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The origin of carbonate veins within the sedimentary cover and igneous rocks of the Cocos Ridge: results from IODP Hole U1414A

The origin of carbonate veins within the sedimentary cover and igneous rocks of the Cocos Ridge: results from IODP Hole U1414A
The origin of carbonate veins within the sedimentary cover and igneous rocks of the Cocos Ridge: results from IODP Hole U1414A
Carbonate veins in the igneous basement and in the lithified sedimentary cover of the Cocos Ridge at IODP Hole 344‐U1414A reveal the hydrologic system and fluid‐rock interactions. IODP Hole 344‐U1414A was drilled on the northern flank of the Cocos Ridge, and is situated 1 km seaward from the Middle America Trench offshore Costa Rica. Isotopic and elemental compositions were analyzed to constrain the fluid source of the carbonate veins and to reveal the thermal history of Hole 344‐U1414A. The formation temperatures (oxygen isotope thermometer) of the carbonate veins in the lithified sedimentary rocks range from 70 to 92 °C and in the basalt from 32 to 82 °C. 87Sr/86Sr ratios of the veins in the altered Cocos Ridge basalt range between 0.707307 and 0.708729. The higher ratios are similar to seawater strontium ratios in the Neogene. 87Sr/86Sr ratios lower 0.7084 indicate exchange of Sr with the igneous host rock. The calcite veins hosted by the sedimentary rocks are showing more primitive 87Sr/86Sr ratios < 0.706396. The isotopic compositions indicate seawater, modified into a hydrothermal fluid by subsequent heating, as the main fluid source. Low‐temperature alteration and the presence of a high temperature fluid resulted in different carbonate precipitates forming up to several cm thick veins. The geochemical data combined with age data of the sedimentary rocks suggest intraplate seamount volcanism in the area between the Galapagos hotspot and the Cocos Island as an additional heating source, after the formation of the Cocos Ridge at the Galapagos hotspot.
1525-2027
Brandstätter, Jennifer
86989160-b530-4259-b65e-54f8deab1fc4
Kurz, Walter
84e3a85d-3697-40f2-9a43-ae4af4b5b884
Richoz, Sylvain
d4fa0c32-37cc-4cfd-b1a9-1b2b17ffcba7
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Teagle, Damon A.H.
396539c5-acbe-4dfa-bb9b-94af878fe286
Brandstätter, Jennifer
86989160-b530-4259-b65e-54f8deab1fc4
Kurz, Walter
84e3a85d-3697-40f2-9a43-ae4af4b5b884
Richoz, Sylvain
d4fa0c32-37cc-4cfd-b1a9-1b2b17ffcba7
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Teagle, Damon A.H.
396539c5-acbe-4dfa-bb9b-94af878fe286

Brandstätter, Jennifer, Kurz, Walter, Richoz, Sylvain, Cooper, Matthew J. and Teagle, Damon A.H. (2018) The origin of carbonate veins within the sedimentary cover and igneous rocks of the Cocos Ridge: results from IODP Hole U1414A. Geochemistry, Geophysics, Geosystems. (doi:10.1029/2018GC007729).

Record type: Article

Abstract

Carbonate veins in the igneous basement and in the lithified sedimentary cover of the Cocos Ridge at IODP Hole 344‐U1414A reveal the hydrologic system and fluid‐rock interactions. IODP Hole 344‐U1414A was drilled on the northern flank of the Cocos Ridge, and is situated 1 km seaward from the Middle America Trench offshore Costa Rica. Isotopic and elemental compositions were analyzed to constrain the fluid source of the carbonate veins and to reveal the thermal history of Hole 344‐U1414A. The formation temperatures (oxygen isotope thermometer) of the carbonate veins in the lithified sedimentary rocks range from 70 to 92 °C and in the basalt from 32 to 82 °C. 87Sr/86Sr ratios of the veins in the altered Cocos Ridge basalt range between 0.707307 and 0.708729. The higher ratios are similar to seawater strontium ratios in the Neogene. 87Sr/86Sr ratios lower 0.7084 indicate exchange of Sr with the igneous host rock. The calcite veins hosted by the sedimentary rocks are showing more primitive 87Sr/86Sr ratios < 0.706396. The isotopic compositions indicate seawater, modified into a hydrothermal fluid by subsequent heating, as the main fluid source. Low‐temperature alteration and the presence of a high temperature fluid resulted in different carbonate precipitates forming up to several cm thick veins. The geochemical data combined with age data of the sedimentary rocks suggest intraplate seamount volcanism in the area between the Galapagos hotspot and the Cocos Island as an additional heating source, after the formation of the Cocos Ridge at the Galapagos hotspot.

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Accepted/In Press date: 13 September 2018
e-pub ahead of print date: 21 September 2018

Identifiers

Local EPrints ID: 423821
URI: http://eprints.soton.ac.uk/id/eprint/423821
ISSN: 1525-2027
PURE UUID: 6325770a-fef3-406c-a8ee-7327e0d515c0
ORCID for Matthew J. Cooper: ORCID iD orcid.org/0000-0002-2130-2759
ORCID for Damon A.H. Teagle: ORCID iD orcid.org/0000-0002-4416-8409

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Date deposited: 02 Oct 2018 16:30
Last modified: 17 Dec 2019 05:12

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