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Our study of boreholes, seismic survey and magnetic data from the region between the Baltic Basin and the Lublin Basin indicates the existence of numerous buried intrusions and effusive complexes, most of them unnoticed so far, together with a few igneous massifs. They are of alkaline character and developed in a time span of c. 348 to 338 Ma. Deep seismic data reveal the presence of large sills (up to 100 km long) within the crystalline basement and the overlying sedimentary cover, at depths of 7–14 km and 5.5–6.5 km, respectively. All these igneous rocks occur in the coherent region and constitute a hitherto unrecognized Lublin–Baltic Mississippian Igneous Province (>120,000 km2). Its denudation is evidenced by the Mississippian volcaniclastic formations of high thickness, developed in the adjacent basins. Igneous activity was triggered by thermal anomaly and/or mantle decompression caused by stress field reorganization, induced by the Variscan collision. [ABSTRACT FROM AUTHOR]

Titanite from various rocks of the Karkonosze granitoid pluton (South-Eastern Poland) was studied, in order to evaluate its precision in recording magma evolution processes. The rocks are of lamprophyric, dioritic, granodioritic and granitic composition, including hybrid structures such as microgranular magmatic enclaves and composite dykes. Based on textures, chemistry and Zr-in-titanite geothermometry, titanites can be divided into magmatic and post-magmatic populations. Late- to post-magmatic titanite is present in almost all rock types, especially in the most evolved ones (where magmatic titanite is absent) and can be characterized by low trace element and high Al and F contents. Magmatic titanite crystallized in temperatures between 610 and 870 °C, after apatite and relatively simultaneously with amphibole and zircon. Titanite from lamprophyre exhibits compositional features typical of titanites formed in mafic rocks: low Al and F, high Ti4+/(Al + Fe3+), LREE (light rare earth elemet)-enriched chondrite-normalized REE patterns, low Y/Zr, Nb/Zr, Lu/Hf, high (Ce + Nd)/Y, Th/U and Zr. Titanite from hybrid rocks inherited these characteristics, indicating major contribution of the mantle-derived magma especially during early stages of magmatic evolution. Titanite compositional variations, as well as a wide range of crystallization temperatures in hybrid granodiorites point to prolonged crystallization from distinct magma domains of variable mafic versus felsic melt proportions. The extent of compositional variations decreases through subsequent stages of magmatic evolution, and titanite with the least contribution of the mafic component is characterized by higher total REE, Al and F contents, lower Ti4+/(Al + Fe3+), (Ce + Nd)/Y and Th/U ratios, LREE-depleted chondrite-normalized REE patterns and higher Y/Zr, Nb/Zr and Lu/Hf ratios. Titanite composition from the intermediate and late stage hybrids bears signature of decreasing amount of the mafic melt and higher degree of its evolution, however, the exact distinction between the former and the latter is very limited. [ABSTRACT FROM AUTHOR]

Abstract: In the Kraków–Lubliniec Fault Zone (KLFZ) late Carbonifereous–Permian volcanic rocks mark the boundary between the Małopolska Block (thinned marginal sector of Baltica) and the Upper Silesian Block (a sector of the Brunovistulia composite Terrane). The Zone is a part of the major Hamburg–Kraków–Dobrogea transcontinental strike–slip tectonic zone separating the Laurussian craton and Gondwana blocks which came together to form it. The geochemistry of the volcanic rocks reflects the collisional nature of the tectonism. However, it also presents a signature compatible with extensional magmatism. The paper presents models of magma generation and evolution in what was a zone of alternating transpression and transtension. The magmatism in this zone of amalgamated terranes was related to two different sources: enriched mantle and primitive crust. The lithospheric mantle beneath some blocks of the amalgamated terranes may have experienced enrichment processes during previous subduction events. The metasomatism may have also occurred as a result of crustal thickening during transpression followed by delamination, subsidence and melting. These metasomatised blocks reacted with decompressional melting. Our results show that magma generation and evolution in the zone seem to be not typical examples of late Carbonifereous–Permian magmatism, which is known from other locations throughout Central Europe. [ABSTRACT FROM AUTHOR]

Abstract: The crystallization history of zoned K-feldspar phenocrysts in microgranular magmatic enclaves in the Karkonosze granite (SW Poland) reveals that the crystals grew in stirred coeval magmas of contrasting compositions. The growth mechanism and crystal compositions are investigated using cathodoluminescence and profiling by Electron Microprobe and Laser Ablation ICP-MS. These methods provide insight into the crystallization process and the varying compositions of the host melt. The phenocrysts show two types of growth patterns — with or without resorption interfaces. The trace-element distribution, heterogeneous across different zones and within single phenocryst zones, reflects a dynamic process of crystal growth from compositionally heterogeneous magma. Hybridization is also reflected in the density of structural Al–O−–Al defects — features that relate to coupled Ba–Al incorporation into the crystal structure. Differences in structural-defect densities and crystal composition trace the degree of hybridization in the granitic magma during the growth of the K-feldspar phenocrysts. [Copyright &y& Elsevier]