赣南晚侏罗世铝质A型花岗岩带及其意义  

Late Jurassic Aluminum A-Type Granite Belt in Southern Jiangxi and Its Geological Significance

作　　者：杨世文[1,2] 楼法生[2] 张芳荣[2] 吴正昌[2] 丰成友[1] Yang Shiwen;Lou Fasheng;Zhang Fangrong;Wu Zhengchang;Feng Chengyou(Institute of Mineral Resources,CAGS,Beijing 100037,China;Geological Survey Institute of Jiangxi Province, Nanchang 330030,China)

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]江西省地质调查研究院,南昌330030

出　　处：《地质科技情报》2019年第3期12-29,共18页Geological Science and Technology Information

基　　金：国家重点研发计划课题(2016YFC0600205);中国地质调查局项目"江南陆块及周缘地质矿产调查工程武夷山成矿带龙泉-上杭地区地质矿产调查"(DD20160037)

摘　　要：赣南燕山早期岩浆作用强烈,岩石成因以I型花岗岩为主,见少量S型花岗岩及A型花岗岩。在赣南兴国地区新识别了晚侏罗世永丰和隆市A型花岗岩,其LA-ICP-MS锆石U-Pb定年结果分别为155 Ma和157～154 Ma,具有铝质A型花岗岩的地球化学特征,如富硅(70.22%～77.08%)、高(Zr+Nb+Ce+Y)(189×10^(-6)～348×10^(-6))、高FeO^T/MgO值(3.39～11.57);具相对较高Ga/Al值(2.4×10^(-4)～2.9×10^(-4));富集Th、U、Hf等高场强元素和轻稀土元素,强烈亏损Ba、Sr、P、Ti等大离子亲石元素,相对亏损Nb和Ta元素。在赣南厘定出了一条北东向晚侏罗世铝质A型花岗岩带(162～152 Ma),它们具有相似的Hf同位素组成,T_(DM2)大部分集中在2.0～1.8 Ga之间,平均为1.9 Ga,暗示它们可能形成于相似的古老地壳物质的部分熔融。根据地球化学特征,并结合邻近的赣南全南地区存在同时代的"裂谷型"黄埠正长岩,认为赣南晚侏罗世铝质A型花岗岩带形成于板内拉张环境,可能与古太平洋板块俯冲-后退有关。The early Yanshanian magmatism in southern Jiangxi is intensive, and the petrogenesis is mainly I-type granite, with a small amount of S-type granite and A-type granite. The Late Jurassic Yongfeng complex, composed of the Yongfeng and Longshi plutons in the Xingguo area, is identified as A-type granites in this study. They have LA-ICP-MS zircon U-Pb dating results of 155 Ma and 157-154 Ma, respectively. The rock has the geochemical characteristics of aluminum A-type granites, such as high Si(70.22%-77.08%),(Zr^+Nb^+Ce^+Y)(189×10^-6-348×10^-6)), FeO^T/MgO(3.39-11.57) and Ga/Al ratios(2.4×10^-4-2.9×10^-4), enriched in high field strength elements such as Th, U, Hf, and depleted in Nb, Ta and large ion lithophile elements such as Ba, Sr, P, and Ti. Combined with the previous achievements, a northeastern Late Jurassic A-type granite belt(162-152 Ma) could be defined in southern Jiangxi, which has similar Hf isotopic composition, with most of TDM2 concentrated between 2.0-1.8 Ga, with the average of 1.9 Ga. This suggests that they may be formed by partial melting of similar ancient crustal material. The geochemical characteristics, combined with the contemporaneous "Rift-type" syenite in Quannan area, reveal that the A-type granite belt is formed in the intraplate extensional environment, which may be connected with the Paleo-Pacific plate subduction-roll back.

关 键 词：永丰复式岩体 晚侏罗世A型花岗岩带 板内拉张 

分 类 号：P588.12[天文地球—岩石学]