© Българско геологическо дружество и Българска академия на науките, 2023 https://bgd.bg/review-bgs Национална конференция с международно участие „ГЕОНАУКИ 2023“ National Conference with International Participation “GEOSCIENCES 2023” СПИСАНИЕ НА БЪЛГАРСКОТО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, год. 84, кн. 3, 2023, с. 63–66 REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 84, part 3, 2023, p. 63–66 Garnet (REE+Y)-bearing mineral association in pegmatite from the Chepino lithotectonic Unit, Western Rhodopes Rossitsa D. Vassileva 1 , Sylvina Georgieva 1 , Jan Cempírek 2 , Valentin Grozdev 1 , Radek Škoda 2 , Elitsa Stefanova 1 1 Geological Institute, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria; E-mails: rosivas@geology.bas.bg; sylvina@geology.bas.bg; val.grozdev@gmail.com; elitsa.s@gmail.com 2 Department of Geological Sciences, Masaryk University, Brno, Czech Republic; E-mails: jan.cempirek@gmail.com; rskoda@sci.muni.cz (REE+Y)-съдържаща минерална асоциация на пегматитов гранат от Чепинската литотоектонска единица, Западни Родопи Росица Д. Василева 1 , Силвина Георгиева 1 , Ян Цемпирек 2 , Валентин Гроздев 1 , Радек Шкода 2 , Елица Стефанова 1 Abstract. Large pegmatite body/bodies are outcropping in the “Suhata Reka” quarry, near the town of Rakitovo. Their bulk mineral composition with dominant K-feldspar (40%), plagioclase (30%), quartz (25%) and mica (≤ 5%) is complemented by (REE+Y)-bearing association of primary and secondary accessories. Zircon, monazite, xenotime, scarce apatite and noticeable amount of garnet are among the pegmatite primary minerals. The cm-sized almandine- spessartine crystals contain numerous fractures which host secondary (REE+Y)-bearing phosphate (xenotime, cher- alite) and silicate minerals (e.g. REE-epidote). Formation of the late-stage REE-mineralization in garnet is due to its hydrothermal alteration and redistribution of REE+Y in the secondary phases. Keywords: pegmatite, garnet, xenotime, ‘Suhata reka’ quarry, SW Bulgaria. Introduction Large pegmatite accumulations are exploited for the ceramic industry in the ‘Suhata Reka’ quar- ry, SW from the town of Rakitovo in Western Rhodopes (Fig. 1A). They form large intrusive bodies with sharp contacts (Fig. 1B, C) in the metamorphic rocks of the Chepino Lithotectonic Unit, in this area represented by metagranitoids, migmatised gneisses (biotite and two-mica), am- phibolites and marbles (Fig. 1B, C; Sarov et al., 2009). The zircon U-Pb age of the pegmatite is 68.7±1.3 Ma (Grozdev et al., 2023). Besides the typical pegmatite minerals such as coarse-grained K-feldspar, plagioclase, quartz and mica, the stud- ied rocks contain diversity of minor accessory minerals, which concentrate significant amounts of incompatible elements (e.g., REE, Y, Th, U etc.) with strategic importance. Garnet crystals and accumulations of various sizes are commonly encountered in the field (Fig. 1 D, E) and repre- sent important hosts for secondary silicate-phos- phate mineralization. The present study is focused on the mineral com- position and chemical characteristics of the garnet (REE+Y)-bearing association of accessory minerals in the pegmatites from the outcrop in the ‘Suhata Reka’ quarry. https://doi.org/10.52215/rev.bgs.2023.84.3.63