Preliminary study on clay minerals of sediments in Western Taiwan Strait

The composition and distribution of main clay minerals from the sediments in the western Taiwan Strait have been determined by x-ray diffraction, infrared absorbtive spectroscopy and chemical methods and their origins are studied. The conclusions are drawn as follows: (1) Hydromica is the most abundant clay mineral of the sediments from the studied area, followed by. kaolinite (for the Fujian alongshore waters) or chlorite, (2) The content of hydromicatends to increase seaward, while kaolinite tends to decrease correspondingly. Kaolinite distribution obviously subjects to the terrestrial effects. Chlorite and montmorillonite distributions show porphyritic pattern in the studied area. (3) Most of the hydromica minerals in the studied area are of muscovite type. The kaolinite is a terrigenous secondary mineral. In addition to terrestrial orgin, the chlorite is mainly alteration producl of basic volcanic substance and of other clay mimerals. Montmorillonite in this area is mainly authigenic mineral. (4) The lobate contours of kaolimite content shows that the dispersive directions of the clay minerals are both southward with turning eastward in the Fujian alongshore waters and northeastward in the region to the east of Dongshan Island, which shows that the dispersive directions of the clay minerals have been influenced by Minzhe alongshore currents and the South China Sea warm current. (5) The vertical changes of clay mineral content provide evidences of paleoclimate and ancient sedimentary environment. In Core 737, the sediments of O-160cm are the product of warm climate in Atlantic stage of postglacial with low montmorillonite and high hydromica contents, and the sediments of 160-652cm are of cold climate in Boreal and Preboreal stages with high montmorillonite and low hrdromica contents, while low montmorillonite contents at 435- 440, 515-520 and 642-652cm show minor sedimentary cycles with warmer climate.