Abstract
This study reports new zircon U-Pb and Hf isotopes and whole-rock elemental and Sr-Nd isotopic data for the gneissic granite and leucogranite from the Nabang metamorphic zone, Yingjiang area (West Yunnan, SW China). The metamorphosed granitoids crystallized during the early Eocene (~55-50Ma) with zircons showing εHf(t) values from +11 to -5.3 and crustal model ages of 1.5 to 0.42Ga, comparable to those of coeval I-type granitoids from the Gangdese batholith, southern Lhasa. The rocks are characterized by metaluminous and weakly peraluminous hornblende-bearing gneissic granites with A/CNK=0.95-1.09, Na2O>K2O, coupled with low initial Sr isotopic values of 0.7049-0.7070 and high εNd(t) values from +1.1 to -7.1. The rocks were derived from crustal materials involving ancient upper crust/sedimentary and juvenile mantle-derived rocks. Together with available data from nearby regions, it is proposed that the early Eocene granitoids in the Nabang and Tengliang area can be correlated to the Gangdese granitoids and represent the southeastward continuation of the magmatic arc resulting from the Neotethyan subduction in southern Tibet. The petrogenesis of early Eocene granitoids in western Yunnan was probably related to the rollback of the subducting Neotethyan slab that caused the remelting of the crustal materials newly modified by the underplated basaltic magma.
Original language | English |
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Pages (from-to) | 401-419 |
Number of pages | 19 |
Journal | Gondwana Research |
Volume | 25 |
Issue number | 1 |
DOIs | |
Publication status | Published - Jan 2014 |
Externally published | Yes |
Bibliographical note
We wish to acknowledge T-P. Peng, F. Guo, and X-P. Xia, for their help during the fieldwork, and Y. Liu and L. Qi and H. Zhang for their assistance during geochemical analyses and LA-ICPMS dating. We are also grateful to Dr. Y-H Zhang for polishing the English. We thank Associate Editor Z-M Zhang and two anonymous reviewers for their critical and constructive review and comments on this paper.Funding
This study was jointly supported by the Natural Science Foundation of China ( 40830319 and 40825009 ), “Closed of Eastern Paleotethys Ocean and Assembly of South China continents” ( 41190073 ) that is the 3rd research project of a Major NSFC Program ( 41190070 ), Most Special Fund from the State Key Laboratory of Continental Dynamics, Northwest University ( BJ081331 ), State Key Laboratory of Ore Deport Geochemistry, CAS ( 201301 ) and GIG, CAS ( GIGCAS-135-Y234 151001 ). This is a contribution to Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.
Keywords
- Gangdese belt
- I-type gneissic granite
- Nd-Hf isotopic composition
- West Yingjiang
- Zircons U-Pb geochronology