Borehole observations of fluid flow from South Chamorro Seamount, an active serpentinite mud volcano in the Mariana forearc

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doi: 10.1016/j.epsl.2007.11.057
Author(s): Wheat, C. Geoffrey; Fryer, Patricia; Fisher, Andrew T.; Hulme, Samuel; Jannasch, Hans; Mottl, Michael J.; Becker, Keir
Author Affiliation(s): Primary:
University of Alaska Fairbanks, Global Undersea Research Unit, Fairbanks, AK, United States
Other:
University of Hawaii at Manoa, United States
University of California, Santa Cruz, United States
Monterey Bay Aquarium Research Institute, United States
University of Miami, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 267(3-4), p.401-409. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. Supplemental information/data is available in the online version of this article. 37 refs.; illus., incl. sketch map
Summary: A sealed borehole observatory (CORK) was deployed on South Chamorro Seamount, an active serpentinite mud volcano in the Mariana forearc to explore subduction-related processes on a non-accretionary, convergent plate margin. Formation fluid was overpressured relative to ambient hydrostatic conditions. Fluid flowed from the borehole at ∼0.2 L/s when the observatory was opened to recover instruments 2 yr after it was installed. The chemical composition of the formation fluid is similar to that extrapolated from trends in pore water data collected during Ocean Drilling Program Leg 195 when the observatory was established. Reduced sulfur is present in this highly-alkaline (pH 12.4) formation fluid, indicative of microbial activity at or below the depth of the screened casing, 149-202 m below the seafloor. Discharge from the open borehole continued for 37 days, until the observatory was resealed. This discharge requires significant permeability at depth (>6×10-14 m2). Zones of high permeability may be associated with the formation of headwall scarps, consistent with numerous slumps on the southeastern flank of the seamount, and likely shape a geochemical environment suitable for an active microbial community. Abstract Copyright (2008) Elsevier, B.V.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Basins; Boreholes; Brucite; CORK; Carbonates; Communities; Connate waters; Fore-arc basins; Formation fluid; Geochemistry; Leg 195; Mariana Trench; Metaigneous rocks; Metamorphic rocks; Metasomatic rocks; Microorganisms; Mud volcanoes; North Pacific; Northwest Pacific; ODP Site 1200; Observatories; Ocean Drilling Program; Ocean floors; Overpressure; Oxides; Pacific Ocean; Plate tectonics; Pore water; Precipitation; Sampling; Sea water; Seamounts; Serpentinite; South Chamorro Seamount; Subduction; West Pacific
Coordinates: N134700 N134800 E1460100 E1460000
Record ID: 2008109576
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands