Scholarly record

PETROLOGY OF ORE-BEARING METASOMATITES OF GOLD DEPOSIT KOKKYIA (SOUTH KAZAKHSTAN)

PhD-student Gulnara Omarova, Prof. Adilkhan Baibatsha, Dr. Aimkhan Kassenova, Eng. Sergei Loparev

Abstract

The deposit Kokkyia is located in the exocontact zone of granodiorite intrusion, and zones of hydrothermal alteration, which enclose gold mineralization, are controlled by small intrusions of diorite and syenite of the Upper Devonian intrusive complex and are located in volcanic rocks of sour alkali and medium composition. Practically all the difference of rocks are affected by the processes of hydrothermal changes and are shown as the processes of propylitic nature: albitization, feldspathization, chloritization, carbonatization, sericitization and others. Zones with gold mineralization gravitate to the internal facies of metamorphism, which are composed of quartz, sericite, muscovite, zuniite, actinolite, tourmaline, diaspor and a group of montmorillonite and kaolinite minerals. Metasomastite occurences of internal facies form a significant in development area hydrothermal zones, which can be classified as secondary quartzites, greisens and beresites. In the quartz-sericite metasomatites micrograins (0,009-0,005 mm) of pyrite (2%) pentagondodekaedral and cubical shapes and aggregates of fine dispersed leucoxene and rutile (3%) of irregular shapes are encountered. In the porphyroblasts aggregates of green chlorite (15%), chloritized hornblend (5%) and pyrite (10%) often occur. Propylitized monzodiorite is of dark-gray colour, in the split on which there is rare dissemination of pyrite. Plagioclase (40%) is of prismatic shape, moreoften in the form of separate grains and less often in the form of clusters of several grains intensively substituted by sericite, sometimes by albite and calcite. Sulfides are in the form of irregular grains up to 0.01 mm in size most are developed in the base tissue, less often at the contact with chloritized hornblend and plagioclase, but everywhere it is in close contact with carbonate.

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