摘要
印度板块相对于我国华南地块的向北运动在滇西三江地区造成许多地块发生大规模的顺时针旋转,其中,由于刚性度上的差异,临沧花岗岩基的旋转对邻近地块的影响最为明显,导致兰坪—思茅盆地的大规模缩短和无量山的隆升。无量山的隆升是一系列逆冲断片的叠置造成的,其中,古生界无量山群浅变质岩位于最上部,三叠系麦初箐组含煤砂板岩位于中部,侏罗-白垩系红层位于最下部。在无量山的北东山前散布有许多飞来峰,盖在侏罗-白垩系红层之上,由于这些飞来峰的岩性和无量山群及麦初箐组很相似,前人将其视为推覆体。近年来,笔者针对这些飞来峰的变形和地貌特征以及与无量山的构造关系开展系统研究,认为它们是在重力作用下从无量山滑覆下来的岩块,并在滑覆的过程中岩石发生了掀斜。无量山的顶部山峰大多位于同一高度,十分平坦,代表一次侵蚀夷平事件,这说明在推覆造山之后发生过大规模的侵蚀作用,在此之前无量山要高的多,因此造山带边缘的推覆岩片具有很大的势能,这是重力滑覆作用得以发生的条件。可以推测飞来峰的滑覆发生在造山期后,很可能发生在无量山大规模的侵蚀作用期间,因为在此时大气降水多,山体边坡稳定性差。
Northward movement of the India block relative to the Yangtze block resulted in clockwise rotation of many blocks in the Three-river fold belt of Western Yunnan. Among the rotational blocks, the rotation of the Lincang granitite body is most influential, which insulted in shortening of the Lanping—Simao basin and uplift of the Wuliangshan Mountains due to different hardness between the granite body and the adjacent areas. The Wuliangshan thrust belt is made up by a series of thrust pieces, in which the low-grade metamorphic rock of the Wuliangshan Group is on the uppermost position, the Maichuqing Group is in the middle and J—K red beds at the bottom. At the NE foot of the Wuliangshan Mountains, there are many klippen covering the red beds, which used to be regarded as thrust nappe because their rock types are similar to the Wuliangshan and Maichuqing groups. Our field study about the deformation and topographic features of the klippen and their tectonic relationship to the Wuliangshan thrust belt revealed that the klippen are landslides due to gravity. The flat top of the Wuliangshan Mountains indicates heavy erosion after thrusting, so the Wuliangshan Mountains were much higher than present before erosion. This means that the rocks have great potential energy at the edge of the thrust belt. We deduce that the landslide of the klippen happened during the erosion period, which features heavy rains and instability of the slope.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2005年第3期317-322,共6页
Acta Geologica Sinica
基金
国家"973"项目"印度与亚洲主碰撞带成矿作用"(编号2002CB412600)资助的成果
