The Posada–Asinara Line is a crustal-scale transpressive shear zone affecting the Variscan basement in northern Sardinia during Late Carboniferous time. We investigated a structural transect of the Posada–Asinara Line (Baronie) with the aid of geological mapping and structural analysis. N-verging F2 isoclinal folds with associated mylonitic foliation (S2) are the main deformation features developed during the Posada–Asinara Line activity (D2). The mineral assemblages and microstructures suggest that the Posada–Asinara Line was affected by a retrograde metamorphic path. This is also confirmed by quartz microstructures, where subgrain rotation recrystallization superimposes on grain boundary migration recrystallization. Crystallographic preferred orientation data, obtained using electron backscatter diffraction, allowed analysis of quartz slip systems and estimation of the deformation temperature, vorticity of flow and rheological parameters (flow stress and strain rate) during the Posada–Asinara Line activity. Quartz deformation temperatures of 400 ± 50 °C have been estimated along a transect perpendicular to the Posada–Asinara Line, in agreement with the syn-kinematic post-metamorphic peak mineral assemblages and the late microstructures of quartz. The D2 phase can be subdivided in two events: an early D2early phase, related to the metamorphic peak and low kinematic vorticity (pure shear dominated), and a late D2late phase characterized by a lower metamorphic grade and an increased kinematic vorticity (simple shear dominated). Palaeopiezometry and strain rate estimates associated with the D2late deformation event showed an intensity gradient increasing towards the core of the shear zone. The D2early deformation developed under peak temperature conditions, while the D2late event was active at shallower structural levels.

中文翻译：

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跨压剪切带的结构设置：来自撒丁岛东北部（意大利）的地质填图、石英岩石结构和运动涡度分析的见解

Posada-Asinara 线是晚石炭世时期影响撒丁岛北部 Variscan 基底的地壳尺度的压断剪切带。我们借助地质填图和结构分析调查了 Posada-Asinara Line (Baronie) 的构造横断面。N 型 F2 等斜褶皱与相关糜棱面理 (S2) 是波萨达-阿西纳拉线活动 (D2) 期间形成的主要变形特征。矿物组合和微观结构表明波萨达-阿西纳拉线受到逆行变质路径的影响。石英微结构也证实了这一点，其中亚晶粒旋转再结晶叠加在晶界迁移再结晶上。使用电子背散射衍射获得的晶体学择优取向数据，允许分析石英滑移系统并估计波萨达-阿西纳拉线活动期间的变形温度、流动涡度和流变参数（流动应力和应变率）。沿着垂直于波萨达-阿西纳拉线的横断面估计石英变形温度为 400 ± 50 °C，这与同运动后变质峰矿物组合和石英的晚期微结构一致。D2 阶段可细分为两个事件：早期 D2 与同运动后变质峰矿物组合和石英晚期微结构一致。D2 阶段可细分为两个事件：早期 D2 与同运动后变质峰矿物组合和石英晚期微结构一致。D2 阶段可细分为两个事件：早期 D2早期的阶段，与变质峰和低运动涡度（纯剪切主导）有关，以及晚 D2晚了以较低的变质等级和增加的运动涡度（简单剪切为主）为特征的阶段。与 D2 相关的古测压和应变率估计晚了变形事件表明强度梯度向剪切带的核心增加。D2早期的在峰值温度条件下发生变形，而 D2晚了事件在较浅的结构层面活跃。