摘要
伏岭花岗岩体,位于江南造山带东段的皖浙相邻区,岩浆岩沿着近北东向的宁国—绩溪深大断裂断分布。笔者等对伏岭岩体鱼龙川(γ_(5)^(3-2))单元花岗岩开展了系统的全岩岩石地球化学、LA-ICPMS锆石U-Pb同位素年龄和锆石原位Lu—Hf同位素地球化学研究,结果表明,花岗岩的侵位年龄为131.8±0.9 Ma,富硅、富碱、贫钙、贫铁,具有较高的Rb、Th、U、Ga、Zr和Y含量,较低的Sr、Ba和Nb含量,稀土配分曲线呈现典型的“海鸥式”分布特征,显示强烈的负Eu异常;微量元素原始地幔标准化蛛网图显示明显的Ba、Sr、Nb的负异常。其高SiO_(2)含量和Rb/Sr值、低Ba、Sr含量具备江南造山带东段皖南地区A型花岗岩的典型特征。岩体具有同源岩浆演化特征,源区可能存在磷灰石、钛铁矿的分离结晶作用,而辉石类的分离较少。伏岭岩体主要来源于地壳中镁铁质岩石的部分熔融,其地球化学特征继承于源岩。锆石ε_(Hf)(t)变化范围较小,均在-7.0~-4.6之间,二阶段模式年龄(TDM2)为1478~1630 Ma,伏岭花岗岩可能由中元古代古老下地壳部分熔融形成。伏岭岩体的形成可能受到碰撞作用的影响,岩体形成于后碰撞期,中元古代的基底岩石被大范围的熔融,从而产生了伏岭A型花岗岩。
Objectives:The Fuling pluton is a granitic body located in the adjacent area of Anhui and Zhejiang provinces,in the eastern section of the Jiangnan Orogenic Belt.The magmatic rocks are distributed along the Ningguo-Jixi deep fault extending near the NE direction.The research work on the Yulongchuan(γ_(5)^(3-2))unit granite in Fuling pluton has been carried out in this paper.Methods:Based on the field work,we finished microscope observation,whole-rock geochemical analysis,LA-ICP-MS zircon U-Pb dating and in situ Lu-Hf isotope geochemistry for the Yulongchuan(γ_(5)^(3-2))unit granite.Results:The LA-ICP-MS zircon U-Pb dating shows that the emplaced age of the granite is 131.8±0.9 Ma,which is the product of magmatic activity in the late stage of the Jiangnan Orogenic Belt.The pluton is rich in silica and alkali,and poor in calcium and iron.The characteristics of trace elements show that there are higher Rb,Th,U,Ga,Zr and Y contents,and there are lower Sr,Ba and Nb.The rare earth element pattern curve presents a typical"seagull"distribution,showing strong negative Eu anomalies.Negative anomalies of Ba,Sr and Nb are found in the primitive normalized mantle spider map of trace elements.The zirconε_(Hf)(t)of Fuling granite varies from-7.0 to-4.6,and the two-stage model age(TDM2)ranges from 1478 to 1630 Ma.Conclusions:The high SiO_(2)content,Rb/Sr value and low Ba and Sr content show that the Fuling granite has the typical characteristics of the A-type granite in the eastern part of Jiangnan Orogenic Belt,southern Anhui Province.The Fuling pluton has the characteristics of homologous magmatic evolution,and the separation and crystallization of apatite and ilmenite minerals may exist in the source area,while the separation of pyroxene minerals is less.The source rocks of Fuling pluton are mainly derived from partial melting of mafic rocks in the crust,and their geochemical characteristics are inherited from the source rocks.The Fuling granite may have been formed by partial melting of the ancient lower crust in Mesoproterozoic,and its source material is mainly the ancient lower crust.The formation of Fuling pluton may be influenced by collision.The Fuling pluton was formed in postcollision.The Mesoproterozoic basement rocks were melted on a large scale,resulting in the formation of Fuling Atype granite.
作者
郑伟
陈天虎
杜建国
陈芳
丁宁
张舒
ZHENG Wei;CHEN Tianhu;DU Jianguo;CHEN Fang;DING Ning;ZHANG Shu(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei,230009;Geological Survey of Anhui Provice(Anhui Institute of Geological Sciences),Hefei,230001;Technology Innovation Center of Coverage Area Deep Resource Exploration Engineering,Ministry of Natural Resources,Hefei,230001)
出处
《地质论评》
CAS
CSCD
北大核心
2024年第1期189-206,共18页
Geological Review
基金
中国地质调查局“中国矿产地质志项目”(编号:DD20221695、DD20190379、DD20160346)
安徽省公益性地质工作项目(编号:2016-g-1-3)
安徽省自然科学基金资助项目(编号:2208085MD94)的成果。
