西藏日土地区弗野岩体的成因——锆石U-Pb年龄及Hf同位素约束  

Petrogenesis of Fuye pluton in Rutog, Tibet: zircon U-Pb dating and Hf isotopic constraints

作　　者：张璋[1,2] 耿全如[1] 彭智敏[1] 丛峰[1] 关俊雷[1] 

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]中国地质调查局青藏高原研究中心,四川成都610081

出　　处：《地质通报》2015年第2期262-273,共12页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:12120113036500;1212011121262);国家自然科学基金项目(批准号:41273047;41303043;41402058)

摘　　要：班公湖—怒江成矿带西段日土—多龙地区为一条燕山期岩浆弧,已相续发现多处大、中型矿产,具有良好的成矿地质条件。弗野岩体位于该岩浆弧西侧,岩性以闪长岩和闪长玢岩为主,蚀变较强;微量元素原始地幔标准化后亏损Ba、Nb、Ta、Sr和Ti,富集Th、U和Pb;稀土元素球粒陨石标准化后表现出整体向右缓倾,显示负Eu异常;D1046和D1049两件样品的锆石LuHf同位素结果显示,εHf(t)主要集中在-5.2^-12.2区间,TDM1模式年龄介于0.98~1.28Ga之间;锆石206Pb/238U年龄加权平均值分别为119.06±0.48Ma和120.03±0.68Ma,均形成于早白垩世中期。结合岩石地球化学特征判断其属于I型花岗岩类,源区物质来源于幔源物质和下地壳物质。根据该岩浆弧带的岩体特征判断,班公湖—怒江特提斯洋至少在中侏罗世已经开始了向北的俯冲作用,且在早白垩世这种向北的俯冲作用仍在持续。A Yanshanian magmatic arc was discovered in Rutog-Duolong area, in the western of Bangong-Nujiang metallogenic belt. It shows good ore-forming geological condition for several large and medium-size minerals had been found in recent years. Fuye pluton, locating in the west of the magmatic arc, is composed of diorite and diorite-porphyrite, with strong alteration. Primitive mantle-normalized spider diagram is loss Ba, Nb, Ta, Sr and Ti, enrichment Th, U and Pb. Chondrite-normalized REE pattern shows Slowly tilted to the right, and negative Eu anomalies. Zircon Lu-Hf isotope results of sample D 1046 and D1049 showεHf（t） mainly focused at the range of-5.2 to-12.2, TDM1 model age concentrated in 0.98~1.28Ga. The 206Pb/238U weighted average age of sample D1046 and D1049 are 119.06±0.48Ma, and 120.03±0.68Ma, representing they formed in the middle age of Early Cretaceous. Combined with geochemical characteristics, it is I-type granitoid, and formed with both mantle and lower crust. According to these magmatic bodies＇ characteristics of this arc, Bangong-Nujiang Tethys ocean at least started northward subduction, in the Middle Ju-rassic. And it last to Early Cretaceous.

关 键 词：日土-多龙岩浆弧 弗野岩体 岩石成因 LA-ICP-MS锆石U-PB年龄 锆石HF同位素 西藏 

分 类 号：P597.3[天文地球—地球化学]