雪峰山西部中生代厚皮逆冲推覆构造样式与变形特征研究

雪峰山厚皮逆冲推覆构造带位于扬子地块东南缘,由南向北,主构造线走向由北北东向渐变为北东东向,形成向北西突出的弧形。构造带内基底新元古界板溪群大面积出露,这些基底出露的原因和构造方式是华南中生代大地构造分析的核心问题之一。以野外构造解析为基础,结合相关地球物理资料解释,对雪峰山西部逆冲推覆构造的构造样式与变形序列进行了系统的解析。结果表明,雪峰山构造带从印支期开始发育由南东向北西的大规模的逆冲推覆构造,逆冲断层在近地表向南东陡倾,向下逐渐收敛于基底内的滑脱断层之上。基底新元古界板溪群及早古生界均卷入了推覆构造,同时逆冲覆盖于中生代地层之上,形成厚皮构造,并造成了基底板溪群的大面积出露。

Structural Style and Deformational Characteristics of the Thick-skinned Thrust Belt in the Western Xuefeng Mountain

A thick-skinned thrust belt is located at the western edge of Xuefeng Mountain.The folds axis and faults are mainly NNE strike to the south portion of the thrust fault belt,and strike to NEE to the north.The basement of Proterozoic Banxi Group is occurred in large area of the thick-skinned thrust belt.While the reasons why the basement strata — Banxi Group occurred in Xuefeng Mountain and the structural styles of the Banxi Group are the key problems to analyze the Mesozoic tectonic of South China.In this paper,we focused and studied the geometry and kinematics of the thick-skinned thrust faults,and interpretation of the data of seismic section and magnetotelluric sounding along Fenghuang-Huaihua tectonic section.We recognized that the thick-skinned thrust faults were activated and moved from southeast to northwest during the Indosinian-Yanshanian stage,and the faults dip to SE and the dip angles appear steep near surface,while to the underground they get together and turn to a main basement fault.The sub back thrust faults are popularly scattered in the hanging wall.The basement of Banxi Group and Early Paleozoic strata are involved in the over thrust fault belt,known as the thick-skinned thrust,resulting into large occurrence of the besement of Banxi Group.