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Sylvain Richoz

Sylvain Richoz

Senior lecturer

Sylvain Richoz

The Origin of Carbonate Veins Within the Sedimentary Cover and Igneous Rocks of the Cocos Ridge : Results From IODP Hole U1414A

Author

  • Jennifer Brandstätter
  • Walter Kurz
  • Sylvain Richoz
  • Matthew J. Cooper
  • Damon A.H. Teagle

Summary, in English

Carbonate veins in the igneous basement and in the lithified sedimentary cover of the Cocos Ridge at International Ocean Discovery Program (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 hot spot and the Cocos Island as an additional heating source, after the formation of the Cocos Ridge at the Galapagos hot spot.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2018-09-21

Language

English

Pages

3721-3738

Publication/Series

Geochemistry, Geophysics, Geosystems

Volume

19

Issue

10

Document type

Journal article

Publisher

American Geophysical Union (AGU)

Topic

  • Geology
  • Geochemistry

Keywords

  • carbonate veins
  • Cocos Ridge
  • elemental composition
  • fluid-rock interaction
  • IODP
  • isotope geochemistry

Status

Published

ISBN/ISSN/Other

  • ISSN: 1525-2027