桐柏—大别造山带中部娘娘顶花岗岩成因——锆石U-Pb年龄、岩石地球化学及Sr-Nd同位素证据  

The genesis of Niangniangding granite in central Tongbai-Dabie Orogen:Evidence from zircon U-Pb age,geochemistry and Sr-Nd isotopes

作　　者：叶健华 方洁 钟石玉 杨成 张凯玲 周梦阁 Ye Jianhua;Fang Jie;Zhong Shiyu;Yang Cheng;Zhang Kailing;Zhou Mengge(Sixth Geological Team of Hubei Geological Bureau,Xiaogan,Hubei 432000;Hubei Geological Survey,Wuhan,Hubei 430034;Inner Mongolia NO.5 Geological and Mineral Exploration and Development Co.,Ltd.,Baotou,Inner Mongolia 014000;Hubei Nuclear Industry Geological Survey,Xiaogan,Hubei 432000)

机构地区：[1]湖北省地质局第六地质大队,湖北孝感432000 [2]湖北省地质调查院,湖北武汉430034 [3]内蒙古第五地质矿产勘查开发有限责任公司,内蒙古包头014000 [4]湖北省核工业地质调查院,湖北孝感432000

出　　处：《资源环境与工程》2024年第4期381-392,共12页Resources Environment & Engineering

基　　金：湖北省自然科学基金联合基金项目“灵山岩体南缘钨钼铍稀有金属成矿规律与找矿潜力分析”(2023AFD230);湖北省地质局科技项目“鄂东北地区燕山期岩浆成矿作用与找矿预测研究”(KJ2024-28)。

摘　　要：娘娘顶花岗岩体位于桐柏—大别造山带中部﹐其侵位时代及形成构造环境还不清楚。采集娘娘顶花岗岩样品,开展锆石U-Pb年代学、岩石地球化学及Sr-Nd同位素研究,探讨其岩浆源区特征、岩石成因、构造环境及其与杨新岩铍矿点的关系。结果表明,娘娘顶花岗岩的锆石U-Pb年龄为(752.6±9.0)Ma,属南华纪岩浆作用产物,仅构成杨新岩铍矿点的赋矿围岩;具有高硅(SiO_(2)含量为72.56%~77.26%)、富碱(Na_(2)O+K_(2)O含量为7.37%~8.86%)、过铝质(A/CNK为0.97~1.22)等特征,Rb、K、Th等元素相对富集,Ba、Sr、Ti、P等元素明显亏损,稀土元素配分曲线呈右倾的轻稀土元素富集型,具明显负Eu异常(δEu为0.2~0.7),表明岩石为铝质A型花岗岩;(^(87)Sr/^(86)Sr)i为0.710605~0.710608,εNd(t)为-4.94~-5.05,相应的Nd模式年龄t_(DM)为1.83~1.84 Ga,具有大陆上地壳特征,可能为古—中元古代古老基底部分熔融的产物;主量元素CaO、MgO、TFeO、TiO_(2)与SiO_(2)均显示负相关关系,其岩浆演化机制应以结晶分异作用为主。综合来看,娘娘顶花岗岩形成于新元古代伸展背景。Niangniangding granite pluton is located in the middle of Tongbai-Dabie Orogen,and its emplacement age and tectonic environment are still unclear.Niangniangding granite samples were collected to carry out zircon U-Pb geochronology,rock geochemistry and Sr-Nd isotope studies,and to explore the characteristics of magma source area,petrogenesis,tectonic environment and its relationship with Yangxinyan beryllium occurrence.The results show that the zircon U-Pb age of Niangniangding granite is(752.6±9.0)Ma,which belongs to the product of Nanhua magmatism and only constitutes the host rock of Yangxinyan beryllium occurrence.Niangniangding granite has the characteristics of high silicon(SiO_(2) content is 72.56% to 77.26%),rich alkali(Na_(2)O+K_(2)O content is 7.37%to 8.86%)and peraluminous(A/CNK is 0.97 to 1.22).Its Rb,K,Th are relatively enriched,Ba,Sr,Ti and P are obviously losses,and REE distribution curve is right-leaning LREE enrichment type,with obvious negative Eu anomaly(δEu is 0.2 to 0.7),indicating that Niangniangding granite is aluminum A-type granite.Its(^(87)Sr/^(86)Sr)i is 0.710605 to 0.710608,εNd(t)is-4.94 to-5.05,and the corresponding Nd model age t_(DM) is 1.83 to 1.84 Ga,which has the characteristics of upper continental crust and may be the product of partial melting of ancient basement in Early-Middle Proterozoic.Its main elements CaO,MgO,TFeO,TiO_(2) and SiO_(2) show a negative correlation,and the magmatic evolution mechanism should be dominated by crystallization differentiation.On the whole,Niangniangding granite was formed in the Neoproterozoic extensional background.

关 键 词：娘娘顶花岗岩体 锆石U-Pb测年 SR-ND同位素 南华纪 伸展环境 桐柏—大别造山带 

分 类 号：P59[天文地球—地球化学] P619.222[天文地球—地质学]