India‐Asia convergence: Insights from burial and exhumation of the Xigaze fore‐arc basin, south Tibet

Abstract

The composite fore‐arc/syncollisional Xigaze basin in south Tibet preserves a key record of India‐Asia collision. New apatite fission track and zircon (U‐Th)/He data from an N‐S transect across the preserved fore‐arc basin sequence near Xigaze show a consistent northward Late Cretaceous to middle Miocene younging trend, while coexisting apatite (U‐Th‐Sm)/He ages are all Miocene. Corresponding detrital zircon U‐Pb data are also reported for constraining the Cretaceous depositional ages of the Xigaze basin sequence in the region. Thermal history modeling indicates that the basin experienced northward propagating episodic exhumation, along with a northward migration of the depocenter and a pre‐existing Cenozoic syncollisional basin sequence which had been removed. In the southern part, fore‐arc exhumation commenced in the Late Cretaceous (~89 ± 2 Ma). Following transition to a syncollisional basin in the Paleocene, sedimentation in the central and northern Xigaze basin continued until the latest Eocene (~34 ± 4 Ma). Ongoing folding and thrusting (e.g., Great Counter Thrusts) caused by progressive plate convergence during late Oligocene‐early Miocene time resulted in regional uplift and considerable basin denudation, which fed two fluvial basins along its northern and southern flanks and exposed the basement ophiolite. Subsequent incision of the Yarlung River resulted in Miocene cooling in the region. Different episodes in the exhumation history of the Xigaze basin, caused by thrusting of an accretionary wedge and ophiolitic basement, can be linked to changes in India‐Asia convergence rates and the changing subduction pattern of the Indian and Neo‐Tethyan slabs.

Low‐Temperature Thermochronology of the Indus Basin in Central Ladakh, Northwest India: Implications of Miocene‐Pliocene Cooling in the India‐Asia Collision Zone

“…Interestingly, along the Yarlung suture of the India‐Asia collision zone in south Tibet, a regional Miocene cooling signal from ~21–7 Ma is well documented from low‐temperature thermochronometric studies (e.g., Carrapa et al, 2014; Ge et al, 2017; Li et al, 2015, 2016, 2017; Orme, 2019; Tremblay et al, 2015). These studies generally attribute the Miocene cooling signal to GCT activity and/or Yarlung River erosion (Carrapa et al, 2014; Ge et al, 2017; Li et al, 2015, 2016, 2017; Orme, 2019), or intensification of Asian monsoon (Carrapa et al, 2014), while considering the regional uplift caused by the northward underthrusting of the Indian plate following Greater Indian slab break‐off in Early Miocene time (DeCelles et al, 2011; Webb et al, 2017). Therefore, it is possible that a similar combination of tectonic, geodynamic, and geomorphologic factors resulted in a tectonic setting that facilitated regional cooling along the India‐Asia collision zone in NW India.…”

“…If the Indus River existed at this location since Early Eocene time, additional tectonic, geodynamic, and geomorphologic factors were also responsible for the initiation of cooling. Interestingly, along the Yarlung suture of the India-Asia collision zone in south Tibet, a regional Miocene cooling signal from 21-7 Ma is well documented from low-temperature thermochronometric studies (e.g., Carrapa et al, 2014;Ge et al, 2017;Li et al, 2015Li et al, , 2016Li et al, , 2017Orme, 2019;Tremblay et al, 2015). These studies generally attribute the Miocene cooling signal to GCT activity and/or Yarlung River erosion (Carrapa et al, 2014;Ge et al, 2017;Li et al, 2015Li et al, , 2016Li et al, , 2017Orme, 2019), or intensification of Asian monsoon (Carrapa et al, 2014), while considering the regional uplift caused by the northward underthrusting of the Indian plate following Greater Indian slab break-off in Early Miocene time (DeCelles et al, 2011;Webb et al, 2017).…”

Recognition of trench basins in collisional orogens: Insights from the Yarlung Zangbo suture zone in southern Tibet

“…The rapid cooling and uplift of Xigaze forearc-basin strata occurred at~90 Ma indicated by the low-temperature thermochronological analysis (Li et al, 2017), could have induced recycling sediments of forearc-basin strata to the trench, which corresponds well with the enriched quartz and sedimentary lithic fragments in trench strata. Prominent abraded overgrowths and rounded outline of quartz in shale, siltstone, and sandstone rock fragments indicating the extensive recycling process, which can also be seen in the Mélange unit in the Indus suture zone of the northwestern Himalaya (Garzanti and Van Haver, 1988).…”

Miocene Subsidence and Surface Uplift of Southernmost Tibet Induced by Indian Subduction Dynamics

“…(b–d) AFT, AHe, and ZHe ages of the Kailas Formation, Gangdese batholith, and Xigaze basin against the distance from Indus‐Yarlung suture zone in different locations. The data are summarized from Carrapa et al (2014); Copeland et al (1995); Dai et al (2013); Ge et al (2017, 2018); Li et al (2016, 2017); Li, Kohn, et al (2015); Li, Tian, et al (2015); Pan et al (1993); Tremblay et al (2015); Wang et al (2007); Wang et al (2015); Yang et al (1999); Zhao et al (2015); and this study.…”

“…To the east, in the Xigaze area, rapid exhumation occurred at circa 16–14 Ma for the Kailas Formation (Ge et al, 2018) and 16–10 Ma for the Liuqu Formation (Li, Tian, et al, 2015), with also AFT ages younger than ~20 Ma (Figure 8c). Between the Kailas Formation to the north and the Liuqu Formation to the south, the rocks from the Xigaze basin also experienced rapid exhumation at circa 16–15 Ma showing <20 Ma AFT (Figure 8c) (Li et al, 2017). In the Zedong area, thermal modeling also suggests rapid exhumation at 20–17 Ma for the Kailas Formation with AFT ages younger than 20 Ma (Li, Kohn, et al, 2015) (Figure 8d).…”