Exploration for buried mineralised pegmatites is challenging because of their lack of distinctive geophysical signatures. The GREENPEG project (project GA869274, EU HORIZON 2020 programme) has developed a multi-method toolset based on an improved understanding of pegmatite properties, settings and genesis.
The Leinster pegmatite belt is located within the narrow (<3 km) but extensive, SW-NE trending East Carlow Deformation Zone (ECDZ) which forms the eastern contact of the late-Caledonian composite Leinster Batholith that intruded previously deformed Lower Palaeozoic metavolcano-sedimentary rocks. The unexposed spodumene pegmatites form up to 20 m thick NW-dipping sheets.
Shear zones/faults, and lithological boundaries can be delineated using airborne geophysics on a province and district scale. At prospect scale, the ECDZ is clearly visible in electrical resistivity tomography (ERT) measurements that also allow the identification of weathered granite, faults, and high resistivity areas prospective for pegmatites.
Lithium concentrations in soils and certain minerals in stream sediments (spodumene, garnet, kaolinite) provide successful pathfinders for subcropping pegmatites.
Orientation data for different structures, obtained from borehole logging combined with field and drill core observations, enabled the identification of several generations of (barren) pegmatite and indicate a relatively late emplacement age for the spodumene pegmatites. This is consistent with quartz from the spodumene pegmatites having lower Ti and higher Al, Li, and Ge concentrations than that in barren pegmatites, indicating more evolved compositions.
We show that complementary geophysical, geochemical, and geological methods can be successfully used for spodumene pegmatite exploration. The data furthermore enhanced our understanding of pegmatite emplacement in SE Leinster.