Publication Date:
2017-10-23
Description:
The Red Sea is a textbook case of a modern-day oceanic rift basin forming as a result of continental break-up. A characteristic feature of this setting in the central and northern Red Sea are more than two dozens of isolated bathymetric depressions, "deeps", filled with brines derived from leaching of the early-breakup Miocene salt deposits that lie beneath the entire Red Sea. The Atlantis II Deep is the largest basin of this type in the axial rift zone of the Red Sea. A topographic depression enclosing a volume of an estimated 15 km3 at water depths from 1900 to 2200 m, the Atlantis II Deep contains layered fluids with temperatures of up to 66°C and salinities of up to 27%. Beneath the brines, up to 30 m of fine-grained metalliferous sediments have been accumulating for the past 23 000 years (Anschutz, 1995). Unlike those in modern hydrothermal systems at mid-ocean ridges, where most of the metals are expelled to the open ocean in buoyant hydrothermal plumes, metals in the Atlantis II Deep are trapped and precipitated beneath a 200-m-thick brine layer. These sediments show extremely high concentrations of zinc, copper, silver, and gold (90 Mt of dry salt-free sediment at Zn〉2%, Cu〉0.5%, Ag〉39 g/t., Au〉0.5 g/t.). While the mode of metal deposition found in the Atlantis II Deep is not known from anywhere else on the seafloor today, it has yet been widely suggested as an analog for many ancient sediment-hosted ore deposits (Laurila et al. 2015). From 1975 to 1981 the German company PREUSSAG was contracted by the Saudi-Sudanese Commission for the Exploitation of the Red Sea Resources to explore the Atlantis II Deep. The project was aimed at assessing the overall technical viability of recovering and processing metalliferous muds on board of a mining vessel. The program encompassed several sampling cruises, a pre-pilot mining test (PPMT), environmental surveys, a study of pre-mining environmental conditions, as well as an economical evaluation. However, despite a highly successful PPMT, economic interest in the project waned due to declining commodity prices in the early 1980s. A substantial data set was derived from this campaign, including several kilometers of well preserved sediment cores and 〉20 000 pages of analog information. Utilizing this information, several GIS-based data mining efforts were carried out in recent years, driven by renewed interest in developing this unique resource. Our presentation will discuss results from these efforts and focus on the technical, economic and environmental boundary conditions of ocean mining of metalliferous sediments. Recently acquired geophysical data in the central Red Sea provide an unprecedented level of ground truth to historic data on Atlantis II.
Type:
Conference or Workshop Item
,
NonPeerReviewed
Format:
text
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