Supporting information - Article: "Fast and spatially heterogeneous cooling rates at amphibolite-facies conditions in the Lepontine Alps (Switzerland)"

1 Introduction In this document we briefly describe the content of the supplementary material for the publication entitled “Fast and spatially heterogeneous cooling rates at amphibolite-facies conditions in the Lepontine Alps (Switzerland)” by Tagliaferri, A., Moulas, E., Schmalholz, S. M., & Schenker, F. L. The contents of the supporting information are divided in the six appendixes below. Appendix A: Samples description and garnet chemistry In the Appendix A, we describe in detail the petrography of the thin sections which have been realized for each sample. We indicate here also few details on the mesoscale rock description and tectonic location of the samples, as well as garnet crystals chemical composition. The orientation of each section is displayed in the white box on top of the relevant photos by two red arrows: one indicates the top of the sample (pointing up or down) and the other the dip direction of the lineation (horizontal arrow). All the samples were cut parallel to the mineral lineation. In the descriptions the following abbreviations have been used: SPO = shape preferred orientation Prp = pyrope LPO = lattice preferred orientation Grs = grossular GBM = grain boundary migration Alm = almandine SR = subgrain rotation Sps = spessartine Appendix B: Microprobe analyses The folder Microprobe analyses contains Excel tables with the results of all the chemical analyses performed using the Electron MicroProbe Analyzer. Each Excel file corresponds to a specific sample. Within each Excel file, there is a list of analyses divided per profile (e.g., profile D10, D14, etc.) and mineral (garnet, biotite, plagioclase, white mica as “grt”, “bt”, “pl”, “wm”). In the Excel sheets, below the list of analyses, there is also a plot which displays the composition of each point analyzed on the specific mineral (e.g., GrossularPyrope-Almandine (Grs-Py-Alm) triplot for garnet compositions). 2 As we mentioned in the main text, for all samples we analyzed the most external diffusion profile of our garnet rims which describes the Alpine history. Therefore, for some samples we considered only part of the profile measured at the microprobe. The considered points are highlighted in yellow in the Excel spreadsheets. The indicated “distance (µm)” is the distance from the garnet border (distance: 0 µm) along the measured profile and corresponds to the distance in the profiles in Appendix C (see below). Appendix C: Profile results In the Appendix C we display all the analyzed garnet profiles. The appendix contains panoramic photos of the analyzed thin and thick sections, garnet photos, microprobe Xray maps, microprobe BSE images, microprobe profiles in garnet, and results of GDIFF simulations. Appendix D: GeoTB The file GeoTB.xlsx is an Excel file containing representative mineral compositions and the geothermometers and geobarometers applied for the calculation of temperature and pressure (T and P) conditions of “outer rims” and “inner rims”. The applied thermometers are garnet-biotite (Holdaway, 2000) and garnet-phengite (Caddick & Thompson, 2008). The applied barometers are garnet-aluminosilicate-quartz-plagioclase (GASP; Caddick & Thompson, 2008) and phengite (Caddick & Thompson, 2008). The references to these geothermometers and geobarometers are in the main text. Appendix E: Thermal models The appendix E contains the results of one-dimensional thermal models for exhumation velocities of 5 mm/yr and 20 mm/yr, and the comparison between the computed heat fluxes (Qs) of the three 2D thermo-kinematic models M-1 (heat flux at 1 Myr), M-2 (heat flux at 3 Myr), and M-3 (heat flux at 3 Myr). Notice that the overall heat flux scales proportional to the velocity. Supporting information F: Thermokinematic2D The file Thermokinematic2D.pdf contains the results of two-dimensional thermo-kinematic models analogous to the results shown in the main text, with different depth of the thrust ramp-flat geometry. The only difference is the location of the flat part of the thrust, which 3 lies at mid-crustal depth (ca. 20 km in the model reference system), and not at the surface. Among the three models M-1, M-2 and M-3, the main differences are seen in the cooling rate of model M-3. Indeed, in this model configuration, the rock marker does not reach the surface.