Based on structural and fabric analyses at variable scales we investigate the evaporitic gypsum-dominated Comeglians-Paularo shear zone in the Southern Alps (Friuli). It represents the lateral western termination of the brittle Fella-Sava Fault. Missing dehydration products of gypsum and the lack of annealing indicate temperatures below 100 °C during development of the shear zone. Despite of such low temperatures the shear zone clearly exhibits mylonitic flow, thus evidencing laterally coeval activity of brittle and viscous deformation. The dominant structures within the gypsum rocks of the Lower Bellerophon Formation are a steeply to gently S-dipping foliation, a subhorizontal stretching lineation and pure shear-dominated porphyroclast systems. A subordinate simple shear component with dextral displacement is indicated by scattered σ-clasts. Both meso- and microscale structures are characteristic of a subsimple shear type of deformation with components of both coaxial and non-coaxial strain. Shortening in a transpressive regime was accommodated by right-lateral displacement and internal pure shear deformation within the Comeglians-Paularo shear zone. The shear zone shows evidence for a combination of two stretching faults, where stretching occurred in the rheologically weaker gypsum member and brittle behavior in enveloping lithologies.

中文翻译：

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低温韧性剪切带：南阿尔卑斯山脆性 Fella-Sava 断层以石膏为主的西部延伸

基于可变尺度的结构和织物分析，我们研究了南阿尔卑斯山（弗留利）中以蒸发石膏为主的 Comegians-Paularo 剪切带。它代表了脆性 Fella-Sava 断层的横向西端。缺少石膏的脱水产物和缺乏退火表明在剪切带发展过程中温度低于 100 °C。尽管在如此低的温度下，剪切带清楚地表现出糜棱流，从而证明了脆性和粘性变形的横向同时期活动。下 Bellerophon 组的石膏岩内的主要结构是陡峭到平缓的 S 倾斜叶理、亚水平拉伸线理和纯剪切主导的斑岩碎屑系统。具有右旋位移的从属简单剪切分量由分散的 σ-clasts 表示。细观和微观结构都是具有同轴和非同轴应变分量的次简单剪切型变形的特征。在 Comeglians-Paularo 剪切带内的右侧位移和内部纯剪切变形适应了压缩状态下的缩短。剪切带显示了两个拉伸断层组合的证据，其中拉伸发生在流变较弱的石膏构件中，而包络岩性中的脆性行为。