造山带蠕动应力场格局与后造山伸展作用

在理解岩石圈内部流变分层性和造山带热异常形成与演化多控制因素的基础上，建立了造山带热－应力作用数值模型，研究了不同参数下造山带不同部位蠕动应力场的格局及其演化。其研究结果表明，碰撞终止后岩石圈内部应力调整或热松驰控制了造山带内部不同层次构造样式。在造山带中心，加厚岩石圈在碰撞附加力终止后40Ma，岩石圈应力强度明显减少，可诱发科迪勒拉式后造山伸展作用；在地壳中下层次或岩石圈深部（约40～60km、120～150km）可发生拆沉作用，但非岩石圈地幔的整体拆沉，其动力源自岩石圈套内部相应层位的应力引张；在40Ma以内或在拆沉作用发生前，岩石圈地幔根部及地壳中下层次作为热的应变软化区段，相应控制着Moho面形态及中上地壳构造样式；缝合带及造山带前缘作为应力挤压区，在10Ma可出现局部应力引张，孕育喜马拉雅式伸展。但在宽度巨大的造山带（1000km以上），后造山伸展作用的发生则与带内其它大规模构造活化有关。

DISTRIBUTION OF STRESS AND POST-OROGENIC EXTENSION IN COLLISION BELTS

In order to assess the conditions of stress leading to post-orogenic extensions, thetemperature and distribution of stress strength after continental collision are calculated. Thecalculations assume that heat is from radiogenic heat, strain-induced and adiabatic heat andtransported by conduction and either that the lithosphere is homogeneously thickened or thatonly the crust is thickened during collision. Distribution of stress strength and its evolutionat the different parts of collision belts are calculated unger different parameters. Because thestress strength of the lithosphere obviously decreases after homogeneous thickening in 40Maat the center of collision belts, Cordilleras- type extension and delamination at the 40-60 kmand 120-150 km depth due to stretch stress, are possiblly induced. Before delamination,strain-soften mantle-root of the lithosphere and the lower crust control the tectonic style ofMoho and the upper crust. The inner part of compressive stress region, breeding partialstretch stress after thickening between 0 to 10 Ma years, appears Himalayas -typeextension. However, when the width of orogenic belts exceeds by 1000 km, the occurrence ofpost-orogenic extension has relevance to other large-scale tectonic activization in collisionbelts.