The record of metamorphic conditions is commonly highly heterogeneous in spatially close rocks of different composition and rheology. The well-studied Cima di Gagnone area in the Central Alps represents such an example, as relatively small, 1– to 100 s-meter scale, ultrahigh–pressure and high–temperature ultramafic lenses are enveloped within amphibolite–facies metasediments. We present new field observations, microstructural and petrological analyses, and thermodynamic modelling results on these metasediments, showing that these rocks generally experienced medium pressure and medium temperature conditions of 1.0–1.2 GPa and 640–700 °C, followed by a retrograde stage around 0.6–0.8 GPa and 600–675 °C. However, a few samples from the immediate proximity of the ultramafic lenses record significantly higher P–T conditions of 1.3–1.7 GPa and 750–850 °C, approaching the high pressure and high temperature conditions of the ultramafic bodies (1.5–3.1 GPa, 650–850 °C). Mineral/bulk chemistry changes during growth of new mineral phases hint to local melt/fluid interaction (i.e., metasomatism) between metasediments and ultramafics during the high temperature deformation. Preliminary U-Pb LA–ICP–MS dating suggests that zircon grains from the metasomatic reaction zone have been fully re–equilibrated during the early stage of Alpine exhumation (~36 Ma), while the large part of the metasediments records only pre–Alpine ages. We finally recast these new data into the regional P–T–t–D paths and discuss the consequences of these findings for understanding the exhumation processes of HP rocks. We found different local equilibria (ΔP up to 2 GPa; ΔT up to 160 °C) that cannot be explained simply by retrograde metamorphism or by tectonic amalgamation. Rather, our work suggests a significant role of deformation in producing variable pressure and temperature record within the rocks.

变质条件的记录通常在具有不同成分和流变学的空间紧密岩石中高度异质。充分研究的西玛二Gagnone区域在中央阿尔卑斯山表示这样的例子中，作为相对小的，1 -至100s米尺度，超高压和高温超镁铁透镜角闪岩相沉积岩内包封。我们对这些沉积物进行了新的野外观测，微观结构和岩石学分析以及热力学模拟结果，表明这些岩石通常经历1.0 – 1.2 GPa和640 –的中等压力和中等温度条件700°C，然后在0.6-0.8 GPa和600-675°C左右逆行。但是，一些来自超镁铁晶状体紧邻区域的样品记录了1.3–1.7 GPa和750–850°C的显着较高的P–T条件，接近超镁铁体的高压和高温条件（1.5–3.1 GPa， 650–850°C）。新矿物相生长过程中矿物/本体化学性质的变化暗示了局部熔体/流体相互作用（即，高温变形过程中超沉积物与超沉积物之间的交变作用）。初步的U-Pb LA-ICP-MS测年表明，在高放化的早期阶段（〜36 Ma），交代反应区的锆石颗粒已完全重新平衡，而大部分的沉积物仅记录了高寒前期。年龄。最后，我们将这些新数据重铸到了区域P–T–t–D路径中，并讨论了这些发现对理解高压岩石挖掘过程的影响。我们发现了不同的局部平衡（ΔP高达2 GPa; ΔT高达160°C），这不能简单地通过逆相变质或构造合并来解释。相反，我们的工作表明，变形在岩石内部产生可变的压力和温度记录方面起着重要作用。