广东白石嶂钼矿区花岗岩U-Pb年代学及其地球化学特征  

U-Pb geochronological and geochemical significance of granites from the Baishizhang Molybdenum area,Guangdong Province

作　　者：谢昊 梁新权[1] 王策[1] 梁细荣[1] 董超阁[1,2] XIE Hao;LIANG Xin-quan;WANG Ce;LIANG Xi-rong;DONG Chao-ge(State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州地球化学研究所同位素地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049

出　　处：《地球化学》2020年第5期479-493,共15页Geochimica

基　　金：国家自然科学基金(41576040,40872080,41072081);广东省自然科学基金(2017A030313250)。

摘　　要：广东白石嶂钼矿区地处南岭成矿带东缘,矿区出露多期侵入岩。本次研究对矿区复式岩体进行了LA-ICP-MS锆石U-Pb测年以及地球化学研究,获得白岗岩的成岩年龄为(242.1±1.6)Ma,为印支期岩浆作用的产物,黑云钾长花岗岩成岩年龄为(150.3±1.1)Ma,是燕山期岩浆作用的产物。两期花岗岩均具有高硅、富钾的特征,但它们的其他地球化学特征存在显著差异。印支期白岗岩具有与高分异I型花岗岩相似的地球化学特征,即Y含量较低,亏损Ba、Sr、P、Ti和Eu,富集Nb元素,P2O5与SiO2呈现出负相关的关系,并且表现出更明显的轻、重稀土分馏,相对亏损重稀土元素。相比之下,燕山期黑云钾长花岗岩则具有类似于A型花岗岩的地球化学组成特征,如10000×Ga/Al值为2.26~4.52,Eu负异常明显,富集Th、U、Ta、Nb、Zr和HREE等高场强元素,明显亏损Ba、Sr和Ti等元素,轻、重稀土分馏不明显。综合研究表明,印支期白岗岩形成于碰撞后拉张岛弧环境,而燕山期黑云钾长花岗岩形成于拉张的板内环境。The Baishizhang ore district is located in Guangdong province,on the eastern edge of the Nanling metallogenic belt,and exposes multi-period intrusive rocks.Through geochemical research and LA-ICP-MS zircon U-Pb dating,ages have been determined for the alaskites and biotite K-feldspar granite of(242.1±1.6)and(150.3±1.1)Ma,indicating that they are related to the Indosinian and Yanshanian events,respectively.Granites from the two stages are calcium-rich and potassium-rich,but their other geochemical characteristics are significantly different.The Indosinian alaskites have similar geochemical characteristics to those of an I-type granite,such as low Y content;depletion in Ba,Sr,P,Ti,Eu;enrichment in Nb;and a negative correlation between P2O5 and SiO2.The alaskite samples exhibit obvious light/heavy REE fractionation,and are depleted in heavy REEs.In contrast,the biotite K-feldspar granites have similar geochemical characteristics to those of an A-type granite.For example,the 10000×Ga/Al value is 2.26–4.52,and there is an obvious negative Eu anomaly.The samples were enriched in high-field-strength elements,such as Th,U,Ta,Nb,Zr,and HREE,but were obviously depleted in other elements such as Ba,Sr,and Ti.The granite samples did not exhibit any obvious light/heavy REE fractionation.According to comprehensive research,the Indosinian alaskites show the characteristics of a post-collision extending arc environment,while the Yanshanian biotite K-feldspar granites show the characteristics of an extensional intraplate environment.

关 键 词：锆石U-PB定年 地球化学 印支期 燕山期 白石嶂钼矿 广东省 

分 类 号：P597[天文地球—地球化学]