Origin of the Filizchay ore field (the southern slope of the Greater Caucasus)

Abstract


 
 
 he article deals with the origin of the Filizchay ore field, which is a valuable object for the extraction of zinc, lead, copper, silver as well as for the extraction of the associated com- ponents. The data and types (VMS, SEDEX, VMT) of the pyrite deposits in the world have been briefly presented. Their comparative analysis has been carried out and it has been revealed that the Filizchay ore field is very different from the VMS-type pyrite deposits and it belongs to the SEDEX type. A direct relationship with vol- canism has not been observed in this deposit. Unlike the containing rocks related to volcanism in the Filizchay field , there are fine-rhyth- mic flyschoids with packages of sandstones, clay shales and silt-clay shales . The ratio of the natural ore types composed of the different mineral associations, with stages of the folded and disjunctive dislocations, allows us to divide the process of the deposit formation into the following three stages of the ore formation: 1. deposits of the massive hydrothermal-sedimentary essentially pyrite ores; 2. formation of the hydrothermal-metasomatic ores of the pyrite-copper-polymetallic composition; 3. deposition of the hydrothermal-meta- morphogenic ores of the copper-pyrrhotite composition. The available data indicate a favorable environment for sedimentary pyrite ore formation subject to a significant role of Corg. and sulfate-reducing bacteria. Moreover, the hydrothermal-sedimentary processes played the main role in the accumulation of the main volume of the sulfide masses. On the basis of the sulfur isotopic composition (according to Zairi, 1992) of the main minerals (pyrite, galena, sphalerite, pyrrhotite, chalcopyrite) from various types of the Filizchay ore field ores it was concluded that the deposit formation occurred from several portions of the entered hydrothermal solutions. It was found that by the period of accumulation of sediments of the ore-bearing horizon in the northern block – there occurred outpouring of the spilites and basalts in the narrow trough-like depression. The iron sulfides supplying the more southern basin with stagnant waters can be associated with their post-volcanic exhalations (as primary sources). The Filizchay ore field being connected with basaltic volcanism is combined according to formation method. It has been formed due to components which have been carried out by hydrothermal flows and due to basalts, which are associated with underwater alteration. The temperatures of the primary pyrite-polymetallic ores formation are relatively low (200-100 0С).