ACCESSORY NATIVE METALS AND THEIR OXIDES FROM MASSIVE CHROMITITES OF KEMPIRSAI ULTRAMAFIC MASSIF (SOUTH URAL, KAZAKHSTAN)

Abstract

The relevance of the work is caused by weakly elaboration of mineralogical aspects of ultramafic restitic massifs, which does not allow their generalization at mineralogical level and restoration of complete history of their formation and transformation, as well as solution of number of controversial questions of petrology of these objects. The mineralogy of native metals and their oxides from restitic ultramafites is extremely poorly studied direction. The main aim of the research is to study the mineralization of native metals and their oxides in densely disseminated and massive chromitites of Kempirsai ultramafic massif, reconstruction of mechanism of its formation. The methods: study of ore mineralization in polished sections using a polarizing microscope AxioScope Carl Zeiss; determination of chemical composition of ore mineralization by the method of X-ray spectrum microanalysis using scanning electron microscope Tescan Vega II LMU, equipped with energy-dispersive spectrometry (with a semiconductor Si (Li) detector INCA x-sight) INCA Energy 350 and wave-dispersive spectrometer INCA Wave 700. The results. The authors have made an attempt to perform detailed diagnostics of accessory mineralization of native metals and their oxides in the chromitites of Kempirsai massif. According to the results native nickel, native silver, native copper, native iron, avaruite, cassiterite, monteponite and zincite were identified and characterized. Concentration of mineralization examined was apparently due to its mobilization in serpentinization and transformation of primary silicates, as well as chromospinelides and sulphides under reducing conditions. The author associates formation of metals with tendency of Ni and subordinate Fe to be liberated from the silicon-oxygen bonds of primary olivine, and Cu and Zn from bonds of sulfides and chromospinelides and transform into form of free elements. Obviously, introduction of a part of elements (Cd, Sn) was carried out by serpentinizing solutions themselves. The further fate of these metals was determined by their concentration and subsequent deposition from highly saturated supercritical fluids.

Keywords

• kempirsai massif
• chromitites
• native metals
• typomorphism
• chemical composition
• genesis