Föstudagserindi Jarðvísindastofnunar og Norræna eldfjallasetursins 30. janúar 2026 - Byron Fabian Pilicita Masabanda (PhD student, IES)

Útdráttur:

A comprehensive understanding of magmatic-hydrothermal fluids associated with felsic intrusions at mid-ocean ridges is crucial for optimizing geothermal resources, yet the complex interplay between magmatic degassing, fluid-rock interaction, and fluid mixing in these systems remains poorly understood. In this study, the origin, composition, and evolution of magmatic-hydrothermal fluids associated with felsic intrusions in Iceland are investigated, focusing on microthermometry and compositional analysis of quartz-hosted fluid inclusions in the Hoffell Granite Intrusion (HGI) within the fossil Geitafell Central Volcano (GCV). The analysis shows evidence for two primary fluid events: a high-temperature (> 430 °C), high-salinity (> 50 wt% NaCl) brines derived from magmatic degassing and salt-saturated conditions, and a lower-temperature (220-300 °C), lower-salinity (0-3 wt% NaCl) fluid likely sourced from meteoric water. Significant mixing between these magmatic and meteoric fluids is indicated by intermediate fluid inclusion compositions and correlations among key trace elements. The fluids are dominated by Na, K, and Fe as major cations, with significant concentrations of Mn, Al, and Ca also present. Trace element analysis reveals notable concentrations of Zn and Pb, along with variations in Rb, Cs, and Ba. Based on these findings, a conceptual model is proposed, detailing the hydrothermal system's evolution: starting with the granite's emplacement and subsequent fracturing that allowed meteoric water influx, and result in fluid mixing and fluid-rock interaction. The characterization of these fluids provides crucial insights for predicting fluid behavior above shallow felsic intrusions in Iceland, mitigating scaling and corrosion challenges, and improving resource exploration and exploitation strategies in comparable active geothermal settings.

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