Analysis Of Structural Characteristics Of Songjiawopu Area In Chengde,Hebei Province

The study area is located at the northern foot of the middle part of Yanshan Mountains and is under the jurisdiction of Weichang Manchu Autonomous County and Longhua County in Hebei Province.The geotectonic location is located in the northeast of the uplift belt of the northern margin of North China(?A₂²)and the Qipanshan-Sujiadian sedimentary-volcanic basin(?B₃^2-1).There is Shanghuangqi-Lingshan regional fault zone in the west,Kangbao-Weichang regional fault in the north and Shangyi-Longhua regional fault in the south.The Mesozoic tectonic and magmatic activities developed and the mineralization was remarkable.This paper makes a comprehensive analysis of the geological and structural development of the study area by means of field geological survey,combined with geophysical exploration,geochemical survey and remote sensing technology,and then reveals its pattern characteristics.The stratigraphic development of the study area is underdeveloped,and the Mesozoic Cretaceous is widely distributed,accounting for about 2/3 of the total area of the study area.The Zhangjiakou formation,Jiufotang formation and Yixian formation are mainly developed in the Cretaceous,in which the Zhangjiakou formation is mainly composed of acidic-subalkaline volcanic lava and pyroclastic rocks,the Jiufotang formation is mainly a set of lacustrine fluvial deposits,and the Yixian formation is a set of andesite pyroclastic rocks.Secondly,Quaternary sediments dominated by residual alluvial and alluvial sediments are developed in valleys and modern rivers.A small amount of Mesozoic intrusive rocks are sporadically distributed.In the study,the structural form is single,the fold structure is not developed,and only a normal fault(F3)develops along the NE direction in the central region,which runs through the whole region.In addition,according to the results of geophysical and geochemical exploration,it is inferred that there are still 6 faults on the left and right sides of F3 fault,which are F1,F2,F4,F5,F6 and F7,respectively.At the same time,five craters are delineated near faults F2,F1 and F6.According to the results of high-precision magnetic survey,it is analyzed that F1,F2 and F4 faults are distributed along the NE direction,while F5,F6 and F7 faults are distributed along the NW direction with small scale and short extension,and the F5 and F7 faults terminate at the F4 fault.According to the geochemical anomaly distribution map,the anomaly concentration center is consistent with the structural distribution obtained from field geological survey and geophysical exploration and analysis,and the NE-trending fault structure is the main ore-forming site.The geological activities of Zhangjiakou period provide material sources for silver-lead-zinc deposits in this area.