TY - JOUR
T1 - Initial Rifting of the Lhasa Terrane from Gondwana
T2 - Insights From the Permian (~262 Ma) Amphibole-Rich Lithospheric Mantle-Derived Yawa Basanitic Intrusions in Southern Tibet
AU - Zeng, Yun Chuan
AU - Xu, Ji Feng
AU - Ducea, Mihai N.
AU - Chen, Jian Lin
AU - Huang, Feng
AU - Zhang, Le
N1 - Funding Information:
We thank Ying Liu, Xiang‐Lin Tu, Sheng‐Lin Sun, Ding‐Shuai Xue, Yong‐ Hai Yuan, Qing Yang, and Fang‐Yue Wang for the geochemical analyses and Ming Lei and Qiu‐Wei Xiong for assistance with fieldwork. We are grateful for the constructive reviews by Kwan‐Nang Pang and an anonymous reviewer and the encouragement and editorial support of Michael Walter and John Lassiter. This research was supported by the following funding agencies: The National Key Research and Development Project of China (project 2016YFC0600304), the Major State Basic Research Program of the People's Republic of China (2015CB452602), and the Natural Science Foundation of China (41730427, 41803030 and 41873037). M. N. Ducea acknowledges a US National Science Foundation grant (EAR 1725002) and the Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding projects PN‐III‐P4‐ ID‐PCE‐2016‐0127 and PN‐III‐P4‐ID‐ PCCF‐2016‐0014. Supporting data are included in a supporting information file and can be obtained from the corresponding author, Ji‐Feng Xu (jifengxu@cugb.edu.cn or jifengxu@gig.ac.cn).
Funding Information:
We thank Ying Liu, Xiang-Lin Tu, Sheng-Lin Sun, Ding-Shuai Xue, Yong-Hai Yuan, Qing Yang, and Fang-Yue Wang for the geochemical analyses and Ming Lei and Qiu-Wei Xiong for assistance with fieldwork. We are grateful for the constructive reviews by Kwan-Nang Pang and an anonymous reviewer and the encouragement and editorial support of Michael Walter and John Lassiter. This research was supported by the following funding agencies: The National Key Research and Development Project of China (project 2016YFC0600304), the Major State Basic Research Program of the People's Republic of China (2015CB452602), and the Natural Science Foundation of China (41730427, 41803030 and 41873037). M. N. Ducea acknowledges a US National Science Foundation grant (EAR 1725002) and the Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding projects PN-III-P4-ID-PCE-2016-0127 and PN-III-P4-ID-PCCF-2016-0014. Supporting data are included in a supporting information file and can be obtained from the corresponding author, Ji-Feng Xu (jifengxu@cugb.edu.cn or jifengxu@gig.ac.cn).
Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.
PY - 2019/3
Y1 - 2019/3
N2 - The Permian tectonic setting of the Lhasa Terrane in southern Tibet remains controversial (i.e., continental rift vs. subduction-collision) and is crucial to palinspastic reconstructions of the eastern Tethys during the breakup of Gondwana. In this study, we present new geochronological, geochemical, and mineralogical data for the Permian (~262 Ma) Yawa intrusions in the southern Lhasa Terrane. These rocks are silica-undersaturated and alkaline, with high TiO2 and moderate MgO, and exhibit enrichments in Th, light rare earth elements, and Nb-Ta, and depletions in K. These chemical compositions, combined with uniform whole-rock (87Sr/86Sr)i (0.7039–0.7044), εNd(t) (1.85–2.81), and εHf(t) (4.21–6.90) values, and zircon εHf(t) (4.53–9.97) and δ18O (5.04‰–5.76‰) values, indicate the magmas were derived by partial melting of amphibole-rich lithospheric mantle. The magmas subsequently underwent fractionation of clinopyroxene, amphibole, and Fe-Ti oxides. The amphibole in the lithospheric mantle likely formed as cumulates from low-degree asthenospheric melts during incipient extension. Given that the amphibole-rich metasomatic veins have a lower melting temperature than the surrounding peridotite, they were susceptible to melting during the early stages of thermal perturbation of the mantle. Because there is no evidence of Permian continental subsidence in the Lhasa Terrane, we suggest the Yawa intrusions were formed at the onset of lithospheric extension associated with initial rifting of the Lhasa Terrane from the Indian Plate during Gondwana breakup, which was a precursor to the opening of the Neo-Tethys Ocean.
AB - The Permian tectonic setting of the Lhasa Terrane in southern Tibet remains controversial (i.e., continental rift vs. subduction-collision) and is crucial to palinspastic reconstructions of the eastern Tethys during the breakup of Gondwana. In this study, we present new geochronological, geochemical, and mineralogical data for the Permian (~262 Ma) Yawa intrusions in the southern Lhasa Terrane. These rocks are silica-undersaturated and alkaline, with high TiO2 and moderate MgO, and exhibit enrichments in Th, light rare earth elements, and Nb-Ta, and depletions in K. These chemical compositions, combined with uniform whole-rock (87Sr/86Sr)i (0.7039–0.7044), εNd(t) (1.85–2.81), and εHf(t) (4.21–6.90) values, and zircon εHf(t) (4.53–9.97) and δ18O (5.04‰–5.76‰) values, indicate the magmas were derived by partial melting of amphibole-rich lithospheric mantle. The magmas subsequently underwent fractionation of clinopyroxene, amphibole, and Fe-Ti oxides. The amphibole in the lithospheric mantle likely formed as cumulates from low-degree asthenospheric melts during incipient extension. Given that the amphibole-rich metasomatic veins have a lower melting temperature than the surrounding peridotite, they were susceptible to melting during the early stages of thermal perturbation of the mantle. Because there is no evidence of Permian continental subsidence in the Lhasa Terrane, we suggest the Yawa intrusions were formed at the onset of lithospheric extension associated with initial rifting of the Lhasa Terrane from the Indian Plate during Gondwana breakup, which was a precursor to the opening of the Neo-Tethys Ocean.
KW - Gondwana
KW - Tethys Ocean
KW - alkaline rock
KW - amphibole-rich lithospheric mantle
KW - continental rifting
KW - kaersutite
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U2 - 10.1029/2018JB016281
DO - 10.1029/2018JB016281
M3 - Article
AN - SCOPUS:85064572675
VL - 124
SP - 2564
EP - 2581
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9380
IS - 3
ER -