Atlantis II deep

We turn our attention now to the hydrothermal brines of the Red Sea. An oceanic survey in 1963 discovered pools of hot, saline, and metal-rich brines along the axial rift of the Red Sea (Degens and Ross, 1969 Hoffmann, 1991). The dense brines pond in the rift s depressions, or deeps. The Atlantis II deep contains the largest pool, which measures 5 x 14 km and holds about 5 km3 of supersaline brine. The deep holds two layers of brine. The lower brine contains about 25 wt.% dissolved salts and exists at temperatures up to 60 °C. Table 6.8 shows the brine s average composition. A somewhat cooler, less saline water overlies the lower brine, separating it from normal seawater. 

Table 6.8. Chemical composition of the lower brine, Atlantis II deep, Red Sea...

From the perspective of ore genesis, these results seem disappointing in light of the fluid s high degree of supersaturation. Shanks and Bischoff (1977), for example, estimate that about 60 mg of sphalerite alone precipitate from each kg of ore fluid feeding the Atlantis II deep. The reaction to form chalcocite,... 

Cole,T.G. (1983) Oxygen isotope geothermometry and origin of smectites in the Atlantis II Deep, Red Sea. Earth Planetary Sci. Letters 66 166-176... 

Atlantis II Deep (Red Sea) and the uptake of amino acids by synthetic P-FeOOH Cln. Geochim. Cosmochim. Acta 47 1465-1470 Holm,T.R., Anderson, M.A., Iverson, D.G. Stanforth, R.S. (1979) Heterogeneous interaction of arsenic in aquatic systems. ACS Symposium Ser. Chemical modelling of aqueous systems Speciation, sorption, solubility, kinetics. 711-736... 

Ramboz, C., and Danis, M. (1990). Superheating in the Red Sea The heat-mass balance of the Atlantis II Deep revisited. Earth Planet. Sci. Lett. 97, 190-210... 

Figure 30. Schematic cross-section of the Atlantis II Deep. From Zierenberg and Shanks (1983) used with permission of the Economic Geology Publishing Company.

Zierenberg RA, Shanks WC III (1983) Mineralogy and geochemistry of epigenetic features in metalliferous sediment, Atlantis II Deep, Red Sea. Econ Geol 78 57-72... 

If the hot vent lies in a depression such as the Atlantis II Deep in the Red Sea, the results of the hydrothermal reactions are very evident (see Figure 1). Water is removed together with magnesium and sulfate, and calcium is released from the basalt. Rock salt (NaCl), anhydrite (CaS04), and silica (SiOa) are formed and the brine becomes saturated with these solids. Sulfide metals are coprecipitated with iron sulfide (FeS). 

Figure 1 Depth profiles of chlorinity (Cl, g kg" ), calcium, magnesium and sulfate (mol kg ) in the Red Sea Atlantis II deep on 22-23 March 1976.

Nawab, Z. (2001). Atlantis II Deep A future deep sea mining site. Proceedings, proposed technologies for mining deep-seabed polymetallic nodules, Kingston, International Seabed Authority, 301-313. 

---