北淮阳东端牛王寨岩体年代学及地球化学研究:对大别造山带早白垩世深部地质过程的制约  

Geochronology and geochemistry of Niuwangzhai pluton in east end of North Huaiyang:constraints on deep geological process of Dabie Orogen in Early Cretaceous

作　　者：张靖怡[1,2] 张舒[1,2,3] 张赞赞 汪晶[1,2] ZHANG Jingyi;ZHANG Shu;ZHANG Zanzan;WANG Jing(Geological Survey of Anhui Province, Hefei 230001, Anhui, China;Anhui Institute of Geological Sciences, Hefei 230001, Anhui, China;Engineering Technology Innovation Center for Deep Resource Exploration in Covered Area, Ministry of Natural Resources, Hefei 230001, Anhui, China)

机构地区：[1]安徽省地质调查院,安徽合肥230001 [2]安徽省地质科学研究所,安徽合肥230001 [3]自然资源部覆盖区深部资源勘查工程技术创新中心,安徽合肥230001

出　　处：《华东地质》2022年第2期141-153,共13页East China Geology

基　　金：安徽省重点研发计划项目“铜陵大型资源基地接替资源勘查研究(编号:201904a07020077)”;安徽省公益性地质调查“安徽省庐枞地区与碱性岩有关的铀(钍)矿调查评价(编号:2016-g-1-7)”;“安徽省稀有、稀散元素矿产远景调查(编号:2016-g-2-16)”项目联合资助。

摘　　要：牛王寨岩体位于大别造山带北部北淮阳构造带东端,岩性主要为花岗岩。LA-ICP MS锆石U-Pb测年结果显示,牛王寨花岗岩形成于(119.4±1.5)Ma,属于大别造山带早白垩世晚阶段岩浆活动的产物。牛王寨花岗岩具有高硅(SiO_(2)含量为71.98%~77.96%)、高碱(全碱含量为7.66%~9.30%)、低钙(CaO含量为0.19%~0.68%)、高FeO_(T)/MgO值(平均值为12.83)和10000×Ga/Al值(2.63~2.82)的特点。岩石富集高场强元素,(Zr+Nb+Ce+Y)平均含量为294×10^(-6),富Rb、贫Ba和Sr,具有显著的Eu负异常,指示牛王寨花岗岩具有A型花岗的特点。牛王寨花岗岩^(87)Sr/^(86)Sr初始值为0.70828~0.70841,ε_(Nd)(t)值为-18.77~-19.15,判断其源区物质可能为大别山中下地壳片麻岩。约130 Ma时,大别造山带加厚下地壳拆沉引发的软流圈上涌,为源区的部分熔融提供了热源。牛王寨岩体的形成受控于约130 Ma之后中国东部统一的伸展构造事件。Niuwangzhai granite is located in the east end of North Huaiyang in Dabie Orogen.LA-ICP MS zircon U-Pb dating indicates that the Niuwangzhai granite was emplaced at(119.4±1.5)Ma and belongs to the late-stage Early Cretaceous magmatism of Dabie Orogen.The granites are characterized with high SiO_(2)(71.98%~77.96%)and high alkali(7.66%~9.30%)contents,low CaO contents(0.19%~0.68%),and high FeO_(T)/MgO(4.04~39.04,mean value of 12.83)and 10000×Ga/Al ratios(2.63~2.82).The granites are also enriched in high field strength elements(average content of Zr+Nb+Ce+Y is 294×10^(-6))and Rb,but are depleted in Ba and Sr with apparent lowδEu values.Geochemical features suggest that the Niuwangzhai granites can be classified into A-type granites.Combined with Sr-Nd isotopic compositions,the granites were probably derived from the gneiss in middle-lower crust of Dabie Orogen.The upwelling of asthenosphere caused by 130 Ma thickened lower crust delamination probably provided heat to melt the intermediate-acid gneiss.The formation of Niuwangzhai granite was possibly associated with extensional tectonic event of eastern China in post 130 Ma.

关 键 词：锆石U-PB年龄 地球化学 牛王寨岩体 北淮阳 大别造山带 

分 类 号：P581[天文地球—岩石学] P595[天文地球—地质学]