Gold of mesothermal Fe-Ni-Co-Bi-As type in alluvial deposits of the Wierzbiak River (Fore-Sudetic Block, SW Poland)

Raman and FTIR spectra of nephrites from the Złoty Stok and Jordanów Śląski (the Sudetes and Fore-Sudetic Block, SW Poland)

The Gogolow-Jordanow Serpentinite Massif (GJSM) and the Braszowice-Brzeźnica Massif (BBM) are the largest serpentinite outcrops in the Fore-Sudetic Block (NE part of the Bohemian Massif, Central Europe). The GJSM is a peridotitic member of the Variscan Śleza Ophiolite (SW Poland). Podiform bodies (veins and pockets) of chromitite are found on the Czernica Hill (GJSM) and on the Grochowiec Hill (BBM) within strongly serpentinized harzburgites which occur several hundred metres below Paleo-Moho. Chromitites consist of rounded chromite grains up to 3 cm across, and of chlorite filling the interstices. The veins are embedded in serpentine-olivine-chlorite aggregates. Relics of Mg-rich olivine (Fo 95-96 ) occur in massive chromitite in the BBM. The bulk-rock total PGEs content is very low (42-166 ppm) and the PGE pattern is negatively sloped towards Pt and Pd and depleted relative to chondrite. The primary chromite I is aluminous (Cr# 0.50-0.52, Mg# 0.60-0.70). The highly aluminous and magnesian (Cr# 0.38, Mg# 0.80) chromite Ia occurs locally in the BBM. The secondary chromite II is enriched in Cr and impoverished in Al (Cr# 0.57-0.69), it replaces chromite I. Both chromite I and II contain small amounts of Ti (<0.14 wt% TiO 2 ). Silicate inclusions in chromite are scarce. The composition and mode of occurrence of both the GJSM and the BBM chromitites are similar, thus they were formed probably under the same conditions. Textures of the chromitites suggest their magmatic origin. Their current geological position indicates their emplacement and crystallization in the uppermost mantle harzburgites occurring below the Moho Transition Zone (MTZ). The chromitites and hosting harzburgites were subjected to the greenschist-facies metamorphic overprint. The moderate Cr# and low PGEs contents suggest that the chromitites originated in the arc setting, thus their host ophiolite is of supra-subduction type.

The Gogołów-Jordanów Massif (GJM) in the Fore-Sudetic Block, SW Poland, hosts nephrites traditionally interpreted as serpentinite-related (ortho-nephrite). This contribution confirms the serpentinite-related origin of the nephrites on the basis of mineralogy, bulk-rock chemistry, and O and H isotopes. Rock-forming amphiboles from nephrites of the GJM have 7.73–7.99 Si apfu, comparable to 7.76–8.03 Si apfu of serpentinite-related Crooks Mountain nephrite amphibole (Granite Mountains, Wyoming, USA). The GJM amphiboles also have Mg/(Mg + Fe 2+ ) values ranging from 0.82 to 0.94, similar to serpentinite-related Crooks Mountain and New Zealand nephrites amphiboles with Mg/(Mg + Fe 2+ ) values of 0.86–0.90 and 0.91 to 0.92, respectively. The GJM nephrite amphiboles differ from the Val Malenco dolomite-related nephrite (Italy) amphibole, e.g., Val Malenco has a higher Si content (~8.0 Si apfu), although it overlaps with some of the GJM nephrite samples, and ~1.0 Mg/(Mg + Fe 2+ ), also higher than the GJM samples. Also, apatite in the nephrite studied from the GJM has a slightly higher Ca content than apatite from dolomite-related nephrite. Chlorites found in the Jordanów nephrite have similar compositions to that of chlorites in the serpentinite-related nephrites and also to chlorites associated with serpentinisation/rodingitisation. The bulk-rock FeO vs. Fe/(Fe + Mg), Cr, Ni, and Co are also typical of the serpentinite-related nephrites. The d 18 O values range from +6.1 to +6.7‰ (±0.1‰), and the average dD values = –61‰, corresponding with the serpentinite-related nephrites range. Based on petrographic observations, we suggest four crystallisation stages (including rodingitisation prior to nephrite formation): 1 – leucogranite rodingitisation and black-wall formation; 2 – tremolite formation at the expense of rodingite diopside and black-wall chlorite (nephritisation) and garnet break-down, with spinel and chlorite formation (chlorite can be a product of garnet break-down or spinel with serpentine reaction); 3 – prehnite vein formation; 4 – tremolite formation at the expense of prehnite veins and actinolite veins formation. Spinels composed of 0.29–1.96 wt.% MgO, 24.87–29.67 wt.% FeO, 8.72–22.82 wt.% Fe2O3, 3.11–4.36 wt.% Al 2 O 3 , and 39.07–54.46 wt.% Cr 2 O 3 suggest nephritisation in the greenschist to lower-amphibolite-facies conditions.

