Petrogenesis of Middle Triassic andesite in Sayaburi area, Laos: Constraints from whole-rock geochemistry, zircon U-Pb geochronology, and Sr-Nd isotopes

作     者：OUYANG Yuan LIU Hong NIE Fei CONG Feng ZHANG Jian-long ZHANG Jing-hua HUANG Han-xiao LIU Shu-sheng LEI Chuan-yang 欧阳渊;刘洪;聂飞;丛峰;张建农;张景华;黄瀚霄;刘书生;雷传扬

作者机构：College of Earth SciencesChengdu University of TechnologyChengdu 610059China Chengdu CenterChina Geological SurveyChengdu 610081China Sichuan Geological SurveyChengdu 610081China 

出 版 物：《Journal of Central South University》 (中南大学学报（英文版）)

年 卷 期：2019年第26卷第12期

页      面：3502-3515页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：Projects(DD20160107,DD20150742)supported by the China Geological Survey Project supported by the International Scientific Plan of the Qinghai-Xizang(Tibet)Plateau of Chengdu Center,China Geological Survey 

主　　题：Laos Sayaburi area zircon U Pb geochronology geochemistry 

摘      要：Despite the presence of a large area of andesite in the Sayaburi Province of Laos, it has received very little attention. Based on a combination of detailed field investigations, geochronology and geochemical analysis, this study aims to explore the geochemical, Sr-Nd isotopic, and source rock characteristics, as well as the genesis and tectonic setting of the andesite in this region. In the Sayaburi Province, the andesite zircon U-Pb age is(241.2±1.2) Ma. The andesite rock is classified in the metaluminous-weak peraluminous calc-alkaline series. The light rare-earth elements(LREEs) are enriched and characterized by clear fractionation, whereas heavy rare-earth elements(HREEs) are relatively depleted and have no signs of fractionation. The average δEu is 0.96 with weak-or-no Eu anomalies. It is enriched in large ion lithophile elements such as Rb and K, while depleted in high field-strength elements such as Nb, Ta, P and Ti. For andesites in the Sayaburi Province, the(87Rb/86Sr)t value ranges in 0.702849-0.704687, the εNd(t) value is between 3.53 and 4.77, the tDM(t) value ranges in 633-835 Ma, and the tDM2(t) ranges in 625–724 Ma. The results based on the synthesis of petrology, geochemistry, and regional tectonic background studies show that 1) the andesitic magma source in the study area is an enriched mantle, which is modified by subduction zone fluids;2) the geotectonic background environment of the andesite in Sayaburi area is the continental island arc environment and related to the tectonic evolution of Jinghong–Nan–Uttaradit back-arc basin, which reflects that the magmatic source is enriched with a mantle wedge component modified by a subduction zone fluid(or melt).