Barnes, Jaime D. and Cisneros, Miguel (2012): Mineralogical control on the chlorine isotope composition of altered oceanic crust

Leg/Site/Hole:
DSDP 52 418
DSDP 53 418
ODP 102 418
ODP 206 1256
IODP 309 U1256
IODP 312 U1256
IODP 335 1256
ODP 118 735
ODP 176 735
ODP 129 801
ODP 185 801
Identifier:
2012-095595
georefid

10.1016/j.chemgeo.2012.07.022
doi

Creator:
Barnes, Jaime D.
University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States
author

Cisneros, Miguel
author

Identification:
Mineralogical control on the chlorine isotope composition of altered oceanic crust
2012
Chemical Geology
Elsevier, Amsterdam, Netherlands
326-327
51-60
Bulk chlorine concentrations and chlorine stable isotope compositions were determined for hydrothermally altered basalt (extrusive lavas and sheeted dikes) and gabbro samples (n=50) from seven DSDP/ODP/IODP drill sites. These altered oceanic crust (AOC) samples span a range of crustal ages, tectonic settings, alteration type, and crustal depth. Bulk chlorine concentrations range from <0.01 wt.% to 0.09 wt.%. In general, higher chlorine concentrations coincide with an increase in temperature of alteration and amphibole content. delta (super 37) Cl values of whole rock AOC samples range from -1.4 to +1.8 ppm. High delta (super 37) Cl values (> or = approximately 0.5 ppm) are associated with areas of higher amphibole content. This observation is consistent with theoretical calculations that estimate amphibole should be enriched in (super 37) Cl compared to co-existing fluid. Negative to near zero delta (super 37) Cl values are found in areas dominated by clay minerals. Chlorine geochemistry is a rough indicator of metamorphic grade and mineralogy. AOC is a major Cl host in the subducting oceanic lithospheric slab. Here we show that bulk chlorine concentrations are approximately 3 times higher than previous estimates resulting in a greater contribution of Cl to the mantle. Abstract Copyright (2012) Elsevier, B.V.
English
Serial
Coverage:Geographic coordinates:
North:25.0207
West:-91.5600East: 156.2136
South:-32.4327

Isotope geochemistry; Igneous and metamorphic petrology; Atlantic Ocean; Atlantis II fracture zone; basalts; Bermuda Rise; chemical composition; chlorine; chromatograms; Cl-37/Cl-35; crust; DSDP Site 418; East Pacific; Equatorial Pacific; Expeditions 309/312; gas chromatograms; Guatemala Basin; halogens; hydrothermal alteration; igneous rocks; Indian Ocean; Integrated Ocean Drilling Program; isotope ratios; isotopes; lithosphere; metasomatism; mineral composition; North Atlantic; North Pacific; Northeast Pacific; Northwest Pacific; Ocean Drilling Program; oceanic crust; oceanic lithosphere; ODP Site 1256; ODP Site 735; ODP Site 801; Pacific Ocean; Pigafetta Basin; Southwest Indian Ridge; stable isotopes; volcanic rocks; West Pacific; X-ray diffraction data;

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