Żabińskiite, ideally Ca(Al_(0.5)Ta_(0.5))(SiO_4)O, a new mineral of the titanite group from the Piława Górna pegmatite, the Góry Sowie Block, southwestern Poland

Żabińskiite, ideally Ca(Al_(0.5)Ta_(0.5))(SiO_4)O, was found in a Variscan granitic pegmatite at Piława Górna, Lower Silesia, SW Poland. The mineral occurs along with (Al,Ta,Nb)- and (Al,F)-bearing titanites, a pyrochlore-supergroup mineral and a K-mica in compositionally inhomogeneous aggregates, ∼120 μm × 70 μm in size, in a fractured crystal of zircon intergrown with polycrase-(Y) and euxenite-(Y). Żabińskiite is transparent, brittle, brownish, with a white streak, vitreous lustre and a Mohs hardness of ∼5. The calculated density for the refined crystal is equal to 3.897 g cm^(–3), but depends strongly on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥1.89. The (Al,Ta,Nb)-richest żabińskiite crystal, (Ca_(0.980)Na_(0.015))Σ=0.995(Al_(0.340) Fe^(3+)_(0.029) Ti_(0.298)V_(0.001)Zr_(0.001)Sn_(0.005)Ta_(0.251)Nb_(0.081))Σ=1.005[(Si_(0.988)Al_0.012)O_(4.946)F_(0.047)(OH)_(0.007))Σ=5.000]; 60.7 mol.% Ca[Al_(0.5)(Ta,Nb)_(0.5)](SiO_4)O; is close in composition to previously described synthetic material. Żabińskiite is triclinic (space group symmetry Ai and has unit-cell parameters a = 7.031(2) Å, b = 8.692(2) Å, c = 6.561(2) Å, α = 89.712(11)°, β = 113.830(13)°, γ = 90.352(12)° and V = 366.77 (11) Å3. It is isostructural with triclinic titanite and bond-topologically identical with titanite and other minerals of the titanite group. Żabińskiite crystallized along with (Al,Ta,Nb)-bearing titanites at increasing Ti and Nb, and decreasing Ta activities, almost coevally with polycrase-(Y) and euxenite-(Y) from Ca-contaminated fluxed melts or early hydrothermal fluids

Vestiges of late Cambrian arc-related magmatism within the Variscan belt of Europe: Zircon geochronological and whole-rock geochemical data from the Leszczyniec Metaigneous Complex, Sudetes, Poland

We present major oxides, trace elements, Sr-Nd-Hf isotope and zircon age data for rock samples from the Leszczyniec Metaigneous Complex (LMC) in the Polish Sudetes. The LMC comprises low/medium-grade metamorphic mafic rocks of basaltic composition that are intimately associated with felsic and amphibole-bearing gneisses. Magmatic precursors to all varieties of gneisses were emplaced between c. 515 Ma and 495 Ma. The age of the metabasite remains unconstrained, but the calculated two-stage Nd model age (0.54 Ga) of the sample with highest radiogenic Nd value may in this case represent a maximum age. This is consistent with the oldest single zircon ages produced for the gneisses that may represent inheritance. The most prominent geochemical feature of the studied samples is a depletion in the HFSE, most notably Nb and Ta, which can be observed in all studied lithologies. The high abundance of basic rocks with troughs at Nb in primitive mantle-normalized multi-elemental diagrams, combined with a limited degree of REE fractionation and highly radiogenic Nd and Hf isotopic compositions favour an intraoceanic volcanic arc tectonic setting for emplacement of the LMC protoliths. The derivation of compositionally diverse magmatic precursors to gneisses can be explained by the combination of slab sediment melts at relatively low-pressure/temperature (high Nb/Y felsic gneiss), heterogeneous mixing of those melts and slab derived fluids with a highly depleted mantle (amphibole-bearing gneiss/metagabbro), and low-degree partial melting of metabasite of a former back-arc domain (low Nb/Y felsic gneiss). This study demonstrates that late Cambrian magmatism, widespread across terranes included in the Variscan belt, cannot be unequivocally attributed to continental rifting. Metaigneous suites belonging to the Variscan Middle and Upper Allochthon, such as the LMC, were presumably derived from marginal basins developed within a convergent tectonic setting outboard of Gondwana or Baltica, which may have remained active until the end of the Cambrian.This work was supported by the Polish National Science Centre grant no. 2016/23/N/ST10/01296 awarded to Maria Młynarska. S.C. additionally acknowledges institutional support of the research project no. 311170 (Strategic Research Plan of the Czech Geological Survey-DKRVO/ČGS 2018–2022). M.B. acknowledges the “Juan de la Cierva” Fellowship JFJC2021-047505-I funded by MCIN/AEI/10.13039/501100011033 and CSIC.Peer reviewe

Albitization as record of the Triassic Paleosurface in the Sudetic Crystalline basement (Poland).

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Zabinskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, a new mineral of the titanite group from the Pilawa Gorna pegmatite, the Gory Sowie Block, southwestern Poland

Zabinskiite, ideally Ca(Al0.5Ta0.5)(SiO4) O, was found in a Variscan granitic pegmatite at Pilawa Gorna, Lower Silesia, SW Poland. The mineral occurs along with (Al, Ta, Nb)-and (Al, F)-bearing titanites, a pyrochlore-supergroup mineral and a K-mica in c

Paleomagnetic datation of hematite remagnetizations inscribed in granito¨ıd rocks of the Polish Sudetes – Implications on the Permo-Triassic paleosurface

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Albitization and oxidation of Variscan granitoid rocks related to the post-Variscan paleosurface in the Sudetes (Bohemian Massif, SW Poland)

International audienceThe reddened granitoid facies in the basement of the Polish Sudetes exhibits two categories of alteration spatially arranged with respect to fractures: (1) saussuritization and sericitization within light-colored facies in the interior of fracture-bounded blocks and (2) albitization and hematization in reddened facies occurring adjacent to fracture walls. These alterations are associated with the chloritization of primary ferromagnesian minerals and the development of secondary minerals such as quartz, K-feldspar, apatite, prehnite, calcite, and titanite. We link these parageneses and the observed zonation to a unique alteration event consisting of an interplay of chemical reactions of variable spatial extent. The complete albitization of the feldspars (plagioclase and K-feldspar) adjacent to fractures points to a significant supply of Na for albite neoformation and the availability of oxygen to form the associated hematite. The dating of the iron oxides by paleomagnetism and the second-ary monazite associated with the albitized facies by U-Th-Pbtotal unambiguously indicates their post-Variscan ages. In this context, the alterations are related to a regionally widespread post-Variscan paleosurface. The weathering profiles formed in phreatic groundwater environments downgradient of highlands that provided a hydrological head. Sodium supply likely originated from gigantic salt playas that characterized Permian and Triassic lowlands. Weathering was interrupted by the Mesozoic transgression. The recognition of these weathering profiles over extensive parts of the Variscan Belt provides the basis for reconstructing the post-Variscan paleosurface and constraining Triassic and post-Triassic geodynamics, including erosion rates and geomorphological evolution of the Paleozoic massifs in Europe

Albitization and oxidation of Variscan granitoid rocks related to the post-Variscan paleosurface in the Sudetes (Bohemian Massif, SW Poland)

Peer ReviewedObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesObjectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables::12.2 - Per a 2030, assolir la gestió sostenible i l’ús eficient dels recursos naturalsPostprint (author's final draft

Restitution de la paléosurface triasique par datation des ré-aimantations inscrites dans les massifs paléozoïques européens

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Paleomagnetic age constrains and magneto-mineralogic implications of the Triassic paleosurface in Europe

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