Advanced Search

Indexed by SCI、CA、РЖ、PA、CSA、ZR、etc .

Volume 41 Issue 4
Aug.  2020
Turn off MathJax
Article Contents

Shenqiang Chen, Hanlin Chen. Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir. Journal of Earth Science, 2020, 31(4): 723-734. doi: 10.1007/s12583-020-1282-1
Citation: Shenqiang Chen, Hanlin Chen. Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir. Journal of Earth Science, 2020, 31(4): 723-734. doi: 10.1007/s12583-020-1282-1

Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir

doi: 10.1007/s12583-020-1282-1
More Information
  • In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon (U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10-5 Ma, and most likely at 6-5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6-0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.
  • 加载中
  • Angiolini, L., Zanchi, A., Zanchetta, S., et al., 2013. The Cimmerian Geopuzzle:New Data from South Pamir. Terra Nova, 25(5):352-360. https://doi.org/10.1111/ter.12042 doi:  10.1111/ter.12042
    Arnaud, N. O., Brunel, M., Cantagrel, J. M., et al., 1993. High Cooling and Denudation Rates at Kongur Shan, Eastern Pamir (Xinjiang, China) Revealed by 40Ar/39Ar Alkali Feldspar Thermochronology. Tectonics, 12(6):1335-1346. https://doi.org/10.1029/93tc00767 doi:  10.1029/93tc00767
    Bershaw, J., Garzione, C. N., Schoenbohm, L., et al., 2012. Cenozoic Evolution of the Pamir Plateau Based on Stratigraphy, Zircon Provenance, and Stable Isotopes of Foreland Basin Sediments at Oytag (Wuyitake) in the Tarim Basin (west China). Journal of Asian Earth Sciences, 44:136-148. https://doi.org/10.1016/j.jseaes.2011.04.020 doi:  10.1016/j.jseaes.2011.04.020
    Brunel, M., Arnaud, N., Tapponnier, P., et al., 1994. Kongur Shan Normal Fault:Type Example of Mountain Building Assisted by Extension (Karakoram Fault, Eastern Pamir). Geology, 22(8):707-710. https://doi.org/10.1130/0091-7613(1994)022<0707:ksnfte>2.3.co; 2 doi:  10.1130/0091-7613(1994)022<0707:ksnfte>2.3.co;2
    Burtman, V. S., Molnar, P. H., 1993. Geological and Geophysical Evidence for Deep Subduction of Continental Crust beneath the Pamir. Geological Society of America Bulletin, 281:1-76. https://doi.org/10.1130/spe281-p1 doi:  10.1130/spe281-p1
    Cai, Z. H., Xu, Z. Q., Cao, H., et al., 2017. Miocene Exhumation of Northeast Pamir:Deformation and Geo/thermochronological Evidence from Western Muztaghata Shear zone and Kuke Ductile Shear Zone. Journal of Structural Geology, 102:130-146. https://doi.org/10.1016/j.jsg.2017.07.010 doi:  10.1016/j.jsg.2017.07.010
    Cao, K., Wang, G. C., van der Beek, P., et al., 2013a. Cenozoic Thermo-Tectonic Evolution of the Northeastern Pamir Revealed by Zircon and Apatite Fission-Track Thermochronology. Tectonophysics, 589:17-32. https://doi.org/10.1016/j.tecto.2012.12.038 doi:  10.1016/j.tecto.2012.12.038
    Cao, K., Bernet, M., Wang, G. C., et al., 2013b. Focused Pliocene-Quaternary Exhumation of the Eastern Pamir Domes, Western China. Earth and Planetary Science Letters, 363:16-26. https://doi.org/10.1016/j.epsl.2012.12.023 doi:  10.1016/j.epsl.2012.12.023
    Chapman, J. B., Scoggin, S. H., Kapp, P., et al., 2018. Mesozoic to Cenozoic Magmatic History of the Pamir. Earth and Planetary Science Letters, 482:181-192. https://doi.org/10.1016/j.epsl.2017.10.041 doi:  10.1016/j.epsl.2017.10.041
    Chen, X. W., Chen, H. L., Lin, X. B., et al., 2018. Arcuate Pamir in the Paleogene? Insights from a Review of Stratigraphy and Sedimentology of the Basin Fills in the Foreland of NE Chinese Pamir, Western Tarim Basin. Earth-Science Reviews, 180:1-16. https://doi.org/10.1016/j.earscirev.2018.03.003 doi:  10.1016/j.earscirev.2018.03.003
    Cheng, X. G., Chen, H. L., Lin, X. B., et al., 2016. Deformation Geometry and Timing of TheWupoer Thrust Belt in the NE Pamir and Its Tectonic Implications. Frontiers of Earth Science, 10(4):751-760. https://doi.org/10.1007/s11707-016-0606-z doi:  10.1007/s11707-016-0606-z
    Cowgill, E., 2010. Cenozoic Right-Slip Faulting along the Eastern Margin of the Pamir Salient, Northwestern China. Geological Society of America Bulletin, 122(1/2):145-161. https://doi.org/10.1130/b26520.1 doi:  10.1130/b26520.1
