甘肃北山泥盆系三个井组的沉积特征及大地构造环境——构造体制转换时期的沉积响应  

Research on sedimentary characteristics and tectonic setting of Devonian Sangejing Formation in Beishan,Gansu Province

作　　者：梁积伟[1] 冯振伟 丁金刚[2] 马晓军 陶文星 刘亚兰 宇振昆 姜柳青 常小斌 Liang Jiwei;Feng Zhenwei;Ding Jingang;Ma Xiaojun;Tao Wenxing;Liu Yalan;Yu Zhenkun;Jiang Liuqing;Chang Xiaobin(College of Earth Science and Rescources,Chang'an University,Xi'an 710054;No.4 Oil Production Plant of Changqing Oilfield Branch,Yulin,Shanxi 718500)

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]长庆油田第四采油厂,陕西榆林718500

出　　处：《地质科学》2020年第4期1012-1024,共13页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：第二次青藏高原综合科学考察研究项目(编号:2019QZKK0704)资助。

摘　　要：北山地区泥盆纪是古亚洲洋由板块体制向板内体制转变的关键时期,晚古生代旱山微大陆与塔里木板块发生碰撞造山作用,两个板块拼接在一起,形成统一大陆。沿红柳河—牛圈子—洗肠井一带形成古生代蛇绿岩,在蛇绿岩带南部为平头山推覆构造。作为这次碰撞的沉积响应,在墩墩山一带形成厚度巨大,横向变化极大的三个井组。通过对三个井组岩性特征和沉积建造的分析研究,认为三个井组整体属于磨拉石建造,其沉积盆地性质为周缘前陆盆地;岩性显示快速堆积的特征,物源区主要为北部逆冲推覆带;垂向层序由下向上表现为粗—细—粗的序列,代表了一个完整的前陆盆地沉降—沉积构造旋回。结合前人的锆石U-Pb测年结果,三个井组的沉积时间应始于晚志留世,而早于晚泥盆世,由此表明北山地区晚古生代的造山作用始于晚志留世,至晚泥盆世,已经完成板块拼接。Devonian of Beishan region was a critical period of the ancient Asian oceanic plate system turned to the inner plate institution,Hanshan micro-continent collided with Tarim plate then occurred orogenesis in the Late Paleozoic,the two plates spliced together to form a unified continent.Paleozoic ophiolite formed along the Hongliuhe-Niujuanzi-Xichangjin,in the south of ophiolite belt was the Pingtoushan nappe structures.As the depositional response of this collision,a huge thickness and lateral varying Sangejing Formation occurred in the Dundunshan region.Through the analysis of the lithological characteristics and sedimentary construction of the Sangejing Formation,we considered that it belonged to Molasse entirely,and the nature of the sedimentary basin was peripheral foreland basin;lithological characteristics showed a rapid accumulation,and the main source area was northern orogenic belt.Vertical sequence is coarse-fine-coarse sequence from bottom to top,which represented a complete foreland basin depression-sedimentary tectonic cycle.Combined with previous zircon U-Pb dating results,the deposition time of Sangejing Formation began in the Later Silurian,yet earlier than Later Devonian,which show that the Late Paleozoic orogenesis of Beishan began in Later Silurian,it has completed the plate splicing till the Late Devonian.

关 键 词：三个井组 磨拉石 碰撞造山 前陆盆地 甘肃北山 

分 类 号：P618.13[天文地球—矿床学]