TY - JOUR
T1 - Brucite chimney formation and carbonate alteration at the Shinkai Seep Field, a serpentinite-hosted vent system in the southern Mariana forearc
AU - Okumura, T.
AU - Ohara, Y.
AU - Stern, R. J.
AU - Yamanaka, T.
AU - Onishi, Y.
AU - Watanabe, H.
AU - Chen, C.
AU - Bloomer, S. H.
AU - Pujana, I.
AU - Sakai, S.
AU - Ishii, T.
AU - Takai, K.
N1 - Funding Information:
The authors would thank the Shinkai 6500 operation team and the crew of the R/V Yokosuka for their professional support during the YK10-08, YK13-08, YK14-13, and YK15-11 Cruise. This study was conducted under the special permit of US Fish and Wildlife Service for studies in the Mariana Trench Marine National Monument. On-board samplings and discussions were performed under the support of the scientific parties of the cruises as listed below; Osamu Ishizuka, Uta Konno, Genki Ozawa, Masakazu Fujii, Masashi Ito, Fernando Martinez, Maryjo Brounce, Yusuke Miyajima, Shoma Oya, Tomoki Mizuno, Takuro Nunoura, Akinori Yabuki, and Miho Hirai. We also gratefully acknowledge Shinsuke Kawagucci and Akihiro Kano for their constructive discussions. Some thin sections were outsourced to Hokushin Koki Factory, Tokyo, Japan. Minoru Ikehara supported a part of stable carbon isotope analysis. We thank two anonymous reviewers for providing constructive comments. This project was partly founded by the Ministry of Education, Culture, Sports, Science, and Technology, Japan, by a grant-in-aids for Young Scientists (15H05468) and a JSPS research fellowship for young scientist (26-10363) to TO. Participation of US scientists was made possible by NSF grants EAR 0840862 and 1026150. The authors have no conflict of interests to declare. A video is provided as supporting information to show appearances of the chimneys at SSF. The data used are listed in the references, tables, figures and supporting information. The cruises information is provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and available via the JAMSTEC data website (http://www.godac.jamstec.go.jp/darwin/e/).
Publisher Copyright:
© 2016. The Authors.
PY - 2016/9/1
Y1 - 2016/9/1
N2 - Brucite-carbonate chimneys were discovered from the deepest known (∼5700 m depth) serpentinite-hosted ecosystem—the Shinkai Seep Field (SSF) in the southern Mariana forearc. Textural observations and geochemical analysis reveal three types (I–III) of chimneys formed by the precipitation and dissolution of constitutive minerals. Type I chimneys are bright white to light yellow, have a spiky crystalline and wrinkled surface with microbial mat and contain more brucite; these formed as a result of rapid precipitation under high fluid discharge conditions. Type II chimneys exhibit white to dull brown coloration, tuberous textures like vascular bundles, and are covered with grayish microbial mats and dense colonies of Phyllochaetopterus. This type of chimney is characterized by inner brucite-rich and outer carbonate rich zones and is thought to have precipitated from lower fluid discharge conditions than type I chimneys. Type III chimneys are ivory colored, have surface depressions and lack living microbial mats or animals. This type of chimney mainly consists of carbonate, and is in a dissolution stage. Stable carbon isotope compositions of carbonates in the two types (I and II) of active chimneys are extremely 13C-enriched (up to +24.1‰), which may reflect biological 12C consumption under extremely low dissolved inorganic carbon concentrations in alkaline fluids. Type III chimneys have 13C compositions indicating re-equilibration with seawater. Our findings demonstrate for the first time that carbonate chimneys can form below the carbonate compensation depth and provide new insights about linked geologic, hydrologic, and biological processes of the global deep-sea serpentinite-hosted vent systems.
AB - Brucite-carbonate chimneys were discovered from the deepest known (∼5700 m depth) serpentinite-hosted ecosystem—the Shinkai Seep Field (SSF) in the southern Mariana forearc. Textural observations and geochemical analysis reveal three types (I–III) of chimneys formed by the precipitation and dissolution of constitutive minerals. Type I chimneys are bright white to light yellow, have a spiky crystalline and wrinkled surface with microbial mat and contain more brucite; these formed as a result of rapid precipitation under high fluid discharge conditions. Type II chimneys exhibit white to dull brown coloration, tuberous textures like vascular bundles, and are covered with grayish microbial mats and dense colonies of Phyllochaetopterus. This type of chimney is characterized by inner brucite-rich and outer carbonate rich zones and is thought to have precipitated from lower fluid discharge conditions than type I chimneys. Type III chimneys are ivory colored, have surface depressions and lack living microbial mats or animals. This type of chimney mainly consists of carbonate, and is in a dissolution stage. Stable carbon isotope compositions of carbonates in the two types (I and II) of active chimneys are extremely 13C-enriched (up to +24.1‰), which may reflect biological 12C consumption under extremely low dissolved inorganic carbon concentrations in alkaline fluids. Type III chimneys have 13C compositions indicating re-equilibration with seawater. Our findings demonstrate for the first time that carbonate chimneys can form below the carbonate compensation depth and provide new insights about linked geologic, hydrologic, and biological processes of the global deep-sea serpentinite-hosted vent systems.
KW - brucite
KW - carbonate
KW - chimney
KW - serpentinite-hosted ecosystem
KW - southern Mariana fore arc
KW - the Shinkai Seep Field
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U2 - 10.1002/2016GC006449
DO - 10.1002/2016GC006449
M3 - Article
AN - SCOPUS:84994045610
VL - 17
SP - 3775
EP - 3796
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
SN - 1525-2027
IS - 9
ER -