Mineralogy and Geochemistry of Deep-Sea Sediments from the Ultraslow-Spreading Southwest Indian Ridge: Implications for Hydrothermal Input and Igneous Host Rock

Detailed mineralogical and geochemical characteristics of typical surface sediments hydrothermal deposits collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) were studied by high-resolution XRD, SEM-EDS, XRF, ICP-MS. The SWIR marine samples can be generally classified into two main categories: sediment (biogenic, volcanic) hydrothermal-derived deposit; moreover, further metalliferous non-metalliferous based on index (MSI). chemical composition biogenic (mainly calcite) was characterized elevated contents Ca, Ba, Rb, Sr, Th, light rare earth elements (LREE), while volcanic volcanogenic debris) relatively enriched in Mn, Mg, Al, Si, Ni, Cr, high field strength (HFSEs). By contrast, deposit pyrite-marcasite, chalcopyrite-isocubanite, low-temperature cherts) contained significantly higher Fe, Cu, Zn, Pb, Co, Mo, Ag, U. In addition, a content As. Compared with their different host (source) rock, basalt-hosted Ti–Al–Zr–Sc–Hf and/or Mo–Ba–Ag; peridotite-hosted typically concentrations Mg–Cu–Ni–Cr Co–Sn–Au. differences element enrichment mineral between these types closely related to sedimentary environments (e.g., near/far away vent sites) inherited rock. Together combinations certain characteristic (such as Al–Fe–Mn Si–Al–Mg), relict products, diagnostic tracers nontronite, SiO2(bio), olivine, serpentine, talc, sepiolite, pyroxene, zeolite, etc.), it would more effective differentiate rock deep-sea detect possible input.