Gory Sowie Research Articles

Uskok Starego Julianowa w sowiogórskim kompleksie gnejsowym i sytuacja geologiczna w miejscu jego występowania (Pogórze Wałbrzyskie, Sudety Środkowe, południowa Polska)

STARY JULIANOW FAULT IN SOWIE GORY GNEISS COMPLEX AND GEOLOGICAL SITUATION IN THE PLACE OF ITS OCCURRENCE (WAŁBRZYCH FOOTHILLS, CENTRAL SUDETES, SOUTHERN POLAND) Abstract. The paper describes localization and architecture of a uranium-bearing fault, called the Stary Julianow Fault (uStJ). The fault studied occurs in a north-western fragment of the sudetic part of the Gory Sowie Gneiss Massif (MGS ), in the area of the Walbrzych Foothills, between Stary Julianow and Dziecmorowice. It is one of faults that make up the northern part of a broad dislocation zone extending from Stary Julianow to Zagorze Ślaskie, in which the occurrence of hydrothermal mineralization, called mineralization from Dziecmorowice, was described. Information about the Stary Julianow Fault obtained during its exploration by underground workings to the depth of 345 m and the extension of 900 m, which were made in the years 1949–1952 in connection with uranium ore mining. The Stary Julianow Fault belongs to “older” faults with direction NW –SE and it is oriented crosswise to macrofold which occurs in Julianow region. The architecture of a fault zone of the Stary Julianow Fault consists of two parts: a fault core and a damage zone. The fault core is represented by narrow zone, composed of the fault rocks with the occurrence of uranium-bearing calcite lenses. The damage zone is brittle deformation with instances of carbonate mineralization and hydrothermal alteration of gneisses. It is particularly wide developed in the east side of the Stary Julianow Fault. The architecture and position of the Stary Julianow Fault in the tectonic structure of the region suggests its formation during the Variscan evolution of the Gory Sowie Gneiss Massif.

SAMARSKITE-GROUP MINERALS AND ALTERATION PRODUCTS: AN EXAMPLE FROM THE JULIANNA PEGMATITIC SYSTEM, PIŁAWA GÓRNA, SW POLAND

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 Pilawa Gorna, the Gory 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 Ca 2+ and Mn 2+ ). 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.

Provenance of Upper Cretaceous quartz-rich sandstones from the North Sudetic Synclinorium, SW Poland: constraints from detrital tourmaline

Upper Cretaceous quartz arenites that fill the North Sudetic Synclinorium on the northern periphery of the Variscan Bohemian Massif show high compositional but low textural maturity. They have been interpreted for years as derived largely from nearby granite plutons, i.e. as first-cycle sediments. A different provenance was revealed on the basis of a combined light and heavy mineral analysis, and particularly a detrital tourmaline study, given that tourmaline is a sensitive indicator of granitic/metamorphic/sedimentary (multi-recycling) origin. Cenomanian, Turonian, Coniacian and Santonian sandstones contain abundant angular tourmaline grains, together with zircon and rutile, and subordinately staurolite, garnet, anatase, kyanite, sillimanite and monazite. The successive – Cenomanian to Santonian – tourmaline populations are similar with regard to shape, colour and chemical composition. The latter points unambiguously to various metamorphic rocks with a predominant group of Al-rich metapelites (Al-rich, F-poor dravite). It is concluded that, in the Late Cretaceous, large Sudetic granite plutons such as the Karkonosze and Strzegom–Sobotka massifs were not exposed but were buried under a thick siliciclastic cover. These results coupled with published apatite fission-track data from the granitic Karkonosze Pluton and the gneissic/migmatitic Gory Sowie Massif reveal that Late Cretaceous quartz arenites of the North Sudetic Synclinorium reflect gradual exhumation of the surrounding massifs, but do not record the final exposure of crystalline rocks. Since the latest Turonian, this exhumation corresponded to the Late Cretaceous inversion episode in Central Europe. The textural immaturity of Upper Cretaceous sandstones is misleading in terms of their recycled origin, and it is inherited from immature clastic source rocks.

