Abstract The GREENPEG project, which is funded by the European Commission Horizon 2020 ‘Climate action, environment, resource efficiency and raw materials’ programme, aims to develop multimethod exploration toolsets for the identification of European, buried, small-scale (0.01–5 million m 3 ) pegmatite ore deposits of the Nb–Y–F (NYF) and Li–Cs–Ta (LCT) chemical types. The project is being coordinated by the Natural History Museum of the University of Oslo and involves four exploration services/mining operators, one geological survey, one non-profit helix association of administration, industry and academia, two consulting companies and five academic institutions from eight European countries. The target raw materials are Li, high-purity quartz for silica and metallic Si, ceramic feldspar, rare earth elements, Ta, Be and Cs, which are naturally concentrated in granitic pegmatites. Silicon and Li are two of the most sought-after green technology metals as they are essential for photovoltaics and Li-ion batteries for electric cars, respectively. GREENPEG will change the focus of exploration strategies from large-volume towards small-volume, high-quality ores and overcome the lack of exploration technologies for pegmatite ore deposits by developing toolsets tailored to these ore types. This contribution focuses on the methods applied in the GREENPEG project and as such provides a potential pathway towards the ‘Green Stone Age’ from the perspective of pegmatite-sourced minerals.

The potential of igneous quartz for providing a better understanding of magmatic processes is demonstrated by studying late-Hercynian rhyolites and granites from central and western Europe. Cathodoluminescence (CL) reveals growth patterns and alteration structures within igneous quartz reflecting the magma crystallisation history. The relatively stable and blue-dominant CL of zoned phenocrysts is principally related to variations in the Ti concentration, which is a function of the crystallisation temperature. The Al/Ti ratio of igneous quartz increases with progressive magma differentiation, as Ti is more compatible, compared to Al, Li, K, Ge, B, Fe, P during magma evolution. The red-dominant CL of the anhedral groundmass quartz in granite is unstable during electron bombardment and associated with OH- and H 2 O-bearing lattice defects. Thus, CL properties of quartz are different for rocks formed from H 2 O-poor and H 2 O-rich melts. Both groundmass and phenocrysts in granites are rich in alteration structures as a result of interaction with deuteric fluids during cooling, whereas phenocrysts in extrusive rocks do not usually contain such structures. The combined study of trace elements along with the analysis of quartz textures and melt inclusion inventories may reveal detailed PTX-paths of granite magmas. This study shows that quartz is a sensitive indicator for physico-chemical changes during the evolution of silica-rich magmas. Common growth textures show a wide variety in quartz phenocrysts in rhyolites and some granites. This paper presents a classification of textures, which formed as a result of heterogeneous intra-granular lattice defects and impurities. The alternation of growth and resorption microtextures reflects stepwise adiabatic and non-adiabatic magma ascent, temporary storage of magma in reservoirs and mixing with more mafic, hotter magma. The anhedral groundmass quartz overgrowing early-magmatic phenocrysts in granites is free of growth zoning.