TRANSFORMATIONAL CONVERSIONS OF MANGANESE HYDROXIDES FROM FERROMANGANESE DEPOSITS OF THE WORLD OCEAN UNDER THE INFLUENCE OF TEMPERATURE

Abstract

The paper is aimed at investigation and characterization as well as at crystal-chemical interpretation of products of thermo conversions of manganese hydroxides from ferromanganese deposits from different areas in the World Ocean. The results of research which are represented in this paper give notions about features of crystal-chemical conversions of manganese minerals with different types of crystal structure, different chemical composition and genesis when they are heated. This allows to generate new diagnostic criteria of these minerals and valuation of such type of mineral resources. Such common minerals, in marine and oceanic nodules, as vernadite, birnessite, buzerit I, mixed-layer asbolan– buzerit, todorokit and pyrolusite, were selected for further research. The samples were taken in certain way to have one mineral phase of manganese hydroxide which is represented by two preparations: one of which is with high ratio of iron and manganese, and the other one with low ratio, and with different quantities of nickel, cobalt and copper. To study changes of mineral composition of ferromanganese deposits the samples were heated in consecutive order in the range of temperatures 20-9000С. The mineral composition of initial samples and the products of annealing was determined by means of x-ray diffraction. Transformations of manganese hydroxides under the influence of high temperatures are as follows: if iron is a dominant component in the initial sample, hematite and yakobsite will be formed; if manganese content will be increased in the initial sample then hematite is absent in the products of annealing and along with yakobsite such mineral as biksbiit appears. Later on, with incensement of manganese content in the initial sample such mineral as gausmanite appears in the products of annealing which corresponds to the area of disruption of miscibility in the system. Along with farther incensement of the ratio between iron and manganese, such mineral as yakobsite cannot be formed anymore and the quantity of gausmanite increases. Initial mineralogical composition of the sample determines the character of conversions of crystal lattice up to 7000C. The composition of the final products of annealing depends first of all on the ratio Mn/Fe in the sample. Thus, the trend of transformation of manganese hydroxides from marine and oceanic ferromanganese deposits under the influence of heating depicts commonality of their structure. Under the influence of temperature on manganese-oxygen octahedrons only the way of connection between layers and bands and their order can be changed. The scheme of transformational conversions of manganese hydroxides is suggested in the paper.