Formation and origin of Fe–Si oxyhydroxide deposits at the ultra-slow spreading Southwest Indian Ridge

Low-temperature hydrothermal systems are generally dominated by Fe–Si oxyhydroxide deposits. However, the formation process and mechanism of modern oxyhydroxides at ultra-slow spreading centers remain poorly understood. This study focused on six deposits collected from different sites a typical center, Southwest Indian Ridge (SWIR). The mineralogical geochemical evidence showed significant characteristics low-temperature origin. Sr Nd isotope compositions SWIR probably reflected combined signature fluids seawater. Pb in exhibited close association with substrate rocks Mössbauer spectra iron speciation data further provided insights into iron-bearing phases all Two types biomineralized forms were also discovered these scanning electron microscopy (SEM) analysis. Energy-dispersive X-ray spectroscopy (EDS) nanoscale secondary ion mass spectrometry (nanoSIMS) revealed that distinct biogenic structures mainly composed Fe, Si, O, together some trace elements. Based findings, we propose microbial activity plays role SWIR. • morphological tracers Fe Si-oxyhydroxides extracted locations Sr-Nd-Pb isotopes rocks, seawater fluids. Biomineralization may be responsible for work furthers our understanding biogeochemical processes associated Si minerals