Clay minerals in an active hydrothermal field at Iheya-North-Knoll, Okinawa Trough

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doi: 10.1111/rge.12078
Author(s): Miyoshi, Youko; Ishibashi, Jun-ichiro; Shimada, Kazuhiko; Inoue, Hiroyasu; Uehara, Seiichiro; Tsukimura, Katsuhiro
Author Affiliation(s): Primary:
Kyushu University, Graduate School of Sciences, Department of Earth and Planetary Sciences, Fukuoka, Japan
National Institute of Adwanced Industrial Science and Technology, Japan
Volume Title: Resource Geology (Tokyo. 1998)
Source: Resource Geology (Tokyo. 1998), 65(4), p.346-360. Publisher: Wiley-Blackwell on behalf of the Society of Resource Geology, Oxford, United Kingdom. ISSN: 1344-1698
Note: In English. 37 refs.; illus., incl. 1 table, sketch map
Summary: Iheya-North-Knoll is one of the small knolls covered with thick sediments in the Okinawa Trough back-arc basin. At the east slope of Iheya-North-Knoll, nine hydrothermal vents with sulfide mounds are present. The Integrated Ocean Drilling Program (IODP) Expedition 331 studied Iheya-North-Knoll in September 2010. The expedition provided us with the opportunity to study clay minerals in deep sediments in Iheya-North-Knoll. To reveal characteristics of clay minerals in the deep sediments, samples from the drilling cores at three sites close to the most active hydrothermal vent were analyzed by X-ray diffraction, scanning electron microscope and transmission electron microscope. The sediments are classified into Layer 0 (shallow), Layer 1 (deep), Layer 2 (deeper) and Layer 3 (deepest) on the basis of the assemblage of clay minerals. Layer 0 contains no clay minerals. Layer 1 contains smectite, kaolinite and illite/smectite mixed-layer mineral. Layer 2 contains chlorite, corrensite and chlorite/smectite mixed-layer mineral. Layer 3 is grouped into three sub-layers, 3A, 3B and 3C; Sub-layer 3A contains chlorite and illite/smectite mixed-layer mineral, sub-layer 3B contains chlorite/smectite and illite/smectite mixed-layer minerals, and sub-layer 3C contains chlorite and illite. Large amounts of di-octahedral clay minerals such as smectite, kaolinite, illite and illite/smectite mixed-layer mineral are found in Iheya-North-Knoll, which is rarely observed in hydrothermal fields in mid-ocean ridges. Tri-octahedral clay minerals such as chlorite, corrensite and chlorite/smectite mixed-layer mineral in Iheya-North-Knoll have low Fe/(Fe + Mg) ratios compared with those in mid-ocean ridges. In conclusion, the characteristics of clay minerals in Iheya-North-Knoll differ from those in mid-ocean ridges; di-octahedral clay minerals and Fe-poor tri-octahedral clay minerals occur in Iheya-North-Knoll but not in mid-ocean ridges. Abstract Copyright (2015), The Society of Resource Geology.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Back-arc basins; Basins; Clay mineralogy; Clay minerals; Expedition 331; Hydrothermal alteration; Hydrothermal vents; Iheya-North-Knoll; Illite; Integrated Ocean Drilling Program; Kaolinite; Marine sediments; Metasomatism; Mid-ocean ridges; North Pacific; Northwest Pacific; Ocean floors; Okinawa Trough; Pacific Ocean; Sediments; Sheet silicates; Silicates; Smectite; West Pacific
Coordinates: N274700 N274800 E1265500 E1265300
Record ID: 2018026780
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom