Rare Metal Deposits of East Kazakhstan : Geologic Position and Prognostic Criteria

In the article the features of the formation and metallogeny of the geological structures of Great Altai (Rudny Altai, Kalba-Narym, Western Kalba and Jarma-Saur) which are included into the system of the Central Asian mobile belt are considered. The characteristic of the main types of rare metal minefields of the Kalba-Narymsky belt genetically connected with the Perm granitoid magmatism of the post-conflict orogenny stage of activization is given. The rhythmical and pulsation model of pegmatitovy ore formation in the conditions of the half-closed magmatic system, reflecting the phasic development of mineral complexes from graphic and oligoclase-microcline (barren) to microcline-albite and albite-spodumene ore (Ta, Nb, Be, Li, Sn, etc.) is developed. On the basis of the revealed criteria of ore formation recommendations about the direction of the further researches are made.


Introduction
The examined territory is a part of the Central-Asian mobile belt zone and unites geological structures of Great Altai including Rudny Altai, Kalba-Narym, Western Kalba both Jarma-Saur and abuted areas of Russia and China (Figure 1).Borders are the northwest deep breaks separating hercine structures of Great Altai from caledonide formations of Gorne Altai (in the northeast) and Chingiz-Tarbagatay (in the southwest).General extent of territory is more than 1000 km while 300 -400 km at width.
The Kalba-Narym zone is composed of Upper Devonian and Carboniferous terrigenous rock that are intruded by the major Kalba-Narym granitic pluton.The main litologies are granodiorite, granite and leucogranite, aplitelike granite, aolite dikes, pegmatite and quartz veins.Early granitic rocks are assigned to the Kalba Complex (P 1 ), whereas the later leucogranite is referred to the Monastyrsky Complex (P 2 ).
Rare metal pegmatite deposits in the Central Kalba ore district (Yubileinoe, Belogorskoe, Verkhne-Baimurzinskoe, Ognevskoe, etc.) are of the most economic importance.Two deposits of the pegmatittype (Yubileinoe) and greisens-quartz vein type (Cherdoyak) are discussed in the text below.
Last years from new theoretical positions-the hy- potheses of global mobilization problematic questions of geodynamic development of Great Altai main ore-bearing structures were considered.The results of researches are published in the monography "Great Altai" [1,2].

The Geological and Metallogenic Evolution
The formation of geological structures contacts to general geodynamic model of Paleoasiatic ocean evolution and was defined by system of complex cooperating continental lages of the Siberian and Kazakhstani subcontinents.Modern geological structures of region are tectonic enclave of ancient paleocontinents and litospheric blocks (or collage terrains), which drifted in Paleasiatic ocean and have confronted in the process of hercinic collision (С 1 -С 2-3 ), having formed uniform structure of Great Altai [3][4][5].
Thus, main rare metal-bearing structures of granitoid region belt have appeared during late hercynion activization differing on geotectonic position, the scale of development, internal structure, material structure and orebearing (Figure 2).Natural spatial time of rare metals belts to tectonic weakened zones in continental blocks terrestrial crust of raised sialic is established.There is marked northwest line and significant extent (500 -800 km).

Kalba-Narym Belt
Kalba-Narym belt is the largest adjoining to Irtysh shear zone and extends in the northwest direction on 500 km and further proceeds in Russia and China.On the geology-geophysical data it is supposed, that this granitoid belt is placed in a head part of huge techtono-magmatic zone, steep fallic on the northeast under Rudny Altai [2].The centers of magmaformation arose, by granite melts structure in metagranited layer or on its border with metadiorited layer.The transit ore-bearing solution have penetrated from the bottom parts of Earth crust and top mantle on system of deep breaks [2,11].
The belt is combined with mainly normal granits and leucogranits of the Perm age, to which the deposits of rare metals are generically connected (Ta, Nb, Be, Li, Cs, Sn, W) [12,13].

The Model of Rare Metal Pegmatite Deposits
The basic model of formation for main industrial rare metal-pegmatite of Kalba-Narym belt deposits is defined by their genetic connection with granite kalba of complex Р 1 and spatial accommodation of ores veins mainly in granite files and their exocontact (Figure 3).The processes of pegmatite formation probably occured in open or semi-closed magmatic system at rhythmicpulsating receipt of ore-bearing distillates (H 2 O, F, B, Cl, Ta, Nb, Be etc.) from cameric center of granite files (under the conditions of the increased activity of ore-controlling breaks).Pulsating receipt of ore-bearing solutions has determined multirhythmical zones of ash value pegmatic veins, the colour quartz-lepidolite-cleavelandite and spodumene with rich complex ores (Ta, Nb, Li, Cs, Be, Sn) and increasing concentration of mineralization veins stagic development of mineral complexes from oligoclase-microcline up to albite.zones raising cracks and zones of increased fissing and independent system of cracks in granite at oreformation rare metal pegmatites of albite subformation, uniting various mineral complexes (albite-microcline, albite, albite-spodumene etc) were generated.Ore bodies contain the unique minerals clevelandit, coloured and polychrome tourmalines, lepidolite, spodumene, petalite, pollucite and othres.The deposits have industrial values (Yubileiny, Belaya Gora, Upper Baymurza etc.) [2,6,7,14].These objects are compared with the large pegmatite deposits in other regions-Bernic Lake (Canada), Koktokay (China) and other [15][16][17].
The carried out researches have shown, that ore-generating ability of granitoide, alongside with petrologic by the factors, in many respects depends on geodynamic conditions stand of files and scales degasazion ore-bearing solution melts [2,6].From these positions certain oremagmatic systems differing on the scale miner were planned.
The above-intrusive system of active interaction granite intrusion with lateral breeds raised carbonaceous and calcindition in mobile tectonic conditions.Rare metal mineralization (Ta, Nb, Be and others) concentrated in a frontal part of stratified intrusivic bodies, in their apofise and branches, and also in lateral breeds of eksocontakte.The main industrial type is Bakenny deposit (Figure 4).

