华北克拉通古元古代条带状铁建造同位素年代学研究进展  

Advances in isotopic chronology of Paleoproterozoic banded iron formations in North China Craton

作　　者：唐荣贞 陈衍景[1] TANG RongZhen;CHEN YanJing(MOE Key Laboratory of Crustal and Orogenic Evolution,Peking University,Beijing 100871,China)

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2024年第11期3663-3684,共22页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(U2244206、U1906207)资助.

摘　　要：世界超大型富铁矿床多为前寒武纪条带状铁建造(BIF)。其中,70%以上的铁形成于成铁纪(2.5~2.3Ga),规模超过10^(5)Gt的铁建造也主要形成于成铁纪,且为Superior型。然而,华北克拉通BIF总体被视为太古宙(>2.5Ga)Algoma型,缺乏成铁纪甚至古元古代Superior型BIF。本文系统搜集和分析了华北克拉通BIF的锆石年龄数据,初步确定太华群铁山庙组、荡泽河群铁山岭组、济宁群颜店组、五台群金岗库组、文溪组、柏枝岩组、大青山地区表壳岩系中的BIF形成于成铁纪;粉子山群小宋组、霍邱群吴集组、周集组中的BIF年龄数据跨越了成铁纪-层侵纪界线,但可能属成铁纪;吕梁群袁家村组、水底沟群孔兹岩系中的BIF形成于层侵纪;嵩山群五指岭组、阜平湾子群中BIF形成于造山纪。五台群中BIF属于Algoma型,其他属于Superior型。古元古代早期,生命活动和生物光合作用显著增强,海洋整体由还原向氧化状态过渡,导致大量Fe(Ⅱ)被氧化为Fe(Ⅲ),全球BIF爆发式沉积。华北克拉通BIF赋矿地层碎屑锆石记录了2.99~2.94Ga、2.76Ga、2.54Ga三次主要的岩浆活动及陆壳增生事件,以2.54Ga岩浆活动最强烈。华北克拉通新太古代末期及古元古代早期稳定性较差,不利于大规模克拉通盆地形成,造成了华北克拉通成铁纪BIF铁矿规模小、品位低。The world s superlarge iron deposits are mainly Precambrian banded iron formations(BIFs),with>70%Fe being formed in Siderian(2.5~2.3Ga).The BIFs with size exceeding 10^(5)Gt were mostly formed in the Siderian and belong to the Superior-type.However,the BIFs in North China Craton(NCC)have been commonly believed to be Archean(>2.5Ga)Algoma-type,lacking Paleoproterozoic(especially Siderian)Superior-type.In this contribution,the authors collect and reassess the zircon U-Pb age data of the BIFs in NCC,and conclude that the BIFs in the Tieshanmiao Formation of Taihua Group,Tieshanling Formation of Dangzehe Group,Yandian Formation of Jining Group,Jingangku,Wenxi,Baizhiyan Formations of Wutai Group and supracrustal rocks of Daqingshan area were formed in the Siderian.The BIFs age of the Xiaosong Formation of Fenzishan Group,Wuji and Zhouji Formations of Huoqiu Group span the Siderian-Rhyacian boundary,but they were most likely formed in the Siderian.The BIFs in the Yuanjiacun Formation of Lüliang Group,khondalite series of Shuidigou Group were formed in the Rhyacian,and those in the Wuzhiling Formation of Songshan Group,Wanzi Group in Fuping area formed in the Orosirian.The BIFs in the Wutai Group belong to Algoma-type,while the other BIFs are Superior-type.In the Early Paleoproterozoic,microbial processes and biological photosynthesis remarkably enhanced,the ocean changed from reducing to oxidic or sub-oxidic,and meanwhile,a large amount of Fe 2+was oxidized to Fe 3+,and subsequently deposited as global BIFs.Detrital zircons from the BIF-bearing strata in NCC recorded three significant magmatic and continental crust accretion events at 2.99~2.94Ga,2.76Ga,and 2.54Ga,respectively.The crustal accretion event at 2.54Ga is the most intense.The instability of the NCC in the late Neoarchean and Early Paleoproterozoic makes it difficult to form large-scale cratonic basins may be the main reason for the low reserves and grade of Siderian BIFs in China.

关 键 词：古元古代大氧化事件 BIF型铁矿 锆石U-PB年龄 物质来源 华北克拉通 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学] P618.31