We conducted a detailed rock magnetic study complemented by sedimentological and mineralogical methods on a 177.2-m-long sediment core of Hole NGHP-01-14A to constrain the influence of high-energy depositional environment on the magnetic mineral diagenesis and formation of gas hydrates in the Krishna-Godavari (K-G) basin, Bay of Bengal. Five sediment magnetic zones were identified based on the downcore variation in rock magnetic parameters. The magnetic mineralogies comprised of detrital titanomagnetite, diagenetically formed magnetic iron sulfides and their mixture. A distinct magnetically enhanced zone (Z-3) close to a bottom simulating reflector (BSR) is dominated by higher magnetite content, sediment bulk density, and grain size and probably represents several sand-rich sediment layers formed as a result of short-duration intense sedimentation events and got rapidly buried and provided conducive environment for the formation of gas hydrate deposits at the studied site. The concurrence of gas hydrates and high gas saturations within the sand-rich layers (Z-3) suggests that the high-energy depositional environment had a larger control over hydrate formation at Hole NGHP-01-14A. Two magnetic iron sulfide bearing sediment intervals in Z-1b and Z-1c below sulfate-methane transition zone (SMTZ) suggest that their formation is controlled by microbially mediated diagenetic reactions fuelled by presence of gas hydrates and probably represents the fossil gas hydrate zones. We propose that the rock magnetic variations in the studied sediment core at Hole NGHP-01-14A is controlled by both differential loading of detrital magnetic minerals as well as hydrate-induced late diagenetic magnetic iron sulfide formation.

中文翻译：

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孟加拉湾 Krishna-Godavari 盆地高能沉积系统中天然气水合物产状的岩磁透视

我们对 NGHP-01-14A 孔 177.2 米长的沉积岩心进行了详细的岩石磁性研究，并辅以沉积学和矿物学方法，以限制高能沉积环境对磁性矿物成岩作用和天然气水合物形成的影响。 Krishna-Godavari (KG) 盆地，孟加拉湾。根据岩石磁参数的下芯变化确定了五个沉积物磁区。磁性矿物包括碎屑钛磁铁矿、成岩形成的磁性硫化铁及其混合物。靠近底部模拟反射器 (BSR) 的明显磁增强区 (Z-3) 主要由较高的磁铁矿含量、沉积物堆积密度、和颗粒大小，可能代表了由于短期强烈沉积事​​件而形成的几个富含砂的沉积层，并被迅速掩埋，为研究地点的天然气水合物沉积物的形成提供了有利的环境。富含砂层（Z-3）内的天然气水合物和高含气饱和度的并发表明高能沉积环境对NGHP-01-14A孔的水合物形成有更大的控制。在硫酸盐-甲烷过渡带 (SMTZ) 下方的 Z-1b 和 Z-1c 中的两个含磁性硫化铁的沉积层段表明它们的形成受由气体水合物的存在推动的微生物介导的成岩反应控制，并且可能代表化石气体水合物带。