华南中生代玄武岩地球化学特征及其地球动力学意义  

Geochemical Characteristics and Geodynamic Significance of Mesozoic Basalts in South China Block

作　　者：李赛 段先哲 牛苏娟 李南 孙浩然 吴鹏 戴浩橦 郭聪 丁心科 LI Sai;DUAN Xianzhe;NIU Sujuan;LI Nan;SUN Haoran;WU Peng;DAI Haotong;GUO Cong;DING Xinke(School of Resource&Environment and Safety Engineering,University of South China,Hengyang,Hunan 421001;Hunan Key Laboratory of the Rare Metal Minerals Exploitation and Geological Disposal of Wastes,Hengyang,Hunan 421001;College of Chemistry and Chemical Engineering,University of South China,Hengyang,Hunan 421001;No.262 Team,Zhejiang Provincial Nuclear Industry,Huzhou,Zhejiang 313000)

机构地区：[1]南华大学资源环境与安全工程学院,湖南衡阳421001 [2]稀有金属矿产开发与废物地质处置技术湖南省重点实验室,湖南衡阳421001 [3]南华大学化学化工学院,湖南衡阳421001 [4]浙江省核工业二六二大队,浙江湖州313000

出　　处：《地质与勘探》2022年第5期1001-1015,共15页Geology and Exploration

基　　金：湖南省自然科学基金(编号:2017JJ3261);南华大学创新科研项目(编号:202110555075,X202010555338);南华大学人才项目(编号:2018XQD22)联合资助。

摘　　要：华南板块是中国东部岩石圈的重要组成部分,广泛发育中生代玄武岩,这些玄武岩为研究华南岩石圈演化提供了重要的窗口。前人对华南中生代玄武岩开展了大量的研究,但是对于玄武岩的源区性质以及构造环境等认识仍存在较大争议。本文系统性分析了华南宁远、道县、长城岭、白面山、汝城等地区中生代玄武岩的主微量元素及Sr-Nd-Pb同位素组成,获得如下主要认识:(1)华南中生代玄武岩主要由碱性和亚碱性玄武岩组成,其SiO_(2)和全碱(Na_(2)O+K_(2)O)含量分别为42.81 wt%~55.54 wt%和1.6 wt%~5.97 wt%;(2)除了宁远玄武岩具有OIB微量元素特征,华南中生代玄武岩具有岛弧玄武岩相似的微量元素配分型式;(3)主量和微量元素特征表明华南中生代玄武岩的形成主要受控于部分熔融,且在岩浆演化过程中经历不同程度的分离结晶作用,未遭受明显的地壳混染作用。Ni-MgO正相关、CaO/Al_(2)O_(3)-CaO正相关和Eu无明显异常表明华南中生代玄武质岩浆经历了橄榄石和单斜辉石结晶,但无明显的斜长石结晶;(4)Sr-Nd-Pb同位素特征表明华南中生代玄武岩为EMⅡ地幔源区,其源区可能有洋壳沉积物的参与;(5)华南中生代玄武岩可能形成于与古太平洋板块俯冲相关的大陆板内环境;(6)华南岩石圈改造可能与中生代古太平洋俯冲板块的交代作用有关,后者所释放的酸性熔体/流体与地幔橄榄岩相互作用,最终造成了华南岩石圈物理化学性质的强烈改变;(7)古太平洋俯冲板块可能对华南有色金属、稀有金属等多金属成矿发挥着重要作用,其释放的熔体或流体为矿石活化和迁移提供了重要的驱动力。The South China Block(SCB),as an important part of the lithosphere in the eastern China,has extensive distribution of Mesozoic basalts.These basalts provide an important window to reveal the lithospheric evolution of the SCB.Previous researchers have extensively studied the Mesozoic basalts from the SCB,but the magma source and tectonic setting of these basalts have been still controversial.In this paper,the major and trace elements and Sr-Nd-Pb isotopic compositions of the basalts from the typical regions in the SCB,such as Ningyuan,Daoxian,Changchengling,Baimianshan,Rucheng,were systematically analyzed,and the following main understandings were obtained:(1)The Mesozoic basalts in the SCB are mainly alkaline and sub-alkaline basalts,with the SiO_(2) and total alkali(Na_(2)O+K_(2)O)contents of 42.81 wt%~55.54 wt%and 1.6 wt%~5.97 wt%,respectively.(2)Except for the Ningyuan basalts with OIB-like trace element features,the Mesozoic basalts from the SCB have the distribution patterns resembling the island arc basalts.(3)The characteristics of major and trace elements show that the formation of Mesozoic basalts from the SCB was mainly controlled by partial melting,and experienced different degrees of fractional crystallization during the magmatic evolution process,with no obvious crustal contamination.The positive correlation of CaO/Al_(2)O_(3)-CaO and Ni-MgO,as well as no obvious abnormality of Eu,indicates that the Mesozoic basaltic magma might experience olivine and clinopyroxene crystallization,but no significant plagioclase crystallization.(4)The Sr-Nd-Pb isotopic characteristics of the Mesozoic basalts from the SCB indicate that these basalts was originated from EMII mantle,with possible involvement of oceanic crust sediments.(5)The Mesozoic basalts from the SCB might be formed in the intraplate setting related to the subduction of the paleo-Pacific Plate.(6)The lithospheric transformation of the SCB may be related to the metasomatism of the Mesozoic subducted paleo-Pacific Plate,from which the released acidic m

关 键 词：华南板块 岩石圈演化 中生代玄武岩 古太平洋俯冲板块 有色金属 稀有金属 

分 类 号：P595[天文地球—地球化学]