Low-temperature thermochronology of the Chatkal-Kurama terrane (Uzbekistan-Tajikistan): insights into the Meso-Cenozoic thermal history of the western Tian Shan

Abstract

The Chatkal‐Kurama terrane represents a key region in understanding the tectonic evolution of the western Tian Shan. In this contribution, we present new thermochronological data (zircon [U‐Th‐Sm]/He, apatite fission track, and apatite [U‐Th‐Sm]/He) and the associated thermal history models for 30 igneous samples from the Chatkal‐Kurama terrane within Uzbekistan and Tajikistan (west of the Talas‐Fergana Fault) and integrate our data with published data from the central Tian Shan (east of the Talas‐Fergana Fault). The Chatkal‐Kurama terrane experienced a phase of rapid cooling during the Triassic‐Jurassic at ca. 225–190 Ma, which we interpret as a far‐field response to the closure of the Palaeo‐Asian Ocean or the accretion of the Qiangtang terrane on to the Eurasian margin. In the Late Jurassic to the Early Cretaceous, the Chatkal‐Kurama terrane experienced a period of tectonic stability and denudation, before transitioning into a period of marine incursions of the Paratethys Sea. In contrast, fast cooling is recorded for the Kyrgyz central Tian Shan to the east of the Talas‐Fergana Fault. The differing thermal histories at either side of the Talas‐Fergana Fault suggest that the fault induced a topographic divide during the Late Jurassic‐Early Cretaceous, with high relief in the east (Kyrgyz Tian Shan) and low relief to the west (Uzbek‐Tajik Tian Shan). Finally, the Chatkal‐Kurama terrane experienced renewed tectonic activity since ca. 30 Ma, related with the distant India‐Eurasia collision and Pamir indentation. The Cenozoic reactivation induced crustal tilting of the Chatkal‐Kurama terrane, progressively exposing deeper rocks to the southwest.