辽东裂谷大映沟金矿区二长斑岩年代学、地球化学、Hf同位素特征及地质意义  

Geochemistry, zircon U-Pb dating, Hf isotopic character and geological significance of monzonitic porphyry in Dayinggou gold deposit, Liaodong rift, China

作　　者：张朋[1] 赵岩[1] 寇林林[1] 杨宏智[1] 毕中伟[1] 李伫民[1] ZHANG Peng;ZHAO Yan;KOU Linlin;YANG Hongzhi;BI Zhongwei;LI Zhumin(Shenyang Geological Survey Center,China Geological Survey,Shenyang 110034,China)

机构地区：[1]中国地质调查局沈阳地质调查中心

出　　处：《成都理工大学学报（自然科学版）》2019年第4期408-420,共13页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家重点研发计划项目(2018YFC0603804,2016YFC0600108-09);国家自然科学基金青年基金项目(41502093)

摘　　要：探讨辽东裂谷大映沟金矿区与成矿有关的二长斑岩的岩石成因机制和形成构造背景。通过LA-MC-ICP-MS锆石U-Pb年龄测定、主元素、痕量元素和Hf同位素地球化学分析,二长斑岩成岩年龄为(138±1)Ma(MSWD=0.53),为燕山期构造岩浆活动产物;岩石具有富硅(SiO2质量分数为61.92%~64.40%)、富钾(K2O/Na2O=0.90)和富碱(K2O+Na2O质量分数为5.91%~6.99%)的属性,具有高钾钙碱性岩石特点;LREE/HREE值为13.98~15.58,显示轻稀土元素富集,重稀土元素亏损特点;δ Eu值为1.18~1.29,正铕异常相对较弱;富集Pb、Rb、K等大离子亲石元素和U、Th等不相容元素,而P、Nb、Ti、Ta等高场强元素亏损;二长斑岩的ε Hf ( t )值为-20.1^-10.1,二阶段模式年龄(tDM2)为2 460~1 833 Ma,指示岩浆来源可能是古元古界形成的古老地壳的再熔融。结合大地构造演化史,认为成岩成矿构造背景为早白垩世古太平洋板块向欧亚板块之下俯冲折返伸张的构造环境。The petrogenesis and tectonic setting of the monzonitic porphyry in Dayinggou gold deposit in Liaodong rift of northeast China are discussed. LA-ICP-MS zircon U-Pb dating for the monzonitic porphyry yields an emplacement age of 138±1 Ma. Geochemical study shows that the monzonitic porphyry is rich in silicon (mass fraction = 61.92%~64.40%) and alkaline (mass fraction of K2O+Na2O = 5.91%~6.99%),and rich in potassium (K2O/Na2O=0.90). It belongs to high-K calc-alkaline series granite,with the characteristics of LREE enrichment (LREE/HREE=13.98~15.58),HREE depletion,and weak positive Eu anomaly (δ Eu=1.18~1.29). LILES such as K,Rb and Pb are enriched and incompatible elements of Th and U are also enriched,while HFSEs such as Nb,Ta,P and Ti are depleted. According to zircon Hf isotope analysis,the ε Hf ( t ) values of monzonitic granite are in the range of -20.1^-10.1,and two-stage model ages ( tDM2 ) range from 2460 to 1833 Ma. These characteristics suggest that the primary magma was derived from the remelting of the Paleoproterozoic crustal materials. Based on the regional tectonic evolution,it is considered that the monzonitic porphyry and Dayinggou gold deposit were formed in an extensional tectonic setting during the subduction of the Pacific Plate beneath Eurasia Plate.

关 键 词：锆石U-PB年龄 HF同位素 二长斑岩 大映沟金矿 辽东 

分 类 号：P588.13[天文地球—岩石学]