We report the first findings of several occurrences of lawsonite and metamorphic aragonite in the meta-sediments from the Combin Zone (Piemonte–Liguria ocean, Western Alps), where the early blueschist-facies episode is poorly documented. New field and metamorphic data (thermodynamic modelling and Raman spectroscopy on carbonaceous material) are used to elucidate the P–T evolution and fluid composition of the Combin Zone and investigate the lawsonite growth and breakdown reactions. Two tectonometamorphic units have been identified within the Combin Zone with distinct geometry, lithological content and P–T conditions. In the higher grade unit, metamorphic aragonite occurs as inclusions in titanite. Lawsonite and garnet were stable at peak P–T conditions (~ 16–17 kbar and 460–480 °C) at very low X(CO₂) values. Lawsonite is systematically pseudomorphed, but preserves hourglass zoning or internal fabric associated with the prograde ductile deformation. The lower grade unit (~ 8 ± 1 kbar ~ 370–400 °C) is discontinuously exposed along the western base of the continental Dent Blanche nappe and records P–T conditions similar to those recorded by the Dent Blanche nappe. A metamorphic discontinuity is, therefore, documented between the largest part of the Combin Zone on the one hand, and the Dent Blanche nappe on the other hand. The discovery of lawsonite and metamorphic aragonite allows a better understanding of the large-scale metamorphic structure of the Western Alps.

我们报告了在 Combin 带（皮埃蒙特-利古里亚海，西阿尔卑斯山）的变质沉积物中发现了几处硬柱石和变质文石的首次发现，那里的早期蓝片岩相事件记录很少。新的现场和变质数据（碳质材料的热力学模型和拉曼光谱）用于阐明组合带的P-T演化和流体组成，并研究硬柱石的生长和分解反应。已在组合带内确定了两个具有不同几何形状、岩性含量和P - T条件的构造变质单元。在更高品位的单元中，变质文石作为钛铁矿中的包裹体出现。劳森石和石榴石在峰值P稳定–在非常低的X (CO ₂ ) 值下的T条件（~ 16–17 kbar 和 460–480 °C）。Lawsonite 被系统地假晶化，但保留了与顺向延展变形相关的沙漏分区或内部结构。低年级单元（〜8±1千巴〜370-400℃）不连续地沿大陆登特布兰奇水舌和记录的西部基地暴露P - Ť条件类似于 Dent Blanche 绒毛记录的条件。因此，一方面在 Combin Zone 的最大部分和另一方面的 Dent Blanche 推覆之间记录了变质不连续性。硬柱石和变质文石的发现，使人们可以更好地了解西阿尔卑斯山脉的大规模变质构造。