An O-isotope profile through the HP-LT Corsican ophiolite, France and its implications for fluid flow during subduction

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doi: 10.1016/S0009-2541(00)00428-9
Authors:Miller, Jodie A.; Cartwright, Ian; Buick, Ian S.; Barnicoat, Andrew C.
Author Affiliations:Primary:
Monash University, Victorian Institute of Earth and Planetary Sciences, Clayton, Victoria, Australia
La Trobe University, Australia
University of Leeds, United Kingdom
Volume Title:Chemical Geology
Source:Chemical Geology, 178(1-4), p.43-69. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541
Publication Date:2001
Note:In English. 68 refs.; illus., incl. 4 tables, geol. sketch map
Summary:Subduction zones are important sites for fluid generation as the downgoing slab undergoes progressive high-pressure metamorphism. These fluids are thought to play an important role in the generation of arc-magmas, but their affect on the subducted slab itself is less clear. In this study, the stable isotope geochemistry of the Corsican ophiolite, which is variably affected by subduction-related metamorphism, was investigated to assess the impact of subduction zone fluid flow on the downgoing slab. A total of 170 stable isotope analyses (oxygen and carbon) showed the following features: (1) overall, the ophiolite preserves the same oxygen isotope profile with depth as unmetamorphosed ophiolites; (2) the variation in oxygen isotope values for different areas does not correlate with metamorphic grade; (3) oxygen and carbon isotope values for calcite in the ophiolite are not in equilibrium with the ophiolite but are similar to those of the overlying calc-schists (Schistes Lustres); and (4) hydrogen isotopes indicate that serpentinitisation of ultramafics occurred during sub-seafloor hydrothermal alteration and probably also during tectonic emplacement of the ophiolite. These features indicate that large-scale fluid flow did not affect the Corsican ophiolite during subduction zone metamorphism. Calcite in the ophiolite was probably precipitated from CO2-bearing fluids derived from decompression dehydration reactions affecting the overlying Schistes Lustres during exhumation of the ophiolite-bearing Schistes Lustres nappes. Given that ocean crust must undergo at least some dehydration during prograde subduction zone metamorphism, the evolved fluids must be either highly channelled or exit the slab relatively quickly so as to not interact with it. The results of this study indicate that the important fluid pathways on Corsica have yet to be identified, but are probably the shear zones and fault systems that bound different slices of the high-pressure nappe stack. Abstract Copyright (2001) Elsevier, B.V.
Subsections:Igneous rocks
Subjects:C-13/C-12; Carbon; Dehydration; Diabase; Exhumation; Fluid dynamics; Fluid phase; Gabbros; Geochemical profiles; Geochemistry; High pressure; Hydrothermal alteration; Igneous rocks; Isotope ratios; Isotopes; Low temperature; Matrix; Metabasalt; Metaigneous rocks; Metamorphic rocks; Metamorphism; Metasomatism; Mineral assemblages; Nappes; O-18/O-16; Ophiolite; Oxygen; P-T conditions; Plutonic rocks; Pressure; Serpentinization; Stable isotopes; Subduction; Subduction zones; Temperature; Corsica; Europe; France; Western Europe
Coordinates:N420000 N430000 E0100000 E0090000
Abstract Numbers:03M/1685
Record ID:2001055326
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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