Recent seafloor metallogeneses: examples from the Atlantis II Deep, Red Sea and 21/sup 0/N East Pacific Rise
Thesis/Dissertation
·
OSTI ID:6000549
Massive sulfide from 21/sup 0/N East Pacific Rise consists of pyrrhotite, cubic cubanite, wurtzite, chalcopyrite, pyrite, sphalerite, marcasite, and traces of galena. The samples show a complex paragenesis with extensive replacement and sulfur isotope disequilibrium. Sulfides in the Atlantis II Deep, Red Sea are very fine grained pyrrhotite, cubic cubanite, chalcopyrite, sphalerite, and pyrite which are interlayered with iron phyllosilicates. Epigenetic veins cutting unlithified metalliferous sediment in the Atlantis II are the conduits for the entry or new hot brine into the Deep. Vein mineralogy is dominated by talc and anhydrite with subordinate sulfides and phyllosilicates. Vertical zoning of vein minerals is related to cooling of hydrothermal fluid. Stable isotope ratios indicate depositional temperatures up to 300/sup 0/C. Stable isotope ratios also suggest that cooling of the hydrothermal fluid is caused by mixing with cooler brine having the approximate composition of the lower brine layer. Geochemical modeling of mixing successfully predicts the observed vertical zonation. The 21/sup 0/N East Pacific Rise deposit and the Atlantis II Deep have similar geochemical systems dominated by interaction with hot tholeiitic basalt. The differences in the deposits are related to their different depositional environments. The 21/sup 0/N East Pacific Rise deposit is forming directly on the seafloor in contact with cold oxygenated seawater, while the Atlantis II Deep deposit is forming beneath a warm, saline, anoxic brine pool.
- OSTI ID:
- 6000549
- Country of Publication:
- United States
- Language:
- English
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