南岭东段龙源坝复式岩体La-ICP-MS锆石U-Pb年龄及其地质意义  

Single-zircon La-ICP-MS Ages of the Longyuanba Pluton in the Eastern Nanling Region and Geological Implication

作　　者：张敏[1] 陈培荣[1] 黄国龙 谭正中 凌洪飞[1] 陈卫锋[1] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学系210093 [2]核工业290研究所,广东韶关512026

出　　处：《地质学报》2006年第7期984-994,共11页Acta Geologica Sinica

基　　金：国家自然科学基金资助项目(编号40372036)的成果

摘　　要：龙源坝岩体是南岭花岗岩体群的一个重要组成部分,位于南岭东段,研究程度十分薄弱,至今未见可靠的同位素年龄报道。本文在运用阴极发光技术对岩体中的锆石进行细致的内部结构分析的基础上,利用La-ICP-MS锆石U-Pb原位定年方法进行了同位素年龄测定。结果表明,龙源坝岩体是一个印支期—燕山期多期次岩浆侵入形成的复式岩体,其中主体形成于印支期,尤其是印支早期。印支早期花岗岩的单颗粒锆石U-Pb年龄为241.0±5.9Ma和241.0±1.3Ma(两个样品),印支晚期花岗岩为210.9±3.8Ma,燕山期正长岩为149.4±1.2Ma。龙源坝岩体在时代和成因上不同于其东侧的陂头岩体,但相同于北侧的诸广山岩体有亲缘关系,因此在探讨该区的铀成矿前景时,应把诸广山与龙源坝两岩体整合起来考虑,并加强对龙源坝岩体的铀矿找矿工作。The Longyuanba pluton in the eastern Nanling Range is an important part of the Nanling granites. However, so far no reliable isotopic dating result is available for this pluton. Based on the interior structures of zircons from the Longyuanba pluton analyzed by the CL technology, in-situ zircon U-Pb dating was performed with La-ICP-MS and reliable age data were obtained. The results show that the Longyuanba pluton was formed in multi-stage magmatism spanning the Indosinian and Yanshanian periods. The main body of the pluton was formed in the Indosinian, especially in the early Indosinian. Single-grain zircon dating for the early Indosinian granites yields ages of 241.0± 5.9 Ma and 241.0± 1.3 Ma （two samples）, for the late Indosinian granite yields 210. 9±3.8 Ma, and for the Yanshanian syenite yields 149.4±4.9 Ma. The ages and geneses of the Longyuanba pluton are different from those of the Pitou--Tabei complex pluton located to its east, but are very similar to those of the Zhuguangshan pluton located to its north. When considering the prospect of uranium mineralization in the region, we should consider it with the integration of Zhuguangshan pluton and Longyuanba pluton, and should enhance the exploration on the Longyuanba pluton.

关 键 词：La—ICP—MS锆石U—Pb年龄 印支期花岗岩 南岭东段 

分 类 号：P597.3[天文地球—地球化学]