大兴安岭南部敖仑花地区阴佩岩体花岗斑岩年代学、地球化学及铪同位素研究  

Early Cretaceous Granite Porphyry in Yinpei Rock Mass of Aolunhua Area,Southern Part of the Great Xing’an Range:Geochronology,Geochemistry and Hf isotope studies

作　　者：李永红 LI Yonghong(Research Institute No.240,CNNC,Shenyang,Liaoning110000,China)

机构地区：[1]核工业二四〇研究所,辽宁沈阳110000

出　　处：《世界核地质科学》2023年第2期236-248,共13页World Nuclear Geoscience

基　　金：国家自然科学基金项目(编号:42172329、41972080);江西省技术创新引导类计划(编号:20212AEI91008);中国铀业有限公司-东华理工大学核资源与环境国家重点实验室联合创新基金(编号:NRE2021-08)联合资助。

摘　　要：大兴安岭南段敖仑花地区阴佩岩体花岗斑岩锆石呈自形-半自形状,清晰的震荡生长环带,较高的w(Th)/w(U)值(0.34~0.83),暗示其为岩浆成因锆石。LA-ICP-MS锆石U-Pb的206Pb/238U加权平均年龄为131.3±1.2 Ma(n=15,MSWD=2.4),形成时代为早白垩世晚期;花岗斑岩中SiO2含量介于71.44%~72.00%之间,K_(2)O含量介于3.48%~4.14%之间,Na_(2)O/K_(2)O值介于0.83~1.17之间,铝饱和指数A/CNK介于1.12~1.32之间,属于高钾钙碱性系列、过铝质花岗岩类。微量元素显示为富集大离子亲石元素铷、钾和活泼不相容元素钍、铀,强烈亏损高场强元素铌、钽、磷和钛等,10000 Ga/Al值介于2.19~2.54(均值2.42)之间,Zr+Nb+Ce+Y值均小于350×10^(-6),判断该岩石为I型花岗岩。锆石176Lu/177Hf比值介于0.000875~0.001545之间,176Hf/177Hf介于0.282735~0.282966之间,εHf(t)值介于1.5~9.6之间,对应的单阶段模式年龄tDM=407~738 Ma,第2阶段模式年龄tDM2=752~1494 Ma,暗示其来源于新元古代新生地壳部分熔融的产物。结合区域构造演化背景,花岗斑岩体的形成与早白垩世晚期古太平洋板块斜向俯冲于欧亚大陆之下的弧后伸展作用有关。The zircon from granite porphyry in Aolunhua area,southern part of the Great Xing’an Range is authigenic-semi-authigenic in shape,with clear oscillatory growth rings and high w(Th)/w(U)values(0.34-0.83).The zircon’s LA-ICP-MS U-Pb has a 206Pb/238U weighted mean age of 131.3±1.2 Ma(n=15,MSWD=2.4)(Late Early Cretaceous).The SiO2 contents of granite porphyry is from 71.44%to 72.00%,K_(2)O=3.48%-4.14%,Na_(2)O/K_(2)O=0.83-1.17,A/CNK=1.12-1.32,which belongs to high potassium-calcium alkaline and peraluminous granite series.The granite enriched in trace elements Rb,K,Th and U,strongly depleted in elements Nb,Ta,P and Ti.The 10000 Ga/Al values ranges from 2.19 to 2.54(mean=2.42),and Zr+Nb+Ce+Y values are less than 350×10^(-6),suggesting an I-type granite.The 176Lu/177Hf value is from 0.000875 to 0.001545,and the 176Hf/177Hf value is from 0.282735 to 0.282966.The corresponding zircon U-Pb dating calculate forεHf(t)=1.5-9.6,and the first-stage Hf mode age is tDM=407-738 Ma,and the second-stage Hf mode age is tDM2=752-1494 Ma,which indicates that the granite porphyry was derived from the partial melting of the Neogene-Cenozoic crust.Based on the regional tectonic evolution,the formation of granite porphyry was related to the postarc extension resulting from the ancient Pacific-Ocean plate subduction to the Eurasian continent in the Late Early Cretaceous.

关 键 词：花岗斑岩 地球化学 锆石U-PB年代学 大兴安岭 

分 类 号：P581[天文地球—岩石学] P618.65[天文地球—地质学]