    Farley, K. A., 2000. Helium Diffusion from Apatite:General Behavior as Illustrated by Durango Fluorapatite. Journal of Geophysical Research:Solid Earth, 105(B2):2903-2914. https://doi.org/10.1029/1999jb900348 doi:  10.1029/1999jb900348
    Flowers, R. M., Ketcham, R. A., Shuster, D. L., et al., 2009. Apatite (U-Th)/He Thermochronometry Using a Radiation Damage Accumulation and Annealing Model. Geochimica et Cosmochimica Acta, 73(8):2347-2365. https://doi.org/10.1016/j.gca.2009.01.015 doi:  10.1016/j.gca.2009.01.015
    Galbraith, R. F., 1981. On Statistical Models for Fission Track Counts:Reply. Journal of the International Association for Mathematical Geology, 13(6):485-488. https://doi.org/10.1007/bf01034500 doi:  10.1007/bf01034500
    Guenthner, W. R., Reiners, P. W., Ketcham, R. A., et al., 2013. Helium Diffusion in Natural Zircon:Radiation Damage, Anisotropy, and the Interpretation of Zircon (U-Th)/He Thermochronology. American Journal of Science, 313(3):145-198. https://doi.org/10.2475/03.2013.01 doi:  10.2475/03.2013.01
    Hacker, B. R., Ratschbacher, L., Rutte, D., et al., 2017. Building the Pamir-Tibet Plateau-Crustal Stacking, Extensional Collapse, and Lateral Extrusion in the Pamir:3. Thermobarometry and Petrochronology of Deep Asian Crust. Tectonics, 36(9):1743-1766. https://doi.org/10.1002/2017tc004488 doi:  10.1002/2017tc004488
    Hurford, A. J., Green, P. F., 1983. The Zeta Age Calibration of Fission-Track Dating. Chemical Geology, 41:285-317. https://doi.org/10.1016/s0009-2541(83)80026-6 doi:  10.1016/s0009-2541(83)80026-6
    Imrecke, D. B., ,., Robinson, A. C., et al., 2019. Mesozoic Evolution of the Eastern Pamir. Lithosphere, 11(4):560-580. https://doi.org/10.1130/l1017.1 doi:  10.1130/l1017.1
    Jiang, Y. H., Liu, Z., Jia, R. Y., et al., 2012. Miocene Potassic Granite-Syenite Association in Western Tibetan Plateau:Implications for Shoshonitic and High Ba-Sr Granite Genesis. Lithos, 134/135:146-162. https://doi.org/10.1016/j.lithos.2011.12.012 doi:  10.1016/j.lithos.2011.12.012
    Jiang, Y. H., Liu, Z., Jia, R. Y., et al., 2013. Origin of Early Cretaceous High-K Calc-Alkaline Granitoids, Western Tibet:Implications for the Evolution of the Tethys in NW China. International Geology Review, 56(1):88-103. https://doi.org/10.1080/01431161.2013.819963 doi:  10.1080/01431161.2013.819963
    Ke, S., Luo, Z., Mo, X., et al., 2008. The Geochronology of Taxkorgan Alkalic Complex, Pamir Syntax. Acta Petrologica Sinica, 24(2):315-324 (in Chinese with English Abstract) http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=ysxb98200802011
    Ketcham, R. A., Donelick, R. A., Carlson, W. D., 1999. Variability of Apatite Fission-Track Annealing Kinetics; Ⅲ, Extrapolation to Geological Time Scales. American Mineralogist, 84(9):1235-1255. https://doi.org/10.2138/am-1999-0903 doi:  10.2138/am-1999-0903
    Ketcham, R. A., Gautheron, C., Tassan-Got, L., 2011. Accounting for Long Alpha-Particle Stopping Distances in (U-Th-Sm)/He Geochronology:Refinement of the Baseline Case. Geochimica et Cosmochimica Acta, 75(24):7779-7791. https://doi.org/10.1016/j.gca.2011.10.011 doi:  10.1016/j.gca.2011.10.011
    Lee, J. K. W., Williams, I. S., Ellis, D. J., 1997. Pb, U and Th Diffusion in Natural Zircon. Nature, 390(6656):159-162. https://doi.org/10.1038/36554 doi:  10.1038/36554
    Liu, X., Fan, H. R., Evans, N. J., et al., 2014. Cooling and Exhumation of the Mid-Jurassic Porphyry Copper Systems in Dexing City, SE China:Insights from Geo-and Thermochronology. Mineralium Deposita, 49(7):809-819. https://doi.org/10.1007/s00126-014-0536-1 doi:  10.1007/s00126-014-0536-1
    Mechie, J., Yuan, X., Schurr, B., et al., 2012. Crustal and Uppermost Mantle Velocity Structure along a Profile Across the Pamir and Southern Tien Shan as Derived from Project TIPAGE Wide-Angle Seismic Data. Geophysical Journal International, 188(2):385-407. https://doi.org/10.1111/j.1365-246x.2011.05278.x doi:  10.1111/j.1365-246x.2011.05278.x
    Murphy, M. A., An, Y., Kapp, P., et al., 2000. Southward Propagation of the Karakoram Fault System, Southwest Tibet:Timing and Magnitude of Slip. Geology, 28(5):451. https://doi.org/10.1130/0091-7613(2000)28<451:spotkf>2.0.co; 2 doi:  10.1130/0091-7613(2000)28<451:spotkf>2.0.co;2
