazumdar;H. M. Joao;D. J. Patil;A. Usapkar;P. Dewangan
中科院分区：
文献类型：
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作者：
A. Peketi;A. Mazumdar;H. M. Joao;D. J. Patil;A. Usapkar;P. Dewangan
本文研究了孟加拉湾Krishna-Godavari(K-G)盆地沉积岩芯(MD161-13)中的C-S-Fe系统学。岩心覆盖晚全新世，总沉积速率高达∼573cmKyr−1。孔隙流体化学分析表明，现今硫酸盐甲烷过渡带的深度为∼6Mbsf。(ΔTA+ΔCa+ΔMg)/ΔSO4 2−比值表明，有机碎屑降解和甲烷的厌氧氧化都驱动了研究地点的硫酸盐还原。总有机碳含量(TOC)与铬可还原硫(CRS)含量呈正相关，表明有机碎屑硫酸盐还原作用对硫化作用有显著影响。富~(34)S硫化物(黄铁矿)与富~(12)C自生碳酸盐带的共生是古硫酸盐甲烷过渡带的可能记录，AOM驱动的聚焦硫酸盐还原作用可能是由下伏富气带持续的高甲烷通量推动的。铝归一化低活性铁(FePR/Al)和La/Yb比值表明，在最近4KYR期间，相对于太古代-元古代花岗岩杂岩，德干玄武岩对Krishna-Godavari盆地沉积通量的贡献有所增加。
In the present study, we have investigated the C–S–Fe systematics in a sediment core (MD161‐13) from the Krishna‐Godavari (K‐G) basin, Bay of Bengal. The core covers the late Holocene period with high overall sedimentation rate of ∼573 cm kyr−1. Pore fluid chemical analyses indicate that the depth of the present sulfate methane transition zone (SMTZ) is at ∼6 mbsf. The (ΔTA + ΔCa + ΔMg)/ ΔSO42− ratios suggest that both organoclastic degradation and anaerobic oxidation of methane (AOM) drive sulfate reduction at the study site. The positive correlation between total organic carbon content (TOC) and chromium reducible sulfur (CRS) content indicates marked influence of organoclastic sulfate reduction on sulfidization. Coupled occurrence of 34S‐enriched iron sulfide (pyrite) with 12C‐enriched authigenic carbonate zones is the possible records of paleo‐sulfate methane transition zones where AOM‐driven‐focused sulfate reduction was likely fueled by sustained high methane flux from underlying gas‐rich zone. Aluminum normalized poorly reactive iron (FePR/Al) and La/Yb ratios suggest increasing contribution from Deccan basalts relative to that of Archean‐Proterozoic granitic complex in sediment flux of Krishna‐Godavari basin during the last 4 kyr.