Geochemistry and provenance study of recent deep-water sediments around Taiwan
Abstract
Deep-water areas around Taiwan encompass two subduction zones and the NE continental margin of the South China Sea. Sediments in the said areas are mainly sourced from the rising Taiwan orogen, volcanic arc terranes and continental hinterland. We study the clay mineralogy and sediment chemistry for deep-water seafloor sediments collected in different tectonic settings around Taiwan to unravel the tectonic and climatic controls on sediment weathering and source-to-sink of the sediments. We collected many sediment gravity cores, piston cores and box cores onboard R/V Ocean Researcher I during OR1-1013 and OR1-1138 cruises and during MD214 EAGER cruise onboard R/V Marion Dufresne. Different oxide and trace element ratio of the sediments and weathering-trend ternary diagrams indicate moderate chemical weathering; however, strong physical erosion can be responsible for high contents of primary minerals. Four characteristic end-members in clay mineral compositions are observed from five major provenances. We found sediments with abundant illite and chlorite and negligible smectite and kaolinite are sourced from Taiwanese rivers. However, the Hateruma forearc basin of the Ryukyu subduction system in the eastern offshore Taiwan shows comparatively more smectite, interpreted as derived mainly from the Ryukyu Islands. The Luzon forearc basin near Taiwan, perched basins in the upper accretionary wedge of the Manila subduction system and the South China Sea domain (Formosa Canyon and the overbanking area of the Manila Trench) show relatively more smectite and kaolinite, most likely derived from the Luzon arc system and from the Pearl River, respectively. Magnetic mineral study suggests the presence of pyrrhotite, a characteristic component of sediments sourced from Taiwan in the eastern offshore of Taiwan and accretionary wedge off SW Taiwan, and along the Gaoping Canyon. Its absence in the Hateruma Basin reveals that sediments are transported transversely downslope from the nearby Ryukyu Islands. Presence of few pyrrhotite along with magnetite in samples from Formosa canyon suggest that there is still contribution of sediments from Taiwanese rivers in addition to rivers from China (e.g., Pearl River).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP11D1417N
- Keywords:
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- 1910 Data assimilation;
- integration and fusion;
- INFORMATICS;
- 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3036 Ocean drilling;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4512 Currents;
- OCEANOGRAPHY: PHYSICAL