    Owen, L. A., Chen, J., Hedrick, K. A., et al., 2012. Quaternary Glaciation of the Tashkurgan Valley, Southeast Pamir. Quaternary Science Reviews, 47:56-72. https://doi.org/10.1016/j.quascirev.2012.04.027 doi:  10.1016/j.quascirev.2012.04.027
    Reiners, P. W., Spell, T. L., Nicolescu, S., et al., 2004. Zircon (U-Th)/He Thermochronometry:He Diffusion and Comparisons with 40Ar/39Ar Dating. Geochimica et Cosmochimica Acta, 68(8):1857-1887. https://doi.org/10.1016/j.gca.2003.10.021 doi:  10.1016/j.gca.2003.10.021
    Reiners, P. W., Brandon, M. T., 2006. Using Thermochronology to Understand Orogenic Erosion. Annual Review of Earth and Planetary Sciences, 34(1):419-466. https://doi.org/10.1146/annurev.earth. 34.031405.125202 doi:  10.1146/annurev.earth.34.031405.125202
    RGSRTK (Regional Geological Survey Report of the People's Republic of China, 2004. 1: 250 000 Tashkurgan County J43C003003. China Geological Survey (in Chinese)
    Robinson, A. C., Yin, A., Manning, C. E., et al., 2004. Tectonic Evolution of the Northeastern Pamir:Constraints from the Northern Portion of the Cenozoic Kongur Shan Extensional System, Western China. Geological Society of America Bulletin, 116(7/8):953-973. https://doi.org/10.1130/b25375.1 doi:  10.1130/b25375.1
    Robinson, A. C., Yin, A., Manning, C. E., et al., 2007. Cenozoic Evolution of the Eastern Pamir:Implications for Strain-Accommodation Mechanisms at the Western End of the Himalayan-Tibetan Orogen. Geological Society of America Bulletin, 119(7/8):882-896. https://doi.org/10.1130/b25981.1 doi:  10.1130/b25981.1
    Robinson, A. C., Yin, A., Lovera, O. M., 2010. The Role of Footwall Deformation and Denudation in Controlling Cooling Age Patterns of Detachment Systems:An Application to the Kongur Shan Extensional System in the Eastern Pamir, China. Tectonophysics, 496(1/2/3/4):28-43. https://doi.org/10.1016/j.tecto.2010.10.003 doi:  10.1016/j.tecto.2010.10.003
    Robinson, A. C., 2015. Mesozoic Tectonics of the Gondwanan Terranes of the Pamir Plateau. Journal of Asian Earth Sciences, 102:170-179. https://doi.org/10.1016/j.jseaes.2014.09.012 doi:  10.1016/j.jseaes.2014.09.012
    Rutte, D., Ratschbacher, L., Schneider, S., et al., 2017a. Building the Pamir-Tibetan Plateau-Crustal Stacking, Extensional Collapse, and Lateral Extrusion in the Central Pamir:1. Geometry and Kinematics. Tectonics, 36(3):342-384. https://doi.org/10.1002/2016tc004293 doi:  10.1002/2016tc004293
    Rutte, D., Ratschbacher, L., Khan, J., et al., 2017b. Building the Pamir-Tibetan Plateau-Crustal Stacking, Extensional Collapse, and Lateral Extrusion in the Central Pamir:2. Timing and Rates. Tectonics, 36(3):385-419. https://doi.org/10.1002/2016tc004294 doi:  10.1002/2016tc004294
    Schmalholz, M., 2004. The Amalgamation of the Pamirs and Their Subsequent Evolution in the Far Field of the India-Asia Collision: [Dissertation]. Universitat Tubingen, Tubingen. 1-103
    Schmidt, J., Hacker, B. R., Ratschbacher, L., et al., 2011. Cenozoic Deep Crust in the Pamir. Earth and Planetary Science Letters, 312(3/4):411-421. https://doi.org/10.1016/j.epsl.2011.10.034 doi:  10.1016/j.epsl.2011.10.034
    Schneider, F. M., Yuan, X., Schurr, B., et al., 2013. Seismic Imaging of Subducting Continental Lower Crust beneath the Pamir. Earth and Planetary Science Letters, 375:101-112. https://doi.org/10.1016/j.epsl.2013.05.015 doi:  10.1016/j.epsl.2013.05.015
    Schneider, F. M., Yuan, X., Schurr, B., et al., 2019. The Crust in the Pamir:Insights from Receiver Functions. Journal of Geophysical Research:Solid Earth, 124(8):9313-9331. https://doi.org/10.1029/2019jb017765 doi:  10.1029/2019jb017765
    Schwab, M., Ratschbacher, L., Siebel, W., et al., 2004. Assembly of the Pamirs:Age and Origin of Magmatic Belts from the Southern Tien Shan to the Southern Pamirs and Their Relation to Tibet. Tectonics, 23(4):TC4002. https://doi.org/10.1029/2003tc001583 doi:  10.1029/2003tc001583
    Shaffer, M., Hacker, B. R., Ratschbacher, L., et al., 2017. Foundering Triggered by the Collision of India and Asia Captured in Xenoliths. Tectonics, 36(10):1913-1933. https://doi.org/10.1002/2017tc004704 doi:  10.1002/2017tc004704
