Component And Structure Studying Of Manganese-dominant Mineral Of Co-rich Crusts From West Pacific

West Pacific is one of the most enriched regions of Co-rich crust. This study selected a multilayered-structure crust, and sampled from an enrichment belt of the main manganese mineral. Through detailed observation under microscope,XRD analysis,IR Spectrum analysis,DSC-thermal analysis and EPMA analysis, studying characteristics of manganese-dominant mineral of microstructure,crystal structure and chemical constitution, discussing its formula and naming and discussing the ancient marine environment of cobalt-rich crusts in the study area. The following conclusions have been obtained:1. The component of the manganese-dominant mineral is MnO₂ with water and a lot of other element (Fe, Ca, Na, Mg, etc.), its formula can be writing as MnO₂ ? XH2O (with Fe, Ca, Na, Mg, and other elements). As it is different completely from vernadite, but its structure and stability similar withδ-MnO₂; for close intergrowth with iron hydroxide, XRD values are larger with the 0.24⁰.245 nm and the 0.14⁰.143 nm. The name is proposed for the marineδ-MnO₂.2. Marineδ-MnO₂ has layer-structure even with tunnel structure, and has good structural stability. When heated to 400℃, its crystal structure remains basically unchanged. Marineδ-MnO₂ changes into Mn2O3 (γ-Mn2O3) around 550℃, then changes into Mn3O4 around 804℃. The temperature of 804℃is lower 146℃than the temperature of 950℃reported by a literature, the structural stability may be related to the metal ions contained.3. The manganese-dominant mineral of Cobalt-rich crusts in this area isδ-MnO₂, for the three main manganese minerals of todorokite, birnessite andδ-MnO₂ in deep seas,δ-MnO₂ is the most thorough oxidized mineral, the O/Mn are 1.74¹.87,1.87².00,1.99. This shows that the crusts underwent the strong oxidative environments and agrees with the enrichment characteristic of the REE.4. Identification of marine manganese minerals should use many means, and the peak of XRD should be determined according to characteristics of marine manganese minerals. Considering different stabilities and structures between marine manganese minerals and the terrestrial counterparts, we should use a new naming system for marine manganese minerals: marine 1 nm manganese mineral, marine 0.7 nm manganese mineral marineδ-MnO₂.