Granites and Earth Evolution.
Prev Up Next

PETROGENESIS AND THE ORE CONTENT OF KYZYLKUM-NURATA AND

CHATKAL-KURAMA BATHOLITHS (REPUBLIC OF UZBEKISTAN)

Akhundjanov R.A.*, Mamarozikov U.D.**, Saidiganiyev S.S.***

*Institute of Geology and Geophysics, AS of Uzbekistan, Tashkent, Uzbekistan rkh.akhundjanov@mail.ru

**Presidium of AS of Uzbekistan Tashkent, Uzbekistan, udmamarozikov@rambler.ru

***Scientific and Applied Center «Geology of Uranium and Rare-Earth Metals» of State Committee of Uzbekistan Republic on Geology and Mineral Resources, Tashkent, Uzbekistan, muzaffarhon82@mail.ru


As a result the study of the deep structure of lithosphere, evolution of magmatism and nature of the connection with them of ore formation in the territory of Uzbekistan are isolated the segments of the earth's crust, where the products of prolonged and diverse magmatism are spatially combined with the polychronic and polygenetic endogenous ore deposits. Areas with the wide and intensive development of magmatic and ore associations are named “ore- magmatic concenters” (Khamrabaev, 2000). Spatial their status is determined by confinement to the bundles of the intersection of the regional faults of sublatitudinal and northeastern direction. By the main characteristic of concenters is the presence in their ranges of polyphase plutons, which have the form of interformational one and multistage laccoliths with the vertical extent of 7-8 kilometers. In the contemporary erosional baring their large protrusions, folded are exposed by diorite and by quartz diorite - I phase, by granodiorite - II main phase, by granites - III phase, and by leucocratic granites (alaskaite) - IV phase. By them are folded Kyzylkum-Nurata and Chatkal-Kurama plutons. According to the geological position, the structural position, the form, the internal structure, the nature of action on the surrounding rocks and other petrological criterions (Isamukhamedov, 1970) they completely can be defined as batholiths. In the limits of their development the unique and large ore deposits of gold, nonferrous and rare metals are placed. These are supergiant - Muruntau, the deposits of gold and silver of Kokpatas, Kosmanachi, Okzhetpes, Amantaytau in Kyzylkum desert; Charmitan, Guzhumsay, Sarmich, Marzhanbulak, Lyangar, and Koytash in Nuratau mountans; Kalmakyr, Sary-Checky, Chorukh-Dayron, Kochbulak, Kyzylalma, Chadak in Chatkal-Kurama mountains. Some ore deposits of tungsten, molybdenum, tin, lithium, niobium, tantalum and other rare metals are connected with the skarns, pegmatites and greisens of both batholiths.

The intrusions, compounding the studied batholiths, are formed in the late Paleozoic period (319-274 mln. years). Forming Homodromic series of rocks with the lime- alkaline trend of evolution and clearly expressed the increasing trends in quantity of silica and alkalis toward the rocks of ending phase. In spite of the presence general of the similarity of Kyzylkum-Nurata and Chatkal-Kurama batholiths pointed out above, they have distinguished features of mineral, chemical composition and ore-bearing. Correspondingly, femic part is represented in the granitoid rocks of Kyzylkum- Nurata and Chatkal-Kurama batholiths: 1) high-ferrous by hornblende and by biotite; 2) midl-ferrous by pyroxene, by hornblende and by biotite. The composition of plagioclase varies: 1) from the andesine (40) to albite; 2) plagioclase - Labrador (63) - albite. Potassium-sodium feldspar - 1) microcline-perthite is distinctly latticed; 2) orthoclase –microperthite, microcline-perthite. The accessory-mineral type of the rocs of the Kyzylkum-Nurata batholith: ilmenite (I phase); titanite-ortite (allanite)-zircon-apatite-ilmenite (II phase); monazite-xenotime-apatite-zirconium (III phase); ilmenite-zircon-apatite-gold-tourmaline (IV phase). In the Chatkal-Kurama batholith: magnetite (I phase); ortite (allanite)-zircon-titanite-apatite-ilmenite (II phase); monazite-orthite (allanite)-zircon-magnetite (III phase); apatite-monazite-zircon-topaz-fluorite (IV phase). A difference in the rocks of batholiths is observed also by the petrochemical composition, which is expressed by the more silica-acidic, sub-alkaline and aluminous nature of the rocks of Kyzylkum-Nurata batholith. The last is distinctly appeared in the presence of normative corundum, whose value gradually rises from granodiorites (0,3) to granites (0,7) and leucocratic granites (1,6). In the rocks of Chatkal-Kurama batholith it is absent, but an increase in its quantity is observed with the phenomena of the boundary assimilation of Lower Paleozoic sedimentary-metamorphic rocks in the weakly eroded intrusive bodies. As is known, the values of this coefficient are index by the crusting of anatektic nature magmas of granitoides. Bright confirmation are the high values of the relation of the isotopes of strontium 87 and 86 (0,708-0,717) and the identical nature of the curves of distribution rare-earth elements (REE) in the granitoid rocks in Nuratau and the metamorphic rocks of Precambrian - steep inclination and the deep Eu-minimum. In the granodiorite of Chatkal with the predominance of light REE above the heavy Eu-minimum is expressed not distinctly.

The formation of the Late Paleozoic batholiths of Uzbekistan is presented by us: 1) as the result of the melting of the significant volumes of melts during repeated (from one phase to the next) processing of the rocks of the lower and upper earth's crust by silico-alkaline fluids. This mechanism of formation of magma chambers was predominant in the Kyzylkum-Nurata segment and it caused its gold-rare-metal metallogenic specialization; 2) as the result of the mixing of ultra basic - basic mantle melts with the crustal material. This was reflected in the manifestation of iron-ore-copper-polymetallic, gold-silver and rare-metal mineralization in the Chatkal-Kurama block of lithosphere.

Wide development in their internal, boundary and outlying parts of the small intrusions is the essential feature of batholiths. They are forming stocks and dike-shaped bodies. They are consist by monzogabbro (I phase), by syenodiorites (II phase), by adamellites (III main phase) and by rare-metal leucogranites (IV phase). The time of their formation relates to the late Carbon - Perm. Regarding the values of data of absolute age of batholiths rocks (319-293 mln. years, C2-C3) and small intrusions (293-274 mln. years, (C3-P2) sub-alkaline associations are formed directly following the apogee of lime-alkaline granite formation. The values of the relations of the isotopes of strontium 87 and 86 in late intrusions are low (0,706-0,707). They indicate the possible participation in the formation of their melts of the mantle substances, which revived the residual chamber of the magmas of batholiths.

The potential ore content of batholiths and small intrusions is determined by the manifestation of petrological-geochemical indications (Kovalenko, 1988) in granitoide associations, concentrated in ore-magmatic consenters with large deposits of Au, Ag, Cu, Pb, Zn W, Mo, Sn and with complex accompanying platinoids, by Se, Te, U, Nb, Ta, Be, Li, REE and fluorite.


References

Isamukhamedov I.M., Losev N.A., Kupchenko P.D. et. al. About batholithes // The problems of geology. Scientific transactions of Tashkent State University. Release 358. Tashkent: Tashkent State University, 1970. P.28-42.

Khamrabaev I.Kh. Most important aspects of the contemporary problems of petrogenesis and oregenesis // Petrology and the ore content of the magmatic formations of plaited regions. Tashkent: University, 2000. P.3-5.

Kovalenko V.I., Rub M.G., Osipov M.A. et. al. Orebearing of magmatic associations. M.: Science, 1988. 231p.