    Shuster, D. L., Flowers, R. M., Farley, K. A., 2006. The Influence of Natural Radiation Damage on Helium Diffusion Kinetics in Apatite. Earth and Planetary Science Letters, 249(3/4):148-161. https://doi.org/10.1016/j.epsl.2006.07.028 doi:  10.1016/j.epsl.2006.07.028
    Smit, M. A., Ratschbacher, L., Kooijman, E., et al., 2014. Early Evolution of the Pamir Deep Crust from Lu-Hf and U-Pb Geochronology and Garnet Thermometry. Geology, 42(12):1047-1050. https://doi.org/10.1130/g35878.1 doi:  10.1130/g35878.1
    Sobel, E. R., Dumitru, T. A., 1997. Thrusting and Exhumation around the Margins of the Western Tarim Basin during the India-Asia Collision. Journal of Geophysical Research:Solid Earth, 102(B3):5043-5063. https://doi.org/10.1029/96jb03267 doi:  10.1029/96jb03267
    Sobel, E. R., Schoenbohm, L. M., Chen, J., et al., 2011. Late Miocene-Pliocene Deceleration of Dextral Slip between Pamir and Tarim:Implications for Pamir Orogenesis. Earth and Planetary Science Letters, 304(3/4):369-378. https://doi.org/10.1016/j.epsl.2011.02.012 doi:  10.1016/j.epsl.2011.02.012
    Sobel, E. R., Chen, J., Schoenbohm, L. M., et al., 2013. Oceanic-Style Subduction Controls Late Cenozoic Deformation of the Northern Pamir Orogen. Earth and Planetary Science Letters, 363:204-218. https://doi.org/10.1016/j.epsl.2012.12.009 doi:  10.1016/j.epsl.2012.12.009
    Stearns, M. A., Hacker, B. R., Ratschbacher, L., et al., 2013. Synchronous Oligocene-Miocene Metamorphism of the Pamir and the North Himalaya Driven by Plate-Scale Dynamics. Geology, 41(10):1071-1074. https://doi.org/10.1130/g34451.1 doi:  10.1130/g34451.1
    Stearns, M. A., Hacker, B. R., Ratschbacher, L., et al., 2015. Titanite Petrochronology of the Pamir Gneiss Domes:Implications for Middle to Deep Crust Exhumation and Titanite Closure to Pb and Zr Diffusion. Tectonics, 34(4):784-802. https://doi.org/10.1002/2014tc003774 doi:  10.1002/2014tc003774
    Strecker, M. R., Frisch, W., Hamburger, M. W., et al., 1995. Quaternary Deformation in the Eastern Pamirs, Tadzhikistan and Kyrgyzstan. Tectonics, 14(5):1061-1079. https://doi.org/10.1029/95tc00927 doi:  10.1029/95tc00927
    Stübner, K., Ratschbacher, L., Rutte, D., et al., 2013a. The Giant Shakhdara Migmatitic Gneiss Dome, Pamir, India-Asia Collision Zone:1. Geometry and Kinematics. Tectonics, 32(4):948-979. https://doi.org/10.1002/tect.20057 doi:  10.1002/tect.20057
    Stübner, K., Ratschbacher, L., Weise, C., et al., 2013b. The Giant Shakhdara Migmatitic Gneiss Dome, Pamir, India-Asia Collision Zone:2. Timing of Dome Formation. Tectonics, 32(5):1404-1431. https://doi.org/10.1002/tect.20059 doi:  10.1002/tect.20059
    Thiede, R. C., Sobel, E. R., Chen, J., et al., 2013. Late Cenozoic Extension and Crustal Doming in the India-Eurasia Collision Zone:New Thermochronologic Constraints from the NE Chinese Pamir. Tectonics, 32(3):763-779. https://doi.org/10.1002/tect.20050 doi:  10.1002/tect.20050
    Weather China, 2016. Climatic Data for Tashkurgan County (1971-2000). (2020-1-20). http://www.weather.com.cn/cityintro/101130903.shtml
    Willett, S. D., Brandon, M. T., 2013. Some Analytical Methods for Converting Thermochronometric Age to Erosion Rate. Geochemistry, Geophysics, Geosystems, 14(1):209-222. https://doi.org/10.1029/2012gc004279 doi:  10.1029/2012gc004279
    Worthington, J. R., Ratschbacher, L., Stübner, K., et al., 2019. The Alichur Dome, South Pamir, Western India-Asia Collisional Zone:Detailing the Neogene Shakhdara-Alichur Syn-Collisional Gneiss-Dome Complex and Connection to Lithospheric Processes. Tectonics, 39(1):e2019TC005735. https://doi.org/10.1029/2019tc005735 doi:  10.1029/2019tc005735
    Yin, A., Robinson, A., Manning, C. E., 2001. Oroclinal Bending and Slab-Break-off Causing Coeval East-West Extension and East-West Contraction in the Pamir-Nanga Parbat Syntaxis in the Past 10 m.y.. American Geophysical Union, 82(47):F1124 https://ui.adsabs.harvard.edu/abs/2001AGUFM.T12F..03Y/abstract
    Yuan, W. M., Carter, A., Dong, J. Q., et al., 2006. Mesozoic-Tertiary Exhumation History of the Altai Mountains, Northern Xinjiang, China:New Constraints from Apatite Fission Track Data. Tectonophysics, 412(3/4):183-193. https://doi.org/10.1016/j.tecto.2005.09.007 doi:  10.1016/j.tecto.2005.09.007
  • 加载中
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Figures(8)  / Tables(1)

