Abstract
To understand deep lithosphere structure beneath the Qinghai-Tibet Plateau more comprehensively and objectively and to explore important scientific issues, such as characteristics of plateau lithospheric deformation, state of strain, thermal structure, plate (or terrane) movement, and crust-mantle rheology, it is necessary to research the variation of crust-mantle electrical structure in the east-west direction in every geological unit. For this purpose, six super-broadband magnetotelluric (MT) sounding profiles have been completed by INDEPTH-MT Project in the Himalayas-Southern Tibet. Based on the imaging results from the six profiles, three-dimensional electrical conductivity structure of the crust and upper mantle has been analyzed for the research area. The result shows that the high-conductivity layers in the middle and lower crust exist widely in Southern Tibet, which extend discontinuously for more than 1000 km in the east-west direction and become thinner, shallower and more resistive toward the big turning of the Yarlung Zangbo River. The discussion on the rheology of lithosphere in Southern Tibet suggests that the mid-lower crust there is of high electrical conductivity, implying the existence of “partial-melt” and “hot fluid” in the thick crust of Tibet, which make the medium hot, soft, and plastic, or even able to flow. Combining the experimental result of petrophysics and the MT data, we estimate the melting percentage of the crustal material to be up to 5%–14%, which would reduce the viscosity of aplite in the crust to meet the flow condition; but for granite, it is likely not enough to cause such a change in rheology.
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References
Zhao W J, Nelson K D, Che J, et al. Deep seismic reflection evidence for continental underthrusting beneath Southern Tibet. Nature, 1993, 366:557–559
Wei W B, Chen L S, Tan H D, et al. MT sounding on Tibetan Plateau—Electrical structure of crust and mantle along profile of Yatung-Bamucuo (in Chinese). Geosci J Graduate School China Univ Geosci, 1997, 11:366–374
Wei W B, Chen L S, Tan H D, et al. An approach on subduction of Indian Plate from INDEPTH-MT results. Geoscience (in Chinese). J Graduate School China Univ Geosci, 1997, 11:379–386
Wei W B, Chen L S, Tan H D, et al. Features of thermal structure and highly conductive bodies in middle crust beneath central and Southern Tibet: according to INDEPTH-MT results (in Chinese). Geosci J Graduate School China Univ Geosci, 1997, 11:387–392
Wei W B, Tan H D, Deng M, et al. Conductivity of crust in Tibetan Plateau-widespread fluids in the Tibetan crust found by magnetotel luric detection. In: The 80th Annual Meeting Collections of Society of Chinese Geology (in Chinese). Beijing: Geological Publishing House, 2002. 487–493
Wei W B, Unsworth M, Jin S, et al. Conductivity structure of crust and upper mantle beneath the northern Tibetan Plateau: Results of super-wide band magnetotelluric sounding. Chin J Geophy, 2006, 49:1098–1110
Wei W B, Jin S, Ye G F, et al. Features of faults in the central and northern Tibetan Plateau based on results of INDEPTH (III)-MT. Earth Sci China, 2007, 2:1–8
Nelson K D, Zhao W J, Brown L D, et al. Partially molten middle crust beneath Southern Tibet: Synthesis of Project INDEPTH Results. Science, 1996, 274:1684–1688
Chen L S, Booker J R, Jones A G, et al. Electrically conductive crust in Southern Tibet from INDEPTH magnetotelluric surveying. Science, 1996, 274:1694–1696
Wei W B, Unsworth M, Jones A, et al. Detection of widespread fluids in the Tibetan crust by magnetotelluric studies. Science, 2001, 292:716–718
Han T L. Himalayan Tectonic Evolution of Lithosphere-Tibet Tectonic Events (in Chinese). Beijing: Geological Publishing House, 1987
Zhou H W, Michael A, Murphy, et al. Tomographic imaging of the tibet and surrounding region: Evidence for wholesale underthrusting of Indian slab beneath the Tibetan Plateau (in Chinese). Earth Sci Front, 2002, 9:285–292
Yin A. Himalayas-The Qinghai-Tibet Plateau orogenic geological evolution-Phanerozoic growth of the Asian continent (in Chinese). Acta Geosci Sin, 2001, 22:195–229
Gber G D, Booker J R. Robust estimation of geomagnetic transfer functions. Geophys Roy Ast Soc, 1986, 87:175–194
Weidelt P, Kaikkonen P. Local 1D interpretation of magnetotelluric B-polarization impedence. Geophys J Int, 1994, 117:733–748
Gary W M, Alan G J. Multisite, multifrequency tensor decomposition of magnetotelluric data. Geophysics, 2001, 66:158–173
Smith J T, Booker J R. Rapid inversion of two-and three-dimensional magnetotelluric data. J Geophys Res, 1996, 96:3905–3922
Degroot-hedlin C, Constable S C. Occam’s inversion to generate smooth, two-dimensional models from magnetotelluric data. Geophysics, 1990, 55:1613–1624
Rodi W, Mackie R L. Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion. Geophysics, 2001, 66, 174–187
Molnar P, Tapponnier P. Cenozoic tectonics of Asian: Effects of a continental collision. Science, 1975, 189:419–426
Tapponnier P. The Ailao Shan-Red Rive metamorphic belt: Tertiary left-lateral shear between Indochina and South China. Nature, 1990, 343:431–437
