Apatite and zircon (U–Th)/He thermochronological evidence for Mesozoic exhumation of the Central Tibetan Mountain Range

Abstract

The Central Tibetan Mountain Range (CTMR) exposes the oldest strata in the Qiangtang Terrane and may record the most complete exhumation history prior to and post‐collision of India and Asia. This article presents apatite and zircon (U–Th)/He thermochronology data of granites from the CTMR. Zircon (U–Th)/He single grain ages range from 116 to 191 Ma, while apatite (U–Th)/He single grain ages vary from 54 to 94 Ma. Thermal modelling results based on (U–Th)/He ages of apatite and zircon indicate that episodic rapid exhumations occurred at the Middle‐Late Jurassic and the Late Cretaceous, respectively. The Middle‐Late Jurassic exhumation is consistent with the provenance analysis of Jurassic strata in the South (SQT) and North Qiangtang Terrane (NQT) which suggested they were derived from the CTMR. This stage of rapid exhumation might be attributed to the northward ridge subduction of the Bangong‐Nujiang Ocean. The Late Cretaceous relatively rapid exhumation is compatible with the angular unconformity between the Abushan Formation and the underlying marine strata. This stage of exhumation may be caused by the collision between Lhasa and QT. Our results, combined with the crust shortening and adakitic rocks in the SQT during the Late Cretaceous, provide robust evidence for crustal thickening and early uplift of central Tibetan Plateau prior to the India‐Asia collision. The CTMR experienced very low exhumation since the early Eocene, implying that low‐relief topography had been established at high elevation with internal drainage prior to India‐Asia collision.

Late Cretaceous-Eocene exhumation of the northern Lhasa terrane and topographic implications for the Central Tibet

“…A similar cooling pattern was observed in southern Qiangtang terrane where most ZHe ages spanned approximately ~150 -80Ma, AFT ages ranged between ~95-44 Ma, and AHe ages are of ~85-40 Ma (Zhao et al, 2017;Yang et al, 2019;Qian et al, 2021;Xue et al, 2022). Thermochronological modelling based on these data indicates at least two episodic rapid exhumations at the Late Jurassic and the Late Cretaceous times, respectively (Yang et al, 2019;Qian et al, 2021). This synchronous cooling history indicates that the interior of Tibet has undergone a relatively uniform exhumation between the Late Cretaceous and Middle Eocene time.…”

“…40 Ma combined with sedimentological evidences suggests that the lower relief, internally drained aspects of the region were initiated around this time. Hetzel et al, 2011;Rohrmann et al, 2012;Haider et al, 2013;Zhao et al, 2019;Yang et al, 2019;Qian et al, 2021;Li et al, 2022;Xue et al, 2022;Tong et al, 2022. JSSZ-Jinsha suture zone; BNSZ-Bangong-Nujiang suture zone; IYSZ-Indus-Yarlung suture zone.…”

Mid‐Cretaceous Exhumation of the Central Qiangtang Mountain Range Metamorphic Rocks as Evidenced by the Abushan Continental Redbeds

“…If the Shuanghu Conglomerate was deposited during the Jurassic, then mid‐Jurassic exhumation would be indicated. A Middle‐Late Jurassic cooling event that could be associated with such interpreted exhumation is recorded by zircon (U‐Th)/He ages from granite, quartzite, and other metamorphic rocks exposed in the Central Qiangtang Mountain Range to the west of the studied section (Qian et al., 2021; Zhao et al., 2017). Additionally, a tectonic event in the mid‐Jurassic is recorded in southern Qiangtang and in the Bangong‐Nujiang suture zone by syn‐orogenic deposits underlain by a major unconformity and inferred to be derived from the Central Qiangtang Mountain Range (Ma et al., 2017, 2018; J. Zhang et al., 2021).…”

“…The central Qiangtang terrane experienced several exhumation events during Jurassic to Cretaceous time. Zircon (U‐Th)/He thermochronology of granitoid rocks shows that the Central Qiangtang metamorphic complex was exhumed to within a few km of the surface during the Middle to Late Jurassic (∼170–150 Ma; Qian et al., 2021; Zhao et al., 2017). As indicated by thermochronologic evidence (Kapp et al., 2005; Raterman et al., 2014; Ren et al., 2015; Song et al., 2013; J. Zhang, Sinclair, et al., 2019; Zhao et al., 2020), the major exhumation episode took place across most of the Qiangtang Block during the late Early to Late Cretaceous (∼120–70 Ma), when rocks as young as Jurassic were deformed into the aforementioned anticlinorium (Kapp et al., 2005).…”