粤北长江岩体的锆石U-Pb定年、地球化学特征及其成因研究  

Zircon U-Pb Dating,Geochemical Characteristic and Genesis of the Changjiang Granite in Northern Guangdong

作　　者：黄国龙 刘鑫扬 孙立强[3] 李钟枢 张世佳 

机构地区：[1]核工业290研究所,广东韶关512029 [2]中国核工业地质局,北京100014 [3]南京大学地球科学与工程学院,南京210093

出　　处：《地质学报》2014年第5期836-849,共14页Acta Geologica Sinica

基　　金：科技部国家科技支撑计划项目"赣南崇义-于都矿集区铀矿深部资源勘查技术研究"(编号2011BAB04B07-5);中国地质调查广东省仁化县-和平县铀矿远景调查项目(编号1212011220781)联合资助的成果

摘　　要：在棉花坑铀矿区,通过钻孔采集深部长江岩体不同结构的花岗岩,并进行LA-ICP-MS锆石U-Pb定年和主量元素、微量元素、稀土元素和Nd-Sr同位素测试.通过分析和对比,长江岩体与浅部印支期油洞岩体接触的细粒不等粒、深部的中粒和更深部的中粗粒黑云母花岗岩具有相近的形成年龄（157.2±1.7～161.6±2.1Ma）、相同的矿物组成和相似的地球化学特征,应为同源岩浆演化的产物.长江岩体的主量元素组成以富硅、富碱、钾大于钠为特征;微量元素以富集大离子元素Rb、Th,明显亏损Ba、Sr、P、Ti和轻微亏损Nb、Ta为特征;稀土总量偏低且变化明显,配分模式呈轻稀土略富集型,Eu明显亏损;（^87Sr/^86Sr）i值较高（平均为0.71066）,εNd（t）值低（平均为10.1）,Nd模式年龄古老（平均为1.77 Ga）,源区成分以砂质岩为主.上述特征表明,长江岩体是在伸展的构造背景下由古元古代地壳组分熔融形成,属于壳源型花岗岩范畴.This study collected the deep Changjiang granite of different structure by drilling in the Mianhuakeng mining area,and LA-ICP-MS zircon U-Pb dating,the main elements,trace elements,rare earth elements and Nd-Sr isotope were carried out.Comparison analysis indicates that the Changjiang granite formed at almost the same time（157.2±1.7~161.6±2.1 Ma）as the biotite granite,which occurs along contact zone between Changjiang and Youdong granites of Indosinian as fine-inequigrain,mesograin and coarse grains from shallow to deeper,and has the similar mineralogical composition and geochemical features. Therefore,hey should be the product of comagmatic evolution.The Changjiang granite shows enrichment in Si and alkali,and K content is higher than Na.The trace elements are characterized by enrichment of large-ion elements（such as Rb,Th）,apparent depletion of Ba,Sr,P,Ti,and minor loss of Nb and Ta. The total amount of REE is low and varies greatly,the REE patterns are characterized by slight enrichment of light REE,as well as obvious Eu depletion.The（87Sr/86Sr）iis higher than the average value（0.71066）;εNd（t）is lower than the average value（-10.1）;the model age of Nd is older than average（1.77Ga）;and component of the source area is dominated by sandy rock.The characteristics above indicate that the Changjiang granite resulted from partial melting of crustal material under the extensional tectonic setting in Paleoproterozoic Era,and belongs to the crust-derived type granite.

关 键 词：长江岩体 地球化学 源区特征 岩石成因 锆石U-PB定年 

分 类 号：P597.3[天文地球—地球化学] P588.121[天文地球—地质学]