Geochemistry and Mineralogy of Ferromanganese Crusts from the Western Cocos-Nazca Spreading Centre, Pacific

Late Pleistocene–Holocene rocks from the western part of Cocos-Nazca Spreading Centre (C-NSC) include ferromanganese crusts that elucidate geochemistry and mineralogy a deep-sea geological setting. Six representative Fe-Mn crust samples were studied using petrological methods, such as optical transmitted light microscopy, energy dispersive X-ray fluorescence spectrometry, inductively coupled plasma mass bulk diffraction, scanning electron microscopy probe microanalysis. Geochemical, mineralogical signatures indicate complex formation influenced by mild hydrothermal processes. These consist mostly mixed birnessite, todorokite-buserite, Mn-(Fe) vernadite with traces diagenetic manganates (asbolane), Fe-oxides oxyhydroxides or hydrothermally associated relatively pure Mn-oxyhydroxides (manganite). The average Mn/Fe ratio is 2.7, which suggests predominant hydrogenous-early influences. mean concentrations three prospective metals (Ni, Cu Co) are low: 0.17, 0.08 0.025 wt %, respectively. total content ?REY also low, ranges 81 to 741 mg/kg (mean 339 mg/kg). We interpret geochemical data reflect origin crusts, initially related plume over region. This process occurred during further interactions seawater additional hydrogenetic elemental acquired.