Cui Z Z, Yin Z X, Gao E Y, et al. Crustal structure of Qinghai-Tibet Plateau and its relationship with the earthquake (in Chinese). China Geol Acad Sci, 1990, 21:215–226
Shen X J, Zhang W R, Yang S Z, et al. Heat flow evidences of different crust-mantle thermal structure in North-South terrain of Qinghai- Tibet Plateau (in Chinese). China Geol Acad Sci, 1990, 21:203–214
Owenst T J, Zandt G. Implications of crustal property variations for models of Tibetan Plateau evolution. Nature, 1997, 387:37–43
Kosarev G K R, Sobolev S V, Yuan X, et al. Seismic evidence for detached Indian lithosphere mantle beneath Tibet. Science, 1999, 283:1306–1309
Kola-ojo O, Meissner R. Southern Tibet: Its deep seismic structure and some tectonic implications. J Asian Earth Sci, 2001, 19:249–256
Cui Z Z, Yin Z X, Gao E Y, et al. Velocity Structure and Deep Tectonics of Qinghai-Tibet Plateau (in Chinese). Beijing: Geological Publishing House, 1992
Xiong S B, Liu H B, Yu G S, et al. Qinghai-Tibet Plateau lithosphere structure and tectonic study of artificial seismic. In: Pan Y S, Kong X R. Evolution of the Qinghai-Tibet Plateau Lithosphere Structure and Dynamics (in Chinese). Guangzhou: Guangdong Science and Technology Press, 1998. 1–35
Kong X R, Wang Q S, Xiong S B. Comprehensive geophysics and lithosphenc structure in the western Xizang (Tibet) Plateau. Sci China Ser D-Earth Sci, 1996, 39:348–358
Zeng R S, Deng Z F, Wu Q J, et al. Seismological evidences for the multiple incomplete crustal subductions in Himalaya and Southern Tibet (in Chinese). Chin J Geophy, 2000, 43:780–797
Li S H, Li M J, Unsworth M, et al. Partial melt or aqueous fluid in the mid-crust of Southern Tibet? Constraints from INDEPTH magnetotelluric data. Geophys J Int, 2003, 153:289–304
Zhao G Z, Tang J, Zhan Y, et al. Relation between electricity structure of the crust and deformation of crustal blocks on the north eastern margin of Qiughai-Tibetan Plateau. Sci China Ser D-Earth Sci, 2005, 48:1613–1626
Zhao Z D, Mo X X, Luo Z H, et al. Subduction of India beneath Tibet: Magmatism evidence (in Chinese). Earth Sci Front, 2003, 10:149–157
Sun J, Jin G W, Dai D H, et al. Sounding of electrical structure of the crust and upper mantle along the eastern border of Qinghai-Tibet Plateau and its tectonic significance. Sci Chin Ser D-Earth Sci, 2003, 46(Suppl):243–253
Ma X B, Kong X R, Liu H B, et al. The electrical structure of northeastern Qinghai-Tibet Plateau (in Chinese). Chin J Geophy, 2005, 48:689–697
Zhao G Z, Chen X B, Wang L F, et al. Evidence of crustal ‘channel flow’ in the eastern margin of Tibetan Plateau from MT measurements. Chin Sci Bull, 2008, 53:1887–1893
Shi Y J, Liu G D, Wu G Y, et al. A Course in Magnetotelluric Method (inChinese). Beijing: Geological Publishing House, 1985. 44–45
Makovsky Y, Klemperer S L. Measuring the seismic properties of Tibetan bright spots: Evidence for free aqueous fluids in the Tibetan middle crust. J Geophys Res, 1999, 104:10795–10825
Armijo R, Tapponnier P, Mercier J L, et al. Quaternary extension in Southern Tibet: Field observations and tectonic implications. J Geophys Res, 1986, 91:13803–13872
Beaumont C, Jamieson R A, Nguyen M H, et al. Himalayan tectonics explained by extrusion of a low-viscosity crustal channel coupled to focused surface denudation. Nature, 2001, 414:738–742
Schilling F, Partzch G, Brasse H, et al. Partial melting beneath the magmatic arc in Central Andres deduced from geoelectromagnetic field data and laboratory experiments. Phys Earth Plan Int, 1997, 103:17–31
Gaillard F, Scaillet B, Pichavant M. Evidence for present-day leucogranite pluton growth in Tibet. Geology, 2004, 32:801–804
Li S, Unworth M, Booker J R, et al. Partial melt or aqueous fluids in the Tibetan crust: Constraints from INDEPTH magnetotelluric data. Geophys J Int, 2003, 153:289–304
Renner J, Evans B, Hirth G. On the rheologically critical melt fraction. Earth Planet Sci Lett, 2000, 181:585–594
Rosenberg C, Handy M R. Experimental deformation of partially melted granite revisited: Implications for the continental crust. J Metamorph Geol, 2005, 23:19–28
Rutter E, Neumann D H K. Experimental deformation of partially molten Westerly granite under fluid absent conditions with implications for the extraction of granitic magmas. J Geophys Res, 1995, 100:15697–15715
Van der Molen I, Paterson M S. Experimental deformation of partially molten granite. Contrib Mineral Petrol, 1979, 70:299–318
Unsworth M, Jones A G, Wei W B, et al. Crustal rheology of the Himalaya and Southern Tibet inferred from magnetotelluric data. Nature, 2005, 438:78–81
Clark M K, Royden L H. Topographic ooze: Building the Eastern margin of Tibet by lower crustal flow. Geology, 2000, 28:703–706
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Wei, W., Jin, S., Ye, G. et al. Conductivity structure and rheological property of lithosphere in Southern Tibet inferred from super-broadband magnetotelluric sounding. Sci. China Earth Sci. 53, 189–202 (2010). https://doi.org/10.1007/s11430-010-0001-7
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DOI: https://doi.org/10.1007/s11430-010-0001-7