Journal of Petrology Advance Access originally published online on October 28, 2005
Journal of Petrology 2006 47(3):435-455; doi:10.1093/petrology/egi080
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Evolution from Oceanic Subduction to Continental Collision: a Case Study from the Northern Tibetan Plateau Based on Geochemical and Geochronological Data
1 KEY LABORATORY OF OROGENIC BELTS AND CRUSTAL EVOLUTION, SCHOOL OF EARTH AND SPACE SCIENCES, PEKING UNIVERSITY, BEIJING 100871, P.R. CHINA
2 SHRIMP LABORATORY, INSTITUTE OF GEOLOGY, CAGS, BEIJING 100037, P.R. CHINA
3 DEPARTMENT OF EARTH SCIENCE, DURHAM UNIVERSITY, DURHAM DH1 3LE, UK
4 GEOLOGIC LAB CENTRE, CHINESE UNIVERSITY OF GEOSCIENCES, BEIJING 100083, P.R. CHINA
RECEIVED DECEMBER 10, 2004; ACCEPTED SEPTEMBER 30, 2005
Two apparently distinct, sub-parallel, paleo-subduction zones can be recognized along the northern margin of the Tibetan Plateau: the North Qilian Suture Zone (oceanic-type) with ophiolitic mélanges and high-pressure eclogites and blueschists in the north, and the North Qaidam Belt (continental-type) in the south, an ultrahigh-pressure (UHP) metamorphic terrane comprising pelitic and granitic gneisses, eclogites and garnet peridotites. Eclogites from both belts have protoliths broadly similar to mid-ocean ridge basalts (MORB) or oceanic island basalts (OIB) in composition with overlapping metamorphic ages (480–440 Ma, with weighted mean ages of 464 ± 6 Ma for North Qilian and 457 ± 7 Ma for North Qaidam), determined by zircon U–Pb sensitive high-resolution ion microprobe dating. Coesite-bearing zircon grains in pelitic gneisses from the North Qaidam UHP Belt yield a peak metamorphic age of 423 ± 6 Ma, 40 Myr younger than the age of eclogite formation, and a retrograde age of 403 ± 9 Ma. These data, combined with regional relationships, allow us to infer that these two parallel belts may represent an evolutionary sequence from oceanic subduction to continental collision, and continental underthrusting, to final exhumation. The Qilian–Qaidam Craton was probably a fragment of the Rodinia supercontinent with a passive margin and extended oceanic lithosphere in the north, which was subducted beneath the North China Craton to depths >100 km at c. 423 Ma and exhumed at c. 403 Ma (zircon rim ages in pelitic gneiss).
KEY WORDS: HP and UHP rocks; subduction belts; zircon SHRIMP ages; Northern Tibetan Plateau
* Corresponding author. Present address: Department of Geology, Peking University, Beijing 100871, P.R. China. Telephone: +86-01-6275-1145. Fax: +86-10-6275-1159. E-mail: sgsong{at}pku.edu.cn
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Zhang, C. G. Mattinson, F. Meng, Y. Wan, and K. Tung Polyphase tectonothermal history recorded in granulitized gneisses from the north Qaidam HP/UHP metamorphic terrane, western China: Evidence from zircon U-Pb geochronology Geological Society of America Bulletin, May 1, 2008; 120(5-6): 732 - 749. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. G. Mattinson, C. G. Mattinson, J. L. Wooden, J. G. Liou, D. K. Bird, and C. L. Wu Age and duration of eclogite-facies metamorphism, North Qaidam HP/UHP terrane, Western China Am J Sci, November 1, 2006; 306(9): 683 - 711. [Abstract] [Full Text] [PDF]
|
|