The New Evidence on Tectonic Uplift in Kepingtage Area, Tarim, China: Constraints from (U‐Th)/He Ages

Abstract

AbstractAs part of Tarim platform, Kepingtage area lies between southwest Tienshan and Tarim basin, and its tectonic‐uplift evolution is closely correlated with Tienshan and Tarim basin. The (U‐Th)/He thermochronometry is used as a new technique to study the tectonic uplift of Kepingtage area in the paper. Based on the measured apatite/zircon (U‐Th)/He ages of Sinian outcrop samples in the region and the thermal modeling, the results reveal four phases of tectonic‐uplift events appeared in Kepingtage area, which made the Sinian formation rise to the surface. The apatite (U‐Th)/He ages reveal two phases of uplift events at Late Cretaceous and Miocene. During Early Carboniferous, the Sinian formation temperature reached a maximum of 133~150°C. Combined with the burial history of the sample, the maximum depth can be derived to be 3400~3900m. Due to the distant effect from the collision of the Indian and Eurasian plates, Kepingtage area thrust over Bachu uplift along Kepingtage‐Shajingzi fault during the Oligocene‐Miocene. The strata were rapidly uplifted and eroded. During 15~10Ma, the Sinian formation in Kepingtage area had been uplifted to the surface. The total exhumation amount is up to 6170m since Early Carboniferous. While the tectono‐thermal evolution history of the Kepingtage area is consistent with the northern margin of Tarim basin in Mesozoic to Cenozoic, it is inconsistent with Tienshan and the Bachu uplift inside Tarim basin. Since Miocene, Kepingtage area and Tienshan was in the same state of uplifting by the distant effect of the Himalayan movement; During Early Eocene, Bachu uplift area was still uplifted and eroded, while Kepingtage area received deposits. This paper successfully reveals the tectono‐thermal evolution history of Kepingtage area since Sinian using the (U‐Th)/He thermochronometry, which is useful for understanding the tectonic uplift in the region correctly. Furthermore, the study can support the hydrocarbon exploration of Tarim basin and the tectonic study of Tarim basin and Tienshan.