Late stage Variscan magmatism

The first suite of epidosite from the Central Sudetic Ophiolites has been discovered in the sheeted dyke complex of the Mount Śleza ophiolite (SW Poland). Epidosites from the Mount Śleza ophiolite represent A-type epidosites which metasomatically replaced diabasic sheeted dykes of the Strzegomiany–Kunow Fe-Ti mineralisation zone. They form decimetre-scale elongated pistachio-green patches or veins within single dykes. Their composition (quartz + epidote + titanite) is analogue to Troodos ophiolite end-member epidosite of Cyprus. The pistacite content of epidote range from Ps 16 to Ps 31 and is similar to those from other ophiolitic epidosites. Titanite is low in Al 2 O 3 (0.61 to 1.10 wt.%) and Fe 2 O 3 (0.43 to 0.63 wt.%) and high in V2O5 (from 0.22 to 0.47 wt.%). The presence of epidosites in the Mount Śleza ophiolite can be considered as an evidence of its supra-subduction zone (SSZ) affinity. Finally, a direct link between the epidosite formation and the release of base metals from its protolith (Cu, Zn and Co) indicates the possibility of the Cyprus-type volcanogenic massive sulphide deposit (VMS) formation in the Mount Śleza ophiolite

Three generations of granitoids emplaced over a 300 My time span in the Strzelin Massif, Fore-Sudetic Block, SW Poland: mutual relationships and implications for secular crustal evolution

Summary The copper-polymetallic ore deposit is situated within the Foresudetic Monocline near its boundary with the Foresudetic Block. The copper-mineralized zone extends through a series of dolomites, dolomite/clay shales and white sandstones of the lowermost Zechstein and, possibly, the uppermost part of the Rotliegendes. Mineral compositions, the manner of their occurrence and the diverse internal structure of this stratified deposit all indicate a multistage origin. Synsedimentary mineralization took place in a reducing environment present both during deposition of the shales and dolomites and during sedimentation of the white sandstones. Black concretions containing large amounts of organic carbon, FeS 2 and FeO occur in the upper part of these sandstones. Mineralization also took place throughout diagenesis, mainly in the sandstones but also in the shales and, to a lesser degree, the dolomites. Sedimentation was on an unstable shelf within the neritic zone. It is considered that natural marine aqueous solutions were enriched in metal ions (mainly Cu, Pb, Zn) by hot brines flowing out into the sedimentary basin through deep fissures, such as those in the Middle Odra fault zone, situated near the deposit.

The crustal section beneath amphibolite Niedźwiedź Massif (Fore-Sudetic Block in NE Bohemian Massif), modelled on the basis of geological and seismic data, is dominated by gneisses with subordinate granites (upper and middle crust) and melagabbros (lower crust). The geotherm was calculated based on the chemical analyses of the heat-producing elements in the rocks forming the crust and the measurements of their density and heat conductivity. The results were verified by heat flow calculations based on temperature measurements from 1,600 m deep well in the Niedźwiedź Massif and by temperature–depth estimates in mantle xenoliths coming from the nearby ca. 4.5 My basanite plug in Lutynia. The paleoclimate-corrected heat flow in the Niedźwiedź Massif is 69.5 mW m−2, and the mantle heat flow is 28 mW m−2. The mantle beneath the Massif was located marginally relative to the areas of intense Cenozoic thermal rejuvenation connected with alkaline volcanism. This results in geotherm which is representative for lithosphere parts located at the margins of zones of continental alkaline volcanism and at its waning stages. The lithosphere–asthenosphere boundary (LAB) beneath Niedźwiedź is located between 90 and 100 km depth and supposedly the rheological change at LAB is not related to the appearance of melt.

