华北克拉通晚前寒武纪镁铁质岩墙群K－Ar年龄及地质意义

K-ArAges and Their Geologlcalsignificance of Late Precambrian Mafic Dyke Swarms in North China Craton

华北克拉通腹地山西地块内广泛发育大规模的晚前寒武纪镁铁质岩墙群。通过对晋北地区新平堡镁铁质岩墙群９个样品的Ｋ－Ａｒ年龄等时线分析，这些岩墙可能形成于１４３０Ｍａ．从山西各地所采集的６４个镁铁质岩墙群样品的Ｋ－Ａｒ表观年龄统计分析可见，华北克拉通腹地内广泛发育的镁铁质岩墙群主要形成于中元古代１０００～１８００Ｍａ间，活动高峰期在１２００～１６００Ｍａ。

Late Precambrian mafic dyke swarms are extensively found cutting Precambrian rocks inShanxi massif of the centraI North China Craton, The isochron age of nine samples fromthese mafic dykes is l430 Ma, The statistical analysis of 64 K-Ar ages from the area showedthat the major emplacement time is between l000 Ma and l800 Ma,and the summit rangesfrom l200 Ma to l600 Ma, So the mafic dyke swarms were mainly occurred in the Mid-proterozolc.