Abstract:

Djanydjer ophiolitic mélange in the Kyrgyzstan, South Tianshan suture are composed of serpentinized peridotite, gabbro, basalt and chert. Two groups UPb zircon ages of 422.0±2.0 Ma（MSWD=1.2） and 397.3±3.9 Ma (MSWD=0.6) have obtained for the gabbro. Considered with chronology studies of ophiolites in ChinaKyrgrz, South Tianshan, the older age (422 Ma) represents the crystallization of gabbro, which implies the oceanic basin separated the Tarim craton and Kyrgyz Middle Tianshan terrane has existed in the early stage of the Late Silurian. The younger age might be related to metamorphism during the oceanic lithosphere obduction or the postcollisional magmatism. Muscovitequartz schist in the same belt with Djanydjer ophiolitic mélange was considered as a part of Precambrian metamorphic terrane. It has similar petrology and deformation characteristics with the host rocks of Atbashi ecologite. Its detrital zircons vary widely in age from 406 Ma to 2856 Ma, which is similar to that reported from the Atbashi greywacke. Compared with the age spectrum of zircons from Tarim Craton and Atbashi greywacke, the protolith of the muscovitequartz schist has a depositional age <406 Ma and the provenance was probably in the North and Middle Tianshan.

Key words: Kyrgyzstan, South Tianshan, phiolite, zircon UPb chronology