松潘-甘孜褶皱带较场弧形构造特征及其大地构造意义

根据详细野外露头特征及显微构造特征将较场弧形带由南向北分为三个变形带:弧顶部、弧核部和弧翼部,不同分带具有明显不同的变形特征。由南向北变形特征由以塑性变形为主过渡为脆性变形为主,变质流体活动喜马拉雅构造期活动强烈,且向北逐渐增强;弧核部以叠瓦状逆冲构造特征分隔弧顶和弧翼部;弧翼部东西两翼变形及变质流体活动特征具有一定差异性。较场弧形带总体体现出多期次南北向挤压—张性应力变形构造特征,叠加北西—北北西向同构造期挤压变质运动,其宏观和微观变形特征与典型"走滑成因"模式弧形构造特征相异,为其大地构造成因机制的解释提出了新的限制条件。

The Structural Features of Jiaochang Arc Belt in Songpan-Garze Fold Belt and Its Tectonic Implications

The Jiaochang arc belt in Songpan-Garze fold belt is composed with three partitions: arc roof, arc kern, arc limbs,which are different from each others according to the structural feature in field and microstructural feature. The deformational strength becomes shallower from the south to the north, which is mainly ductile strain in south and brittle deformation in north, as well as metamorphic fluid becomes stronger active in Himalayan Epoch according to ESR. Arc kern separates the arc roof from arc limbs, which imbricatly thrusts from south to north, while the later has different feature in activity of metamorphic fluid and deformational strength between western limb and eastern limb. In a word, the Jiaochang arc belt is totally characteristic of multi-phase compressional-tensional movements in north-south trending, overprinted compressional metamorphose in (NW-NNW)-(SE-SSE) trending on orogenic epoch. The macro- and micro- structural feature in Jiaochang arc belt is different from the "strike-slip" mechanism of arc belt, compared with the tectonic setting, it is concluded that the mechanism of the Jiaochang arc belt is owe to combined effect of the Qinling orogen belt and Upper Yangtze block.