The Geochemical Features and Genesis of Ferromanganese Deposits from Caiwei Guyot, Northwestern Pacific Ocean

The ferromanganese deposit is a type of marine mineral resource rich in Mn, Fe, Co, Ni, and Cu. Its growth process is generally multi-stage, and the guyot environment and seawater geochemical characteristics have a great impact on the growth process. Here, we use a scanning electron microscope, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) to test and analyze the texture morphology, microstructure, mineralogical features, geochemical features of ferromanganese crusts deposits at different distribution locations on Caiwei Guyot. The ferromanganese deposits of Caiwei Guyot are ferromanganese nodules on the slope and board ferromanganese crusts on the mountaintop edge, which are both of hydrgenetic origin. Hydrgenetic origin reflects that the metal source is oxic seawater. Global palaeo-ocean events control the geochemistry compositions and growth process of ferromanganese crusts and the nodule. Ferromanganese crusts that formed from the late Cretaceous on the mountaintop edge have a rough surface with black botryoidal shapes, showing an environment with strong hydrodynamic conditions, while the ferromanganese nodule that formed from the Miocene on the slope has an oolitic surface as a result of water depth. What is more, nanoscale or micron-scale diagenesis may occur during the growth process, affecting microstructure, mineralogical and geochemical features.