Article Metrics

Article views(19) PDF downloads(1) Cited by()

Related
Proportional views

Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir

doi: 10.1007/s12583-020-1282-1

Abstract: In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon (U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10-5 Ma, and most likely at 6-5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6-0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.

Shenqiang Chen, Hanlin Chen. Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir. Journal of Earth Science, 2020, 31(4): 723-734. doi: 10.1007/s12583-020-1282-1
Citation: Shenqiang Chen, Hanlin Chen. Late Cenozoic Activity of the Tashkurgan Normal Fault and Implications for the Origin of the Kongur Shan Extensional System, Eastern Pamir. Journal of Earth Science, 2020, 31(4): 723-734. doi: 10.1007/s12583-020-1282-1
  • In order to reveal the activity history of the Tashkurgan normal fault, we mapped the main lithological units and structures and collected samples for fission track and (U-Th)/He analyses along the Xingungou and Qumangou sections (Figs. 3 and 4).

    Figure 4.  Google Earth images of (a) the sampling area and (b) the mouth of the Xingungou Valley showing distribution of active faults, normal fault-related springs and low-temperature thermochronological samples. Photos showing outcrops of (c) the hanging-wall of the Tashkurgan fault at the Xingungou Section, (d) the footwall of Tashkurgan fault at the Xingungou Section and (e) the footwall of the Tashkurgan fault at the Qumangou Section.

  • The Tashkurgan fault is not well exposed at the Xingungou Section, but it can be inferred from the satellite images from Google Earth and previous field observations to the north and south of the section (e.g., Imrecke et al., 2019; Robinson et al., 2007) (Fig. 4b). Because of the relatively low elevation, the hanging-wall of the Tashkurgan fault at the Xingungou Section is almost entirely covered by Quaternary fluvial and glacial deposits (Figs. 3 and 4b). Only an area of ~0.12 km2 of granite, which is a portion of the Tashkurgan Complex (Imrecke et al., 2019; Jiang et al., 2012), is exposed at the hanging-wall (Figs. 4b and 4c). The footwall of the Tashkurgan fault at this section has the characteristic of emergence of the Tashkurgan Complex (Fig. 4d). We collected one hanging-wall (TX-1) and six footwall (TX-3, TX-6, 1.10.10.10G, 2.10.10.10G, 4.10.10.10G and 7.10.10.10G) samples from the Xingungou Section (Figs. 3 and 4a).

  • Due to the impact of glaciers during the Quaternary Period (Owen et al., 2012), the Qumangou Section, approximately 10 km north from the Xingungou Section (Figs. 3 and 4a), is almost covered by moraines (Fig. 4e). According to the locations of the fault-related springs to the north of the Qumangou Section, the exposure of the Tashkurgan fault to the south of the section and previous observations (e.g., Imrecke et al., 2019; Robinson et al., 2007), we inferred the location of the Tashkurgan fault at the section (Figs. 3 and 4a). Three bedrock samples (9.10.10.10G, 10.10.10.10G and 11.10.10.10G) were collected from the footwall of the Tashkurgan fault at the Qumangou Section (Figs. 3 and 4a), where the Tashkurgan Complex is observed in the gaps of the moraines (Fig. 4e).

  • One hanging-wall sample and nine footwall samples in total were collected from surface exposures of the Tashkurgan Complex (Figs. 3 and 4a; Table 1). Apatite and zircon crystals for fission track and (U-Th)/He analyses were extracted from crushed samples using conventional methods of heavy liquid and magnetic separation.

    Sample Latitude (°N) Longitude (°E) Elevation (m) Location Lithology and zircon U-Pb agea Methodb Age±1σ (Ma)c Exhumation rate ±1σ (mm/a) (modern geothermal gradient is 40 ℃/km)d Exhumation rate ±1σ (mm/a) (modern geothermal gradient is 50 ℃/km)d Comment
    Xingungou Section
    TX-1 37.771 45 75.175 65 3 241 Hanging-wall Granite, ~12–10 Ma AHe 11.4±0.3 Average of 5 aliquots
    AFT 11.9±1.1 Pooled age
    ZHe 10.5±0.5 Average of 4 aliquots
    TX-3 37.766 68 75.166 67 3 305 Footwall Granite, ~12–10 Ma AFT 3.7±0.4 0.69±0.09 0.46±0.06 Central age
    TX-6 37.727 15 75.133 65 3 539 Footwall Granite, ~12–10 Ma AFT 2.0±0.3 1.59±0.30 1.09±0.20 Central age
    1.10.10.10G 37.763 07 75.160 89 3 322 Footwall Granite, ~12–10 Ma AFT 3.3±0.3 0.79±0.08 0.53±0.05 Central age
    2.10.10.10G 37.754 17 75.158 22 3 426 Footwall Diorite, ~12–10 Ma AFT 4.6±0.3 0.57±0.04 0.39±0.03 Pooled age
    4.10.10.10G 37.734 27 75.144 41 3 465 Footwall Granite, ~12–10 Ma AHe 1.0±0.1 1.24±0.09 0.76±0.06 Average of 4 aliquots
    AFT 3.0±0.2 0.95±0.07 0.65±0.05 Pooled age
    ZHe 4.6±1.0 1.43±0.54 0.93±0.30 Average of 4 aliquots
    7.10.10.10G 37.711 44 75.115 08 3 569 Footwall Diorite, ~12–10 Ma AHe 2.6±0.5 0.42±0.11 0.26±0.07 Average of 3 aliquots
    AFT 4.5±0.5 0.63±0.08 0.44±0.06 Pooled age
    ZHe 0.9±0.2 Average of 3 aliquots
    Qumangou Section
    9.10.10.10G 37.849 03 75.129 92 3 619 Footwall Granodiorite, ~12–10 Ma AFT 10.3±0.8 Pooled age
    ZHe 7.4±0.6 Average of 3 aliquots
    10.10.10.10G 37.846 91 75.123 18 3 623 Footwall Granodiorite, ~12–10 Ma AHe 10.3±0.2 Average of 5 aliquots
    AFT 8.7±0.8 Pooled age
    ZHe 7.7±0.5 Average of 2 aliquots
    11.10.10.10G 37.845 14 75.118 37 3 631 Footwall Granodiorite, ~12–10 Ma AHe 9.9±1.1 Average of 5 aliquots
    AFT 10.9±0.9 Pooled age
    Analytical details of the measurements are shown in electronic supplementary materials in Tables S1–S3. a. Zircon U-Pb ages are sourced from Robinson et al. (2007), Ke et al. (2008) and Jiang et al. (2012); b. AFT is apatite fission track; AHe is apatite (U-Th)/He; ZHe is zircon (U-Th)/He; c. available ages are shown in bold type; d. time-averaged exhumation rates are calculated by the method of Willett and Brandon (2013).

