云南卓玛成矿斑岩体锆石U-Pb年龄及地球化学特征  

Zircon U-Pb Age and Geochemical Characteristics of the Quartz Monzonite Porphyry from the Zhuoma Deposit,Yunnan,China

作　　者：刘学龙[1] 李文昌[1,2] 张娜[1] 

机构地区：[1]昆明理工大学,昆明650093 [2]云南省地质调查局,昆明650051

出　　处：《矿物岩石地球化学通报》2016年第1期109-117,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局项目(12120114013701);中国博士后科学基金项目(2014M552547XB);昆明理工大学省级人培项目(KKSY201421042)

摘　　要：格咱岛弧是西南三江地区重要的铜多金属矿集区,卓玛铜矿是格咱岛弧近年来新发现和评价的与中酸性岩浆侵入有关铜多金属矿床之一。采用锆石LA-ICP-MS定年方法,获得卓玛成矿岩体石英二长斑岩的锆石U-Pb年龄为218.88±0.63Ma(MWSD=0.99),属于印支晚期。岩石地球化学特征表明石英二长斑岩属高钾钙碱性-钾玄岩岩石系列,稀土元素总含量中等(ΣREE=50.50×10^(-6)~101.87×10^(-6)),轻稀土较富集(LREE/HREE=12.53~15.53),轻重稀土元素分馏明显((La/Yb)_N=17.58~18.32);且富集大离子亲石元素(LILE)Ba、Rb、Sr、K,亏损高场强元素(HFSF)Ta、Nb、P、Ti和重稀土元素(HREE),具有岛弧花岗岩的特征,属I型花岗岩。研究表明,卓玛成矿斑岩体的形成时代属晚三叠世格咱岛弧岩浆作用的高峰时段,岩石成因与印支期甘孜-理塘洋壳的俯冲作用密切相关。The Zhuoma deposit is a recently discovered copper-polymetallic deposit in the Geza arc,which is an important copper polymetallic ore concentration area in the Sanjiang region,southwestern China,with its mineralization closely related to acidic magmatic intrusion. In this article,we obtained zircon U-Pb age of 218. 88±0. 63 Ma（ MWSD = 0. 99）,corresponding to Late Indosinian,for the quartz monzonite porphyry by using the LA-ICP-MS dating technique. Geochemical characteristics of the Zhuoma quartz monzonite porphyry shown that it belongs to potassium calc-alkaline shoshonite series,with moderate total REE contents（ Σ REE = 50. 50 × 10^-6- 101. 87 × 10^-6）,enriched light rare earth elements（ LREE /HREE = 12. 53-15. 53）,high degree fractionation of LREE and HREE[（ La/Yb）_N= 17. 58-18. 32],enriched LILE elements including Ba,Rb,Sr,and K,depleted high field strength elements（ HFSF） including Ta,Nb,P,Ti,and heavy REE（ HREE）. This indicates that the Zhuoma porphyry has features of island arc granite and belongs to I-type granite.Thus,it is believed that the Zhuoma porphyry was formed in the peak period of the Late Triassic magmatism which is closely related to the subduction of the Ganzi-Litang oceanic crust in Late Indosinia.

关 键 词：锆石U-PB年龄 地球化学特征 石英二长斑岩 卓玛岩体 云南 

分 类 号：P597.3[天文地球—地球化学] P618.2[天文地球—地质学]