Aplicação de cartografia LiDAR aéreo no controlo estrutural de filões aplitopegmatitos com Sn-Li na região do Alvão, Portugal

Abstract

The Alvão region in northern Portugal hosts a significant field of aplite-pegmatite dykes enriched in lithium, tin, niobium, and tantalum. These aplite-pegmatite dykes from the Alvão region are emplaced within the parautochthonous succession of the Galicia-Trás-os-Montes Zone, deformed during the Variscan orogeny. Throughout the deformation process, a series of developed structures may have served as preferential channels, allowing aplite-pegmatite melts to rise and settle, thus controlling their spatial orientation and final geometry. This study employs high-resolution airborne and drone-based LiDAR topographic mapping to analyze the structural controls on aplite-pegmatite emplacement, now visible as longitudinal trenches from artisanal tin exploitation during Roman times and in the 20th century. It also delineates elongated magmatic structures obscured by dense vegetation. By integrating LiDAR digital elevation models with regional geological surveys, we document the spatial distribution and orientation patterns of the aplite-pegmatite dykes and examine their relationship to regional tectonic structures. Spatial analysis identified a clustered distribution of aplite-pegmatite dykes near regional deformation zones indicating that melt emplacement was guided by structures associated with the Variscan orogeny. Analysis of the dyke orientations revealed two dominant orientation families, N150° and N170°, and two subordinate families, N030° and N120°. These orientations are consistent with the regional shear zones described by Pereira et al. (1993) for this area, supporting a model in which aplite-pegmatite melts were emplaced along extensional jogs associated with regional deformation zones. This approach demonstrates the effectiveness of LiDAR in mapping elongated magmatic structures in densely vegetated terrains, where traditional field work may be limited. These findings contribute to understanding the tectonic and structural influences on the emplacement and geometry of aplite-pegmatite dykes enriched in critical materials, and improve predictive models for critical mineral exploration. This study supports Portugal potential role in Europe’s critical raw materials supply chain, aligning with EU strategies.