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东秦岭造山带北缘的陶湾岩群中分布着一套碳酸盐质糜棱岩,具明显的塑性变形,其展布和变质变形特征严格受洛南—栾川断裂带控制,是陶湾岩群碳酸盐岩在洛南—栾川断裂带晚加里东—早海西期构造活动过程中形成的。因此,对这套碳酸盐质糜棱岩的变质—变形特征及形成环境分析,可揭示洛南—栾川断裂带在这一时期构造活动的运动学、动力学及流变学特征。本文通过野外详细的观察和测量,结合室内显微构造分析和温压条件的计算,确定其变质相属低绿片岩相,变形机制是以方解石动态重结晶和细粒化作用为主的塑性变形。变形温度为350~420℃,差异应力为50~110 MPa。石英应变椭球体形态显示陶湾岩群遭受了强烈挤压变形。所以,陶湾岩群碳酸盐质糜棱岩是在强烈的斜向挤压碰撞环境下形成的,是秦岭微陆块向华北板块下斜向俯冲碰撞的结果 。
A set of carbonate mylonites are distributed in the Taowan group in the northern margin of the East Qinling orogenic belt with obvious plastic deformation. The characteristics of spreading and metamorphism are strictly controlled by the Luonan-Luanchuan fault zone, Formation of carbonate rocks of Wan-Yan Group formed during the Late Caledonian-Early Hercynian period in the Luonan-Luanchuan fault zone. Therefore, the metamorphic-deformation characteristics and environmental analysis of this carbonate mylonite can reveal the kinematics, dynamics and rheology of the structural activity of the Luonan-Luanchuan fault during this period. Based on detailed observation and measurement in the field, combined with the analysis of microstructures in the interior and the calculation of temperature and pressure conditions, the metamorphic low-greenshed lithofacies are identified. The deformation mechanism is plastic deformation mainly based on dynamic recrystallization and fine graining of calcite . The deformation temperature is 350 ~ 420 ℃, the differential stress is 50 ~ 110 MPa. Quartz strain ellipsoid morphology shows that the Tauwan group suffered a strong extrusion deformation. Therefore, the Taowan group of carbonate mylonites are formed under strong oblique extrusion collision environment and are the result of oblique subduction collision of the micro-continental blocks in the Qinling Mountains to the North China plate.