    Table 1.  Results of apatite fission track, apatite (U-Th)/He and zircon (U-Th)/He analyses

  • Apatite fission track (AFT) analysis was performed following procedures modified from Yuan et al. (2006) at the Institute of High Energy Physics, Chinese Academy of Sciences. The selected apatite grains were first mounted in epoxy resin on glass slides and then polished to expose internal grain surfaces. Spontaneous tracks in apatite were etched with 5.5 M HNO3 for 20 s at 21 ℃. The sample mounts to which muscovite external detectors were attached were irradiated in a well-thermalized neutron flux in the 492 Swim Reactor. Afterwards, the mica detectors were detached from the sample mounts and etched in 40% HF for 40 min at 25 ℃ to reveal the induced tracks. Track densities in both spontaneous and induced track populations were measured with a dry objective at a total magnification of ×1 250.

    Fission track ages were calculated using the zeta calibration method (Hurford and Green, 1983). Samples from TX-1 to TX-6 had a zeta value of 389±19 (1σ), and samples from 1.10.10.10G to 11.10.10.10G had a zeta value of 353±18 (1σ). The pooled (central) ages are reported for the samples with P(χ2) greater (less) than 5% (Galbraith, 1981).

  • Five apatite and five zircon samples were analyzed for (U-Th)/He at the John de Laeter Centre for Isotope Research, Curtin University. The analytical procedures are described in detail in Liu et al. (2014). The apatite and zircon (U-Th)/He (AHe and ZHe) ages from all tested grains were corrected using α-ejection correction (Ketcham et al., 2011).

    Previous studies demonstrate that helium retentivity in apatite and zircon grains is associated with accumulation of radiation damage, which can be reflected by effective uranium concentration (eU=U+0.235×Th) (Guenthner et al., 2013; Flowers et al., 2009; Shuster et al., 2006). The second apatite grain from sample 4.10.10.10G has an extremely high eU concentration of 1 233 ppm and yields an anomalously young AHe age of 0.2 Ma (Fig. 5a; Table S2), implying that this young age could be caused by radiation damage. Apatites from the other samples contain low eU contents (< 51 ppm) (Fig. 5a), indicating an insignificant influence of radiation damage on their AHe ages. Moreover, five out of twenty-two zircons yield abnormally old ages (14.9–132.1 Ma) (Fig. 5b; Table S3), which exceed the intrusion age of the Tashkurgan Complex (12–10 Ma) (Jiang et al., 2012; Ke et al., 2008; Robinson et al., 2007). The first zircon grain from sample 9.10.10.10G gives a high Th/U ratio of 3.7 and a significantly young age of 2.7 Ma. The eU contents in the other zircons vary from 351 ppm to 3 617 ppm and have no significant relationships with the ZHe ages (Fig. 5b). The mean AHe and ZHe ages from the samples were calculated after removing the outlier single-grain ages.

    Figure 5.  Effective uranium concentration (eU) versus corrected (a) apatite (U-Th)/He (AHe) and (b) zircon (U-Th)/He (ZHe) ages.

  • The AFT, AHe and ZHe results are respectively presented in Tables S1, S2 and S3 and depicted in Fig. 6a.

    Figure 6.  Xingungou swath elevation profile with (a) low-temperature thermochronological ages and (b) exhumation rates (for location, see Fig. 3).

    One hanging-wall sample (TX-1) from the Xingungou Section (Figs. 3 and 4b) gives an AFT age of 11.9±1.1 Ma, a mean AHe age of 11.4±0.3 Ma and a mean ZHe age of 10.5±0.5 Ma. Six footwall samples (TX-3, TX-6, 1.10.10.10G, 2.10.10.10G, 4.10.10.10G and 7.10.10.10G) from the same section yield six AFT ages of 3.3±0.3, 4.6±0.3, 3.0±0.2, 4.5±0.5, 3.7±0.4 and 2.0±0.3 Ma, two mean AHe ages of 1.0±0.1 and 2.6±0.5 Ma, and two mean ZHe ages of 0.9±0.2 and 4.6±1.0 Ma.

    Three footwall samples (9.10.10.10G, 10.10.10.10G and 11.10.10.10G) from the Qumangou Section (Figs. 3 and 4a) yield three AFT ages of 10.3±0.8, 8.7±0.8 and 10.9±0.9 Ma, two mean AHe ages of 10.3±0.2 and 9.9±1.1 Ma, and two mean ZHe ages of 7.4±0.6 and 7.7±0.5 Ma.

    The mean ZHe age from sample 7.10.10.10G is much younger than the AFT age and the mean AHe age from the same sample. The AFT age from sample 10.10.10.10G and the mean ZHe ages from samples 9.10.10.10G and 10.10.10.10G are much younger than the other low-temperature thermochronological ages from the Qumangou Section. Therefore, we discard the AFT age from sample 10.10.10.10G and the mean ZHe ages from samples 7.10.10.10G, 9.10.10.10G and 10.10.10.10G.