High (ultrahigh) pressure metamorphic terrane rocks as the source of the detrital garnets from the Middle Jurassic sands and sandstones of the Cracow Region (Cracow-Wieluń Upland, Poland)

ABSTRACT Aubrecht, R., Meres, Š., Gradziński, M. and Sykora, M. 2012. High (ultrahigh) pressure metamorphic terrane rocks as the source of the detrital garnets from the Middle Jurassic sands and sandstones of the Cracow Region (Cracow- Wieluń Upland, Poland). Acta Geologica Polonica, 62 (2), 231-245. Warszawa. The Middle Jurassic (Upper Bathonian/Lower Callovian) sands and sandstones of the Cracow-Wieluń Upland contain detrital garnets with high contents of the pyrope molecule (30-73 mol %). The predominance of detrital pyrope garnets, and inclusions represented mainly by omphacite and kyanite, show that the garnets were derived from high (ultrahigh) pressure (H/UHP) metamorphic terrane rocks (garnet peridotites, eclogites and granulites). Their source is unknown. The Moldanubian Zone of the Bohemian Massif is closely comparable. However, the terranes between this zone and the Cracow- Wieluń Upland are dominated by almandine garnets. The relatively low proportion of almandine garnets in the examined samples indicates that transport of the detrital material could not have been from a far distant source as the garnet assemblage would otherwise be strongly dominated by almandine. A less distant possible source could have been the Gory Sowie Mts., which incorporate UHP/HP metamorphic rocks, but the exposed areal extent of these rocks is too small. It is possible that larger portions of these metamorphic rocks are buried beneath the Cenozoic cover and might have earlier represented a larger source area. Reworking of the entire heavy mineral spectra from older clastics is improbable because of the low maturity of the heavy mineral assemblages (higher proportion of less stable minerals). The source area therefore remains unknown. Most probably it was formed by primary crystalline complexes of lower crust to mantle origin, outcrops of which were not far distant from the area of deposition. Similar detrital garnet compositions were also recorded in the Outer Western Carpathians (Flysch Zone, Pieniny Klippen Belt), i.e. the crustal segments which formed the Silesian and Magura cordilleras; the Czorsztyn Swell was also formed by similar rocks.

Fission-track dating of apatite from the Gory Sowie Massif, Polish Sudetes, NE Bohemian Massif: implications for post-Variscan denudation and uplift

Six samples from the Gory Sowie Massif gneisses in the West Sudetes, analyzed for the purpose of apatite fission- track dating (AFT) yielded ages ranging from 43 to 57 Ma. No regional variation in the results was observed and the samples form a rather uniform population. From confined-track length measurements, short values between 8.8 and 9.6 µm were obtained. Track length distribution in four of the six samples is bimodal. This suggests residence in temperatures corresponding to the par- tial annealing zone until relatively recent times and subsequent rapid cooling to ambient conditions. We propose a mid-Tertiary rise in the geothermal gradient as a possible factor responsible for reheating the Gory Sowie Massif after it had cooled to temper- atures around 60 - 40 uC in the Oligocene. According to reverse-modelling results, the cooling began in the Cretaceous and there- fore correlates with the event reported from elsewhere in the northern part of the Bohemian Massif. As Lower Carboniferous sed- imentary rocks overlie the gneisses, the overburden which was responsible for keeping temperatures above 100 uC until early Ter- tiary was probably the Carboniferous-Permian Variscan molasse. The amount of the Cretaceous/early Tertiary denudation can be estimated to be 4 - 8 km. The recent, rapid cooling phase began 7- 5 Ma ago and is interpreted as the combined result of decrease of geothermal gradient and/or increased tectonic activity in the Sudetes as evidenced by the presence of the Pliocene, coarse-clas- tic Gozdnica formation.

Mafic rocks in a deep-crustal segment of the Variscides (the Góry Sowie, SW Poland): evidence for crustal contamination in an extensional setting

