Stable chlorine isotopes in pore waters from DSDP Hole 79-546 and ODP Hole 131-808C

Stable Cl isotope ratios, measured in marine pore waters associated with the Barbados and Nankai subduction zones, extend significantly (to ~-8 per mil) the range of d37Cl values reported for natural waters. These relatively large negative values, together with geologic and chemical evidence from Ba...

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Bibliographic Details
Main Authors: Ransom, Barbara, Spivack, Arthur J, Kastner, Miriam
Format: Other/Unknown Material
Language:English
Published: PANGAEA 1995
Subjects:
131-808C
79-546
Deep Sea Drilling Project
DRILL
Drilling/drill rig
DSDP
Glomar Challenger
Joides Resolution
Leg131
Leg79
North Atlantic/PLATEAU
Ocean Drilling Program
ODP
Philippine Sea
North Atlantic
Online Access:https://doi.pangaea.de/10.1594/PANGAEA.712358
https://doi.org/10.1594/PANGAEA.712358
Description
Summary:Stable Cl isotope ratios, measured in marine pore waters associated with the Barbados and Nankai subduction zones, extend significantly (to ~-8 per mil) the range of d37Cl values reported for natural waters. These relatively large negative values, together with geologic and chemical evidence from Barbados and Nankai and recent laboratory data showing that hydrous silicate minerals (i.e., those with structural OH sites) are enriched up to 7.5 per mil in 37Cl relative to seawater, strongly suggest that the isotopic composition of Cl in pore waters from subduction zones reflects diagenetic and metamorphic dehydration and transformation reactions. These reactions involve clays and/or other hydrous silicate phases at depth in the fluid source regions. Chlorine therefore cannot be considered geochemically conservative in these systems. The uptake of Cl by hydrous phases provides a mechanism by which Cl can be cycled into the mantle through subduction zones. Thus, stable Cl isotopes should help in determining the extent to which Cl and companion excess volatiles like H2O and CO2 cycle between the crust and mantle.

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