Influence of sedimentation on enrichment of manganese and growth of ferromanganese micronodules, Bengal Fan, India

摘要

Based upon down core variations in O/Mn ratio insediment and in micronodules, Mn content,organic carbon andabundance of micronodules in two box cores from high and lowsedimentation regions of the Bay of Bengal, 0-20 and 0-40 cmlevels were identified as "Mn oxidation zone" in the western andthe eastern regions of the bay. Despite similarity in bottom waterO2 and organic carbon contents of the region, a higher abundanceof micronodules down to the deeper levels was observed in thearea of low sedimentation. But, in the upper surfaces increasedenrichment of Mn was observed in core 1 located in the area ofhigher sediment accumulation. Rapid recycling of Mn (fasterburial-transfer to Mn reduction zone-Mn dissolution and itsupward diffusion-re-precipitation) increasing upward flux ofMn(II) and associated higher consumption of O2 limits the width ofMn oxidation zone and appears to be responsible for enhancedenrichment of Mn in the area of high sedimentation. The results ofthe present study also suggest that though the availability of Mncontrols the formation of micronodules, their resident time in Mnoxic zone regulates their growth and influences their morphology.