The Garze-Litang suture zone, located in the eastern part of the Tethyan tectonic domain, is notable for widespread Late Triassic granitic plutons, which are genetically associated with the evolution of the Paleo-Tethys Ocean. The Daocheng granitic pluton in the eastern Yidun Arc, SW China, is located in the middle of the Garze-Litang suture zone and has an outcrop area of similar to 2800 km(2). In the present study, we report zircon U-Pb ages and elemental and Sr-Nd-Hf isotopic data for the Daocheng granitic intrusion. Secondary ion mass spectrometry and laser ablation inductively coupled plasma mass spectrometry U-Pb analyses on zircons yield consistent ages of ca. 216 Ma for three samples from the pluton. All the Daocheng granitic rocks are enriched in Si (SiO2 = 68.1-76.4%) and large-ion lithophile elements but depleted in high-field-strength elements (e.g., Nb, Ta, and Ti). Mineralogical and geochemical features indicate that these are high-l( and calc-alkaline and I-type granites. They are characterized by relatively variable initial Sr-87/Sr-86 ratios (0.7059-0.7102), negative epsilon(Nd)(t) values (-5.7 to -7.8), wide-ranging epsilon(Hf)(t) values (-9.8 to +3.4), and two-stage Hf model ages of 1.04 to 1.88 Ga. These isotopic signatures indicate that the source for the Daocheng granite was probably derived from partial melting of a Late Paleoproterozoic to Early Mesoproterozoic mafic-intermediate lower crust with a variably minor addition (<20%) of depleted mantle-derived magma. The parental magma thereafter underwent extensive fractional crystallization of ferromagnesian minerals, plagioclase, apatite, ilmenite, and rutile during emplacement, under temperatures from 785 degrees C to 839 degrees C. In combination with previous studies on synchronous magmatism in the Yidun Arc, we propose that the Daocheng granite was generated in a syncol-lisional tectonic setting. The westward subduction and closure of the Garze-Litang paleo-ocean triggered the underplating of large-scale mantle-derived magma and provided heat for the anatexis of the lower crust. Hybrid melts including minor depleted mantle-derived magma and lower crustal magma were then generated; these thereafter were continuously injected into a shallow-level chamber and gave rise to the Daocheng granite. (C) 2013 Elsevier Ltd. All rights reserved.

Publication name	JOURNAL OF ASIAN EARTH SCIENCES　Volume: 67-68　 Pages: 1-17　 Published: MAY 2013
Author(s)	He, De-Feng; Zhu, Wei-Guang; Zhong, Hong; Ren, Tao; Bai, Zhong-Jie; Fan, Hong-Peng
Corresponding author	ZHU Weiguang  zhuweiguang@vip.gyig.ac.cn  Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, 46 Guanshui Rd, Guiyang 550002, Peoples R China.

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