Spatial relations and bulk chemical compositions of three bodies of multiphase leucogranites and two categories of granitic pegmatites in the Archean Red Cross Lake greenstone belt, Sachigo Subprovince of the Superior Province in the Canadian Shield, indicate a comagmatic origin and an enormous range of fractionation. The leucogranite + pegmatite assemblages, probably emplaced at similar to 2.65 Ma, represent an upward fingering-out system presumably rooted in a deeper-seated granitic parent, which was derived by anatexis of felsic lithologies of the greenstone belt, with possible contribution from granitoid components of the flanking plutonic terranes. The leucogranitic melts so derived underwent extensive fractionation, culminating in the lepidolite pegmatites that solidified within the relatively low-P -high-T stability field of petalite. The most primitive fine-grained NGR leucogranite shows a K/Rb of 303. In contrast, the most evolved LPG lepidolite-type pegmatites [with albite >> K-feldspar, K-, Rb-and Cs-dominant lepidolite, spodumene + quartz after petalite, elbaite, beryl, pollucite, amblygonite, and (Ta, Sn)oxide minerals] average K/Rb 1.8, and Cs 4199, Be 236, Ga 161, Nb 14, and Ta 349 ppm. Crystal-liquid and gravity-assisted liquid-liquid fractionation and differential solubilities of HFSE in the melts could have cooperated with selective complexing of elements and mass-controlled diffusion rates to attain the extreme enrichment and fractionation observed at the scale of pegmatite dikes down to local crystal-matrix levels. The bulk chemical composition of the dikes was not affected by mylonitization. The oxygen-isotope signature of the pegmatites also suggests relatively dry conditions during shearing, with very limited exchange with the host rocks. In contrast, the Rb-Sr isotopes are extensively disturbed in both the leucogranites and LPG dikes.

Intimate intergrowths of ferrotantalite and ferrotapiolite occur in a pegmatite in Spittal a.d. Drau, Carinthia. They are associated with muscovite, albite, smoky quartz, cassiterite, and microscopic uranmicrolite, zircon and uraninite. An assemblage of secondary uranium minerals is also present, generated by extensive alteration and leaching of the uranmicrolite and zircon. Textures of the ferrotantalite-ferrotapiolite intergrowths suggest considerable recrystallization that obliterated most of their primary features; neither coprecipitation nor exsolution can be recognized with certainty. Despite intersecting tielines indicating disequilibrium, the ferrotantalite and ferrotapiolite compositions show very restricted ranges (Mn/(Mn + Fe) 0.08–0.11, Ta/(Ta + Nb) 0.53–0.57 for ferrotantalite, and 0.01–0.04, 0.84–0.89 for ferrotapiolite, respectively), particularly in comparison with compositions from other localities featuring primary textures. A degree of compositional equilibration could have been attained during recrystallization. This process may also explain the high level of structural order characterizing both minerals; they are considerably disordered in other localities. Extensive deformation typical of pegmatites in the southern Ostalpen in general, and specifically of the Spittal pegmatite, is probably responsible for the recrystallization phenomena in the Ta, Nb, Sn-bearing mineral assemblage.