摘要:兴国旋卷构造是华南中部发育的一套典型构造形迹，其形成机制能较好的反映华南内部的大地构造格局及其大地构造演化特征。兴国旋卷构造的主体构造要素主要包含两条近北东向走向的剪切带及剪切带所夹的一系列呈弧形或大致弧形展布的走滑断层和3个向斜盆地，以及核部的两个花岗岩体砥柱。本文通过对兴国旋卷构造中岩体砥柱的年代学、边界剪切带的几何学、运动学等研究，发现兴国旋卷构造核部的岩体砥柱为多期幕式侵入就位，侵位时代获得加权平均年龄233～193 Ma、151～149 Ma，其侵位和变形主要受控于其两侧的走滑断裂，两条边界断裂具多期活动特征，其中发育的左行剪切作用最为强烈和典型，活动时间主要为中生代，该左行走滑活动是控制和改造兴国旋卷构造形成和演化的关键因素。兴国旋卷构造中边界断裂在中生代的左行剪切活动与区域上华南内部微地块之间的断裂缝合带的走滑活动具有可对比性，这些大型的断裂缝合带通常反映了华南内部多个微地块之间的碰撞—拼贴活动，因此我们推测兴国旋卷构造可能是华南内部微地块左行走滑式拼贴所产生的远程效应的结果。
关键词: 旋卷构造/
华南/
形成机制/
左行剪切
Abstract:There are different understandings on the Mesozoic tectonic evolution model in South China. The Xingguo vortex structure is developed in the center of South China Block as a set of typical structural features. Its formation mechanism is a commendable indicator for the tectonic evolution of South China Block. The Xingguo vortex structure mainly include two nearly NE trending shear zones, a series of cambered strike-slip faults and three synclinal basins sandwicked between the shear zones, and two granite as pillars in the core. On the basis of the geochronological study on the granite and structural analysis of the NE trending shear zones in the Xingguo vortex structure, we obtained weighted average ages of 233~193 Ma and 151~149 Ma in the granitic pillars, and the Xingguo vortex structure is mainly controlled by the boundary shear zones. Both of the two boundary shear zones developed sinistral shearing in Mesozoic. The structure activities of the sinistral shearing in Mesozoic are consistent with those of the alternative suture-shear zones between the micro-terrenes in the South China. The large fault suture zones usually reflect a collision activity of multiple micro-terranes in the interior of South China. We speculate that the Xingguo vortex structure may be the result of remote effects caused by strike-slip collage of micro-terrenes in the interior of South China Block, which provides some enlightenment for the understanding of microplate tectonics in South China.
Key words:Vortex structure/
South China Block/
Formation mechanism/
Sinistral shear
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