Types of Deposits
The inside-intrusic system of cameric conter formation of ore pegmatite veins in granite files complicated by explosive tectonic.Ore-controlling was the regional breaks of sublatitudic stream line, opening residual cameric of ore-bearing melts, and ore-locading were System of ore-bearing granite domes.It is characterized by concentration of Sn-Ta mineralization in albitic and greisenic granite intrusive-above-intrusive zone of a blind dome (type Karasu) (Figure 5).Rare metal mineralization is generically connected with medium musco- vite phase of granites the II phase of Kalba complex.The latter on geochemical features are referred to Sn-W-Ta type of ore-bearing granite close to liti-ftoric granite according to W. I. Kovalenko (1977).
The prognosic resources of tantalite and tin are significant.
System of imposed rare metal mineralization.It is characterized by migration of ore-bearing fluidizations from crystallizing granite melts in the tectonic weakened zones in containing breeds and imposing here mineralization on earlier hypabyssal small intrusions and dykes of Cunush complex С 3 .The latter became favorable physics-chemical environment for adjournment and concentration of mineralization, acting in a role of structural -litologic and geochemical traps (deposits Medvedka, Tochka etc.).
The system field of dispersion RE is typical for large files of leucogranite Monastyr complex (Р 2 ), which differ by flying and mineralizer riches (H 2 O, F, B etc.) and geochemical specialization on Ta, Li, W, Sn, TR etc. However owing to crystalle-chemical dispersion of rare elements leucogranitic formation has appeared to be loose ore bearing.It is connected with chamber crustbearing pegmatite and fine greisene-quartzvein wolframic demonstration (deposit Dungaly).
Concerning rating of territory prospects it is possible to note, that Kalba-Narym belt is the main rare metal structure of Great Altai.Perspective are the northwest and southeast flanks granitoide of a belt where the detection of new rare metal deposits are latent on depth and hide under a cover of friable deposits.Further we'll briefly consider the characteristics of others granitoidic belts [6].On the border of Great Altai with caledonion of Gorny Altai Tigireksko-Chernevinsky belt of normal and increased alkali granitoide was generated.The main here are skarnic and greizic deposits with W-Мо (Ekipetsky, Ivanovsky etc.), and in alkaline granite Nb-Zr-rare earths mineralization is shown (Azutau).In Gorny Altai and Chinese Altai in zones of hercinic tectone-magmatic activization Uryl-Koktokay belt of normal and subalkaline granite with pegmatite Ta-Nb-Be-Li is allocated with greisene and hydrothermal W-Mo-Be deposits (Koktokay, Kalguty, Kokkol etc.) and displays rare earths.
In an axial part of Great Altai (on the Kazakhstani border and Gorny-Altaisk continental edges) in Zaysan suturn zone with suboceanic type of earth crust Semi-palatinsk-Buran-Byrgyn belt of monzonite sienite and granosienite with Zr-Ti geochemical specialization was generated.Granitoid massives of this belt (Preobrazhenska, Buran etc.) are perspective for search of zircon-ilmenite deposits in mesozoic residual soils (Karaotkel deposit), on the account of washupagain which the ilmenite looses (Satpaev placer) are formed.
The revealed laws of formation and spatial accommodation of deposits of rare metals in Kalba-Narym zone and other geological structures are the important criterion for forecasting and searching the new ores objects on East Kazakhstan territory.

Conclusions
Kalba-Narym is considered as allogenic cluster (Terrane), attached to the structure of the Great Altai in Hercynian collision period.The main ore-bearing structures are confined to clusters of sialitic profile with increased capacity of Meta granite layer and the earth's crust in whole.Granite Belt has a regional growth (the length of more than 500 km).Large scale of granitoids expansion emphasizes high energy and material resources for the processes of ore formation.Structural and metallogenic model of Kalba-Narym belt reflects the connection between the ore-magmatic systems with depth zones of the Earth crust and upper mantle, and therefore granitoid belt was formed as a result of long-term abyssal evolution of earth's sial zone matter.
Granite intrusions are presented to be the most orebearing, which are formed in the mobile geodynamic environment that promotes more intensive processes of ore formation in nonequilibrium PT conditions and, ultimately, formation of commercial deposits (Priirtyshsky, Belogorsky solids).On this basis, ore and magmatic systems of varied productivity degrees have been identified and described.Developed geological and genetic models and ore petrochemical typification of granitoids seem to be major factors for rare metal deposits prediction.
Recommendations to geological explorations: Involvement in the assessment reserve perspective areas, and semi-closed and covered unconsolidated sediments (Shulbinsky area, etc.).Additional appraisal of flanks and deep levels of the known ore fields and deposits (Belaya Gora, Bakenny, Upper Baymurza, Yubileiny, etc.).The search for hidden tin-tantalum mineralization in the hidden granite domes of the (Karasu, Shuruk, etc.).Development by small enterprises of small pegmatite deposits with tantalum reserves (Medvedka, Ahmetkino, Tochka, Komarovsky, etc.).Development of new prognostic and search technologies based on modern geological and geodynamic concepts of ore formation, leading ore petrological, geophysical, and mineralogical and geochemical estimation criteria, using high-precise analytical base.
Conducted metallogenic studies have shown that there are perspectives in the region to strengthen the mineral resource base for rare metal production.