The origin of hydrothermal chlorite- and anhydrite-rich sediments in the middle Okinawa Trough, East China Sea
Humphris, Susan E.
MetadataShow full item record
KeywordHydrothermal alteration; Chlorite-rich sediments; Okinawa Trough; Terrigenous; Pumice; Sr-Nd isotopes; Integrated Ocean Drilling Program
During the Integrated Ocean Drilling Program (IODP) Expedition 331, five sites were drilled into the Iheya North Knoll hydrothermal system in the Okinawa Trough (OT) — a back-arc basin characterized by thick terrigenous sediment. Following up on the previous study by Shao et al. (2015), we present new mineralogical, geochemical, and Sr-Nd isotope data to investigate the origin of the hydrothermal sediments and characterize the hydrothermal system. The substrate at the Iheya North Knoll is dominated by pumiceous sediment and other volcanoclastic materials interbedded with hemipelagic (terrigenous and biogenous) sediments. Impermeable layers separate the hydrothermal sediments into distinct units with depth that are characterized by various assemblages of alteration materials, including polymetallic sulfides, sulfates, chlorite- and kaolinite-rich sediments. The rare earth elements (REEs) and Nd isotope data suggest that the chlorite-rich and kaolinite-rich layers primarily resulted from the alteration of pumiceous materials in different chemical and physical conditions. Kaolinite-rich sediment likely reflects low pH and low Mg concentration fluids, while chlorite-rich sediment formed from fluids with high pH and increased Mg contents, likely at higher temperatures. The Sr isotopic compositions of subsurface anhydrite reflect high seawater/hydrothermal fluid ratios in the mid-OT hydrothermal area. Compared with chlorite-rich sediments from other sediment-covered or felsic-hosted hydrothermal systems, the chlorite-rich sediments in the mid-OT are characterized by lower concentrations of Al and Fe but much higher Y, Zr, Hf, Th and REEs, indicative of the distinct nature of the precursor rocks in this region.
© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Chemical Geology 465 (2017): 35-51, doi:10.1016/j.chemgeo.2017.05.020.
Suggested CitationPreprint: Shao, Hebin, Yang, Shouye, Humphris, Susan E., Cai, Di, Cai, Feng, Li, Jiangtao, Li, Qing, "The origin of hydrothermal chlorite- and anhydrite-rich sediments in the middle Okinawa Trough, East China Sea", 2017-05-18, https://doi.org/10.1016/j.chemgeo.2017.05.020, https://hdl.handle.net/1912/9094
Showing items related by title, author, creator and subject.
Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation : evidence from the sedimentation rate and planktonic foraminiferal record Xiang, Rong; Sun, Youbin; Li, Tiegang; Oppo, Delia W.; Chen, Muhong; Zheng, Fan (2006-08-25)Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since ~18 to ...
Last deglaciation in the Okinawa Trough : subtropical northwest Pacific link to Northern Hemisphere and tropical climate Sun, Youbin; Oppo, Delia W.; Xiang, Rong; Liu, Weiguo; Gao, Shu (American Geophysical Union, 2005-06-23)Detailed deglacial and Holocene records of planktonic δ18O and Mg/Ca–based sea surface temperature (SST) from the Okinawa Trough suggest that at ∼18 to 17 thousand years before present (kyr B.P.), late spring/early summer ...
Monsoon hydrography and productivity changes in the East China Sea during the past 100,000 years : Okinawa Trough evidence (MD012404) Chang, Yuan-Pin; Chen, Min-Te; Yokoyama, Yusuke; Matsuzaki, Hiroyuki; Thompson, William G.; Kao, Shuh-Ji; Kawahata, Hodaka (American Geophysical Union, 2009-08-29)We analyzed the high-resolution foraminifer isotope records, total organic carbon (TOC), and opal content from an Okinawa Trough core MD012404 in order to estimate the monsoon hydrography and productivity changes in the ...