|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 MOE Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China
2 Department of Geosciences, University of Houston, Houston, Texas 77204, U.S.A.
Correspondence: * E-mail: lfzhang{at}pku.edu.cn
Exsolution textures are observed in garnet and olivine crystals found in an orogenic garnet peridotite massif in the North Qaidam ultrahigh-pressure metamorphic (UHP) belt, northern Tibetan Plateau, NW China. Exsolutions in garnet consist of densely packed rods of rutile, orthopyroxene, and clinopyroxene. Exsolutions in olivine includes needles of ilmenite and Al-chromite. The occurrence of pyroxene exsolution lamellae in garnet crystals suggests that the precursor phase originally must have possessed excess Si, i.e., they were majoritic garnets that are stable only at very high pressures. The exsolution of ilmenite and Al-chromite needles from olivine is also consistent with the peridotite once being equilibrated at depths in excess of 200 km. Geotheromobarometric calculations using matrix minerals of the peridotite yield re-equilibrium conditions of T = 960–1040 °C and P = 5.0–6.5 GPa. These observations and inferences, together with other petrological data and field observations, allow us to conclude that the garnet peridotite in the North Qaidam UHP belt may represent mantle materials exhumed form depths of greater than 200 km.
This article has been cited by other articles:
|
|
 |
|
  W. L. Griffin, S. Y. O'Reilly, J. C. Afonso, and G. C. Begg The Composition and Evolution of Lithospheric Mantle: a Re-evaluation and its Tectonic Implications J. Petrology, July 1, 2009; 50(7): 1185 - 1204. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Scambelluri, T. Pettke, and H.L.M. van Roermund Majoritic garnets monitor deep subduction fluid flow and mantle dynamics Geology, January 1, 2008; 36(1): 59 - 62. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Kawasaki and Y. Osanai Empirical thermometer of TiO2 in quartz for ultrahigh-temperature granulites of East Antarctica Geological Society, London, Special Publications, January 1, 2008; 308(1): 419 - 430. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W.G. Ernst, B.R. Hacker, and J.G. Liou Petrotectonics of ultrahigh-pressure crustal and upper-mantle rocks--Implications for Phanerozoic collisional orogens Geological Society of America Special Papers, January 1, 2007; 433(0): 27 - 49. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. SONG, L. ZHANG, Y. NIU, L. SU, B. SONG, and D. LIU Evolution from Oceanic Subduction to Continental Collision: a Case Study from the Northern Tibetan Plateau Based on Geochemical and Geochronological Data J. Petrology, March 1, 2006; 47(3): 435 - 455. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Katayama, S.-i. Karato, and M. Brandon Evidence of high water content in the deep upper mantle inferred from deformation microstructures Geology, July 1, 2005; 33(7): 613 - 616. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Song, L. Zhang, J. Chen, J. G. Liou, and Y. Niu Sodic amphibole exsolutions in garnet from garnet-peridotite, North Qaidam UHPM belt, NW China: Implications for ultradeep-origin and hydroxyl defects in mantle garnets American Mineralogist, May 1, 2005; 90(5-6): 814 - 820. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
