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Pegmatitic deposits of critical metals (e.g., Li, Ta, Be) are becoming increasingly significant, with growing interest in understanding metal enrichment processes and potential vectors to aid the discovery of new resources. In southeast Ireland, the Leinster pegmatite belt comprises several largely concealed Li-Cs-Ta albite-spodumene-type pegmatites. We carried out detailed mineralogical characterization and whole-rock geochemical analyses of six drill cores intersecting pegmatite bodies and their country rocks. Exomorphic halos 2–6 m thick, enriched in Li, Rb, Be, B, Cs, Sn and Ta, are identified in both mica schists and granitic rocks adjacent to spodumene pegmatites. Metasomatism in wall rocks visible to the naked eye is restricted to a few tens of centimeters, suggesting country rock permeability plays a key role in the dispersion of these fluids. We propose that halos result from the discharge of rare element-rich residual fluids exsolved near the end of pegmatite crystallization. Halo geochemistry reflects the internal evolution of the crystallizing pegmatite system, with residual fluid rich in incompatible elements accumulated by geochemical fractionation (Be, B, Cs, Sn, Ta) and by auto-metasomatic resorption of spodumene and K-feldspar (Li, Rb). The possibility of identifying rare-element enrichment trends by analysis of bedrock, stream sediments and soils brings opportunities for mineral exploration strategies in Ireland and for similar albite-spodumene pegmatites worldwide. [ABSTRACT FROM AUTHOR]

Trace element concentrations in quartz were determined from two major LCT pegmatite occurrences in Europe to test the applicability of quartz as a pathfinder mineral for Li mineralized pegmatites. The Wolfsberg spodumene pegmatite deposit and pegmatites throughout the wider Austroalpine Unit (Austria), and the Moylisha spodumene pegmatite deposit (SE Ireland), present two distinctly different geological histories. Spodumene pegmatites at Wolfsberg are associated with late Permian lithospheric extension that formed the Austroalpine Unit Pegmatite Province spanning the Eastern Alps. They were metamorphosed at up to eclogite-facies conditions during the Alpine orogeny. Contrastingly, the simple and spodumene pegmatites at Moylisha form a late Silurian to early Devonian NE-SW-striking pegmatite belt that intruded the East Carlow Deformation Zone along the SE margin of the late Caledonian S-type Leinster Batholith. All analyzed pegmatites contain assemblages including K-feldspar, albite, quartz, muscovite ± spodumene. LA-ICP-MS analysis shows quartz from spodumene pegmatites in both regions is distinguishable from that in simple pegmatites by higher concentrations of Al, Li, Ge and B, whereas simple pegmatite quartz contains higher Ti. Increasing concentrations of Al, Li and Ge and decreasing Ti in quartz from simple pegmatites (to leucogranites in the Austroalpine Unit) to spodumene pegmatites reflects increasing degree of fractionation, resulting from either magmatic differentiation or separately generated but increasingly fractionated melts. Chemical profiles through individual spodumene pegmatite bodies show relatively little chemical variation, consistent with Li saturation through most of their crystallization history. Principal component analysis of quartz data shows that high Ge, Be and B concentrations characterize quartz in pegmatites from the Austroalpine Unit whereas high Al and Li concentrations characterize quartz in pegmatites from Moylisha. Concentrations of >100 μgg−1 Al and >30 μgg−1 Li in pegmatite quartz represent an important threshold for potential spodumene mineralization, which may also be indicated by host rocks (e.g., mica schist) metasomatized by fluids expelled by pegmatites during emplacement and/or crystallization and generating a chemical halo. Retention of pegmatite chemical signatures at Wolfsberg supports the robustness of quartz as an effective pathfinder tool for Li mineralized pegmatites in regions that have been affected by high-pressure metamorphism. LA-ICP-MS of quartz in soil and stream sediments may also be a useful pathfinder in pegmatite provinces where Li-rich quartz is not too diluted by other quartz. • Quartz trace elements determined for LCT pegmatites at Wolfsberg and Moylisha. • Respective Ge-Be-B and Al-Li signatures in Wolfsberg and Moylisha pegmatite quartz. • Increasing Al, Li, Ge/decreasing Ti in quartz from simple to spodumene pegmatites. • >100 μgg−1 Al and > 30 μgg−1 Li in pegmatite quartz indicative of Li mineralization. [ABSTRACT FROM AUTHOR]