Geochemical Investigations of Fe-Si-Mn Oxyhydroxides Deposits in Wocan Hydrothermal Field on the Slow-Spreading Carlsberg Ridge, Indian Ocean: Constraints on Their Types and Origin

摘要: We have studied morphology, mineralogy and geochemical characteristics of Fe-oxyhydroxide deposits from metal-enriched sediments the active (Wocan-1) inactive (Wocan-2) hydrothermal sites (Carlsberg Ridge, Northwest Indian Ocean). on Wocan-1 site are reddish-brownish, amorphous subangular. They occur in association with sulfides (e.g., pyrite, chalcopyrite sphalerite) sulfate minerals gypsum barite). The composition shows enrichment transition metals (Ʃ (Cu + Co Zn Ni) = ~1.19 wt. %) low (<0.4 values Al/(Al Fe Mn) ratio. Wocan-2 samples show poorly crystallized reddish brown yellowish Fe-oxyhydroxide, minor peaks goethite manganese oxide minerals. mineral assemblage includes sulfide phases. compositions two distinct types (type-1 type-2). type-1 Fe-oxyhydroxides enriched (up to ~1.23 %), Fe/Ti vs. ratio similar Fe-oxyhydroxides. type-2 depleted metals, 0.003–0.58 (mean value, 0.04). ridge flank oxyhydroxides exhibit an extremely value ~ 0.01) Fe/Mn a concentration metals. Our results revealed that range precipitated by mass wasting corrosion pre-existing sulfides. alteration seawater oxygenated environment relative type-1. biogenic detritus flanks suggests hydrogenous/biogenic processes formation masked signatures distance away Wocan field.