摘要
大兴安岭地区是中亚造山带构造演化的重要区域,其中关于古亚洲洋的闭合时限以及额尔古纳-兴安地块和松嫩地块的拼贴时空关系一直存在争议。本文对大兴安岭北段扎兰屯地区晚古生代海相火山岩进行了年代学和地球化学的研究,显示扎兰屯大民山组安山岩U-Pb锆石年龄为362.2±3.3Ma,结合古生物资料,大民山组火山岩喷发时代应为晚泥盆世法门期。大民山组基性火山岩具有高Al2O3、TiO2和Mg^#的特点,稀土、微量元素特征与板内洋岛玄武岩（OIB）特征一致;中酸性岩石具有高Al2O3,低TiO2和Mg~#的特点,稀土、微量元素特征反映出具有弧火山岩性质。综合年代学和地球化学特征,确定了扎兰屯地区发育有洋岛玄武岩,并同时存在中酸性弧火山岩的特点,说明晚泥盆世古亚洲洋在扎兰屯地区正处于闭合阶段,早期存在陆间洋盆,后期洋-陆碰撞作用持续发生而形成活动大陆边缘,也为贺根山-扎兰屯-嫩江缝合带北延及古亚洲洋构造域演化提供了新的基础地质资料。
Great Xing＇an range is a key area to theevolution of Central Asia Orogenic Belt（CAOB）,where some debates,such as the closure time of Paleo-Asian Ocean and the suturing time and space relationship between Erguna-Xing＇an and Songnen block,still remain controversial till today.This study carrys out the U-Pb dating and geochemical analysis on the basis of researches on late Paleozoic sea face volcanic.The result shows that the andesite age of Daminshan Formation at Zhalantun area is 362.2±3.3Ma.Combining with the paleontology data,it is suggested that the explosion time of Daminshan Formation volcanic rock is in late Devonian epoch Famennian.The geochemical characteristics of the basic volcanic rock of Daminshan Formation are high content of Al2O3、TiO2and Mg^#,and the features of REE and trace elements are similar with Ocean Island Basalt（OIB）.Those of the felsic rocks are high content of Al2O3,but low content of TiO2 and Mg^#,and the REE and trace elements patterns reveal a volcanic arc characteristic.Compositing geochronology and geochemistry information we conclude that ocean island basalt had developed at Zhalantun area,and middle to felsic volcanic arc rocks are present,which suggest that the Paleo-Asian Ocean was at closing period at Zhalantun area during late Devonian epoch. The intercontinental sea basin existed at early period,and after that the active continental margin formed due to the collision of ocean and continent slabs in the late stage.The results here provide new geological information to the evolution of northward extension of Hegenshan-Zhalantun-Nenjiang suture and PaleoAsian Ocean tectonic domain.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第10期2706-2720,共15页
Acta Geologica Sinica
基金
中国地质调查局地质调查区调项目(No.1212011120664
1212011120665
1212011120666
1212010781031
12120113053900
121201007000150008-4)联合资助
关键词
大兴安岭北段
晚古生代
海相火山岩
U-PB年代学
地球化学
构造环境
Northern DaHinggan Mountains
late Paleozoic
marine volcanic
U-Pb geochronology
geochemistry
tectonic environment
