Paleoenvironmental Study by the Mineralogical and Geochemical Analyses of the Deep-Sea Drilling Cores

对墨西哥湾、阿拉伯海和孟加拉扇的DSDP和ODP岩心进行了矿物学和地球化学研究。研究的目的是通过岩心的矿物学和地球化学特征来厘清古环境因素。所得结果差异显著。例如，墨西哥湾的沉积物柱具有丰富的蒙脱石和高岭石的特征。阿拉伯海沉积物的主要特征是坡缕石的存在。早中新世以来，孟加拉扇的沉积物确实具有变化的粘土矿物组成。影响黏土矿物组成的因素有地质、成岩作用、土壤形成、河流径流、海流和气候等。例如，墨西哥湾的沉积物柱很大程度上受到密西西比河径流的影响，而密西西比河径流是岩石矿物的主要来源。更重要的是，孟加拉扇的沉积物从喜马拉雅山脉的布拉马普特拉山脉吸收了大量的碎屑矿物。作者指出，早中新世以来，喜马拉雅山脉的运动与粘土矿物组成的垂直变化密切相关。阿拉伯海沉积物中坡缕石在沉积柱中所占比例不同，且比例随地质年代的变化而变化。同样，地球化学参数如K/Al、Ti/Al、Fe/Al、Cr/Al、Zn/Al、Ni/Al的比值。沉积柱中Si/Al、P/Al、Sr/Ca和Cu/Al的比值反映了地质历史时期的环境变化，反映了古环境事件。研究表明，沉积柱中黏土矿学与地球化学的关系并不一定是相互认识的，而是相互作用的。例如，沉积柱中Fe/Al、Cr/Al、Ni/Al和Zn/Al比值表明，除粘土矿物外，还含有其他岩性矿物，且与沉积环境变化密切相关。少

Mineralogical and geochemical studies carried out on the DSDP and ODP cores from the Gulf of Mexico, the Arabian Sea, and the Bengal Fan. The purpose of this study is to clarify the paleoenvironmental factors from the mineralogical and geochemical characteristics of these cores. The results obtained differ conspicuously. For example, the sediment columns of the Gulf of Mexico is characterized by the abundance of smectite and kaolinite. The sediments of the Arabian Sea is essentially characterized by the presence of palygorskite. The sediments of the Bengal Fan have indeed variable clay mineral compositions since the Early Miocene. The factors influencing the clay mineral compositions are such as geology, diagenetic transformation, soil formation, river runoff, sea currents, and climatology so on. For example, the sediment columns of the Gulf of Mexico are greatly influenced by the river runoff from the Mississippi which is the major source of the lithogenic minerals. The sediments of t … More he Bengal Fan have received a tremendus quantity of clastic minerals from the Burahmaputra which originates from the Himalayas. The authors point that the movements of the Himalayas are closely related to the vertical change in clay mineral compositions since the Early Miocene. The Arabian Sea sediments contain the palygorskite in various proportion of sedimentary columns and the proportion changes with geological time. In the same manner, the geochemical parameters such as the ratios of K/Al, Ti/Al, Fe/Al, Cr/Al, Zn/Al, Ni/Al. Si/Al, P/Al, Sr/Ca, and Cu/Al in sedimentary columns indicate the changes of environments in geological past and suggest the paleoenvironmental events. The present study shows that the relationshie between the clay minealogy and geochemistry in sedimentary columns is not neccessarily recognized each other but play a comelementary role. For example, the ratios of Fe/Al, Cr/Al, Ni/Al, and Zn/Al in sedimentary columns suggest that other lithogenic minerals except clay minerals are contained and closely related to the changes of sedimentary environments. Less