Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mechie, J. Articles by Zhao, W. Search for Related Content GeoRef GeoRef Citation

Precise temperature estimation in the Tibetan crust from seismic detection of the -ß quartz transition

J. Mechie^*,1, S.V. Sobolev^*,2, L. Ratschbacher^*,3, A. Y. Babeyko^*,4, G. Bock⁴, A.G. Jones^*,5, K.D. Nelson^,6, K.D. Solon^*,6, L.D. Brown^*,7 and W. Zhao^*,8

¹ GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany
² GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany, and Institute of Physics of the Earth, Moscow, Russia
³ Institut für Geologie, Technische Universität Freiberg, 09599 Freiberg, Germany
⁴ GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany
⁵ Geological Survey of Canada, Ottawa, Ontario, Canada, and Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA
⁶ Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA
⁷ Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA
⁸ Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037, China

In the deep crust, temperature, which is among the key parameters controlling lithospheric dynamics, is inferred by extrapolation from the surface using several assumptions that may fail in regions of active tectonics and fluid migration. In the rare case that temperatures of 700 °C or higher are exceeded in the upper and middle continental crust composed of quartz-rich felsic rocks, the -ß quartz transition (ABQT) will occur, generating a measurable seismic signature and offering the possibility for precisely estimating temperature from the known ABQT phase diagram. Here it is shown that all expected seismic features of the ABQT are met by the boundary between the upper and middle crust below the INDEPTH III profile in central Tibet. This finding implies that a temperature of 700 °C is achieved at a depth of 18 km under the southern Qiangtang block, which agrees with the depth to the top of a high electrical conductivity anomaly, likely representing partially melted crust. To the south in the northern Lhasa block, the ABQT is at 32 km depth, corresponding to a temperature of 800 °C. It thus appears that this seismic boundary representing the ABQT is the result of recent geologic processes rather than being a lithologic boundary.

Key Words: Tibet • -ß quartz transition • seismic profiles • crustal structure

This article has been cited by other articles:

				J.P. PLATT From orogenic hinterlands to Mediterranean-style back-arc basins: a comparative analysis Journal of the Geological Society, March 1, 2007; 164(2): 297 - 311. [Abstract] [Full Text] [PDF]

				M. A. Carpenter Elastic properties of minerals and the influence of phase transitions American Mineralogist, February 1, 2006; 91(2-3): 229 - 246. [Abstract] [Full Text] [PDF]

				S. L. Klemperer Crustal flow in Tibet: geophysical evidence for the physical state of Tibetan lithosphere, and inferred patterns of active flow Geological Society, London, Special Publications, January 1, 2006; 268(1): 39 - 70. [Abstract] [PDF]

				K. V. Hodges A synthesis of the Channel Flow-Extrusion hypothesis as developed for the Himalayan-Tibetan orogenic system Geological Society, London, Special Publications, January 1, 2006; 268(1): 71 - 90. [Abstract] [PDF]

				T. M. Harrison Did the Himalayan Crystallines extrude partially molten from beneath the Tibetan Plateau? Geological Society, London, Special Publications, January 1, 2006; 268(1): 237 - 254. [Abstract] [PDF]

				M. A. Edwards and L. Ratschbacher Seismic and aseismic weakening effects in transtension: field and microstructural observations on the mechanics and architecture of a large fault zone in SE Tibet Geological Society, London, Special Publications, January 1, 2005; 245(1): 109 - 141. [Abstract] [PDF]