The Lower Silesian Block outcrops in the NE part of the Bohemian Massif with its northeasternmost fragment, the Fore-Sudetic Block, buried under the Cenozoic sediments. The AMINV K-1 borehole drilled in 2013 and located in this area provides a unique insight into geology of the scarcely exposed part of Variscan crystalline basement. The borehole profile exhibits the metamorphosed volcano-sedimentary sequence composed mainly of quartz-rich schists, chlorite-schists and mica schists with garnet-rich layers covered with 100 m of Paleogene sediments.&amp;#160;In this study, we have focused on the metamorphic record of garnet-bearing mica schists. Petrological investigation conducted with use of electron microscopy (SEM, EMPA) reveals the following, interesting features recurring in many studied samples: 1) presence of chloritoid inclusions in garnet; 2) progressive zoning of garnet; 3) diverse composition of white mica ranging from phengite to muscovite. Thermodynamic modeling shows that mineral parageneses including i.e. chloritoid, garnet and phengite crystallized in the conditions corresponding to high-pressure low-temperature (HP-LT) metamorphism, followed by the stage of regional metamorphism, marked by the growth of i.e. muscovite, feldspar and biotite. P-T conditions of HP-LT stage may have reached up to 17 kbar and 550oC, while subsequent regional metamorphism most probably haven&amp;#8217;t exceeded&amp;#160; 10 kbar and 650oC. QuiG Raman elastobarometry and Zr-in-rutile thermometers has been used to evaluate the modeled P-T conditions. EMPA U-Pb monazite dating determined the average age of crystallization at 339&amp;#177;12 Ma based on 45 point analyses of 18 monazite grains.

Geothermobarometry in staurolite-grade mica schists from the southern part of the Niemcza-Kamieniec Metamorphic Complex (Fore-Sudetic Block, SW Poland)

Experimental designs for determination of the anisotropy of remanence-test of the efficiency of least-square and bootstrap methods applied to metamorohic rocks from southern Poland

Studies of chrysoprase and microcrystalline silica varieties from serpentinites of Szklary Massif (Foresudetic Block, SW Poland) by Raman spectroscopic technique – preliminary results

During the last few years, the determination&amp;#160;of the crust and upper mantle structures in southern Poland is the target of passive seismic experiments such as AniMaLS and PACASE. In this research, the area of Sudetes has been focused on that is located at the margin of the Bohemian Massif. This region represents the NE-most part of the Variscan internides&amp;#160;between the Elbe Fault in SW and the Odra Fault in NE.&amp;#160;The lithosphere of the region is a mosaic of several distinct units/terranes with complex tectonic history ranging from the upper Proterozoic to the Quaternary.&amp;#160; To provide information about the crust and upper mantle structure beneath the Sudetes region, Ambient Noise Tomography Analysis has been used. As the input, continuous seismic data acquired during about 2 years (2017 to 2019)&amp;#160;&amp;#160;&amp;#160;have been used. The acquisition involved 41 broadband seismic stations &amp;#8212; 23 temporary stations deployed in the area of Sudetes and Fore-Sudetic block in SW Poland, supplemented with the data from 12 permanent seismic stations, operating in this area in the Czech Republic, Germany, and Poland. Furthermore, data from 6 broadband seismic stations of the Alp Array Seismic Network have been used.&amp;#160; Ambient seismic noise methods are now well-established and used in different period bands for different scales. To retrieve the surface wave dispersion curves from the vertical component of recorded noise for a given station pair, the cross-correlation in the frequency domain and stacking of noise records has been done. Then, the spectra from every combination of station pairs are cross-correlated by selecting the longest common time window available between the two stations and the average inter-station dispersion measurements with respect to the periods that have been retrieved. In the next step, the Multiple Filter Analysis technique was applied to analyze the waveforms and obtain the group velocity dispersion curves. In the final step, we are working on surface wave tomography and applying inversion for the shear (or compressional) velocities in the region. Based on the preliminary results, the depth resolution is between 5-50 km and the average shear velocity that is calculated so far is about 2.8 to 4.5 km/s at these depths.&amp;#160; &amp;#160;Financial support&amp;#160; This presentation is supported by the National Science Centre, Poland, according to the agreements UMO-2019/35/B/ST10/01628 and UMO-2016/23/B/ST10/03204.&amp;#160; Acknowledgments&amp;#160; "The AniMaLS Working Group comprises: Monika Bociarska, Wojciech Czuba, Marek Grad, Tomasz Janik, Kuan-Yu Ke, Weronika Materkowska, Marcin Polkowski and Monika Wilde-Pi&amp;#243;rko."&amp;#160; &amp;#160;

