Fluid migration, albitization, and metal concentration in the Munster Basin, SW Ireland

Fluids exert a fundamental control on mineral reactions and mass transfer in intracratonic basins, yet the drivers of Na-metasomatism in basins lacking classical evaporite sequences remain poorly understood. The Devonian–Carboniferous Munster Basin of SW Ireland, hosting widespread Cu mineralization, has traditionally been described as containing super-mature arenites with limited feldspar content. However, recent Raman spectroscopic mapping has identified feldspathic sandstones displaying pervasive albitization with at least three different structural varieties of albite providing new insights into a complex history of fluid-rock interaction, and associated metal concentration, across multiple scales.

A detailed petrographic and geochemical analysis is proposed to map the spatial and temporal evolution of albitization in the Munster Basin and investigate how this corresponds with sediment leaching, faulting, and the distribution of metalliferous deposits. To achieve this, three N–S traverses across the basin are conducted, integrating in-situ portable X-ray fluorescence (XRF) measurements to acquire major and trace element data and systematic hand-sampling for laboratory analyses. These basin-scale observations are combined with micro- to nano-scale analytical approaches to investigate (1) the distribution and timing of albitization, (2) the identification of precursor feldspar compositions (K-feldspar vs. plagioclase) through Raman geochemistry, and (3) the implications for sediment leaching and trace-metal mobilization. Portable XRF data are complemented by 2D confocal Raman imaging, petrography, and targeted LA-ICP-MS analysis to constrain fluid chemistry, flow pathways, and the conditions driving feldspar alteration. Particular attention is given to areas adjacent to volcanic centers and major faults, which may have acted as conduits for downward-migrating saline fluids during transgressive events, providing a source capable of inducing pervasive albitization even in the absence of evaporite sequences. 

Preliminary results show systematic variations in albite structural types and associated geochemical signatures that correlate with basin architecture and fault-controlled fluid pathways. By linking grain-scale mineral transformations to basin-scale structural and geochemical frameworks, this study provides new insights into the mechanisms controlling fluid migration, diagenetic alteration, and metalliferous enrichment in post-orogenic intracratonic basins.