深圳市观澜断裂第四纪活动性研究

Quaternary Activity of Guanlan Fault in Shenzhen City

观澜断裂是深圳陆域地区规模最大的北北西向断裂。通过地质地貌调查、联合钻孔探测及地质年代测定等技术方法对观澜断裂的第四纪活动性进行了详细考察与综合研究。结果表明:穿越低丘陵台地地貌区的观澜断裂两侧未见地貌差异或现代构造形变现象;4个典型地质露头和2条钻孔联合剖面显示断裂没有扰动上覆第四系,观澜大布巷钻孔探测剖面还获得了断裂上覆冲洪积砂层底部12.6±2.4 Ka的光释光测年数据;断裂物质主要由碎裂岩、构造角砾岩、硅化岩等组成,可见硅质被膜及半固结岩屑或岩粉状物质;7个断层样品的电子自旋共振测试结果显示断裂的最新活动年龄为距今21.1±2.1万年。结合12条浅层地震测线探测未发现断裂错移第四纪覆盖层底界的事实,得出了观澜断裂最新一次活动发生在中更新世晚期,自晚更新世中期以后没有新的近地表活动的结论。

Guanlan fault is the largest NNW fault in Shenzhen the quaternary activity of Guanlan fault was investigated with city. Based on previous studies, the methods of geological and geomorphic survey, combined borehole detecting, OSL and ESR dating. The results indicate that neither the physiognomy divergence nor the deformation of recent tectonics can be found on both sides of Guanlan fault which cuts across the low hills and tableland region. The fault does not disturb the upper quaternary at four typical geologic observation spots and two boreholes composite profiles. The OSL data of 12.6±2.4Ka was obtained at the bottom of sand which covers the fault. The fracture substances are mainly composed of cataclastie, tectonic greccia and silicificd rocks. Silicic integument and semi-conglutination detritus or meal can be found in the fracture substances. The ESR data of seven samples show that the latest movement of the fault took place at the time of 211±21Ka B.P. Considering the fact that the fault does not incise the quaternary at 12 shallow earthquake detection profiles, the conclusion can be drawn that the latest activity of the fault occurred at the late period of middle Pleistocene and since later Pleistocene, it was lacking in evidence of activity.