  • At the Xingungou Section, the AFT age, the mean AHe age and the mean ZHe age from hanging-wall sample TX-1 range from 11.9 to 10.5 Ma (Fig. 6a; Table 1). These low-temperature thermochronological ages are consistent with the emplacement age (12–10 Ma) of the hypabyssal Tashkurgan Complex (Jiang et al., 2012; Ke et al., 2008; Robinson et al., 2007). In this context, we believe that the hanging-wall sample experienced fast cooling (> 400 ℃/Ma) following magmatism (Fig. 7b). Six AFT ages, two mean AHe ages and one mean ZHe age from the six footwall samples (TX-3, TX-6, 1.10.10.10G, 2.10.10.10G, 4.10.10.10G and 7.10.10.10G) vary from 4.6 to 1.0 Ma (Fig. 6a; Table 1). The relatively slow cooling history (~40 ℃/Ma) recorded by these ages is attributed to the exhumation of the footwall of the Tashkurgan fault (Fig. 7d). The gap between the hanging-wall ages (11.9–10.5 Ma) and the footwall ages (4.6–1.0 Ma) indicates that the Tashkurgan fault initiated at 10–5 Ma.

    Figure 7.  Temperature-time evolution of plutonic rocks from (a) the northeastern Tashkurgan Complex; (b) the hanging-wall of the Tashkurgan fault at the Xingungou Section; (c) the footwall of the Tashkurgan fault at the Qumangou Section; and (d) the footwall of the Tashkurgan fault at the Xingungou Section (for location, see Fig. 2). TKF. Tashkurgan fault. Thermochronological data are sourced from Robinson et al. (2007), Ke et al. (2008), Jiang et al. (2012), Cao et al. (2013a), Sobel et al. (2013) and this study. Approximate closure temperatures are > 900 ℃ for zircon U-Pb (ZUPb) (Lee et al., 1997), 360±20 ℃ for biotite 40Ar/39Ar (Ar bt), 280±50 ℃ for zircon fission track (ZFT), 190±10 ℃ for Zircon (U-Th)/He (ZHe), 130±20 ℃ for apatite fission track (AFT), 65±5 ℃ for apatite (U-Th)/He (AHe) (Reiners and Brandon, 2006).

    At the Qumangou Section, three footwall samples (9.10.10.10G, 10.10.10.10G and 11.10.10.10G) give two valid AFT ages of 10.9 and 10.3 Ma, and two valid mean AHe ages of 10.3 and 9.9 Ma (Fig. 6a; Table 1). These four ages are almost consistent with the low-temperature thermochronological ages (11.9–10.5 Ma) from the hanging-wall sample (TX-1) and the emplacement age (12–10 Ma) of the Tashkurgan Complex (Jiang et al., 2012; Ke et al., 2008; Robinson et al., 2007). It indicates that the footwall samples from the Qumangou Section also experienced fast cooling (> 400 ℃/Ma) following magmatism (Fig. 7c). Furthermore, the footwall samples from the Qumangou and Xingungou sections were respectively collected from the regions with elevations of 3 619–3 631 and 3 305– 3 569 m (Fig. 8; Table 1). There is a significant difference of the low-temperature thermochronological ages between the two groups of footwall samples collected above and below the elevation of 3 600 m (Fig. 8). Therefore, we suggest that the Tashkurgan fault is most likely to initiate at 6–5 Ma, though the two groups of footwall samples are from different sections.

    Figure 8.  Apatite fission track (AFT) and zircon and apatite (U-Th)/He (ZHe and AHe) ages versus elevation. Group Ⅰ: hanging-wall ages from the Xingungou Section; Group Ⅱ: footwall ages from the Qumangou Section; Group Ⅲ: footwall ages from the Xingungou Section.

    The one-dimensional method by Willett and Brandon (2013) was used to obtain the exhumation rates of the footwall of the Tashkurgan fault from the cooling ages. The constant geothermal gradients in the footwall of the southern segment of the Kongur Shan fault and the footwall of the Tashkurgan fault are respectively set to 40 and 30 ℃/km by Robinson et al. (2007), while Thiede et al. (2013) gives an initial geothermal gradient of 50 ℃/km for the footwall of the Kongur Shan fault. In this study, we chose bounds to the modern geothermal gradient of 40 and 50 ℃/km. Between 1971 and 2000, the annual mean temperature of Tashkurgan County, located at the hanging-wall of the Tashkurgan fault (Fig. 3), is 3.6 ℃ (Weather China, 2016). Thus, we assumed that the mean surface temperature in the footwall of the Tashkurgan fault is 3.6 ℃. The onset of exhumation of the footwall is set at 5.5 Ma because the Tashkurgan fault probably initiated at 6–5 Ma. Furthermore, the mean elevation of the footwall is ~4.2 km (Fig. 6). The kinetic parameters for AFT, AHe and ZHe dating are from Ketcham et al. (1999), Farley (2000) and Reiners et al. (2004), respectively.

