四川盐源西范坪渐新世含矿二长斑岩成因浅析  

Petrogenesis analysis of the oligocene ore-bearing monzonite porphyry in Xifanping of Yanyuan,Sichuan

作　　者：黄景厚 周清[3] 张锦让[3] 王宏[3] 王生伟[3] 朱斯豹[3] 刘宇杰[3] HUANG Jinghou;ZHOU Qing;ZHANG Jinrang;WANG Hong;WANG Shengwei;ZHU Sibao;LIU Yujie(Chinese Academy of Geological Science ,Beijing ,100037;China University of Geosciences(Beijing) , Beijing, 100083;Chengdu Geological Survey Center , Chinese Geological Survey ,Chengdu ,610081)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质大学(北京),北京100083 [3]中国地质调查局成都地质调查中心,成都610081

出　　处：《地质学报》2019年第3期622-632,共11页Acta Geologica Sinica

基　　金：国家自然科学基金青年基金项目(编号41202067);四川省科技计划项目应用基础研究面上项目(编号2018JY0175);中国地质调查局项目(编号121201010000160920)资助成果

摘　　要：四川盐源西范坪斑岩型铜矿位于扬子板块西南缘,通过对含矿二长斑岩进行锆石U-Pb定年,获得年龄为31.68±0.28 Ma(MSWD=1.2;2σ),表明其形成时代为古近纪渐新世早期,与区内碱性斑岩岩浆活动的高峰期一致。岩石碱度率指数(A.R.)为3.59～3.69,K/N为0.89～1.11,A/NK为1.16～1.24,A/CNK为0.97～1.13,属准铝—过铝质碱性石英二长斑岩;岩石高度富集轻稀土元素,相对亏损重稀土元素,δEu(0.80～0.85)异常不明显,并且富Sr贫Yb(Y),具高Sr/Yb和Sr/Y比值,系典型的埃达克岩。西范坪埃达克质含矿斑岩为印度板块与欧亚大陆板块碰撞造山晚期远程压力释放环境下,拆沉下地壳部分熔融的产物。The Xifanping porphyry copper deposit, Yanyuan, is located in the southwestern Yangtze block. LA-ICP-MS zircon U-Pb dating yields an age of 31.68±0.28 Ma(MSWD=1.2;2σ) for the ore-bearing monzonite porphyry, indicating that it formed in the Oligocene and is consistent to the peaking period of alkali-rich porphyritic magmatism in the region. A.R. value of 3.59~3.69, K/N ratio of 0.89~1.11, A/NK ratio of 1.16~1.24 and A/CNK ratio of 0.97~1.13 indicate that the ore-bearing monzonite porphyry are metaluminous-peraluminous and alkaline. The rock is highly enriched in LREE relative to HREE, without distinct Eu anomalies(δEu: 0.80~0.85). High Sr and low Yb and Y, and high Sr/Yb and Sr/Y ratios all suggest a typical adakite. The Xifanping adakitic ore-bearing porphyry should be the product of partial melting of delaminated lower crust in a late orogenic setting caused by stress released from the collision of the Indian and Eurasian blocks.

关 键 词：西范坪 二长斑岩:U-Pb定年 埃达克岩 元素地球化学 

分 类 号：P588.1[天文地球—岩石学] P618.41[天文地球—地质学]