Olga Demina, Gražina Skridlaitė, Laurynas Šiliauskas, Marcin Łącki, Beata Marciniak-Maliszewska, Bogusław Bagiński

Post-magmatic alteration in the Kabeliai granite, Lithuania: evidence from petrography, mineral chemistry, and accessory minerals

Santrauka This study reconstructs the sequence of secondary mineral transformations in the Kabeliai granite (southern Lithuania) based on detailed petrographic, mineral chemical, and isotopic data from samples obtained from a drill core Marcinkonys-7. The selected samples represent various lithologies and grades of alteration, from melanocratic diorite to pegmatitic granite. Several alteration steps were identified. The earliest is marked by the late-magmatic re-equilibration of feldspars and accessory minerals. The following subsolidus re-equilibration leads to perthitic textures and albite replacement. The later stage reflects infiltration of Na–Ba–SO₄-bearing fluids, which caused feldspar metasomatism, biotite alteration, barite precipitation, and partial titanite breakdown. Finally, F–CO₂-rich fluids induced advanced replacement of titanite by anatase, calcite, and REE-carbonates, accompanied by widespread albitisation, hematite formation, and REE mobilisation. The observed mineral assemblages and textural relationships are consistent with progressive fluid-driven modification under increasing fO₂ and decreasing temperature. These results demonstrate that accessory minerals such as titanite and apatite can preserve complex records of post-magmatic processes and highlight the role of oxidising REE-bearing fluids in the late evolution of granitic systems.

Doi https://doi.org/10.5200/baltica.2025.2.3

Raktažodžiai granite alteration; titanite replacement; fluid-rock interaction; REE mobilisation; albitisation; metasomatism; Mesoproterozoic; secondary mineralisation

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