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Characterizing syn-convergent extension along the Neybaz-Chatak detachment shear zone, Central Iran: Insights from microstructures, quartz petrofabrics and flow vorticity analysis
Journal of Structural Geology ( IF 3.1 ) Pub Date : 2020-12-19 , DOI: 10.1016/j.jsg.2020.104270
Siamak Mahmoudi Sivand , Ali Faghih , Saeede Keshavarz , Masoumeh Soleimani

Integrated microstructural, quartz petrofabric and flow vorticity analyses on mylonitic rocks in the lower plate of the Neybaz Chatak Detachment Shear Zone provide significant information regarding the kinematic characteristics coeval with the Chapedony metamorphic core complex development within the Central East Iranian Microcontinent. Several kinematic shear sense indicators including quartz c-axis fabrics, S–C fabrics, rotated feldspar and mica fish reveal that the detachment shear zone has experienced a consistent top-to-the NE-directed progressive shear deformation. Detailed investigations on recrystallization types of quartz and feldspar in the mylonites demonstrate that the deformation occurred under the amphibolite facies condition corresponding to mid-crustal levels. A combination of investigations on mineral assemblages, microstructures of quartz and feldspar, and quartz lattice preferred orientations (LPOs) show that deformation temperatures ranged from 400 to 645 °C that were varied across a distance of ~21 km in the extension direction (NE-SW). The western and eastern parts of the study area experienced lower temperatures compared to the central parts. The gneissic mylonite record sub simple shear deformation (Wm = 0.56–0.85, 64–36%) associated with an increasing of pure shear component. These data highlight that the metamorphic rocks of the study underwent a non-coaxial shear with ductile low-angle normal faulting, resulting in subvertical thinning in the extensional deformation regime responsible for formation of the core complex.



中文翻译:

伊朗中部Neybaz-Chatak分离剪切带的同收敛扩展特征:微观结构,石英岩屑和流动涡度分析的见解

Neybaz Chatak分离剪切带下部板块中的长条性岩石上的微结构,石英岩屑和流动涡度的综合分析提供了有关伊朗中东部微大陆上Chapedony变质核心复合体发育的运动学特征的重要信息。几种运动学的剪切感测指标,包括石英c轴织物,SC织物,旋转长石和云母鱼,都表明分离剪切带经历了从顶向NE方向一致的渐进剪切变形。对my石中石英和长石的再结晶类型的详细研究表明,变形是在与中地壳水平相对应的闪石相条件下发生的。结合矿物成分的研究,石英和长石的显微结构以及石英晶格的优选取向(LPO)表明,变形温度范围为400至645°C,沿延伸方向(NE-SW)的距离约为21 km。与中部地区相比,研究区域的西部和东部地区温度较低。片麻质镁铁矿记录了简单剪切变形(Wm = 0.56-0.85,64-36%),这与纯剪切组分的增加有关。这些数据突出表明,该研究的变质岩经历了具有低角度延性法向断裂的非同轴剪切作用,从而导致负责岩心复合体形成的伸展变形带的亚垂直变薄。石英晶格的首选取向(LPO)表明,变形温度范围为400至645°C,在延伸方向(NE-SW)上约21 km的距离内变化。与中部地区相比,研究区域的西部和东部地区温度较低。片麻质镁铁矿记录了简单剪切变形(Wm = 0.56-0.85,64-36%),这与纯剪切组分的增加有关。这些数据突出表明,该研究的变质岩经历了具有低角度延性法向断裂的非同轴剪切作用,从而导致负责岩心复合体形成的伸展变形带的亚垂直变薄。石英晶格的首选取向(LPO)表明,变形温度范围为400至645°C,在延伸方向(NE-SW)上约21 km的距离内变化。与中部地区相比,研究区域的西部和东部地区温度较低。片麻质镁铁矿记录了简单剪切变形(Wm = 0.56-0.85,64-36%),这与纯剪切组分的增加有关。这些数据突出表明,该研究的变质岩经历了具有低角度延性法向断裂的非同轴剪切作用,从而导致负责岩心复合体形成的伸展变形带的亚垂直变薄。与中部地区相比,研究区域的西部和东部地区温度较低。片麻质镁铁矿记录了简单剪切变形(Wm = 0.56-0.85,64-36%),这与纯剪切组分的增加有关。这些数据突出表明,该研究的变质岩经历了具有低角度延性法向断裂的非同轴剪切作用,从而导致负责岩心复合体形成的伸展变形带的亚垂直变薄。与中部地区相比,研究区域的西部和东部地区温度较低。片麻质镁铁矿记录了简单剪切变形(Wm = 0.56-0.85,64-36%),这与纯剪切组分的增加有关。这些数据突出表明,该研究的变质岩经历了具有低角度延性法向断裂的非同轴剪切作用,从而导致负责岩心复合体形成的伸展变形带的亚垂直变薄。

更新日期:2020-12-23
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