Authigenic Carbonates as Archives for Fluid Venting: Insights from drill cores off-shore Costa Rica & Nicaragua.

Augustin, Nico , Liebetrau, Volker, Eisenhauer, Anton and Kutterolf, Steffen (2010) Authigenic Carbonates as Archives for Fluid Venting: Insights from drill cores off-shore Costa Rica & Nicaragua. [Talk] In: SFB 574 Subduction Workshop. , 04.-07.11.2010, Pucon, Chile .

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Continuous seep carbonate cores were recovered with the BGS Rockdrill-I device offshore pacific Nicaragua and Costa Rica (Meteor 66/3). Three carbonate drill cores from the mud mounds Iguana, Perezoso, Baula V and one from the Jaco Scarp (JS) escarpment were used for mineralogical,
petrological and isotope studies in order to decipher the late stage evolution of mound growth and related methane enriched fluid emanation. The combination of X-ray diffractometry and X-ray fluorescence (core scanner)
analyses reveals that aragonite is the most dominant carbonate phase, followed by Mg-calcite and calcite. The proportions of Pyrrhotite and Pyrite within the cores indicate lower H2S concentrations within the mound systems
relative to JS environment of formation. The presence of kutnohorite, associated struvite and monohydrocalcite can be most likely interpreted as product of microbial CO2 consuming activity (Idiomarina sp.; Gonzáles-Muñoz et al., 2008). Isotopic data show that JS is significantly lighter in !13C (-43 to - 56‰) than the mound samples (-22 to -36‰) indicating systematic variations in fluid composition and related methane source. The !18O values vary in the mound cores from 3.8 to 5.3‰ and in JS samples from 4.2 to 5.1‰ which correlate by their U/Th ages (Hammerich et al., 2007; Kutterolf et al., 2008) with major changes of seawater composition during the last 70,000 years. Fluorescence microscopy of aragonite cements, combined with electron microprobe data show multiple phases of crystal growth separated by residual organic matter which was attached to crystal surfaces during phases of stagnant or low fluid flow.

Document Type: Conference or Workshop Item (Talk)
Keywords: Meeresgeologie
Research affiliation: OceanRep > SFB 574 > C4
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
OceanRep > SFB 574 > B6
OceanRep > SFB 574
Date Deposited: 07 Dec 2010 13:25
Last Modified: 23 Feb 2012 06:31

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