Plenarist Abstracts

The esthetics and usefulness of phase diagrams. The scientific vision of Stefano Poli

Max W. Schmidt

The beauty of phase diagrams arises from an intrinsic property: when constructed correctly, they represent ground truth and although their applicability and underlying data may be debated, a phase diagram itself can be objectively correct. As graphical representations of thermodynamic calculations or topological constrains, phase diagrams are uniquely suited to visualize and communicate complex metamorphic, metasomatic and magmatic reactions, and their relevant compositional space; all of which were the scientific endeavor that characterized Stefano Poli's career. Stefano began in the 1980s with volcanological and then metamorphic field-based petrology, and he continued this line of research during his entire career through projects mainly in metamorphic and anatectic terranes across the globe. This start of Stefano Poli's scientific production was synchronous with the search for understanding metamorphic petrology within a rigorous framework of quantitative thermodynamic assessment. In the early 1990s Stefano started to build what would become the most versatile experimental petrology laboratory in Italy, a career move that was to dominate his scientific production and led to the application of petrology to industrial processes. During this first decade of experimental work, hydrous phases in subduction zones were the primary focus, resulting in the 1998 and 2002 landmark papers that today may appear almost self-evident, but which transformed the entire field of subduction related research. The 2000's were then dominated by application of high-pressure petrology to industrial processes, resulting in the foundation of Petroceramics, which, e.g., produced and analyzed all ceramic brakes of Ferrari F1 cars, and has since expanded into activities related to space technology. From the 2010s onward, Stefano's subduction related research moved on to redox processes both in the slab and in the mantle, subsequently evolving naturally to the mobilization and effects of carbon in these environments. Stefano's fascination with carbon extended from the global carbon cycle to carbon-fiber-based ceramics, and led him to move on to his last own experimental project (unimaginable he would ever stop conducting experiments himself), namely CO₂-driven melilititic magmatism. Another pillar of Stefano's research concerned migmatization and granites, integrating fieldwork, melt inclusion studies and experiments into a unified approach. Throughout his career, Stefano strived to explain nature through experiments and thermodynamics, inspiring many generations of students and also collaborators, often moving decisively forward through his theoretical developments. Indeed, theoretical papers on phase petrology and the crystallography of new phases were always interspersed in his publication record. Thriving to understand the true reasons driving reactions and textures, Stefano Poli is leaving a rich inheritance, which through its fundamental nature will last.

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