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Crystalline basements are the association of metamorphic and magmatic rocks and form the backbone of the Earth’s crust. They originated from multiple petrogenetic phases involving magmatic and metamorphic processes generally related in space and time with the growth and destruction of an orogenic chain. If magmatic rocks are familiar to the large audience, metamorphic rocks and metamorphism are somewhat less known. Metamorphism is when a rock enjoys pressure and temperature conditions different from those under which the rock originally formed. Metamorphic rocks can be subjected to higher temperatures and pressures as they are buried deeper in the Earth’s crust/upper mantle along convergent margins. These pressure and temperatures gradients have profound consequences on the mineralogy and the (micro)structure of metamorphic rocks. After residing for a lapse of time at depths, crystalline basements undergo exhumation towards the Earth surface: during their travel back to the surface they experience additional deformation phases, partial melting and/or intrusions of silica-rich liquids (melt or fluids). Despite the high potential to retain the geological record of fundamental events occurring in the deep Earth, exposures of crystalline basement have a limited impact on the popularisation of geosciences and they rarely appear as the main attraction of outreach activities. This study, which stems from the results of an undergraduate mapping project, demonstrates the wealth of information gathered in the crystalline basement outcropping near the Villaggio Filatura in Tollegno, Biella (Figure 1). These information will help to design popularisation activities using apparently difficult-to-understand rocks but with a distinctive beauty and appeal for both local inhabitants and visitors. |
