2011

Тезисы международной конференции

Рудный потенциал щелочного, кимберлитового

 и карбонатитового магматизма

Abstracts of International conference

Ore potential of alkaline, kimberlite

and carbonatite magmatism

Multi-formational intrusive massifs of the Southern Uzbekistan

Dalimov T.N.*, Yudalevich Z.A.**, Divaev F.K.***, Ganiev I.N.*

* National University of Uzbekistan named after Mirzo Ulugbek, Tashkent, Republic of Uzbekistan;

** Ben Gurion University of the Negev, Beer-Sheva, Israel; *** The State Geology Committee Republic of Uzbekistan.

The formations analysis of numerous granitoid intrusives is based on the assumption that genetic related, sequential differentiated and contrast magmatic series are common. Gabbro-diorite-granodiorite-granite and gabbro-granite sequence are such examples. In the particular orogenic belts magmatic series may be somewhat differ, e.g. gabbro-tonalite-plagiogranite, gabbro-monzodiorite-granite etc. Such magmatic series are often used as rather reliable criterions for the reconstruction of particular geodynamic situations, for example island arc, continental margin, rifting, and plate collision.

Doctrine on magmatic formations that was born in formed century has been successfully developed by such famous geologists as Usov M.A., Afanasiev G.D., Favorskaya M.A., Heraskov N.P., Kuznetsov Y.A., Fershtater G.B., Masaytis V.L. and many others. Main principals of the determination of magmatic formations and their representatives (magmatic complexes) have been widely discussed in the periodic and were finally formulated in the monograph «Main type of magmatic formations» (Kuznetsov, 1964). That classification was then significantly supplemented in the monograph «Magmatic formations of the USSR» (Masaytis et.al., 1979).

«The map of magmatic formations» and «The map of magmatic complexes» of Uzbekistan have been composed in the middle 80-th of the formed century. From that time magmatic associations of Uzbekistan are shown as magmatic complexes.

A multi-year experience of the study of magmatic rocks of the Uzbekistan showed that the best approach to the division of magmatic rocks is a geological mapping on the scale of 1:50 000 – 1:25 000 (and bigger) that accompanied be complex of detailed petrographical and geochemical studies. This report provides some results that were obtained owing to such investigations.

Most part of intrusive massifs of the Uzbekistan show relatively simple composition. They are mainly composed from one and rarely two intrusive complexes. Nevertheless, in the Western Tian-Shan there are massifs that have quite simple composition and rather big massifs with compound structure. The latest type massifs may be subdivided into two subtypes. Massifs of first subtype, such as Bokalinsky and Koshrabadsky, composed from the rocks of one magmatic complex but have extremely compound structure with up to 27 sequential intrusions showing sharp intrusive contact. Massifs of the second subtype, such as Gissarsky batholith, Machitlinsky and Kugitangsky intrusives, are composed from rocks of the several complexes. We divided here 5–7 complexes; each one has its own metallogenic specifics.

It is important to note that all intrusive complexes mentioned above have multi-phase compound structure. In each one there are between 5 – 10 phases of intrusions with sharp cross cut contacts. This fact is important for a row of petrological problems. One of them is a problem of space. It is important to understand how during relatively long period of the time of about 30 - 40 Ma the intrusions of magma that originated from different sources have been possible into almost the same place. Another problem is a question about the period of time that was necessary for separate intrusion of magma to solidity. If we do not consider the volume and temperature of intruded magma, the parameters of thermoconductivity of surrounding rocks, specific conditions of and possible mechanisms of loss of heat and would only consider the radiometric data on the intrusion, then crystallization time will be 1 Ma or probably less.

In the geological history of the nappe-fold system of the West Tian-Shan there are several periods (stages) of geodynamic evolution, such as continental rifting, spreading, oceanic crust formation, subduction, collision, and within plate. Thus, this is a complete Wilson cycle which characterizes the evolution of Kirgiz-Terskey, Turkistan paleoceans and Zarafshan, South-Gissar and Baysun paleobasins. Kirgiz-Terskey and Turkistan Paleoceans are related to Paleoasian Ocean whereas other paleobasins are parts of the Paleotethys basin. The analysis of the available geological and petrological data and the classification of magmatic processes according to specific geodynamic conditions can build consistent model of the formation and evolution of Tian-Shan orogen. However, such model will not be possible without consideration space-time problem and particularities of the natural magmatic associations.

Magmatic complexes of multi-formational intrusives of the Southern Uzbekistan

References:

Geology and minerals of the Republic of Uzbekistan.Tashkent: "University", 1998. 724 p. (in Russian).

Dalimov T.N., Ganiev I.N., Shpotova L.V., Kadyrov M. H. Geodynamics of Tian-Shan. Volume 1 - (Magmatism and geodynamic conditions of Paleozoic). Tashkent: "University", 1993. 208 p. (in Russian).

Dalimov T.N., Ganiev I.N. Evolution and types of magmatism of Western Tian-Shan. Tashkent: "University", 2010. 228 p. (in Russian).

Tuljaganov H.T., Yudalevich Z.A., Korzhaev V.P, et al. Card of magmatic complexes of Uzbekistan. Tashkent: "Fan", 1984. 346 p. (in Russian).