Textural relationships and compositional variations of (Fe,Mn)-(Ti,Sn)-(Nb,Ta) oxides and associated minerals from low- to moderately fractionated, mixed (NYF + LCT) anatectic pegmatites, which belong to the Julianna pegmatitic system, exposed at Piława Górna, Lower Silesia, Poland, were studied to elucidate the geochemical evolution of the pegmatite-forming melt. The primary Nb-Ta oxides crystallized in the following sequence: (1) columbite-(Fe) evolving to columbite-(Mn), associated with Nb- and Ta-bearing ilmenite-pyrophanite + almandine-spessartine garnet + Ti-poor schorl, (2) columbite-(Fe), (3) tantalite-(Fe), (4) Ti- and Sn-bearing ixiolite ± ferrowodginite ± Nb- and Ta-bearing cassiterite ± columbite-(Fe), all crystallizing along with Ti-enriched schorl evolving to dravite. The most characteristic features of the mineral assemblages are the reversed Mn-Fe fractionation trends and increasing Ca concentrations at the final stage of crystallization. These compositional variations are explained by a possible pre-emplacement contamination of the pegmatite-forming melt and re-equilibration of biotite and plagioclase from the early-crystallized outer zones of the pegmatites with rapidly cooling pegmatitic melt. Local changes in melt composition were of minor importance. Late alterations, such as chloritization and muscovitization of biotite or albitization of Ca-rich plagioclase were significant only at the hydrothermal stage

The Julianna pegmatite vein system at the Piława Górna Mine, Góry Sowie Block, SW Poland – preliminary data on geology and descriptive mineralogy

Tourmalines are a group of minerals which may concentrate various accessory components, e.g., Cu, Ni, Zn, Bi, Ti, and Sn. The paper presents fluor-elbaite and elbaite from a dyke of the Julianna pegmatitic system at Piława Górna, at the NE margin of the Bohemian Massif, SW Poland, containing up to 6.32 and 7.37 wt % ZnO, respectively. Such high amounts of ZnO are almost two times higher than in the second most Zn-enriched tourmaline known to date. The compositions of the Zn-rich tourmalines from Piława Górna, studied by electron micropropy and Raman spectroscopy, correspond to the formulae: ^X(Na_0.733Ca_0.013☐_0.254)_Σ1^Y(Al_1.033Li_0.792Zn_0.755Fe²⁺_0.326Mn_0.094)_Σ3^ZAl₆(^TSi₆O₁₈)(BO₃)₃^V(OH)₃^W(F_0.654OH_0.344), and ^X(Na_0.779Ca_0.015☐_0.206)_Σ1^Y(Al_1.061Li_0.869Zn_0.880Fe²⁺_0.098Mn_0.094)_Σ3^ZAl₆(^TSi₆O₁₈)(BO₃)₃^V(OH)₃^W(OH_0.837F_0.163), respectively, with Zn as one of the main octahedral occupants. A comparison with other tourmalines and associated Zn-rich fluor-elbaite and elbaite from the pegmatite indicates that atypically high Zn-enrichment is not a result of Zn-Fe fractionation, but dissolution and reprecipitation induced by a late (Na,Li,B,F)-bearing fluid within the assemblage of gahnite spinel and primary schorl-type tourmaline. This strongly suggests Na-Li-B-F metasomatism of gahnite-bearing mineral assemblages as that is the only environment that can promote crystallization of a hypothetical Zn-dominant tourmaline. The compositions of the Zn-rich fluor-elbaite and elbaite suggest three possible end-members for such a hypothetical tourmaline species: NaZn₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH), ☐(Zn₂Al)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH) and Na(Zn₂Al)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O by analogy with other tourmalines with divalent Y occupants, such as schorl/foitite/oxy-schorl and dravite/magnesio-foitite/oxy-dravite.

Ishikawaite and samarskite-(Y) are indicators of an NYF signature in the mildly to moderately fractionated parts of the hybrid NYF + LCT Julianna pegmatitic system at Piława Górna, the Góry Sowie Block, SW Poland. The minerals were metasomatically altered by a Ca-bearing and Ta-enriched highly fluxed residual silicate melt. The intensity of the metasomatism and the chemical composition of its products strongly depended on the efficiency of the transport of ions to and from the replacement front. Restricted access of the fluid promoted the formation of calciosamarskite and oxycalciopyrochlore. Where the fluid could migrate more easily, with decreasing pH and temperature the alteration products became deficient in A-site cations (mainly Ca²⁺ and Mn²⁺). Consequently, earlier-crystallized pyrochlores transformed to zero-valent-dominant pyrochlores and microlites enriched in U+Th, Y+REE, or Ca. Low-temperature hydrothermal fluids were responsible for the final enrichment in Pb and Bi.