云南剑川-鹤庆一带新生代推覆构造成因机制分析

THE GENETIC MECHANISM ANALYSIS OF THE NAPPES IN THE JIANCHUAN-HEQING REGION, YUNNAN

通过对剑川 -鹤庆一带地质资料和最新地球物理探测资料综合分析 ,客观地揭示了这一带推覆构造集中发育产生条件和形成机制。由于川滇菱形断块内广为发育的壳内低速层在剑川 -鹤庆一带缺失 ,导致上、下地壳层间滑动在这里受阻 ,致使构造应力在受阻断块前缘产生高度集中 ,古近纪 (早第三纪 )主压应力东西向应力场作用下形成的南北向推覆构造 ,中新世中晚期主压应力为近南北向应力场作用下形成的东西向推覆构造。这一独特的地球动力学环境也是造成这里成为地震多发地的主要原因之一。论文用离散元模拟了这一形成过程。

The Jianchuan Heqing region is located at the northwest of Yunnan Province, where nappes are well developed. There are not only E W strike nappes, but also S N nappes in the region. Unfortunately, the mechanism of the nappes had still been an open question up to the present. Based on the field investigation and composite analyses of geological data and geophysical prospecting data which have been collected from the literature , the authors have solved the genetic mechanism of the nappes in Jianchuan Heqing region, i.e. as the region is lack of the widely developed low velocity zone in the crust of Chuan Dian (Sichuan Yunnan) rhombus fault block, whether in E W stress field or S N stress field in the Cenozoic, the bedding slide between the upper and lower crust is resisted and the tectonic stress is highly concentrated at the Jianchuan Heqing region where the resisted fault block frontier is located, therefore, the upper wall frontier is easily thrusted along existing faults, forming imbricate nappes. This idea not only can be proved by the obvious occurring of geophysical anomaly and basic intrusive activities in the Himalayan, but also can be restorated by the simulation of discrete element.