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Mineralogy of a hydrothermal sequence in a core from the Atlantis II Deep, Red Sea

Published online by Cambridge University Press:  09 July 2018

A. Singer
Affiliation:
The Seagram Center for Soil and Water Sciences, The Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
P. Stoffers
Affiliation:
Geologisch-Paläontologisches Institut und Museum der Universität Kiel, Olshausenstrasse 40/60, Kiel 2300, W. Germany

Abstract

The clay fractions from a 1191-cm long sediment core in the SW Basin of the Atlantis II Deep, Red Sea, were investigated by XRD, electron microscopy and chemical analysis. Talc dominates in the botton portion of the core, near the brine discharge vent. At 1183 cm depth, the clay consists of vermiculite/chlorite and chrysotile. These minerals are of hydrothermal origin and two possible formation pathways are proposed: (i) vermiculite/chlorite and chrysotile formed by the submarine alteration of previously deposited talc; (ii) vermiculite/chlorite and chrysotile authigenically precipitated as a result of changes in the chemical composition of the brine. At 1170 cm depth, a new depositional sequence results from the progressive alteration of swelling 2:1 minerals into vermiculite. At 1025 cm, Mg-rich clay minerals such as chlorite, chrysotile and talc again become prominent. The upper part of the core is characterized by a transition from non-expanding Mg-rich clay minerals to Fe-rich expanding clays, principally nontronite. Periodically, the content of well-crystallized oxides such as hematite in the layers increases. At 1025 cm, some of the Fe-oxides have a morphology similar to that of akaganéite. In the uppermost part of the core, iron oxides appear to consist of a poorly crystalline hydrothermal hematite. An attempt has been made to correlate the various mineralogical assemblages geochemically.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1987

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