Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet
Loading...
Date
2021-05
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI AG
Abstract
North-trending rifts throughout south-central Tibet provide an opportunity to study the
dynamics of synconvergent extension in contractional orogenic belts. In this study, we present new
data from the Dajiamang Tso rift, including quantitative crustal thickness estimates calculated from
trace/rare earth element zircon data, U-Pb geochronology, and zircon-He thermochronology. These
data constrain the timing and rates of exhumation in the Dajiamang Tso rift and provide a basis for
evaluating dynamic models of synconvergent extension. Our results also provide a semi-continuous
record of Mid-Cretaceous to Miocene evolution of the Himalayan-Tibetan orogenic belt along the
India-Asia suture zone. We report igneous zircon U-Pb ages of ~103 Ma and 70–42 Ma for samples
collected from the Xigaze forearc basin and Gangdese Batholith/Linzizong Formation, respectively.
Zircon-He cooling ages of forearc rocks in the hanging wall of the Great Counter thrust are ~28 Ma,
while Gangdese arc samples in the footwalls of the Dajiamang Tso rift are 16–8 Ma. These data
reveal the approximate timing of the switch from contraction to extension along the India-Asia suture
zone (minimum 16 Ma). Crustal-thickness trends from zircon geochemistry reveal possible crustal
thinning (to ~40 km) immediately prior to India-Eurasia collision onset (58 Ma). Following initial
collision, crustal thickness increases to 50 km by 40 Ma with continued thickening until the early
Miocene supported by regional data from the Tibetan Magmatism Database. Current crustal thickness
estimates based on geophysical observations show no evidence for crustal thinning following the
onset of E–W extension (~16 Ma), suggesting that modern crustal thickness is likely facilitated by an
underthrusting Indian lithosphere balanced by upper plate extension.
Description
Keywords
crustal thickening dajiamang
Citation
Burke, W. B., Laskowski, A. K., Orme, D. A., Sundell, K. E., Taylor, M. H., Guo, X., & Ding, L. (2021). Record of crustal thickening and synconvergent extension from the Dajiamang Tso Rift, Southern Tibet. Geosciences, 11(5), 209.