Origin of fluids and the evolution of the Atlantis II deep hydrothermal system, Red Sea: Strontium isotope study
- Centre de Geochimie de la Surface, Strasbourg (France)
Atlantis II is the largest and most mineralized of the deeps along the axis of the Red Sea spreading center. Its basaltic substratum is covered by recent layered metalliferous sediments, which precipitated from an overlying brine pool. The {sup 87}Sr/{sup 86}Sr ratio and the strontium concentration of interstitial waters within these sediments range between 0.70708 and 0.70725 and between 43 and 53 ppm, respectively. They are close to what is found for the present-day deep brine pool (0.707105, 45.10 ppm). The strontium concentration and the {sup 87}Sr/{sup 86}Sr ratio of the Atlantis II Deep brines can be derived from those of the interstitial waters of the surrounding Miocene evaporite by hydrothermal interaction with oceanic basaltic rocks at a maximal water/rock ratio 2-3. This water/rock ratio is similar to that calculated for oceanic hydrothermal systems on sediment-free ridges. Interstitial waters show a linear trend on plot of {sup 87}Sr/{sup 86}Sr vs. 1/Sr. The highest strontium concentration and the most radiogenic interstitial waters correspond to sediment samples enriched in iron and manganese oxide minerals. These waters reflect the diagenetic release of strontium by oxide minerals and initially precipitated at the interface between the brine pool and more radiogenic seawater. The solid fraction of the sediment has {sup 87}sr{sup 86}Sr isotopic compositions intermediate to those of the brines and seawater. The solid fraction of the sediment has {sup 87}Sr/{sup 86}Sr isotopic compositions intermediate to those of the brines and seawater. The most radiogenic strontium values were observed in samples strongly enriched in marine microbiota. The gradual isotopic evolution in the lowest part of the western basin sediments testifies to the gradual influence of the hydrothermal activity in the deep in the beginning of the Atlantis II Deep sedimentary history. 62 refs., 6 figs., 2 tabs.
- OSTI ID:
- 549036
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 23 Vol. 59; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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