Geochemical classification of brine-filled Red Sea deeps.

Schmidt, Mark , Al-Farawati, R. and Botz, R. (2015) Geochemical classification of brine-filled Red Sea deeps. In: The Red Sea: The Formation, Morphology, Oceanography and Environment of a Young Ocean Basin. , ed. by Rasul, N. and Stewart, I. C. F.. Springer Earth System Sciences . Springer, Berlin, pp. 219-233. ISBN 978-3-662-45200-4 DOI 10.1007/978-3-662-45201-1_13.

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Abstract

The major geochemical characteristics of Red Sea brine are summarized for 11 brine-filled deeps located along the central graben axis between 19°N and 27°N. The major element composition of the different brine pools is mainly controlled by variable mixing situations of halite-saturated solution (evaporite dissolution) with Red Sea deep water. The brine chemistry is also influenced by hydrothermal water/rock interaction, whereas magmatic and sedimentary rock reactions can be distinguished by boron, lithium, and magnesium/calcium chemistry. Moreover, hydrocarbon chemistry (concentrations and δ13C data) of brine indicates variable injection of light hydrocarbons from organic source rocks and strong secondary (bacterial or thermogenic) degradation processes. A simple statistical cluster analysis approach was selected to look for similarities in brine chemistry and to classify the various brine pools, as the measured chemical brine compositions show remarkably strong concentration variations for some elements. The cluster analysis indicates two main classes of brine. Type I brine chemistry (Oceanographer and Kebrit Deeps) is controlled by evaporite dissolution and contributions from sediment alteration. The Type II brine (Suakin, Port Sudan, Erba, Albatross, Discovery, Atlantis II, Nereus, Shaban, and Conrad Deeps) is influenced by variable contributions from volcanic/magmatic rock alteration. The chemical brine classification can be correlated with the sedimentary and tectonic setting of the related depressions. Type I brine-filled deeps are located slightly off-axis from the central Red Sea graben. A typical “collapse structure formation” which has been defined for the Kebrit Deep by evaluating seismic and geomorphological data probably corresponds to our Type I brine. Type II brine located in depressions in the northern Red Sea (i.e., Conrad and Shaban Deeps) could be correlated to “volcanic intrusion-/extrusion-related” deep formation. The chemical indications for hydrothermal influence on Conrad and Shaban Deep brine can be related to brines from the multi-deeps region in the central Red Sea, where volcanic/magmatic fluid/rock interaction is most obvious. The strongest hydrothermal influence is observed in Atlantis II brine (central multi-deeps region), which is also the hottest Red Sea brine body in 2011 (~68.2 °C).

Document Type: Book chapter
Keywords: brine chemistry, Red Sea tectonic, hydrocarbons, stable isotopes, thermal maturation, RV Poseidon, POS408
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Open Access Journal?: No
DOI etc.: 10.1007/978-3-662-45201-1_13
Projects: Jeddah Transect
Expeditions/Models/Experiments:
Date Deposited: 28 Oct 2014 09:08
Last Modified: 10 Dec 2015 10:20
URI: http://oceanrep.geomar.de/id/eprint/25890

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