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Odnawianie się rozsypisk złotonośnych przedpola Sudetów Wschodnich

Wierchowiec J.

Biuletyn Państwowego Instytutu Geologicznego

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2018

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nr 472

213--229

PL

W obrębie sekwencji okruchowych przedpola Sudetów Wschodnich wyróżniono w sumie pięć różnowiekowych poziomów złotonośnych związanych z preglacjalnymi „białymi” żwirami typu serii Gozdnicy, wodnolodowcowymi piaskami i żwirami plejstocenu oraz osadami holoceńskich tarasów Złotego Potoku i Białej Głuchołaskiej. Maksymalne zawartości Au (0,4 g/m3 osadu) notuje się w grubookruchowych żwirach kwarcowych, przestrzennie związanych z preglacjalną (eoplejstoceńską) doliną paleo-Białej Głuchołaskiej. Na powierzchni wyróżnionych dwóch podtypów złocin (ziarna blaszkowo-płytkowe, płaskie lub wtórnie zdeformowane oraz cementacyjno-grudkowe) rozpoznano i opisano nano- i mikrostruktury (morfotypy) Au oraz wewnętrzne tekstury (widoczne w przekroju ziaren), wskazujące na procesy tzw. odnawiania się rozsypisk złotonośnych. Są one wiązane z selektywnym rozpuszczaniem złota w warunkach hipergenicznych, jego wytrącaniem z roztworu i wtórną rekrystalizacją prowadzącą w rezultacie do formowania skupień złota autogenicznego. Rozpoznano dwa morfotypy złota autogenicznego: banieczkowate lub drobnorobaczkowe skupienia Au oraz krystaliczne skupienia i przerosty złota. Wspomniane morfotypy są bardzo dobrze zachowane i nie noszą oznak abrazji. Szczegółowa analiza SEM pokazuje, że pojedyncze banieczkowate nanocząsteczki z czasem zrastały się formując inkrustacje Au, a ostatecznie warstwę złota autogenicznego na powierzchni złociny pełniącej rolę swego rodzaju osadnika dla nowych nanocząstek. Występowanie banieczkowatych lub drobnorobaczkowych skupień Au w paragenezie z minerałami ilastymi oraz brak jakichkolwiek oznak abrazji tych skupień wskazują, że utworzyły się one in situ, to jest są pochodzenia autogenicznego. Nano- i mikroskupienia złota robaczkowo-pęcherzykowego zbudowane ze złota amorficznego mogą być wynikiem koagulacji koloidów lub ich adsorpcji przez minerały ilaste wypełniające kawerny na powierzchni złocin. Krystaliczne przerosty złota są prawdopodobnie efektem rekrystalizacji złota koloidalnego wytrącanego na powierzchni złocin po depozycji w rozsypisku.

EN

Auriferous sequences in the East Sudetic Foreland include up to five gold-bearing horizons and are associated with the so-called preglacial “White Gravels”, Pleistocene and Holocene fluvial deposits overlying the Neogene sediments of the Poznań formation or Paleozoic metamorphic rocks. The significant placer potential for gold in the region lies in the preglacial (Eopleistocene) fluvial drainage system, primarily in paleo-channels of the Biała Głuchołaska River. The White Gravels, the richest gold-bearing deposits, contain up to 0.4 g/m3 Au near the base of the auriferous horizon. Two visibly distinct gold sub-types are identified based on their overall morphology: 1) flaky gold, flattened or reshaped by refolding; 2) craggy, irregular grains. All the grains are alloys of gold and silver, with Te and Se occurring as trace amounts. Two distinct gold sub-types of detrital gold display surface morphotypes and internal textures of Au and Ag dissolution indicative of supergene gold modification, as well as authigenic Au formation and aggregation resulting in the renewal of gold-bearing placers. The indicative morphotypes include nano- to microparticulate bud- or bubble-like gold, as well as overgrowths and aggregates of crystalline plate-like gold. They are well preserved and lacking any signs of physical damage. Stages of the gold particles growth have been observed during the nano- to microtextural investigations of gold grains, from the isolated semi-spherical nanoparticles, agglomerates, to irregularly shaped plates of gold. The presence of nano- to microphase gold embedded in the fine-grained assemblages of clayey masses and the lack of any signs of grain surface abrasion confirmed that bud- and babble-like Au, as well as complex aggregates of plate-like gold, must have formed in situ, i.e. are authigenic in origin. Chemical transfer may be related to both the Au precipitation from a colloidal solution as well as the adsorption by clay minerals and surface precipitation of Au on particles of mineral substrate.

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Chronione i rzadkie gatunki roślin użytków zielonych w Sudetach

Paszkiewicz-Jasińska A.

Inżynieria i Ochrona Środowiska

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2015

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T. 18, nr 2

259--270

PL

Przedstawiono występowanie gatunków roślin chronionych, zagrożonych i rzadkich na użytkach zielonych usytuowanych w makroregionach: Pogórze Zachodniosudeckie, Sudety Środkowe i Wschodnie. Na podstawie badań florystyczno-fitosocjologicznych, przeprowadzonych w latach 2009-2014, stwierdzono dziesięć gatunków chronionych, w tym cztery taksony objęte ochroną gatunkową ścisłą. W składzie florystycznym użytków zielonych odnotowano dwa taksony podawane jako gatunki zagrożone wyginięciem na terenie Polski oraz osiem zagrożonych gatunków flory naczyniowej Dolnego Śląska o różnych kategoriach zagrożenia. Użytki zielone objęte badaniami, występujące w Sudetach Środkowych, charakteryzują się większym udziałem gatunków zagrożonych i rzadkich niż w Sudetach Wschodnich i Pogórzu Zachodniosudeckim.