Coronitic metagabbronorites (so-called hyperites) and metabasites occur within gneisses, migmatites and minor granulites in the high-grade metamorphic Gory Sowie Block in the Sudetes (SW Poland). Incompatible trace-element and eNd data, combined with field and petrographic evidence, suggest that three groups may be distinguished: (1) "enriched" amphibolites (Zr/Nb ca. 8, eNd500 +1 – +2.5), (2) "depleted" amphibolites (Zr/Nb >30, eNd500 +5 – +6), and (3) metagabbronorites (Zr/Nb 13–19, eNd500 scattered between +5.3 and –1). These characteristics favour an extensional within-plate setting, consistent with their field occurrence as small bodies scattered within metasedimentary and felsic metaigneous gneisses. In that setting, enriched mantle sources were partially melted to produce a range of basic magmas, showing affinities with continental tholeiites (within plate-type basalts). Presumably, in a more advanced stage of rifting, more depleted varieties, transitional to N-MORB, were emplaced. These mafic magmas were variably contaminated during their ascent in the crust. The metagabbronorites, with their well-preserved igneous textures, were previously interpreted as having been intruded after the main deformation and after the peak of amphibolite facies metamorphism (some authors suggesting a relation to the "circum Gory Sowie ophiolites"). However, the geochemical characteristics and P–T estimates suggest that the metagabbronorites are unrelated to the ophiolitic gabbros found in the neighbourhood of the Gory Sowie Block and, in contrast to them, have experienced a complex, polybaric P–T path.

U-Pb zircon isotopic evidence for mid-Devonian migmatite formation in the Gory Sowie domain of the Bohemian Massif, Sudeten Mountains, SW Poland

U-Pb isotopic data for 5 measured fractions of zircon from a homophonous granitoid-looking plagioclase-quartz-biotite diatexite in the GOry Sowie domain of SW Poland scatter about a projection of the chord (LI 369 ′ 15 Ma; UI 1750 ′ 270 Ma) for a gneiss elsewhere in the domain and their distribution is consistent with an age of metamorphism-migmatization generally corresponding to c. 380 Ma concordant U-Pb monazite ages from the diatexite. A 0.65-1.2 Ga range of 2 0 7 Pb/ 2 0 6 Pb apparent ages is interpreted as the result of the presence of varying proportions of a hybrid population of Precambrian xenocrystic zircon in the different fractions and as supporting the derivation of the migmatite from a sedimentary protolith. The mid-Devonian episode of tectonothermal (and igneous) activity has coeval counterparts in some Czech and German domains of the Bohemian Massif and is significant in evolution of the Hercynian orogen. Arguments are presented against previous interpretations of the metamorphism-migmatization having taken place in Ordovician times.

Petrological and Isotopic Studies on Palaeozoic High-pressure Granulites, Gory Sowie Mts, Polish Sudetes

Petrological and Isotopic Studies on Palaeozoic High-pressure Granulites, Gory Sowie Mts, Polish Sudetes

Petrological and Isotopic Studies on Palaeozoic High-pressure Granulites, Gory Sowie Mts, Polish Sudetes

2154·7-1·4 Ma, whereas 19 analyses of grain fractions and single grains of multi-faceted zircons interpreted, from their char- acteristic spherical 'football' shape, as newly crystallized meta-

Saxothuringian zone in Germany and Poland: differences and common features

The classical correlation by kossmat (1927) of the Saxothuringian belt of Germany with the West Sudetes of Poland is re-evaluated with special reference to the crystalline massifs of Munchberg and the Gory Sowie and the surrounding areas. Important common features are: Cambro-Ordovician magmatism and sedimentation; Silurian to Devonian radiolarian cherts in the low grade to unmetamorphosed units; Early Devonian (and older?) pressure-dominated metamorphism followed by rapid uplift; the incorporation of high pressure and mantle rocks; and Early Carboniferous mass flow deposits with ‘Saxothuringian’ clasts. Differing features in the West Sudetes are: tectonic contacts in and around the Gory Sowie are mostly subvertical and mainly (semi-)brittle (in contrast with subhorizontal and ductile contracts in the Munchberg); the Gory Sowie has undergone late re-equilibration of the earlier tectonic fabrics; an ophiolite juxtaposed with the Gory Sowie crystallized in (?) Devonian time and became only statically metamorphosed, as opposed to the regionally metamorphosed Cambro-Ordovician mafic rocks of the Saxothuringian belt; localized depocenters with Upper Devonian to Lower Permian elastic rocks relating to north-west trending strike-slip faults instead of the north-east trending cylindroidal foreland basin in the Saxothuringian. It is possible that the West Sudetes originated as an easterly continuation of the Saxothuringian belt, but then became involved, from the Late Devonian onwards, in a strike-slip system parallel with the margin of the East European Platform.