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Article

Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet

1
Department of Earth Sciences, Montana State University, Bozeman, MT 59715, USA
2
Department of Geosciences, University of Arizona, Tuscon, AZ 85721, USA
3
Department of Geology, University of Kansas, Lawrence, KS 66045, USA
4
Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100049, China
*
Author to whom correspondence should be addressed.
Academic Editors: Rodolfo Carosi, Mario da Costa Campos Neto, Haakon Fossen, Chiara Montomoli, Matteo Simonetti and Jesus Martinez-Frias
Geosciences 2021, 11(5), 209; https://doi.org/10.3390/geosciences11050209
Received: 25 March 2021 / Revised: 19 April 2021 / Accepted: 10 May 2021 / Published: 12 May 2021
(This article belongs to the Special Issue Evolution of Modern and Ancient Orogenic Belts)
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. View Full-Text
Keywords: Tibet; E–W extension; crustal thickness; T/REE geochemistry; geochronology; thermochronology Tibet; E–W extension; crustal thickness; T/REE geochemistry; geochronology; thermochronology
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MDPI and ACS Style

Burke, W.B.; Laskowski, A.K.; Orme, D.A.; Sundell, K.E.; Taylor, M.H.; Guo, X.; Ding, L. Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet. Geosciences 2021, 11, 209. https://doi.org/10.3390/geosciences11050209

AMA Style

Burke WB, Laskowski AK, Orme DA, Sundell KE, Taylor MH, Guo X, Ding L. Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet. Geosciences. 2021; 11(5):209. https://doi.org/10.3390/geosciences11050209

Chicago/Turabian Style

Burke, William B.; Laskowski, Andrew K.; Orme, Devon A.; Sundell, Kurt E.; Taylor, Michael H.; Guo, Xudong; Ding, Lin. 2021. "Record of Crustal Thickening and Synconvergent Extension from the Dajiamang Tso Rift, Southern Tibet" Geosciences 11, no. 5: 209. https://doi.org/10.3390/geosciences11050209

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