地质学报2018，Vol.92Issue(1)：125-141,17.
华北克拉通南缘太华群铁山庙铁矿床沉积时代的约束——锆石U-Pb定年及Hf同位素证据
Depositional Time of the Tieshanmiao Iron Ore Deposit in the Taihua Complex,Southern Margin of the North China Craton:Constraint from Zircon U-Pb Dating and Hf Isotope Evidence
摘要
Abstract
The Wuyang area in the southern margin of the North China Craton (NCC) hosts several large-sized iron deposits,which occur mainly in the early-Precambrian Taihua Complex.The Tieshanmiao iron ore deposit covers most of the Wuyang area,with various sized orebodies distributed mainly in Jingshansi,Lenggang,Tieshanmiao,Tiegukeng and Gangmiaoliu.The Tieshanmiao Formation is major ore-hosting strata.Recently,a large amount of study has been carried out for the Tieshanmiao iron ore deposit,and many workers believe that it belongs to Superior BIF-type iron deposit.But there has been no report about the primary sedimentary age of the Tieshanmiao iron deposit.In this study,migmatitic granite cutting through Tiegukeng orebody and clinopyroxene-biotite-plagioclase gneiss from the roof rock of the orebody were collected to constrain the upper and lower limits of metallogenic deposition time using SHRIMP zircon U-Pb dating and in-situ Hf isotope techonolgy.The results reveal that the zircons of the two samples record two groups of age data,with the error ranges being in consistency.The 207 pb/206pb age of the old group is 2463～2478 Ma,and that of the new group 1918～1961 Ma.Besides,the εHf(t) ranges from-6.96 to-12.83 in the old zircons,and from-7.19 to-15.75 in the new ones,of the migmatitic granite,two of which show consistent ranges,indicating that the old zircons belong to inherited genetic type,and the new ones to metamorphic genetic types.The old ages possibly represent the formation time of the source rock,and the new ages indicate the metamorphic recrystallization time during anataxis process,meaning the age of the formation time of the migmatitic granite.In the clinopyroxene-biotiteplagioclase-gneiss,the εHf(t) value ranges between-0.55 and 2.75 in the old zircons and between-5 and -10.06 in the new zircons.Both of the εHf(t) values differ distinctly,with the age of old detrital zircons constraining the maximum age of protolith rock and the age of new metamorphic growth zircons representing a metamorphic event.Comprehensive analysis shows that the deposition age of the Tieshanmiao iron deposits could be constrained within a range of 2.46～1.96 Ga,most likely at ca 2.30 Ga,and then went through a strong regional metamorphism at ～1.96 Ga.关键词
舞阳铁山庙铁矿/太华群/SHRIMP锆石U-Pb定年/原位锆石Hf同位素/年代学研究Key words
Wuyang Tieshanmiao iron deposit/Taihua Group/SHRIMP zircon U-Pb dating/in-situ zircon Hf isotope/geochronological research引用本文复制引用
孟洁,李厚民,李立兴,李洁茹..华北克拉通南缘太华群铁山庙铁矿床沉积时代的约束——锆石U-Pb定年及Hf同位素证据[J].地质学报,2018,92(1):125-141,17.基金项目
本文为国家自然科学基金项目(编号41672078)和中国地质科学院矿产资源研究所基本科研业务费(编号K1410)资助的成果. （编号41672078）