    The time-averaged exhumation rates of the footwall samples from the Xingungou Section are given in Table 1 and illustrated in Fig. 6b. Exhumation rates derived from the six AFT ages (4.6–2.0 Ma) at the modern geothermal gradient of 40 ℃/km range from 0.6 to 1.6 mm/a with an average of 0.9±0.3 mm/a, while at the modern geothermal gradient of 50 ℃/km they range from 0.4 to 1.1 mm/a with an average of ~0.6±0.1 mm/a. Two mean AHe ages (2.6 and 1.0 Ma) yield four exhumation rates of 0.4±0.1, 0.3±0.1, 1.2±0.1 and 0.8±0.1 mm/a. One reliable mean ZHe age (4.6 Ma) yields two exhumation rates of 1.4±0.5 and 0.9±0.3 mm/a. The exhumation rates from the AHe and ZHe ages are consistent with those from the AFT ages within the margin of error. The above modeling results show that the footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. The average exhumation rate of the footwall of the Tashkurgan fault is consistent with that of the core of the northern portion of the Muztag Ata dome (~1±0.5 mm/a) (Thiede et al., 2013), but lower than that of the Kongur Shan dome (~4.2 or > 2–3 mm/a) (Thiede et al., 2013; Robinson et al., 2010).

  • Previously published thermochronological ages from the northeastern Tashkurgan Complex indicate that this area experienced fast cooling (> 400 ℃/Ma) from ~12 to 10 Ma (Figs. 2 and 7a) (Cao et al., 2013a; Sobel et al., 2013; Robinson et al., 2007). This fast cooling history is also recorded by the sample (TX-1) from the hanging-wall of the Tashkurgan fault at the Xingungou Section (Fig. 7b) and the samples (9.10.10.10G, 10.10.10.10G and 11.10.10.10G) from the footwall of the fault at the Qumangou Section (Fig. 7c). Thus, the fast cooling of the northeastern Tashkurgan Complex is also attributed to the post-emplacement cooling of the complex rather than the rapid exhumation of the complex. Our new results support that the rapid exhumation of the Muskol-Shatput domes ceased at ≥12 Ma (Rutte et al., 2017b). The Tashkurgan Complex was emplaced at shallow crustal levels after the termination of rapid exhumation of the Muskol-Shatput domes.

    The thermochronological ages of 10–7 Ma are observed both in the hanging-wall and the footwall of the southern segment of the Kongur Shan fault (Fig. 2) (Cai et al., 2017; Cao et al., 2013a; Robinson et al., 2007). Because of the intrusion of the Tashkurgan Complex, the hanging-wall and the footwall of the southern segment of the Kongur Shan fault experienced regional heating initially and regional cooling subsequently. The period of 10–7 Ma is regarded as a history of regional cooling following magmatism rather than rapid exhumation. In other words, the rapid cooling in the western Muztag Ata dome at 10–7 Ma is unrelated to the continued eastward propagation of the Muskol-Shatput domes. The thermochronological ages of < 6 Ma are only observed in the footwall of the southern segment of the Kongur Shan fault (Fig. 2) (Cao et al., 2013a; Thiede et al., 2013; Sobel et al., 2011). This observation, together with the results of detrital zircon fission track analysis (Cao et al., 2013b), shows that the initiation age of the Kongur Shan fault along the Muztag Ata dome is 6–5 Ma (Cao et al., 2013a, b; Thiede et al., 2013; Robinson et al., 2007).

    Robinson et al. (2004) suggests that the northernmost segment of the Kongur Shan fault began its slip at 8–7 Ma (Fig. 2). This initiation age seems to be suspicious, because it is determined by using the K-feldspar 40Ar/39Ar multiple diffusion domain model. Based on the mica 40Ar/39Ar ages of < 5 Ma, the two-dimensional thermo-kinematic models show that the Kongur Shan fault along the Kongur Shan dome initiated at ~7 Ma (Fig. 2) (Robinson et al., 2010). Comparing these two modeling results, we tend to believe that the initiation age of east-west extension along the Kongur Shan dome is 6–5.5 Ma (Fig. 2), which is constrained by the detrital zircon fission track results (Cao et al., 2013b).

    The reliable low-temperature thermochronological ages from the hanging-wall and the footwall of the Tashkurgan fault indicate that the initiation age of the fault is 10–5 Ma, and most likely 6–5 Ma. This result, combined with the initiation ages of east-west extension along the Kongur Shan fault, supports a model of synchronous Late Miocene rift initiation. The gravitational collapse model predicts that the onset of east-west extension along the entire Kongur Shan extensional system is simultaneous (Cao et al., 2013b), while the synorogenic extension model, the radial thrusting model, the oroclinal bending model and the northward propagation model predict that the extension begins at either the center, the northern portion or the southern end of the extensional system (Thiede et al., 2013; Robinson et al., 2004). Consequently, the origin of the Late Cenozoic east- west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust (Cheng et al., 2016; Cao et al., 2013b; Strecker et al., 1995).

  • In this study, low-temperature thermochronology is applied to determine the timing of activity of the Tashkurgan normal fault. The results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.

  • We thank the editors and three anonymous reviewers for their detailed and constructive comments. Dr. Maria Giuditta Fellin is thanked for improving the original manuscript. This study was funded by the National Natural Science Foundation of China (Nos. 41720104003 and 41330207) and the National Science and Technology Major Project of China (Nos. 2017ZX05008-001 and 2016ZX05003-001). Chen S Q receives a PhD grant (No. 201706320352) from the China Scholarship Council. The final publication is available at Springer via https://doi.org/10.1007/s12583-020-1282-1.

    Electronic Supplementary Materials: Supplementary materials (Tables S1–S3) are available in the online version of this article at https://doi.org/10.1007/s12583-020-1282-1.

Reference (60)

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return