东秦岭卢氏盆地最新活动特征及铁炉子断裂尾端构造特点

The latest activity of Lushi Basin in east Qinling and the characteristic of the tectonic at the end of Tieluzi fault

利用区域水系形态研究构造活动特征已有丰富经验,可知铁炉子—栾川—南召断裂带西段——铁炉子断裂,晚更新世以来左旋走滑速率为1.25 mm/a,而东段——栾川—南召断裂则为早—中更新世活动段,2段具有明显的活动性差异,研究二者的构造转换方式,有助于了解块体运动在该断裂带内不同段落间的平衡方式。铁炉子段在洛南盆地分为南北两支,南支断裂下盘发育的冲沟普遍流向北,呈"平行状"水系,而北支断裂下盘发育的冲沟则流向南,并在断层附近有左旋扭动迹象;卢氏盆地中部发育NE走向的沉降中心,剖面分析结果表明,该沉降中心东侧普遍高出西侧70—80 m,结合遥感影像,初步认为卢氏盆地的最新活动或已由盆地边缘向盆地内部迁移,并与铁炉子段尾端组成伸展转换区,最终导致铁炉子断裂与栾川—南召断裂的活动性差异。

Tectonic activity is one of the important factors in influencing regional drainage patterns. Much experience has been acquired by analyzing the relationship between drainage patterns and tectonic activities. The western segment of the Tieluzi-Luanchuan-Nanzhao fault is named Tieluzi fault, which starts in Weihe Basin, heading east to the south of Lushi Basin, and has a strike-slip rate of 1.25 mm/a. By contrast, Luanchuan-Nanzhao fault, the eastern segment of the Tieluzi-LuanchuanNanzhao fault, was active during early-mid Pleistocene. More information about the way to keep a balance of displacement between different segments with different slip rates and the relative movements between the Huabei Block and the Hua’nan Block would be accessible. Parallel water systems are developed on the footwall of the two branches of the Tieluzi fault in the Luonan Basin. One sedimentary center in the Lushi Basin strikes NE and the east of the center is 70— 80 m higher than the west according to profile analysis. Lushi fault has replaced Luohe fault to represent the latest activity in Lushi Basin. Lushi fault and the eastern end of the Tieluzi segment comprise a horsetail structure, leading to the inactivity of the Luanchuan-Nanzhao fault.