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PETROGENESIS AND THE ORE
CONTENT OF KYZYLKUM-NURATA AND
CHATKAL-KURAMA BATHOLITHS
(REPUBLIC OF UZBEKISTAN)
*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 (¹40) to
albite; 2) plagioclase - Labrador (¹63) - 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.
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