REE and Y Mineralogy of the Krudum Granite Body (Saxothuringian Zone)

The Krudum granite body comprises highly fractionated granitic rocks ranging from medium-F biotite granites to high-F, high-P2O5 Li-mica granites. This unique assemblage is an ideal site to continue recent efforts in petrology to characterize the role of zircon, monazite, and xenotime as hosts to rare earth elements (REEs). The granitic rocks of the Krudum body analyzed in this study were found to contain variable concentrations of monazite and zircon, while xenotime was only found in the high-F, high-P2O5 Li-mica granites and in the alkali-feldspar syenites of the Vysoký Kámen stock. Intermediate trends between cheralite and huttonite substitutions are characteristic for analyzed monazite grains from all magmatic suites. The highest concentration of cheralite was found in monazite from the alkali-feldspar syenites (up to 69.3 mol %). The proportion of YPO4 in analyzed xenotime grains ranges from 71 to 84 mol %. Xenotime grains are commonly enriched in heavy rare earth elements (HREEs; 9.3–19.5 wt % HREE2O3) and thorite-coffinite and cheralite exchange was observed. Some xenotime analyses return low totals, suggesting their hydration during post-magmatic alterations. Analyzed zircon from granite suites of the Krudum granite body contains moderate Hf concentrations (1.0–4.7 wt % HfO2; 0.010–0.047 apfu Hf). The highest concentrations of HfO2 were found in zircon from the high-F, high-P2O5 Li-mica granites (1.2–4.7 wt % HfO2). Analyzed zircon grains from the high-F, high-P2O5 Li-mica granites and alkali-feldspar syenites are enriched in P (up to 8.29 wt % P2O5; 0.24 apfu P), Al (0.02–2.0 wt % Al2O3; 0.00–0.08 apfu Al), Ca (up to 3.9 wt % CaO; 0.14 apfu Ca), Y (up to 5.5 wt % Y2O3; 0.10 apfu Y), and Sc (up to 1.17 wt % Sc2O3; 0.03 apfu Sc). Zircon grains from the high-F, high-P2O5 Li-mica granites were sometimes hydrated and fluorized. The concentrations of F in zircon from partly greisenised high-F, high-P2O5 Li-mica granites reached up to 1.2 wt % (0.26 apfu F)