Asel Togonbaeva (Kyrgyzstan)

Email: asel_togonbaeva @hotmail.com

Thesis title:  Early Paleozoic subduction and collision tectonics of the North Tien-Shan (Kyrgyzstan).

Supervisor:  Prof. Akira Takasu (2007-2010).

Three eclogite-bearing complexes occur in the Kyrgyz Tien-Shan. The Makbal and the Aktyz eclogite-bearing complexes occur in the northern Tien-Shan, and the Atbashy eclogite-bearing complex occurs in the southern Tien-Shan. The Kyrgyz Tien-Shan is bounded by the Tarim Basin to the south and the relatively stable Kazakh platform to the north within the Ural-Mongolian folded belt. The Kokchetav–North Tien-Shan area is surrounded by Caledonian rocks of the Ural-Mongolian folded belt.

The metamorphic rocks exposed in the Makbal area consist of the Makbal and the Neldy Formations. The Makbal Formation is characterized by quartz schists alternating with pelitic schists, and intercalated eclogite blocks of varying size. Coesite inclusions in garnets have been described from garnet-chloritoid-talc schists in the Makbal Formation. The Neldy Formation, which tectonically overlies the Makbal Formation, is composed mainly of garnet-muscovite schists, pelitic schists, amphibolites, and eclogites, along with minor marbles and meta-quartzites.

Eclogites in the Makbal complex experienced two metamorphic events: HP eclogite facies metamorphism and overprinted relatively HP epidote-amphibolite facies metamorphism . An isochron age of 480±25Ma has been determined for monazites from the garnet-talc-chloritoid schists. Layers and lenses of the garnet-talc-chloritoid schists are intercalated within the meta-quartzite layers and are folded together.

The aims of my study are:

1. Petrographic study of the HP and UHP metamorphic rocks of the Makbal and Neldy Formations.
2. To determine the metamorphic ages of the HP and UHP rocks.
3. To correlate the T-P-t paths of the eclogites and host metamorphic rocks (relationship between garnet-talc-chloritoid schists and pelitic schists).

I will carry out detailed petrographic descriptions and EPMA analyses of constituent minerals of the metamorphic rocks. Age determinations of the eclogites and surrounding rocks will be made using Sm-Nd, Rb-Sr and CHIME methods. Using these techniques, cooling histories of the eclogites and the host metamorphic rocks can be obtained.

These new findings will contribute to better understanding of the exhumation processes of the eclogites and the host metamorphic rocks during the subduction and subsequent collision environments. They will also allow discussion of the tectonics of the Northern Tien-Shan during Middle Cambrian to Ordovician time (520-450 Ma).