Search Results (3)

Graphite is a critical raw material due to its pivotal role in the green transition; hence, there is a renewed interest in its exploration across Europe. The Chisone and Germanasca Valleys (Piemonte, IT) were home to significant graphite exploitation until the 20th century, owing to the widespread presence of graphite ore bodies hosted in the metasedimentary succession of the Pinerolo Unit in the Dora-Maira Massif (Western Alps). This contribution presents a renewed study on the geology, mineralogy, petrography, and geochemistry of graphite ores and their host rocks, employing OM, SEM-EDS, and BSE, μRaman, and ICP-OES/MS and INAA analyses. Mineralization occurs in two metasedimentary successions: (i) the Bourcet-type succession (meta-conglomerates and meta-sandstones intercalated with meta-siltstones/metapelites) and (ii) the Pons-type succession (meta-siltstones/metapelites intercalated with minor meta-arenites). Graphite occurs as (i) high-purity, fine-grained crystals dispersed within or concentrated in layers along the regional schistosity, or (ii) low-purity, coarse-grained crystals within shear zones. Based on crystallinity, three types of graphite were distinguished: high (Type I), intermediate (Type II), and poor (Type III) crystalline graphite, likely formed under different genetic conditions. The comparison of these findings has implications for future exploration and provides new insights into the metallogeny and geological evolution of the area. Full article

Geological mapping, stratigraphic observations, and U/Pb dating allow reconstructing the pre-orogenic setting of the transition zone between the distal European passive margin and the Alpine Tethys in the southwestern Alps. Although convergent tectonics overprinted the syn-rift Jurassic tectonic features, our data document an articulated Jurassic physiography. From the distal European passive margin oceanward, we distinguished: the Dronero Unit (the southernmost Dora Maira massif), represents a continental margin composite basement wherein monometamorphic metasediments are interlayered with Late Permian (253.8 ± 2.7 Ma) metavolcanic rocks; the Sampeyre Unit, represents a structural high consisting of Lower Triassic Verrucano-facies siliciclastic metasediments unconformably sealed by Cretaceous calcschist bearing Globotruncana sp.; the Maira Unit, corresponds to a Middle Triassic platform succession detached from the Sampeyre Unit; the Grana Unit, corresponds to a Late Triassic–Late Jurassic platform to basin succession; the Queyras Schistes Lustrès Complex, represents the ocean basin succession. Tectonic slices of Cambrian (513.9 ± 2.7 Ma) metadiorite hosted in the Valmala Shear Zone, separating the Dronero Unit from the underlying (U)HP units of the Dora Maira massif, suggests a potential pre-Alpine activation of the shear zone. Full article

The study of ancient marble plays an important role in the interpretation of historical and archaeological sites and gives interesting information about building materials used in ancient times and their trade routes. The present work focuses on Chianocco marble that represents one of the most important ancient white marbles for cultural heritage exploited in the Piedmont region (Northwest Italy) and employed for the Palazzo Madama façade. A multi-analytical study based on petrographic (optical and scanning electron microscopy), electron microprobe, cathodoluminescence and stable isotope analyses was carried out on these marbles in order to perform an archaeometric study. Chianocco marble was used in Turin during the baroque era by the Savoy architect Filippo Juvarra (1678–1736) in historical buildings, such as the façade of the Palazzo Madama, the plinth of the façade of the town Cathedral and the columns (now plastered) of the portico of Piazza San Carlo. This stone is a dolomitic rock belonging to the Mesozoic cover of the Dora Maira Massif (Pennidic Unit). It shows a vuggy fabric characterized by a vacuolar texture due to tectonic brecciation and subsequent selective dissolution during subaerial exposure. This kind of research is useful to highlight the importance of the use of local stones as building materials and to investigate stone materials for the restoration and maintenance of historical buildings. Full article