摘要
通过同位素地质年代学研究初步建立的吕梁山地区早前寒武纪主要地质事件的年代格架是:界河口群形成在2600～2400Ma期间。吕梁群近周峪组火山岩形成在2360～2350Ma期间,2124Ma时野鸡山群白龙山组火山岩喷发。赤坚岭杂岩约在2150Ma时侵位,随后发生了钾质花岗岩的侵入(2031 Ma左右),界河口群和吕梁山群都受到这次构造热事件的影响。芦芽山紫苏花岗岩在1800Ma左右侵位。
Based on the chronological data and relevant geological evidence, the chronological framework of the early Precambrian important geological events in the Luliang area has been established in this paper. There are two types of zircon in the biotite leptynite of the Jiehekou Group. One is detrital zircon with a rounded-ovoid shape and an upper intercept age of 2803±108 Ma, which is interpreted as the formation time of the source rock of the biotite leptynite. The other is metamorphic zircon with a short-prismatic shape and an upper intercept age of 2028\a45 Ma, which represents a later tectono-thermal event. After synthesizing the relationships between various geological events and the results of Sm-Nd isotopic study, the authors put the sedimentary event of the Jiehekou Group in the time span of 2600±2400 Ma. The metabasic volcanics of the Jinzhouyu Formation of the Liiliang Group have a Sm-Nd isochron age of 2351 ± 56 Ma. The magmatic zircons from meta-tuff of the same formation yields a concordia age of 2360±95 Ma. Therefore, the volcanic eruption of the Jinzhouyu Formation of the Luliang Group occurred in the time span of 2360 ±2350 Ma. The 2124 ±38 Ma age of zircons from the meta-tuff of the Bailongshan Formation of the Yejishan Group represents the formation time of the volcanic rocks. The hornblende-plagioclase gneiss and biotite-plagioclase gneiss from the Chijianling complex yield zircon U-Pb concordia ages of 2151 ±12 Ma and 2152±35 Ma respectively, which means that the complex formed at 2150 Ma. The monzonitic granite in the Jiaoloushen area intruded at 2031±47 Ma, and finally charnockite intrusion in the Luyashan area took place around 1800 ± 7 Ma.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2000年第3期216-223,共8页
Acta Geologica Sinica
基金
原地质矿产部重点科技项目(编号950116) 国家自然科学基金(编号49832030)
关键词
早前寒武纪
同位素年代学
地质事件
吕梁地区
early Precambrian
isotopic chronology
geological event
Luliang area
Shanxi Province
