Taiwan river muds from source to sink: Provenance control, inherited weathering, and offshore dispersal pathways

Clay mineralogy and geochemistry of river muds around Taiwan Island reveal dominant provenance control. Abundant illite with subordinate chlorite in the western, northern, and southern parts of the island are derived from Cenozoic mudrocks of the axial Slate Belt and Western Foothills. In eastern Taiwan, chlorite is most common in muds generated from the Tananao Complex, whereas smectite is produced by erosion of arc andesites of the Coastal Range. Kaolinite occurs in minor amounts in western Taiwan, where it is mostly recycled from mudrocks originally generated in mainland China and accumulated along the Chinese passive margin before being tectonically accreted in the Western Foothills of the Taiwan thrust belt. Only locally in more humid regions of northern Taiwan may moderate kaolinite content associated with relatively high illite chemistry index hint at present kaolinite formation. Mineralogical and geochemical indications of weathering are thus considered to be mostly inherited rather than indicative of present climatic and geomorphological conditions. A comparison of clay-mineral assemblages in Taiwan river muds and offshore deep-sea clays allows us to trace sediment transport from the land to the deep-sea. Mostly illite is supplied to the Taiwan Strait and the South China Sea, whereas subequal amounts of illite and chlorite are delivered to the Ryukyu forearc basin from eastern Taiwan rivers draining the Tananao Complex. Smectite from Coastal Range andesites is transferred via the Xiuguluan River and Chimei Canyon directly to the Ryukyu trench. Additional amounts of smectite produced in the Ryukyu and Luzon arcs are transported southward to the Ryukyu forearc basin and northward by the Kuroshio Current, northwestward to the northern South China Sea and northeastward to the Huatung Basin and Okinawa Trough.