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《Geoscience》 2018-05
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Discovery of the Early Indosinian Granite in Lujing Area,Hunan and Jiangxi Border and Its Geological Significance

ZHANG Wanliang;GAO Mengqi;L Chuan;HUANG Chao;HUANG Di;XIE Zhicong;Research Institute No.270,Nuclear Industry;  
Indosinian granites are widely distributed in Southern China. Previous studies indicate that the Indosinian granites mainly concentrated in the Middle-Late Triassic are attributed to post-collisional granite type.In this paper,we reported a Jiaoyelong concealed granite from Lujing area,the border of the Hunan and Jiangxi provinces. The results show that this granite with medium-coarse grained granitic texture and muscovite is characterized by high contents of silicon( SiO_2= 73. 97%-76. 92%),aluminum( Al_2O_3= 12. 56%-13. 86%),potassium( K_2O = 4. 02%-5. 13%),and K_2O Na_2O,and belongs to high potassium calcalkaline series.The A/CNK ranges from 1. 17 to 1. 30,suggesting a peraluminous series. It is rich in large ion lithophile elements( Rb,K,etc.) and high field intensity elements( Th,U,Ta,Nb,Zr,Hf,etc). The contents of U range from 3. 24 × 10~(-6) to 15. 40 × 10~(-6),with the average content of 8. 31 × 10~(-6). The ratio of Th/U is 1. 21-1. 98,indicating a rich uranium pluton property. This granite enriched in LREE has a relatively high fractionation between LREE and HREE. LA-ICP-MS zircon U-Pb dating of the granite yields a mean age of( 247 ±2. 2) Ma,belonging to the early Indosinian intrusion. Furthermore,the aluminum saturation index and Rb/30-Hf-3 Ta diagram show that the pluton formed in the collisional continental margin tectonic background,suggesting that a tectonic transition from compression to extension took place in Southern China during the EarlyMiddle Triassic.
【Fund】: 中国核工业集团有限公司集中研发项目“南方重点花岗岩铀矿基地资源预测和扩大”(LTD1602)
【CateGory Index】: P588.121
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