Rustam Orozbaev (Kyrgyzstan)

Email: rustamot76 @mail.ru

Thesis title:  Petrological study of metamorphic rocks of the Aktyuz eclogite-bearing complex, Zaily Range, Kyrgyzstan.

Supervisor:  Prof. Akira Takasu (2003-2005).

The Aktyuz eclogite-bearing complex crops out in part of the Caledonides of the Northern Tien-Shan, where formations as old as Archean or early Proterozoic occur. The Aktyuz Complex and the Kopurelisay Ophiolite Complex are the oldest formations in the region. Paleozoic volcanogenic sedimentary rocks in the area are not metamorphosed, and igneous intrusive rocks ranging from Proterozoic to Paleozoic in age are also present. Several tectonic structures can be distinguished, and these are grouped into five stages of activity, namely the Precambrian, Late Precambrian, Caledonian, Hercynian and Alpine periods.

The Aktyuz eclogite-bearing complex was deformed and metamorphosed many times, and is now composed of gneisses, migmatites, crystalline schists, and lens-shaped bodies of amphibolized eclogites and retrograded eclogites. Serpentinites occur in the northern and southwestern margins of the Aktyuz Complex. This complex is almost entirely bordered by faults, but grades into the Kopurelisay Complex in the western part of the Zaily Range. In the southeastern part of this range, the Aktyuz Complex is separated by faults from migmatites of the Kemin Series, and from Precambrian and Caledonian granitoids.

The Kopurelisay Complex is composed of weakly deformed metagabbros, metabasalts and meta-ultrabasites, and intercalated metasediments. These rocks have been subjected to greenschist facies regional metamorphism, and are completely bounded by faults. The shape of these rock bodies is lensoidal. However, primary structures are observable in gabbros and basalts in the central parts of large lenses.

The general aim of my research is to study the petrology, mineralogy, and geochronology of the metamorphic rocks of the Aktyuz and Kopurelisay Complexes. I will carry out petrographic description of thin-sections by microscope, chemical analyses of minerals by EPMA, determine metamorphic ages by TIMS, and analyze the rocks for trace and REE elements by ICP-MS. This will lead to discussion of the P-T histories and tectonics of these metamorphic rock suites.