&amp;lt;p&amp;gt;The area of Sudetes, located at the margin of the Bohemian Massif, represents the NE-most part of the Variscan internides between the Elbe Fault in SW and the Odra Fault in NE. The lithosphere of the region is a mosaic of several distinct units/terranes with complex tectonic history ranging from the upper Proterozoic till the Quaternary. The crustal and uppermost mantle structure of this region was studied by seismic wide-angle experiment SUDETES 2003 and the results of 2-D isotropic modelling were published. Recently, this dataset, comprising off-line recordings from a net of intersecting profiles, was interpreted using anisotropic delay-time inversion. This resulted in models of 2-D distribution of upper crustal and uppermost mantle anisotropy based on azimuthal variability of the Pg and Pn traveltimes, respectively. The upper mantle of Sudetic region was the target of a passive seismic experiment AniMaLS. The project involved 23 broadband seismic stations deployed in the area of Sudetes and Fore-Sudetic block in SW Poland, supplemented with the data from 6 permanent seismic stations, operating in this area in Czech Republic and Poland. The measurements cover a ~200x100 km large area, with ~30 km inter-station spacing. The stations, deployed for a period of 24 months (2017-2019), provided broadband recordings of local, regional and teleseismic events. The aim of the experiment is to study the structure, seismic velocity variations including anisotropy distribution, and to map the upper mantle seismic discontinuities (Moho, lithosphere-asthenosphere boundary, mantle transition zone). Currently, the AniMaLS data are being interpreted using shear wave splitting method and receiver function method. The analysis of SKS and SKKS splitting was based on cross-correlation, eigenvalue minimization and transverse energy minimization methods. Resulting time delays between slow and fast S-wave components are ~1.2 sec on average, with fast velocity axis oriented largely in WNW-ESE direction, consistently with results of delay-time inversion of Pn phase traveltimes. Crustal anisotropy is characterized by similar fast axis orientation, but with lower amplitude of anisotropy. The orientation of fast axes in the crust and mantle correlates well with surface trends of tectonic units and with strike directions of major fault zones. This suggests vertically coherent deformation throughout the lithosphere, most likely during consolidation of the Sudetic region in Variscan times.&amp;lt;/p&amp;gt;

Zircon ages recorded in gneissic rocks have recently been used as criteria to define and correlate various tectonic units and crustal blocks in the central European Variscides. A SHRIMP U–Pb zircon geochronological study of the Strzelin gneiss in the Fore-Sudetic Block (SW Poland) indicates the presence of: (1) inherited zircon cores of Palaeo- to Mesoproterozoic 206Pb-238U ages (between ca. 2,000 and 1,240 Ma), and (2) zoned rims of Neoproterozoic age with two distinct means of 600±7 and 568±7 Ma. The Proterozoic age range of the cores suggests that different Precambrian crustal elements were the source for the protolith of the gneiss. A likely scenario is the erosion of various Proterozoic granites and gneisses, sedimentation (after 1,240 Ma), and partial resistance of the original components to subsequent metamorphic dissolution and/or anatectic resorption (in Neoproterozoic times). The zoned zircon rims of both of the younger Neoproterozoic ages are indistinguishable in the cathodoluminescence images. The data are interpreted in terms of two different thermal events inducing zoned zircon overgrowth at ca. 600 and 568 Ma. In general, the new results confirm earlier assumptions of the Proterozoic age of the gneiss protoliths, and indicate their similarity to orthogneisses in the East Sudetes tectonic domain (e.g. the Velke Vrbno and Desna gneisses). The Neoproterozoic dates are different from the age of 504±3 reported earlier for the Gościecice gneiss from a neighbouring locality in the Strzelin Massif. The new data strongly indicate a Moravo-Silesian (Bruno-Vistulian) affinity for the Strzelin gneiss and support the hypothesis that the Strzelin Massif lies within the tectonic boundary zone between the West- and East Sudetes domains, which represents the northern continuation of the Moldanubian Thrust.