马里亚纳海槽和西菲律宾海盆更新世以来沉积物中的粘土矿物

Clay Mineralogy of the Sediments Deposited Since the Pleistocene in the Mariana Trough and the West Philippine Basin

根据三个沉积岩芯的研究,马里亚纳海槽和西菲律宾海盆更新世以来的沉积物中粘土矿物明显不同:前者以海槽内基性火山物质蚀变形成的蒙皂石为主,伴随少量铁镁绿泥石和伊利石;后者以来自海盆以西陆上岩石风化形成的伊利石为主,其次为蒙皂石、普通绿泥石和高岭石。这种差别除与物源有关外,主要与两个海盆中的火山活动有关。海槽内粘土矿物也有差异,迷可能与海底热液活动的影响有关。古气候对粘土矿物也有影响,但在海槽则被频繁的火山活动所掩盖。

Clay mineralogy of the sediments deposited since the Pleistocene in the Mariana Trough and the West Philippine Basin was investigated by means of X-ray diffractometry and chemical analysis, based on three sediment cores (61KL, 57KL, 85KL) collected during the 'SONNE'Cruise 57 in 1988. Predominant, well-cyrstallized smectite, with certain amount of Fe Mg chlorite, small amount of illite and no kaolinite, were identified in the sediments of the Mariana Trough (61KL, 57KL). Smectite and Fe Mg chlorite are authigenic in origin and were mainly formed by submarine alteration of basic volcanic material in the Trough, whereas illite is detriral in origin and was mainly derived from the continents west of the Philippine Sea. In the sediments of the West Philippine Basin (85KL), however, illite is predominant, followed by certain amount of poorly-crystallized smectite, small amount of normal chlorite and kaolinite. These minerals are chiefly detrital in origin and were mostly derived from the continents west and northwest of the Philippine Sea, except for smectite which may be mostly derived from the alteration of basic volcanic material on the Palau-Kyushu Ridge east of the basin, but at least small part of the smectite may probably be derived from the nonvolcanic rocks on the land. The main factors affecting the associations and distributions of clay minerals in the Mariana Trough and the West Philippine Basin were discussed. The volcanic activity is the most important factor controlling the clay mineral associations and distributions of the two basins. Material sources also play an important roll. The variations in chemical characteristics of clay minerals found in the Mariana Trough may reflect the influence of submarine hydrothermal activities possibly present in this basin. The changes in paleoclimate is an important factor controlling the clay mineral distributions, but in the Mariana Trough such an influence is seriously masked by the frequent volcanic activities.