Non-conventional pressure estimates by using transmission electron microscopy coupled with energy-dispersive spectroscopy (TEM-EDS): testing on submicrometer white mica from low-grade metapelites

Abstract. Chemical compositions of mineral phases obtained using a common electron probe micro-analyzer are generally used in many fields of geosciences, like the reconstruction of pressure–temperature paths, because their accuracy ensures high-quality data. However, on submicrometric mineral phases, mostly present in low-grade rocks, the chemical analysis can be contaminated by the surrounding. Energy-dispersive X-ray spectroscopy coupled with a transmission electron microscope is demonstrated to be a valid alternative approach to get high-quality data on submicrometric phases. In this work, we use this approach for geobarometric application on white mica-rich low-grade metapelites from the Internal Ligurian Units (Northern Apennines). Our pressure estimates gave satisfactory results supporting previously geobarometric constraints performed on the same rock samples. The innovative methodological procedure used in this work confirms the tectonic scenario proposed for the Internal Ligurian Units.