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Ultrapotassic rocks and xenoliths from south Tibet; contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision

Xu Bo, William L. Griffin, Qing Xiong, Hou Zengqian, Suzanne Y. O'Reilly, Zhen Guo, Norman J. Pearson, Yoann Greau, Yang Zhiming and Zheng Yuanchuan
Ultrapotassic rocks and xenoliths from south Tibet; contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision
Geology (Boulder) (January 2017) 45 (1): 51-54

Abstract

Widespread Miocene (24-8 Ma) ultrapotassic rocks and their entrained xenoliths provide information on the composition, structure, and thermal state of the sub-continental lithospheric mantle in southern Tibet during the India-Asia continental collision. The ultrapotassic rocks along the Lhasa block delineate two distinct lithospheric domains with different histories of depletion and enrichment. The eastern ultrapotassic rocks (89 degrees E-92 degrees E) reveal a depleted, young, and fertile lithospheric mantle ( (super 87) Sr/ (super 86) Sr (sub t) = 0.704-0.707 [t is eruption time]; Hf depleted-mantle model age [T (sub DM) ] = 377-653 Ma). The western ultrapotassic rocks (79 degrees E-89 degrees E) and their peridotite xenoliths (81 degrees E) reflect a refractory harzburgitic mantle refertilized by ancient metasomatism (lavas: (super 87) Sr/ (super 86) Sr (sub t) = 0.714-0.734; peridotites: (super 87) Sr/ (super 86) Sr (sub t) = 0.709-0.716). These data integrated with seismic tomography suggest that upwelling asthenosphere was diverted away from the deep continental root beneath the western Lhasa block, but rose to shallower depths beneath a thinner lithosphere in the eastern part. Heating of the lithospheric mantle by the rising asthenosphere ultimately generated the ultrapotassic rocks with regionally distinct geochemical signatures reflecting the different nature of the lithospheric mantle.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 1
Title: Ultrapotassic rocks and xenoliths from south Tibet; contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision
Affiliation: China University of Geosciences, School of Earth Science and Mineral Resources, Beijing, China
Pages: 51-54
Published: 201701
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 25
Accession Number: 2017-006055
Categories: Isotope geochemistryIgneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017013
Illustration Description: illus. incl. geol. sketch map
N29°00'00" - N33°00'00", E80°00'00" - E95°00'00"
Secondary Affiliation: Macquarie University, AUS, AustraliaChinese Academy of Geological Sciences, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201705
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