Decoding multiple ore mineral remobilization processes during polyphase deformational phases from the Precambrian Pyhäsalmi VMS deposit halo, Central Finland: new insights from mineralogy, mineral chemistry and micro-CT
: Islam, Sk Rakibul; Heilimo, Esa; Kuva, Jukka; Mäkilä, Ermei; Mäki, Timo
Publisher: Springer Science and Business Media LLC
: NEW YORK
: 2025
: International Journal of Earth Sciences
: International Journal of Earth Sciences
: INT J EARTH SCI
: 21
: 1437-3254
: 1437-3262
DOI: https://doi.org/10.1007/s00531-025-02511-4
: https://doi.org/10.1007/s00531-025-02511-4
: https://research.utu.fi/converis/portal/detail/Publication/498514568
The Precambrian bimodal Pyh & auml;salmi Zn-Cu-Ag-Au VMS deposit in the Svecofennian domain of Finland has undergone various degrees of metamorphism and deformation, which have altered the composition and texture of the minerals, resulting in sulfide remobilization. However, studies on metamorphism and its influence on the ore mineral remobilization in the Pyh & auml;salmi region are lacking. Our study provides insights into the remobilization history of ore minerals during polyphase deformational and metamorphic events in the deposit halo region by integrating mineralogical, textural, mineral chemical, microtextural, and 3D micro-CT analyses. We propose that the Pyh & auml;salmi deposit has experienced two distinct ore mineral remobilization stages: (a) The first stage, associated with D1-D2 deformational phase, is dominated by solid-state (mechanical) remobilization processes demonstrated by cataclastic flow, foliated, elongated sulfide, which possibly occurred before the metamorphic peak denoted by staurolite + garnet + cordierite, and (b) The second stage, linked to D4 deformational phase, is characterized by mixed-state remobilization processes evidenced by the spatial distribution of disseminated pyrrhotite around the grain boundaries of silicate porphyroblasts, attenuation of sulfides around the hinge zone of the crenulation cleavages and fracture filling sulfides, which possibly occurred during metamorphic peak conditions represented by sillimanite + garnet + cordierite + biotite. Published studies on ore remobilization often overlook the potential of linking ore minerals to metamorphic mineral assemblages through petrographic and microstructural observations. Our study addresses this gap by providing a framework to decode the ore mineral remobilization events in polyphase deformational and metamorphic environments using metamorphic mineral assemblages, garnet porphyroblasts, and microstructural analysis.Graphical abstract The schematic diagram illustrates Pyh & auml;salmi sulfide remobilization processes during polyphase deformational events. The ore minerals underwent two stages of remobilization: a) The first stage, associated with D1-D2 phase, is dominated by solid-state remobilization processes that possibly occurred before the metamorphic peak denoted by staurolite + garnet + cordierite, and b) The second stage, linked to D4 phase, is characterized by mixed-state remobilization processes that possibly occurred during metamorphic peak conditions represented by sillimanite + garnet + cordierite + biotite.
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We are grateful to the K.H. Renlund foundation (K.H. Renlunds Stiftelse) for providing financial support. We thank Arto Peltola from the University of Turku and Soeren Froejdoe from Abo Akademi University for thin section preparation and imaging. We thank Jani Jaesperi from the Geological Survey of Finland for providing drill core data. We acknowledge the Materials Research Infrastructure (MARI) at the Department of Physics and Astronomy, University of Turku for access and support with the SEM facilities. Micro-CT was funded by the Research Council of Finland via the RAMI infrastructure project (#293109). We like to express gratitude for the editorial handling by Ulrich Riller and constructive reviews by Stephanie Bruckner and an anonymous reviewer.
