Differential Exhumation and Crustal Tilting in the Easternmost Tianshan (Xinjiang, China), Revealed by Low‐Temperature Thermochronology

Abstract

The easternmost Tianshan forms the eastern extremity of the modern Central Asian Orogenic Belt and represents a key locality to investigate strain propagation from the Meso‐Cenozoic plate margins to the Eurasian interior. The Tianshan as a whole has been reactivated multiple times throughout the Meso‐Cenozoic, but the extent of these reactivation events is yet to be fully understood. This study applies apatite fission track and apatite (U‐Th‐Sm)/He thermochronology to the mountain ranges of the easternmost Tianshan. Our new results suggest that the area experienced two phases of rapid cooling in the Mesozoic—during the Early to Middle Triassic and the Late Cretaceous. These cooling phases are linked to tectonic events at the distant plate margins such as the Permian to Middle Triassic closure of the Paleoasian Ocean and the Late Jurassic to Early Cretaceous Mongol Okhotsk orogeny. Fault‐controlled differential exhumation and block tilting are recorded in the distribution of apatite fission track ages across the region. Finally, we show through a combination of multiple thermochronometers and the integration of structural analysis that the easternmost Tianshan has experienced insufficient exhumation to constrain the timing of reactivation in response to the Cenozoic collision of India with Eurasia and instead records older, Mesozoic tectonic events.

Detrital zircon geochronology analysis of the Late Mesozoic deposition in the Turpan‐Hami basin: Implications for the uplift history of the Eastern Tian Shan, north‐western China

“…The dashed line in A illustrates the proposed boundary of regions with different provenances for the Jurassic deposits according to Greene et al (). The scenario since the Cenozoic (d) was determined based on thermochronology studies conducted by Wang et al (), Zhu et al () and Gillespie et al (), as well as a topography analysis of the Turpan‐Hami basin by Pullen et al ()…”

“…Apatite fission‐track (AFT) ages presented by Wang, Li, Zhang, Liu, and Ma () illustrated that major uplift of the eastern Tian Shan occurred between 30 and 20 Ma, with uplift migrating from west to east. These results were challenged by Gillespie et al (), who suggested that the easternmost Tian Shan experienced two phases of rapid cooling during the Early to Middle Triassic and the Late Cretaceous. They also demonstrated that an initial planation surface formed during the Jurassic and was reworked during the Late Cretaceous (Gillespie et al, ).…”

“…These results were challenged by Gillespie et al (), who suggested that the easternmost Tian Shan experienced two phases of rapid cooling during the Early to Middle Triassic and the Late Cretaceous. They also demonstrated that an initial planation surface formed during the Jurassic and was reworked during the Late Cretaceous (Gillespie et al, ). Another thermochronology study indicated that the western Bogda Mountain experienced two stages of rapid uplift during the Late Jurassic to Cretaceous and Oligocene to Miocene (Tang et al, ).…”

“…Therefore, the most probable source for these sediments is the Early Triassic granites in the Harlik mountain. Thermochronological studies show that these granites started being exhumed by the Early Cretaceous with AFT ages mostly ranging from ~ 141 to 90 Ma (Gillespie et al, ; Zhu et al, ), simultaneous with the deposition age of the Dahaidao Formation, which was determined by the occurrence of pterosaur fossils (Wang, Kellner, et al, ).…”

“…The zircon U‐Pb ages are from [1] Jin et al (); [2] Shu et al (); [3] Gao et al (); [4] Gao et al (); [5] Chen, Shu, & Santosh (); [6] Greene et al (); [7] Sun, Li, Gao, & Yang (); [8] Wang and Gao (); [9] Zhang et al (); [10] Mao et al (); [11] Song et al (); [12] Zhou et al (); [13] Xiao et al (); [14] Cui, Wang, Ma, Sun, and Zhu (). AFT ages are from Zhu et al (), Shen et al (), Wang et al (), Gillespie et al (), and Tang et al (). NTS, CTS and STS are abbreviations of the North, Central and South Tian Shan respectively.…”