Fluid Venting Activity on the Costa Rica Margin: New Results from Authigenic Carbonates.

Han, Xiqiu, Suess, Erwin, Sahling, Heiko and Wallmann, Klaus (2004) Fluid Venting Activity on the Costa Rica Margin: New Results from Authigenic Carbonates. International Journal of Earth Sciences, 93 . pp. 596-611.

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Abstract

Carbonate precipitates on mounds and along tectonic scarps off the Costa Rica margin are manifestations of subduction-induced dewatering. The long-term dewatering history is recorded in mineralogical, petrological and isotope signals of carbonates recovered from these sites. The carbonates are strongly depleted in δ13C (−11 to −53‰ PDB) and enriched in δ18O (+4 to +8‰ PDB). Thermogenic methane and biogenic methane were identified as sources of the carbon. Chemoherm carbonates and seepage-associated carbonates formed in a focused flow regime have lighter δ13C values, while others formed in a more diffusive flow regime have slightly enriched C isotope values. Three fluid components were inferred based on the calculation of equilibrium δ18O: clay dehydration water, gas hydrate water and seawater. Calculated equilibrium δ18O values of carbonates from different down-core depths as well as from different precipitation stages show that the δ18O of the precipitating fluid is progressively depleted with time. Dolostones showing a methane-C source and a well constrained O-isotope signature are thought to have formed at depth in the sediment and subsequently became exhumed. Glauconitic sandstones cemented by methane-derived carbonate provide evidence that fluid and solid material have been expelled by the mud volcano.

Document Type: Article
Keywords: Authigenic carbonates; C- and O- isotopes; Petrology; Fluid venting; Costa Rica margin
Research affiliation: OceanRep > SFB 574 > A3
OceanRep > SFB 574 > B6
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > SFB 574
OceanRep > SFB 574 > B3
Refereed: Yes
Open Access Journal?: No
ISSN: 1437-3254
Contribution Number:
ProjectNumber
SFB 57450
Expeditions/Models/Experiments:
Date Deposited: 24 Mar 2009 16:22
Last Modified: 23 May 2017 09:14
URI: http://oceanrep.geomar.de/id/eprint/7652

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