摘要
LA-ICP-MS锆石U-Pb定年结果显示,桂北新寨花岗岩形成于中奥陶世(465±2Ma)。该花岗岩的地球化学特征表现为化学成分较均一,具有高硅(SiO_2=68.54%~74.57%)、富碱(K_2O+Na_2O=7.61%~8.31%)、更富钾(K_2O/Na_2O=1.77~2.35)、强过铝质(A/CNK=1.09~2.39)和富集大离子亲石元素而亏损高场强元素等特征,属于S型花岗岩。新寨花岗岩具有比较均一的Sr、Nd同位素组成(I_(Sr)=0.71137~0.71328,ε_(Nd)(t)=-7.89^-7.26)。锆石Hf同位素组成为:(^(176)Hf/^(177)Hf)_i=0.28232~0.28252,ε_(Hf)(t)=-6.18^+0.61,Hf同位素两阶段模式年龄TDM2变化于1.67~2.11Ga之间。元素及Nd-Sr-Hf同位素分析结果显示,新寨花岗岩可能源自古元古代地壳变质泥岩的部分熔融,在成岩过程中有少量幔源组分的参与。新寨S型花岗岩可能是广西运动第二幕在桂北地区的岩石学响应,为早古生代构造-岩浆群事件的建立提供了新证据。
LA-ICP-MS zircon U-Pb dating shows that the Xinzhai granites,emplaced in northern Guangxi,were generated in Mid?dle Ordovician(465±2Ma).These granites are characterized by uniform silicon content(SiO2=68.54%~4.57%),enrichment of alkali val?ues and considerable enrichment of K values(K2O+Na2O=7.61%~8.31%,K2O/Na2O=1.77~2.35),concentration of peraluminous(A/CNK=1.09~2.39)and high large ion lithophile elements(LILE)(e.g.,Rb,K,Th)but relative depletion of high field-strength el?ements(HFSE)(e.g.,Nb,Ta,P,Ti)and Sr.They belong to S-type granite.Granitic samples have homogeneous Sr-Nd isotopecompositions(ISr=0.71137~0.71328,εNd(t)=-7.89^-7.26).Zircon Hf isotope compositions of the Xinzhai granites have relativelywide ranges(176Hf/177Hf=0.28232~0.28252,εHf(t)=-6.18^+0.61,TDM2=1.67~2.11Ga).The authors hold that the Xinzhai granites werelikely generated by partial melting of Paleoproterozoic metapelite,with the addition of small amounts of mafic magma mantle-derivedmaterial.The Xinzhai S-type granites might have been the petrological response to the second activity of the Kwangsian orogen innorthern Guangxi,which provided new evidence for the establishment of the Early Paleozoic tectonic-magma events in South China.
作者
贾小辉
王晓地
杨文强
JIA Xiaohui;WANG Xiaodi;YANG Wenqiang(Wuhan Center of Geological Survey, CGS, Wuhan 430223, Hubei, China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks, CGS, Wuhan 430223, Hubei, China)
出处
《地质通报》
CAS
CSCD
北大核心
2017年第5期738-749,共12页
Geological Bulletin of China
基金
国家自然科学基金项目《粤北罗岗钾玄质侵入岩的岩石成因及其动力学意义》(批准号:41302046)
中国地质调查局项目《南岭关键地区区域地质调查》(编号:12120113063600)和《国家地质数据库建设与整合》(编号:1212011220512)
关键词
中奥陶世
S型花岗岩
SR-ND-HF同位素
广西运动
桂北
Middle Ordovician
S-type granite
Sr-Nd-Hf isotope composition
Kwangsian orogen
northern Guangxi
作者简介
贾小辉（1980- ），男，硕士，助理研究员，岩石地球化学专业。E-mail: jxh1226@126.com;王晓地（1974- ），男，博士，高级工程师，从事岩石学和矿床学研究。E-mail: 178372234@qq.com
