| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Petrology | Volume 44 | Number 10 | Pages 1833-1865 | 2003
© Oxford University Press 2003; all rights reserved
Cenozoic Volcanism in Tibet: Evidence for a Transition from Oceanic to Continental Subduction
1 INSTITUTE OF GEOLOGY AND GEOPHYSICS, CHINESE ACADEMY OF SCIENCES, BEIJING 100029, PEOPLE'S REPUBLIC OF CHINA
2 DEPARTMENT OF GEOSCIENCES, UNIVERSITY OF ARIZONA, TUCSON, AZ 85721-0077, USA
* Corresponding author. Telephone: (520) 626-8763. E-mail: pkapp{at}geo.arizona.edu
Geochronological (K–Ar or 40Ar/39Ar), major and trace element, Sr–Nd–Pb isotopic and mineral chemical data are presented for newly discovered Cenozoic volcanic rocks in the western Qiangtang and central Lhasa terranes of Tibet. Alkali basalts of 65–45 Ma occur in the western Qiangtang terrane and represent primitive mantle melts as indicated by high mg-numbers [100 x Mg/(Mg + Fe)] (54–65), Cr (204–839 ppm) and Ni (94–218 ppm) contents, and relatively low ratios of 87Sr/86Sr (0·7046–0·7061), 206Pb/204Pb (18·21–18·89), 207Pb/204Pb (15·49–15·61) and 208Pb/204Pb (38·42–38·89), and high ratios of 143Nd/144Nd (0·5124–0·5127). In contrast, younger volcanic rocks in the western Qiangtang terrane (
30 Ma) and the central Lhasa terrane (23, 13 and 8 Ma) are potassic to ultrapotassic and interpreted to have been derived from an enriched mantle source. They are characterized by very high contents of incompatible trace elements, negative Ta, Nb and Ti anomalies, and radiogenic Pb isotopic compositions (206Pb/204Pb = 18·43–19·10; 207Pb/204Pb = 15·64–15·83; 208Pb/204Pb = 39·14–39·67). 87Sr/86Sr (0·7088–0·7092) and 143Nd/144Nd (0·5122) ratios of the western Qiangtang terrane potassic lavas are similar to those of 45–29 Ma potassic volcanic rocks in the north–central Qiangtang terrane, whereas 87Sr/86Sr (0·7167–0·7243) and 143Nd/144Nd (0·5119) ratios of central Lhasa terrane lavas are similar to those of 25–16 Ma ultrapotassic volcanic rocks in the western Lhasa terrane. The 65–45 Ma alkali basalts in the western Qiangtang terrane, along with widespread calc-alkaline volcanic rocks of this age in the Lhasa terrane, may be related to roll-back of a previously shallow north-dipping slab of Tethyan oceanic lithosphere beneath Tibet. Subduction as opposed to convective thinning of continental lithosphere is favored to explain potassic volcanism in Tibet because of its occurrence in distinct, east–west-trending belts (45–29 Ma in the Qiangtang terrane; 25–17 Ma in the northern Lhasa terrane; 16–8 Ma in the southern Lhasa terrane) and temporal and spatial relationships with major thrust systems.
KEY WORDS: Tibet; geochemistry; Indo-Asian collision; sodic and potassic volcanism; continental subduction
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. LIU, R.-Z. HU, C.-X. FENG, H.-B. ZOU, C. LI, X.-G. CHI, J.-T. PENG, H. ZHONG, L. QI, Y.-Q. QI, et al. Cenozoic high Sr/Y volcanic rocks in the Qiangtang terrane, northern Tibet: geochemical and isotopic evidence for the origin of delaminated lower continental melts Geological Magazine, July 1, 2008; 145(4): 463 - 474. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Wang, X. Zhao, Z. Liu, P. C. Lippert, S. A. Graham, R. S. Coe, H. Yi, L. Zhu, S. Liu, and Y. Li Constraints on the early uplift history of the Tibetan Plateau PNAS, April 1, 2008; 105(13): 4987 - 4992. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P.G. DeCelles, P. Kapp, L. Ding, and G.E. Gehrels Late Cretaceous to middle Tertiary basin evolution in the central Tibetan Plateau: Changing environments in response to tectonic partitioning, aridification, and regional elevation gain GSA Bulletin, May 1, 2007; 119(5-6): 654 - 680. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. GUO, M. WILSON, J. LIU, and Q. MAO Post-collisional, Potassic and Ultrapotassic Magmatism of the Northern Tibetan Plateau: Constraints on Characteristics of the Mantle Source, Geodynamic Setting and Uplift Mechanisms J. Petrology, June 1, 2006; 47(6): 1177 - 1220. [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]
|
|
|
|
|
|
M. S. Spurlin, A. Yin, B. K. Horton, J. Zhou, and J. Wang Structural evolution of the Yushu-Nangqian region and its relationship to syncollisional igneous activity, east-central Tibet GSA Bulletin, September 1, 2005; 117(9-10): 1293 - 1317. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Kapp, A. Yin, T. M. Harrison, and L. Ding Cretaceous-Tertiary shortening, basin development, and volcanism in central Tibet GSA Bulletin, July 1, 2005; 117(7-8): 865 - 878. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. Wang, F. McDermott, J.-f. Xu, H. Bellon, and Y.-t. Zhu Cenozoic K-rich adakitic volcanic rocks in the Hohxil area, northern Tibet: Lower-crustal melting in an intracontinental setting Geology, June 1, 2005; 33(6): 465 - 468. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. L. Booth, P. K. Zeitler, W. S.F. Kidd, J. Wooden, Y. Liu, B. Idleman, M. Hren, and C. P. Chamberlain U-Pb zircon constraints on the tectonic evolution of southeastern Tibet, Namche Barwa Area Am J Sci, December 1, 2004; 304(10): 889 - 929. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Evidence for present-day leucogranite pluton growth in Tibet Geology, September 1, 2004; 32(9): 801 - 804.
|
|