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Mineralogical studies of the Karkonosze granite (ca. 322–312 Ma) and its surroundings in West Sudetes (SW Poland) have provided data on Nb-Ta-REE minerals from pegmatites in the NE part of the pluton and several new finds of Ag minerals and 15 oxygenic Bi phases, hitherto not reported from the massif. The Karkonosze pegmatites are enriched in HREE as fergusonite-(Y) or xenotime-(Y) appear in almost every studied pegmatite, together with a subordinate assemblage of the aeschynite, euxenite or columbite group. The abundance of LREE minerals such as allanite-(Ce) and the monazite group, correlates inversely with the Nb-Ta-Ti minerals, whilst an early generation of monazite-(Ce) revealed an exceptionally high amount of Nd (up to 22 wt.% of Nd2O3). The physical and chemical conditions during the magmatic and post-magmatic processes were reconstructed and the effects of contact metamorphism in amphibolites from hornfelsed zones examined. Changes in solution composition and concentration at the early magmatic stage (825–920ºC), pegmatitic stage overlapping with hydrothermal (560°C which ended at 160–90°C) and clearly hydrothermal stage (400 to 110°C) were studied in detail by means of melt and fluid inclusions in quartz. Furthermore, post-magmatic fluids, including some enriched in Li and B, were identified in rock-forming quartz from the whole pluton. In turn, study of the amphibolites indicates that the pair cummingtonite + anorthite or the presence of Ca-rich plagioclase with actinolite seem to be reliable mineral proxies of the thermal impact of the granitoid body on amphibolites in its envelope. The inferred conditions of the contact processes (450–550°C, 2.5–4.8 kbar) point to an elevated geothermal gradient (ca. 32–45°C/km) probably reflecting the heat flow induced by the Karkonosze intrusion. Moreover, despite the textural and mineral changes imposed by regional and contact metamorphism, the amphibolites have their pre-metamorphic (magmatic) geochemical features undisturbed.
The fast-growing discipline in the field of geothermal research is the prospecting for geological structures useful for HDR (Hot Dry Rock) or EGS (Enhanced Geothermal Systems) technologies. In Poland, an interesting area for such research is the Sudetes, particularly the Karkonosze Mts. pluton and Fore-Sudetic Block. The article presents issues of scientific projects prepared in the Division of Renewable Energy of Mineral and Energy Economy Research, Institute of the Polish Academy of Sciences in Kraków, related to the recognition of geothermal conditions of the Sudetic region. On the background of global research, these projects demonstrate an innovative character mainly by targeting research on the analysis of tectonics and volcanism of the Sudetes as important factors of the presence of local positive thermal anomalies. Implementation of the afore-mentioned projects would create the possibility of extending still modest knowledge of the deep geological structure of the Sudetic area.
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