EVIDENCE FOR EPISODIC HYDROTHERMAL ACTIVITY IN THE RED-SEA FROM THE COMPOSITION AND FORMATION OF HYDROTHERMAL SEDIMENTS, THETIS DEEP

Sediments obtained from the NE Thetis Deep during the Sonne cruise SO-29 consist of a manganite-facies and various types of Fe-facies (hematite, magnetite, goethite, and lepidocrocite facies). The sediments have a chemical and mineralogical composition similar to some of the lithological units previously described from the Atlantis II Deep, 160 km to the southeast. In contrast to the Atlantis II Deep, no stable brine pool recently exists in the NE Thetis Deep. However, based on the Fe/Mn fractionation in the Fe-facies types an intermittent brine filling of the NE Thetis Deep has probably existed. We propose that the formation of the brine pools correlate to the volume of discharging fluids. The chronology of hydrothermal deposition in the NE Thetis Deep seems to correlate with similar events in the Atlantis II Deep, suggesting that major tectonic events in the Red Sea may have caused large-scale pulses of hydrothermal activity.