Oxygen isotope evidence for short-lived high-temperature fluid flow in the lower oceanic crust at fast-spreading ridges

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doi: 10.1016/j.epsl.2007.06.013
Authors:Coogan, Laurence A.; Manning, Craig E.; Wilson, Robert N.
Author Affiliations:Primary:
University of Victoria, School of Earth and Ocean Sciences, Victoria, BC, Canada
Other:
University of California, Los Angeles, United States
University of Leicester, Canada
Corporate Authors:Edinburgh Ion Microprobe Facility, Edinburgh
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 260(3-4), p.524-536. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:2007
Note:In English. Supplemental information/data is available in the online version of this article. 46 refs.; illus., incl. 1 table
Summary:Millimeter-scale amphibole veins in the lower oceanic crust record fracture-controlled fluid flow at high-temperatures but the importance of this fluid flow for the thermal and chemical evolution of the lower oceanic crust is unclear. In the section of lower oceanic crust recovered at Hess Deep from ODP Hole 894G, which formed at the fast-spreading East Pacific Rise, these veins are randomly distributed with an average spacing of ∼1 m. We unravel the history of fluid flow through one of these veins by combining in situ O-isotope analyses of wall-rock plagioclase with major element analyses, geothermometry and diffusion modeling. Thermometry indicates vein sealing by amphibole at ∼720 °C over a narrow temperature interval (20 °C). In situ O-isotope analyses by ion microprobe, with a precision of <0.5ppm, reveal zoning of O-isotopes in plagioclase adjacent to the vein. The zoning profiles can be reproduced using a diffusion model if the duration of O-isotope exchange was ≤100 yr. A similar interval of fluid-rock exchange is suggested by modeling potassium depletion in plagioclase adjacent to the vein. If representative of fracture controlled fluid flow in the lower oceanic crust the limited duration of fluid flow, and its occurrence over a narrow temperature interval, suggest that high-temperature fluid flow in this porosity network does not transport significant heat. Abstract Copyright (2007) Elsevier, B.V.
Sections:Geochemistry; Petrology; Physical properties of rocks and minerals
Subjects:Amphibole group; Amphibolite facies; Chain silicates; Circulation; Crust; Diffusion; Facies; Feldspar group; Fractures; Framework silicates; Gabbros; Geologic thermometry; High temperature; Hydrothermal conditions; Igneous rocks; Isotope ratios; Isotopes; Mid-ocean ridges; Numerical models; O-18/O-16; Ocean Drilling Program; Ocean floors; Oceanic crust; Oxygen; Plagioclase; Plutonic rocks; Silicates; Spatial distribution; Spreading centers; Stable isotopes; Temperature; Thermal history; Veins; Water-rock interaction; Zoning; East Pacific; East Pacific Rise; Equatorial Pacific; Hess Deep; Leg 147; North Pacific; Northeast Pacific; ODP Site 894; Pacific Ocean
Coordinates:N021757 N021806 W1013129 W1013136
Abstract Numbers:07M/3840
Record ID:2008044505
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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