Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional Sys
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Late Cenozo C oic Activvity of the t Tash hkurgan n Norm mal Fault and Impliccations for the Origin n of the Kongur K r Shan Extensiional Syystem, Eastern E n Pamirr Shenqiang Chen C *1, 2, Hanlin H Chen n1 1. School of Eaarth Sciences, Zhejiang Z Univerrsity, Hangzhouu 310027, Chinaa 2. Departmennt of Earth Sciennces, ETH Zuriich, Zurich 8092, Switzerland Shennqiang Chen: htttps://orcid.org//0000-0002-22665-6313 AB BSTRACT: In n the northwesst of the Himaalayan-Tibetan n orogen, the ~250 ~ km-long K Kongur Shan exten nsional system m in the easterrn Pamir was formed durin ng the convergence between n the Indian and a Assian plates. Tecctonic activity of the Kongur Shan norma al fault and thee Tashkurgan normal fault can c heelp to reveal th he origin of easst-west extensioon along the Kongur K Shan extensional e systtem. The Kong gur Sh han fault has been b extensivelly studied, whiile the Tashkurgan fault callls for systemicc research. In this t stu udy, low-tempeerature therm mochronology in ncluding apatiite fission tracck analysis and d apatite and zirz con (U-Th)/He analyses a is app plied to constrrain the timing g of activity off the Tashkurggan fault. Resu ults ind dicate that thee Tashkurgan fault f initiated at 10–5 Ma, an nd most likelyy at 6–5 Ma. Th he footwall of the Taashkurgan faullt has been exh humed at an avverage exhuma ation rate of 0.6–0.9 mm/a siince the initiattion of the Tashkurgan fault. Com mbined with prrevious researcch on the Konggur Shan faultt, we believe that t thee origin of eastt-west extensioon along the Kongur K Shan ex xtensional systtem was driven n by gravitatio onal colllapse of over-tthickened Pam mir crust. KE EY WORDS: Pamir, P Late Ceenozoic, extenssion, normal fa ault, low-tempeerature thermoochronology. 0
INTRODU UCTION The Pam mir salient is siituated at the western w end of the Himalayan-Tibbetan orogen annd is surroundeed by the Tarim m and Tajik basins and a the Tianshhan, Hindu Kuush and Karakoram Mountain beltts (Fig. 1a). Thhe salient is com mposed of the KunK lun, Karakul-M Mazar, Central Pamir P and Soutthern Pamir terrranes (Fig. 1b), which were progrressively accreted to the soutthern margin of the Asian Plate duuring the Late Paleozoic to MesoM zoic (Robinsoon, 2015; Anggiolini et al., 2013; 2 Burtmann and Molnar, 1993)). Due to the coonvergence betw ween the Indiann and Asian plates, the south-dippping intraconttinental subduuction along the Maiin Pamir thrust started at 25–220 Ma (Sobel et e al., 2013; Bershaw w et al., 2012; Sobel and Dumitru, D 1997). The Late Cenozoicc tectonic activvity in the Pamiir interior is chharacterized by crustal extension and a doming (Ruutte et al., 20177a, b; Stearns et al., 2015; Sobel et al., 2013; Thiedde et al., 2013). The Kongur Shan extensional sysstem, consistingg of the Muji, KonK gur Shan, Taahman and Tashkurgan T fauults, is the laargest east-west exteensional system m in the Pamir. It I has resulted in the exhumation off the Kongur Shhan-Muztag Atta gneiss domess and the Tashkurgaan complex (F
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