Diachronous Growth of the Altyn Tagh Mountains: Constraints on Propagation of the Northern Tibetan Margin From (U‐Th)/He Dating

Abstract

The sinistral Altyn Tagh strike‐slip fault demarcates the northern boundary of the Qinghai‐Tibetan Plateau; however, the significance and timing of activity along the fault are debated. Here new apatite and zircon (U‐Th)/He data are presented, revealing the exhumation history of the Altyn Tagh Mountains from crustal depths of ~2–7 km. Studies of rock samples from the Altun Shan region show that they were located close to the surface during the Early Cretaceous and remained so until about 40 Ma. Samples from the Subei and Dangjin Pass areas, on the other hand, record a period of rapid exhumation at 20 ± 2 Ma, and samples from the Qiemo area record a period of continuous exhumation between ~20 and 12 Ma at a rate of 0.046−0.013+0.007 mm/year, plus a further rapid cooling event at 7–5.5 Ma. Thus, significantly more exhumation has occurred toward the southwestern section of the Altyn Tagh Fault Zone, indicating a decrease in tectonic uplift toward the northeast since the Miocene. During the late Miocene, the Tarim Block began to subduct beneath the northern Tibetan margin, resulting in rapid exhumation of the central section of the Altyn Tagh Fault Zone. In accordance with previous studies, the present results support a model of northward propagation and expansion of the Qinghai‐Tibetan Plateau during the Cenozoic.

Miocene Range Growth Along the Altyn Tagh Fault: Insights From Apatite Fission Track and (U‐Th)/He Thermochronometry in the Western Danghenan Shan, China

“…The proposed rapid exhumation commencing in the middle Miocene coincides with the onset of a suite of significant phenomena along the Altyn Tagh fault: (1) thermochronology on basement rocks along the Altyn Tagh fault (e.g., Jolivet et al, , ; Ritts et al, ; Shi et al, ; Sobel et al, ; Zhuang et al, ); (2) acceleration in sedimentation rate, provenance change and growth strata recorded by paleomagnetic studies in the western Qaidam Basin and along the Altyn Tagh fault (e.g., Chang et al, ; Gilder et al, ; B. Li et al, ; Lu et al, ; Wang, Zhang, Pang, et al, ; W. Zhang et al, ); (3) provenance analyses based on lithofacies variations and detrital zircon U–Pb ages along the Altyn Tagh fault (e.g., F. Cheng et al, , ; Wu, Xiao, Wang, et al, ; Wu, Xiao, Yang, et al, ; Yue et al, ; Zhu et al, ; T. Zhang et al, ); and (4) initiation of growth strata in the basins along the Altyn Tagh fault and western Qaidam Basin revealed by seismic data (e.g., F. Cheng et al, , , ; B. Li et al, ; R. Liu, Allen, et al, ; Yin et al, ).…”

“…Topographic map of north Tibet with major faults and initial deformation timing in (a) middle Miocene and (b) Paleocene to Eocene. Initiation ages were derived from: 1—This study; 2—Ritts et al (); 3—Shi et al (); 4—Yue and Liou (); 5—Y. Wang et al (); 6—R.…”

“…The onset of its left‐lateral slip and how it was accommodated are two prominent issues for understanding the geodynamics of uplift of the Tibetan Plateau (Yin et al, ; Yin & Harrison, ; Yue & Liou, ). A large number of studies have investigated the geology along the Altyn Tagh fault (e.g., Chang et al, ; F. Cheng et al, , ; Cowgill et al, ; Dupont‐Nivet et al, ; Gilder et al, ; Jolivet et al, ; Lin et al, ; B. Li et al, ; Lu et al, ; Ritts et al, ; Shi et al, ; Sobel et al, ; Sun et al, ; Wang, ; Wu, Xiao, Wang, et al, ; Wu, Xiao, Yang, et al, ; Yin et al, ; Yue et al, , ; Zhuang et al, , ). But despite this large body of data, there is no consensus about its temporal–spatial evolution due to a lack of ideally dated geological or geomorphological records on the Cenozoic slip.…”

“…But despite this large body of data, there is no consensus about its temporal–spatial evolution due to a lack of ideally dated geological or geomorphological records on the Cenozoic slip. Estimates for the onset of movement along the Altyn Tagh fault range from the Eocene, not long after the India‐Eurasia collision (e.g., Yin et al, ; Jolivet et al, ; F. Cheng et al, , ), to the Miocene (e.g., Chang et al, ; Lin et al, ; B. Li et al, ; Meyer et al, ; Ritts et al, ; Shi et al, ; Sun et al, ; Wu, Xiao, Yang, et al, ; Yue et al, ). Others have proposed a model with multiple stages of accelerated faulting to reconcile all available data along the Altyn Tagh fault (Yue et al, ; Yue & Liou, ; Zhuang et al, , ).…”

“…Cheng et al, , 2016Cowgill et al, 2003;Dupont-Nivet et al, 2004;Gilder et al, 2001;Jolivet et al, 2001;Lin et al, 2015;B. Li et al, 2017;Lu et al, 2016;Ritts et al, 2004;Shi et al, 2018;Sobel et al, 2001;Sun et al, 2005;Wang, 1997;Wu, Xiao, Yang, et al, 2012;Yin et al, 2002;Yue et al, 2001Yue et al, , 2004Zhuang et al, 2011Zhuang et al, , 2018. But despite this large body of data, there is no consensus about its temporal-spatial evolution due to a lack of ideally dated geological or geomorphological records on the Cenozoic slip.…”