The inherited localization model for shear zone development suggests that ductile deformation in the middle and lower continental crust is localized on mechanical anisotropies, like fractures, referred to as shear zone brittle precursors. In the Neves area (Western Tauern Window, Eastern Alps), although the structural control of these brittle precursors on ductile strain localization is well established, the relative timing of the brittle deformation and associated localized fluid flow with respect to ductile deformation remains in most cases a matter of debate. The present petrological study, carried out on a brittle precursor of a shear zone affecting the Neves metagranodiorite, aims to determine whether brittle and ductile deformations are concomitant and therefore relate to the same tectonic event. The brittle precursor consists of a 100–500 µm wide recrystallized zone with a host mineral‐controlled stable mineral assemblage composed of plagioclase–garnet–quartz–biotite–zoisite±white mica±pyrite. Plagioclase and garnet preserve an internal compositional zoning interpreted as the fingerprint of Alpine metamorphism and fluid–rock interactions concomitant with the brittle deformation. Phase equilibrium modelling of this garnet‐bearing brittle precursor shows that metamorphic garnet and plagioclase both nucleated at 0.6 ± 0.05 GPa, 500 ± 20°C and then grew along a prograde path to 0.75 ± 0.05 GPa, 530 ± 20°C. These amphibolite facies conditions are similar to those inferred from ductile shear zones from the same area, suggesting that both brittle and ductile deformation were active in the ductile realm above 500°C for a depth range between 17 and 21 km. We speculate that the Neves area fulfils most of the required conditions to have hosted slow earthquakes during Alpine continental collision, that is, coupled frictional and viscous deformation under high‐fluid pressure conditions ~450°C. Further investigation of this potential geological record is required to demonstrate that slow earthquakes may not be restricted to subduction zones but are also very likely to occur in modern continental collision settings.

中文翻译：

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关于剪切带脆性前体的岩石学——“韧性”大陆地壳中伴随的脆性变形和流体-岩石相互作用的表达？

剪切带发展的继承定位模型表明，中下大陆地壳的韧性变形集中在机械各向异性上，如断裂，被称为剪切带脆性前兆。在 Neves 地区（Western Tauern Window，Eastern Alps），虽然这些脆性前驱体对韧性应变局部化的结构控制已经很好地建立，但在大多数情况下，脆性变形和相关局部流体流动与韧性变形的相对时间仍然存在一个争论的问题。目前的岩石学研究是对影响 Neves 变花岗闪长岩的剪切带的脆性前体进行的，旨在确定脆性和韧性变形是否伴随并因此与同一构造事件相关。脆性前驱体由一个 100-500 µm 宽的重结晶带和由斜长石-石榴石-石英-黑云母-黝帘石-白云母-黄铁矿组成的宿主矿物控制的稳定矿物组合组成。斜长石和石榴石保留了内部成分区带，被解释为高山变质作用和伴随脆性变形的流体-岩石相互作用的指纹。这种含石榴石的脆性前驱体的相平衡模型表明，变质石榴石和斜长石均在 0.6 ± 0.05 GPa、500 ± 20°C 下成核，然后沿升序路径生长至 0.75 ± 0.05 GPa、530 ± 20°C。这些角闪岩相条件与从同一区域的韧性剪切带推断出的条件相似，表明在 17 至 21 公里的深度范围内，在 500°C 以上的韧性领域，脆性和韧性变形都活跃。我们推测 Neves 地区满足了在阿尔卑斯大陆碰撞期间承载慢地震的大部分条件，即在约 450°C 的高流体压力条件下耦合摩擦和粘性变形。需要对这种潜在的地质记录进行进一步调查，以证明慢地震可能不仅限于俯冲带，而且很可能发生在现代大陆碰撞环境中。