||Kueishantao Island is located in Ilan bay, Northeast Taiwan, the southwestern end of the Okinawa Trough, which has marine shallow-water hydrothermal activities and uncommon chimney-like hydrothermal plume formed by the precipitation of Sulfur.In this thesiswe analyzedOR2-1666 B and OR21666 S2 two marine sediment cores, rocks at or surrounding the marine hydrothermal plume (yellow and white smokers), and clay mineral near Kueishantao Island. In order to understand the influences caused by hydrothermal activity, the present study has used petrographic and scanning electron microscopy, and electron microprobe analysis to study mineral assemblages and mineral compositions in the marine sediment cores and rocks nearby the hydrothermal plumes. The composition and distribution of clay minerals in sediments are analyzed by X-ray Powder Diffraction method (XRD).|
Rocks around white smoker are two-pyroxene andesite, the mineral assemblage is dominated by plagioclase (andesine, labradorite), augite, enstatite, small amount of pyrite and sanidine. The matrix is composed of plagioclase, pyroxene, quartz, some sulfate and clay minerals. Yellow smoker was formed by massive sulfide which precipitated from hydrothermal fluid. Rocks around yellow smoker contain more pyrite, illite and chlorite than rocks around white smoker, consider as hydrothermal alteration caused by hydrothermal fluid.Clay minerals quantitative X-ray diffraction (XRD) analysis results shows that illite was the most abundant, followed by chlorite and kaolinite and nearly no smectite in both B and S2 core.
Compare the composition of clay minerals, Esquevin-Index (EI) and illite crystallinity data from Kueishantao Island sediment cores with sediments from rivers of eastern Taiwan, Yangtze River and the East China Sea continental shelf. The result shows that Kueishantao Island marine sediments are similar to sediments from rivers of eastern Taiwan, especially the Ilan River. Thus the Ilan River is the major source to the silt grain size sediments (<25 μm), and andesite debris in the fine sand grain size sediments (>125 μm) was provided by the Kueishantao Island.