Geochemistry of rare earth elements in the zone of interformational contact in the Maldynyrd Range (Near-Polar Urals)

Metamorphic rocks-hydrolysates, which are strongly enriched in Al and Fe (s ericite, pyrophyllite, chloritoid, diaspore, and hematite schists), are dev eloped in the interformational contact zone between Precambrian pre-Uralide and Paleozoic Uralide complexes in the Maldynyrd Range (Near-Polar Urals). These rocks have various origins. Some of them are metamorphosed Cambrian weathering crusts (Ti-rich hematite schists, as well as pyrophyllite and ch loritoid schists in many localities) or products of their redeposition (Al' kesvozh Sequence, epsilon (3)-O(1)al). Others are products of Late Paleozoi c fault-zone metasomatism (sericitolites, diasporites?, and some boron-rich chloritoid schists). By Ti index (TI), the following two series of metamor phic rocks can be distinguished: low-titanium aporhyolites and high-titaniu m rocks. The latter are genetically related to metamafic rocks and ancient weathering crust upon them. The greisenized aporhyolitic rocks compose thic k zones of REE accumulation. Microprobe analysis shows that REE are concent rated in phosphates, arsenates, silicates, and molybdate-tungstates. Some o f these phases could be considered new minerals.