张广才岭南部横道河子岩体地球化学特征及其成因

Geochemistry of Hengdaohezi Pluton from southern Zhangguangcai Range and its petrogenesis

对张广才岭南部地区横道河子岩体进行锆石U-Pb测年、锆石原位Lu-Hf同位素、主量元素、稀土元素和微量元素测试分析.结果表明,横道河子岩体主体岩性为黑云母正长花岗岩,由石英（40％ ～45％）、条纹长石（35％ ～ 40％）、斜长石（12％ ～ 15％）、黑云母（3％ ～5％）和角闪石（1％～3％）组成.

Zircon U—Pb ages and geochemical characteristics of Hengdaohezi pluton as well as Lu—Hf isotope,major,trace and REE elements were determined. The Hengdaohezi pluton mainly consists of biotite syenogranites.The biotite syenogranite contains quartz( 40% ~ 45%),perthite( 35% ~ 40%),plagioclase( 12% ~ 15%),biotite( 3% ~ 5%) and amphibole( 1% ~ 3%). Zircon U—Pb isotopic dating is 198. 5 ± 1. 6 Ma,belonging to Early Jurassic. The A / CNK values ranging from 1. 01 to 1. 03 with high fractionated index( DI) are 93. 69 ~ 94. 95.Trace elements of the granites are characterized by enrichment in K,Rb and LREE,depletion in Ba,Sr,Nb,Ta,P,Ti,and high Rb / Sr ratio( 2. 06 ~ 2. 76). Chondrite- normalized REE patterns are right-inclined and display moderate negative europium anomalies( δEu = 0. 26 ~ 0. 57). The geological and geochemical data suggest that the Hengdaohezi pluton can genetically be ascribed to slightly peraluminous I-type granites. Its variable zircon Hf isotope composition( εHf( t) = 5. 7 ~ 9. 7,TDM2= 618 ~ 874 Ma) shows that the primary magma originated from the partial melting of the juvenile crusts during the Neoproterozoic,and formed in an active continental margin setting related to the subduction of the Paleo—Pacific plate.