摘要
本文报道了安徽洪镇地区董岭群片麻岩中高精度的独居石SIMS U-Th-Pb定年结果,以^(207)Pb含量为基准对普通Pb进行校正后得到^(206)Pb/^(238)U的加权平均年龄为128.4±0.7 Ma(MSWD=1.6),^(208)Pb/^(232)Th年龄的加权平均值为128.6±0.4 Ma(MSWD=1.4)。作者认为独居石的SIMS U-Th-Pb年龄(128.4±0.7 Ma)代表了董岭群片麻岩的前进变质年龄。综合区域地质资料,提出董岭群片麻岩为新元古代沉积物在中生代经岩浆热动力接触变质的产物。这一发现不仅否定了前人提出的董岭群为前寒武纪区域变质地体的观点,而且否定了这一地区的"洪镇变质核杂岩",对进一步研究中国东部零星出露的中高级片麻岩的大地构造属性和构造演化具有借鉴意义。
Geochronological investigation was carried out on monazite in the gneiss from the Dongling Group atHongzhen,Anhui province.Sixteen SIMS analyses yield U contents of334–949μg/g,Th of1223–62990μg/g,andTh/U of1.57–135.76.After207-based common Pb correction,the weighted average206Pb/238U age is128.4±0.7Ma(MSWD=1.6),the independent Th-Pb ages averaged at128.6±0.4Ma(MSWD=1.4).The weighted average206Pb/238Uage is interpreted as pro-metamorphic time of the Neoproterozoic Dongling Group.The dating results along withprevious geological investigations suggest that the metamorphism of the Dongling Group is magmatic dynamicmetamorphism.This study not only provides key evidence to deny the view that Dongling Group is Precambrianregional metamorphic block and the Mesozoic structure of Hongzhen is metamorphic core complex,but also provides areference to research tectonic of gneisses in other areas in East China.
作者
王继林
何斌
WANG Jilin;HE Bin(Shandong Bureau Testing Center of China Metallurgical Geology Bureau, Jinan 250014, Shandong, China;Faculty of Earth Science, China University of Geoscience, Wuhan 430074, Hubei, China;State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640,Guangdong, China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2017年第4期777-784,共8页
Geotectonica et Metallogenia
基金
中国科学院知识创新项目(KZCX2YW128
KZCX1YW151)
国家自然科学基金(41173037)联合资助
关键词
董岭群
独居石SIMSU-Th-Pb定年
变质时代
变质机制
变质核杂岩
岩浆底辟成因
Dongling Group
SIMS U-Th-Pb dating of monazites
pro-metamorphic time
metamorphic mechanism
metamorphic core complex
magmatic diapiric structure
