Ti FERRIALLANITE-(Ce), Ti AND Ti-V ALLANITE-(Ce), ALLANITE-(Ce), ALLANITE-(Y), REE EPIDOTE IN BIOTITE-BEARING QUARTZ GABBROIDS AND PLAGIOGRANITOIDS OF THE ISLAND-ARC PERVOMAYSKO-AIUDAGSKY COMPLEX OF THE CRIMEAN MOUNTAINS

The unique association of rare-earth minerals of the epidote group, as well as the evolution of lantanides and actinides, titanium and vanadium in their composition are described. Allanite-(Ce), often with a ferriallanite-(Ce) core, an outer zone of allanite-(Y) and a rim of REE epidote, forms pseudomorphs after chevkinite-(Ce) and perrierite-(Ce), as well as isolated crystals. They form intergrowths with biotite, developing near it in quartz gabbronorite-dolerites and gabbronorite-diorites of the island-arc mafic hypabyssal Pervomaysk-Ayudag complex within Mountain Crimea. Zonal allanite-(Ce) of similar composition, accompanied by REE epidote rims, is widespread in quartz diorites and plagiogranites of the same complex, where it is often developed in granophyric quartz-oligoclase intergrowths. Brown ferriallanite-(Ce) enriched in Ti (± Th) forms cores in brown allanite-(Ce) crystals enriched in Ti (± V) (up to 4.9 wt. % TiO). Allanite-(Ce) enriched in titanium (up to 3.5 wt. % TiO), which replaced ilmenite, is extremely rich in vanadium (up to 4.5 wt. % VO). Light colored low-titanium allanite-(Ce) has grown on titanium enriched allanite-(Ce). The distribution of lanthanides and yttrium in allanite-(Ce) and ferriallanite-(Ce) is: Ce > La > > Nd > Y > Pr > Sm ~ Dy ~ Gd > Er ~ Tb. The outer zones of allanite-Ce) crystals and rare-earth epidote are relatively enriched in Nd, whereas Nd > La in some instances. The ratio of yttrium and lanthanides in allanite-(Y) is specific: Y >> Ce ~ Nd ~ Dy ~ Er > La ~ Gd ~ Yb. Allanite-(Ce) of Crimean gabbroids is noticeably richer in La, Ti, V and poorer in Y, Sm, Gd in comparison with allanite-(Ce) of Crimean plagiogranitoids. According to (Fleischer, 1985), the distribution of lanthanides and yttrium in allanite-(Ce) of Crimean plagiogranitoids is close to the similar distribution in standard granites, differing in an increased proportion of Gd. The coloration causes and matter sources for magmatic Crimean allanite formation are considered. Allanite was partially replaced by monazite-(Ce) during the processes of regional metamorphism under the conditions of the prehnite-pumpellyite facies.