Characterization of microstructures and elemental composition of Fe-Mn crusts in fossil whale bone structure from the Rio Grande Rise (South Atlantic)

• Grant number: 23/07878-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2023
• End date: December 31, 2024
• Field of knowledge: Physical Sciences and Mathematics - Oceanography - Geological Oceanography
• Principal Investigator: Christian Millo
• Grantee: Victoria Duarte Moreno
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Iron (Fe) and manganese (Mn) oxides are major components of the large mineral reserves of the deep ocean. These deposits take two forms, nodules and crusts, which derive from the chemical precipitation of colloidal oxides and accessory elements present in seawater, depositing in the form of micrometric layers. The crusts are typically deposited on the rocky substrate of seamounts, but recent studies show the deposition of these oxides on carbonate material from fossils, such as those from whales. The present study aims to characterize the microscopic structure, elemental composition and oxidation state of Fe and Mn of a whale fossil collected in the Rio Grande Elevation (ERG). The ERG is an oceanic elevation of the South Atlantic highlighted by its potential for allocation of mineral resources from Fe-Mn crusts. This project aims to investigate the formation mechanism and highlight potential morphologies and chemical biosignatures that would be linked to the activity of microorganisms during the formation of the sample crusts. The analyzes to be carried out at IOUSP and partner laboratories involve: optical and scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), electron probe microanalysis (EPMA), X-ray microfluorescence ( ¼XRF), micro-X-ray absorption spectrometry (¼XANES) and mineralogical analysis by X-ray diffraction (XRD) and Raman spectrometry. This project is part of an internationally relevant line of research that is rapidly developing in Brazil. The results promise to fill important gaps in the understanding of the initial mechanisms of formation of polymetallic oxides.