The characteristic and transfer model of Micang Mountain structural transfer zone
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摘要: 米仓山构造带被北东走向的龙门山陆内复合造山带及北北西走向的大巴山前陆冲断带夹持于其间,两个构造带平面上组成一个“八”字形构造,空间上为一个向北收敛,向南发散背倾型的Ⅰ型三角带构造。在两大构造带前展式扩展变形晚期的过程中,米仓山则起到调节这两大构造带构造平衡的作用,因此为一构造转换带。米仓山构造转换带由北向南可以分为基底冲断隆起带、南缘滑脱变形带、川北类前陆盆地平缓褶皱带。基底冲断隆起带与川北类前陆盆地平缓褶皱带,在调节两侧造山带构造平衡时表现出明显的差异性。米仓山基底隆冲断带,由于其岩石的刚性,主要是发育脆性的断裂作用,通过垂向上的抬升,横向上的缩短来调节构造平衡。而川北类前陆盆地平缓褶皱带,岩石能干性较基底岩石弱,主要是通过北东走向及北西走向的褶皱作用、少量北西走向的断层作用和垂向上相对下降作用等调节来自两侧造山带的构造平衡。通过对米仓山构造转换带的构造特征分析表明,米仓山岩石的物理性质及先存的基底隆起构造是导致其变形差异性的主因,构造缩短量及缩短率是其次因。Abstract: Micang Mountain structure belt,locating between the NEstriking Longmen Mountain intracontinental composite orogenic belt and the NWstriking Daba Mountain forelandthrust belt,forms a triangle structural zone,like Chinese eight,which is converge to north and diverge to south.Micang Mountain structure belt plays as an important structural transfer zone in adjusting structural balance between the Longmen Mountains intracontinental composite orogenic belt and the Daba Mountain forelandthrust belt in the process of piggyback deformation.Micang Mountain structural transfer zone can be divided to basement thrustuplift zone,detachment deformation zone,northern Sichuan paraforeland zone,from north to south.Due to basement rock rigidity,basement thrustuplift zone and northern Sichuan paraforeland zone have marked disparity in the process of adjusting structural balance.Brittle faults mainly took place at the basement thrustuplift zone with the way of vertical uplift and horizontal contract to adjust structural balance.While northern Sichuan paraforeland zone,with weakly competent rock,mostly formed NWand NWstriking folds and faults to adjust structural balance.Our research on structural feature of the Micang Mountain shows that,physical character of basement rock and preexist basement structure are the firstorder factor of deformation diversity,and structure shrinkage and the contract ratio are subordination factor.
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