摘要
最古老大陆地壳的形成、组成和演化是阐释地球壳幔物质分异、构造演化的逻辑起点。由于长期地质作用改造,地球上保存的古老陆壳物质十分稀少,寻找和研究都极具挑战性。在冀东卢龙喇叭山地区,早期研究发现含有大量3.4~3.8 Ga碎屑锆石的铬云母石英岩,岩石特征和碎屑锆石年龄分布与迁安黄柏峪地区的铬云母石英岩十分类似。本文对喇叭山地区与铬云母石英岩共生的变质碎屑沉积岩进行了锆石定年。黑云斜长片麻岩(J2006)94个数据点分析,碎屑锆石普遍显示强烈铅丢失,数据点主要沿上交点年龄为~3.8 Ga和~3.45 Ga的两条不一致线分布。获得3084±6 Ma的变质锆石年龄。长石石英岩(J2009)68个数据点分析,除大量3.4~3.8 Ga碎屑锆石外,还发现3.92~4.0 Ga碎屑锆石(6颗)。始太古代早期—冥古宙碎屑锆石的发现表明华北克拉通无疑存在4.0 Ga以上的形成演化历史。本文新定义的曹庄-喇叭山岩系形成于3.1~3.4 Ga之间,主要由变质碎屑沉积岩和变质基性-超基性岩组成,可能代表了地幔柱与大陆壳相互作用的构造环境。根据碎屑锆石形态特征和不同样品碎屑锆石年龄分布存在差异,物源区具有近源和规模大的特征,存在3.92~4.0 Ga、3.8 Ga、3.6~3.7 Ga和3.4~3.45 Ga等不同期次花岗质岩浆作用。
The formation,composition and evolution of the oldest continental crust is the logical starting point for discussing the differentiation and development of the crust-mantle system of the Earth.However,the rarity of preserved ancient continental crust due to its long-term reworking make this research extremely challenging.Fuchsite quartzite with abundant 3.4~3.8 Ga detrital zircons have been discovered in early study in the Labashan area,Lulong,which is very similar in rock feature and detrital zircon age distribution to that in the Huangbaiyu area,Qian’an.This study carried out SHRIMP U-Pb dating on zircons from meta-sedimentary rocks associated with fuchsite quartzite in the Labashan area.Ninety-four analyses on zircons from biotite plagioclase gneiss(J2006)reveal that detrital zircons commonly show strong lead loss with data being mainly distributed along two discordant lines with upper intercept ages of 3.8 Ga and 3.45 Ga.An age of 3.08 Ga was obtained for metamorphic zircons.In feldspar quartzite(J2009)for which 68 analyses have been finished,six detrital zircons of 3.92~4.0 Ga have been identified together with abundant 3.4~3.8 Ga detrital zircons.The discovery of early Eoarchean to Hadean detrital zircons assuredly indicates that the North China Craton has a long-term history of formation and evolution up to 4.0 Ga.The 3.1~3.4 Ga Caozhuang-Labashan rock series defined in this study is mainly composed of meta-sedimentary rocks and meta-mafic to ultramafic rocks,suggesting an environment of plume-continental crust interaction.In terms of the shape features of detrital zircons and the different age distribution of abundant ancient detrital zircons from different samples,it is speculated that the source region from which the detrital materials were derived is at short range and in a large scale,and contains multiple granitic magmatism at the periods of 3.92~4.0 Ga,3.8 Ga,3.6~3.7 Ga and 3.4~3.45 Ga,respectively.
作者
万渝生
颉颃强
王惠初
刘守偈
初航
肖志斌
李源
郝光明
李鹏川
董春艳
刘敦一
WAN Yusheng;XIE Hangqiang;WANG Huichu;LIU Shoujie;CHU Hang;XIAO Zhibin;LI Yuan;HAO Guangming;LI Pengchuan;DONG Chunyan;LIU Dunyi(Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037;Tianjin Center of Geological Survey,China Geological Survey,Tianjin,300170)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2021年第2期277-291,共15页
Acta Geologica Sinica
基金
国家自然科学基金重大项目(编号41890834)
国家自然科学基金项目(编号41890834,41772200)
中国地质调查局项目(编号DD20190009,DD20190358,DD20190370,DD20190003)资助成果。
