北秦岭光石沟铀矿区花岗岩、伟晶岩锆石U-Pb年代学、地球化学及成因意义

发布时间：2018-04-29 08:35

  本文选题：锆石U-Pb年龄 + 地球化学特征　； 参考：《地学前缘》2017年06期

【摘要】：光石沟铀矿床是中国重要的伟晶岩型铀矿,铀矿体产在黑云母花岗伟晶岩和黑云斜长片麻岩的接触带上。本文对矿区出露的花岗岩、花岗伟晶岩开展了详细的年代学和岩石地球化学研究以约束花岗质岩石的成因和形成环境。LA-ICP-MS锆石U-Pb测年获得了黑云母花岗闪长岩、黑云母正长花岗岩、产铀黑云母花岗伟晶岩、非矿黑云母花岗伟晶岩的加权平均年龄,分别为(440.3±2.6)Ma、(420.4±2.7)Ma、(415.1±2.6)Ma和(413.6±2.4)Ma。地球化学数据显示,从矿区花岗岩到花岗伟晶岩分异程度逐渐升高,富集LILE(Rb、Ba、Sr),亏损HFSE(Nb、Ta、Ti),并且具有I型花岗岩的特征。花岗伟晶岩为具有稀土元素四分组效应(TE1,3=1.06~1.14)的NYF型(NbTa、Y、F)伟晶岩,指示了熔体与出溶的富挥发分流体间强烈的相互作用。黑云母花岗闪长岩、黑云母正长花岗岩、黑云母花岗伟晶岩的锆饱和温度TZr分别为730~765℃、700~723℃和518~640℃。花岗质岩浆在深成中等还原(ΔO_x=-0.54~-0.25)的环境上升侵位,源区为石榴石和斜长石稳定区。黑云母花岗闪长岩的岩石成因与混入幔源物质的加厚下地壳部分熔融有关。伴随汇聚挤压作用的减弱,同源母岩浆的缓慢分离结晶形成了黑云母正长花岗岩-花岗伟晶岩组合。产铀黑云母花岗伟晶岩中较高含量的FeO~T、MgO、TiO_2、MnO、LILE(Rb、Ba、K)和较低的HFSE(Nb、Ta)是伟晶岩浆和黑云斜长片麻岩发生化学交换的结果。伟晶岩浆的同化分离结晶(AFC)导致了U在接触带的饱和,在中等还原的环境下富集成矿。光石沟花岗岩和花岗伟晶岩形成于北秦岭同造山-造山晚期。
[Abstract]:The Guangshigou uranium deposit is an important pegmatite type uranium deposit in China. The uranium orebody occurs in the contact zone of biotite granitic pegmatite and biotite plagioclase gneiss. Detailed geochronological and petrogeochemical studies of granite and granitic pegmatite have been carried out in this paper in order to constrain the genesis of granitic rocks and their forming environment. LA-ICP-MS zircon U-Pb dating has obtained biotite granodiorite. The weighted mean ages of biotite syenite, uranium-bearing biotite granipegmatite and non-mineral biotite granitic pegmatite are 420.4 卤2.7 and 415.1 卤2.6)Ma and 413.6 卤2.4 Ma. respectively. Geochemical data show that the differentiation from granitoids to granitic pegmatites in the ore area is gradually increasing, and they are enriched in LILEN RbSU Bajiu Sr ~ (2 +) and depleted HFSE ~ (2 +) NB ~ (+) Tatiao, and have the characteristics of I-type granites. The granitic pegmatite is a pegmatite of the NYF type NbTaOYF with the te1- (31.06- (1.14) effect of REE, indicating the strong interaction between the melt and the dissolved volatile fluid. The zirconium saturation temperature (TZr) of biotite granodiorite, biotite syenite and biotite granitic pegmatite is 730 ~ 765 鈩，

本文编号：1819189