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研究区位于大兴安岭晚古生代增生造山带中北段,在漫长的地质演化过程中发生多期次的沉积作用、岩浆作用及变质变形作用,经历了基底形成—岛弧演化—挤压造山—伸展变形—火山活动等多个阶段。以早古生代奥陶系裸河组碎屑岩为研究目标,对其物源及物源区大地构造环境进行探讨。研究表明利用碎屑岩化学成分判断源区构造环境是一种行之有效的方法。选取大兴安岭中北段奥陶系裸河组碎屑岩样品共计7块,对其进行了主量元素、微量元素分析,并采用Bhatia等人建立的标准及图解进行了源区构造环境的讨论。主量元素分析结果显示裸河组碎屑岩具有高SiO2、低Fe2O3、FeO、MgO的特点,表明源区主要为长英质岩石。稀土元素具轻稀土元素富集,重稀土相对亏损,具弱的负Eu异常,与上地壳元素特征类似。微量元素特征指示裸河组碎屑岩源区具有大陆岛弧构造背景及活动大陆边缘构造背景,为大陆岛弧弧后盆地沉积。
The study area is located in the middle-northern section of the Late Paleozoic accretionary orogenic belt in the Greater Hinggan Mountains. During the long geological evolution process, multiple sedimentary, magmatic and metamorphic deformations occurred, and experienced basement formation-island arc evolution-extrusion orogeny-extensional deformation - volcanic activity and other stages. Taking the Early Paleozoic Ordovician Nühe Formation clastic rock as the research target, the geotectonic environment of its provenance and provenance area was discussed. The research shows that it is an effective method to judge the tectonic setting of the source area by using the chemical composition of clastic rocks. A total of seven clastic samples of the Ordovician Member Niuhe Formation in the middle-north section of the Greater Xing’an Mountains were selected for analysis of major and minor elements. Based on the criteria and diagrams established by Bhatia et al., The tectonic environment of the source area was discussed. The main elemental analysis shows that the Bihe Formation clastic rocks have the characteristics of high SiO2, low Fe2O3, FeO and MgO, indicating that the source area is mainly felsic rocks. Rare earth elements with light rare earth element enrichment, heavy rare earth relative loss, with weak negative Eu anomaly, and the upper crustal elemental features similar. Trace element characteristics indicate that the bare river group clastic source area has continental island arc tectonic setting and active continental margin tectonic setting, which is the continental island arc backarc basin.