Isotopic evidence (B, C, O) of deep fluid processes in fault rocks from the active Woodlark Basin detachment zone

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doi: 10.1016/S0012-821X(03)00016-5
Author(s): Kopf, Achim; Behrmann, Jan H.; Deyhle, Annette; Roller, Sybille; Erlenkeuser, Helmut
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Other:
Universität Freiburg, Federal Republic of Germany
Universität Kiel, Federal Republic of Germany
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 208(1-2), p.51-68. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 52 refs.; illus., incl. sects., 1 table, sketch map
Summary: We report results from boron, carbon and oxygen stable isotope analyses of faulted and veined rocks recovered by scientific ocean drilling during ODP Leg 180 in the western Woodlark Basin, off Papua New Guinea. In this area of active continental extension, crustal break-up and incipient seafloor spreading, a shallow-dipping, seismically active detachment fault accommodates strain, defining a zone of mylonites and cataclasites, vein formation and fluid infiltration. Syntectonic microstructures and vein-fill mineralogy suggest frictional heating during slip during extension and exhumation of Moresby Seamount. Low carbon and oxygen isotope ratios of calcite veins indicate precipitation from hydrothermal fluids (δ13CPDB down to -17 per mil; δ18OPDB down to -22 per mil) formed by both dehydration and decarbonation. Boron contents are low (<7 ppm), indicating high-grade metamorphic source rock for the fluids. Some of the δ11B signatures (17-35 per mil; parent solutions to calcite vein fills) are low when compared to deep-seated waters in other tectonic environments, likely reflecting preferential loss of 11B during low-grade metamorphism at depth. Pervasive devolatilization and flux of CO2-rich fluids are evident from similar vein cement geochemistry in the detachment fault zone and splays further updip. Multiple rupture-and-healing history of the veins suggests that precipitation may be an important player in fluid pressure evolution and, hence, seismogenic fault movement. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 16 Structural Geology; B-11/B-10; Boron; C-13/C-12; Calcite; Carbon; Carbon dioxide; Carbonates; Cement; Deformation; Detachment faults; Emission spectra; Experimental studies; Extension fractures; Faults; Fluid phase; Fluid pressure; Fractures; Friction; Geochemistry; Geophysical profiles; Heating; ICP mass spectra; Isotope ratios; Isotopes; Leg 180; Low-grade metamorphism; Mass spectra; Metamorphism; Microstructure; Moresby Seamount; O-18/O-16; ODP Site 1108; ODP Site 1110; ODP Site 1111; ODP Site 1112; ODP Site 1113; ODP Site 1114; ODP Site 1117; Ocean Drilling Program; Ocean floors; Oxygen; Pacific Ocean; Seamounts; Seismic profiles; South Pacific; Southwest Pacific; Spectra; Stable isotopes; Syntectonic processes; Thermal effects; Veins; Volatilization; Water-rock interaction; West Pacific; Woodlark Basin
Coordinates: S120000 S073000 E1570000 E1520000
Record ID: 2003029642
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands