吉林百草沟金矿闪长玢岩锆石U_Pb年代学、地球化学及其地质意义  

Zircon U_Pb chronology and geochemistry of diorite_porphyrite from Baicaogou gold deposit in Yanbian region, Jilin Province, and its geological significance

作　　者：李睿华[1,2,3] 孙丰月[3] 刘金龙[3] 李良[3] 赵拓飞 闫佳铭 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]吉林大学地球科学学院,吉林长春130061

出　　处：《矿床地质》2016年第5期1023-1034,共12页Mineral Deposits

基　　金：吉黑东部区域成矿规律综合研究项目(编号:1212011085485);中央高校基本科研业务费专项资金(编号:310827161011)联合资助

摘　　要：文章对延边地区百草沟金矿床与成矿有关的闪长玢岩脉进行了锆石LA_ICP_MS U_Pb年代学和地球化学研究。闪长玢岩中的锆石U_Pb定年结果显示,闪长玢岩形成时代为早白垩世（（128±3）Ma,MSWD=0.29）。岩石元素地球化学研究表明岩石属于高钾钙碱性系列,明显富集大离子亲石元素（如K、Ba、Rb）、LREE和强不相容元素（如Th、U）,相对亏损高场强元素（如Ta、Nb、Ti、P）,Mg#值为42～54,其地球化学特征与活动大陆边缘背景下形成的火成岩相似。岩石中w（Cr）为20.0×10^（-6）～33.4×10^（-6）,Nb/Ta比值为9.7～16.5,La/Nb比值为2.54～3.67,Th/La比值为0.19～0.43,Rb/Sr值比为0.10～0.33,闪长玢岩岩浆是由地壳物质和地幔物质混合形成的。结合野外地质特征及年代学,认为与矿床近同时形成的闪长玢岩,其形成的构造背景应为古太平洋板块斜向亚洲大陆俯冲的活动大陆边缘。LA_ICP_MS zircon U_Pb dating and geochemical data of the diorite_porphyrite rocks, which are related to ore formation, from the Baicaogou gold deposit of Yanbian region were obtained to restrain their formation time and the regional tectonic background. The dating results indicate that these rocks were formed in the Early Cretaceous（（ 128 ± 3） Ma,MSWD = 0. 29）. The element compositions of these rocks are transitional from shoshonite series to potassium_high calc_alkaline series, characterized by enrichment of LILE（ such as K, Ba and Rb）,LREE and more mobile incompatible elements（ such as Th, U）, and relatively depleted in HFSE（ such as Ta, Nb, Ti and P）. Incombination with their Mg#values（ 42 ～ 54）, it is suggested that the features of the rocks are similar to the characteristics of active continental margin magma. Based on the data Cr =（ 20. 0～33. 4） × 10^（-6）, Nb/Ta = 9. 7～16. 5,La/Nb = 2. 54～3. 67, Th/La = 0. 19～0. 43, and Rb/Sr = 0. 10～0. 33, it can be concluded that the magma was derived from mixture of the crust and the mantle. Together with the research on geological features and geochronology, the authors mainly studied diorite_porphyrite rocks similar to ore in formation time, and the formation background of diorite_porphyrite rocks was that of active continental margin closely related to the subduction of paleo_Pacific plate towards the Eurasia continent.

关 键 词：地球化学 锆石U_Pb年龄 百草沟金矿 闪长玢岩 活动大陆边缘 

分 类 号：P618.31[天文地球—矿床学]