论文部分内容阅读
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Al_2O_3、TiO_2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Al_2O_3,低TiO_2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。
The Daxinganling area is an important area for tectonic evolution of the Central Asian orogenic belt. The time-space relationship between the closing time of the ancient Asian oceans and the Ergun-Xingan block and the Songnen block has been controversial. In this paper, the study of the Paleozoic marine volcanic rocks in the Zhalantun area in the northern section of the Greater Hinggan Mountains shows that the U-Pb zircon ages of the Andesite of the Damonthan Formation in Zhalantun are 362.2 ± 3.3Ma. According to paleontological data, The volcanic eruption age of the Min Shan Formation should be the Late Devonian Famennian period. The basic volcanic rocks in the DaMenShan Formation have the characteristics of high Al 2 O 3, TiO 2 and Mg ~ #. The characteristics of REE and trace elements are consistent with those of the plate oceanic basalts (OIB). The moderately acidic rocks have high Al 2 O 3, low TiO 2 and Mg ~ # Features, rare earth, trace elements reflect the characteristics of arc volcanic rocks. According to the integrated geochronology and geochemical characteristics, it is confirmed that there are oceanic island basalts in the Zalantun area, and the characteristics of intermediate-acid arc volcanic rocks exist at the same time. It shows that the Upper Devonian Paleo-Asian Ocean was in the closed stage in the Zhalantun area and existed in the early stage The inter-oceanic basin and the subsequent ocean-continent collision continue to occur and form the active continental margin. It also provides new basic geological data for the evolution of the Heyuanshan-Zhalantun-Nenjiang suture northward and the paleo-Asian ocean tectonic evolution.