EN

An important part of the landscape of the Sudetes are grassland. They account approximately 50% of agricultural area. These are most often semi-natural communities which their origin, complexity of the structure and species composition are due to human activity. Over the past decades, the disappearance of many meadow communities and related taxons are observed. Intensification of this phenomenon makes it necessary to conduct a study on the current state of grassland. The floristic and phytosociological study was carried out in the years 2009-2014 with the Braun-Blanquet method on the grassland in Sudetes Mts (the Western Sudetes Foothills, The Central Sudetes, The East Sudetes). The resulting material was analysed in terms of endangered and rare species. Evaluation of the plant species was based on the Regulation of the Minister of Environment of 9 October 2014, on the protection of species of plants. In addition, a list of endangered and rare vascular plants of Lower Silesia has been taken into account, which was developed based on the International Union for Conservation of Nature (IUNC) and supplemented by criteria and regional categories. The studies showed that in the floristic composition of part of the analysed grasslands there were 4 strictly protected species and 6 partial protected species. To the most commonly reported include: Colchicum autumnale L., reported slightly less frequently: Platanthera bifolia (L.) Rich., Dactylorhiza majalis (Rchb.) P. F. Hunt & Summerh.), Colchicum autumnale L. Occasionally the presence of Gymnadenia conopsea (L.) R. Br. subsp. conopsea, Trollius europaeus L., Iris sibirica L., Lilium martagon L., Epipactis helleborine (L.) Crantz were reported. Most of these species is placed on the endangered species list of vascular flora of Lower Silesia, as a species exposed to extinction and species with a lower risk of extinction (rare). Trollius europaeus L., Gymnadenia conopsea (L.) R. Br. subsp. conopsea. are in danger of becoming extinct. From species close to the threat but at a lower risk of extinction occurred Dactylorhiza majalis (Rchb.) P.F. Hunt & Summerh and poorly threatened - Colchicum autumnale L. and Platanthera bifolia (L.) Rich. Most of the rare and protected species was found on grassland located in the Central Sudetes, which can be associated with taking inventory more research areas (meadows and pastures), than on the Western Sudetes Foothills and in the East Sudetes.

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A vestige of an Early Devonian active continental margin in the East Sudetes (SW Poland) - evidence from geochemistry of the Jegłowa Beds, Strzelin Massif

Szczepański J.

Geological Quarterly

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2007

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Vol. 51, No 3

271-284

EN

The Early Devonian metasandstones of the Jegłowa Beds (Strzelin Massif, NE Bohemian Massif) are low- to medium-grade metamorphosed siliciclastic deposits showing differences in modal composition, especially in the amount of micas and feld spars. Despite the similarity in relative concentrations of trace elements, three chemical groups can be distinguished among the metasandstones that differin the total amounts of major and trace ele ments. The negative Ta and Nb anomalies visible on a spider plot normalised to the average upper continental crust and spe cific ratios of e.g. Th, Zr, Hf, La/Th and Ti/Sc characterize the majority of the metasandstones, indicating the provenance of their sedimentary precursors from a subduction-related tectonic setting. However, few of the samples analysed show strongly differentiated geochemical characteristics with high Zr and Hf contents. This suggests input of relatively strongly reworked mate rial. Thus, it seems that a back-arc setting can account for the mixed nature of the inferred source ar eas with old basement and arcrelated detritus respectively as the end-members of the mix tures. The composition of the metasandstones indicates deposition of the siliciclastic material near an Early to Middle Devonian volcanic arc that was super imposed on rocks originally forming a part of the pre-De vo nian continental margin of the Brunovistulicum microplate. A plausible tectonic scenario in volves formation of the Devonian arc due to east-directed subduction of an oceanic domain between the Brunovistulian microcontinent in the east and the Central Sudetic terrain located fur ther west.

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Placer gold and other economic minerals from the remnants of palaeofan deposits in the foreland of the East Sudetes, Poland

Wierchowiec J.

Acta Geologica Polonica

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2007

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Vol. 57, no. 4

523-537

EN

Gold-bearing palaeofan deposits in the East Sudetic Foreland region are associated with the White Gravel series, which is the richest gold-bearing horizon. The remnants of the White Gravels in the vicinity of Gierałcice and Sławniowice contain between 0.33 g/m[^3] Au near the base and <0.05 g/m[^3] Au in the upper part. The gold is associated with other heavy minerals, such as Fe-Ti oxides (magnetite, ilmenite, and hematite), zircon and rutile. Concentration of these minerals increases significantly with depth and three-quarters of the total gold is found in the lower half of the palaeofan deposits. The alluvial palaeofan placers were formed by repeated scouring and reconcentration of resistant heavy minerals from a number of sources, including pre-existing placers and bedrock. The gold grains are composed of variable proportions of Au and Ag with trace amounts of Cu, Te and Se. Rims have high gold (>93 wt % Au) and low silver (<6 wt % Ag) contents, whereas cores contain average 85 wt % Au and 14 wt % Ag. Porous gold grains are homogeneous and of high purity (>95 wt % Au). The bedrock source of gold is probably related to quartz veins in Palaeozoic schist and quartzite. There are several local point sources of gold, mainly quartz veins of the Zlaty Chlum Massif. Data presented for the Gierałcice.Sławniowice palaeofan placers may be useful for prospecting and exploration for similar deposits.

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Preglacial to Holocene auriferous sediments from the East Sudetic Foreland: gold grades and exploration

Wierchowiec J.

Geological Quarterly

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2006

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Vol. 50, No. 2

289-302

EN

Auriferous sediments in the East Sudetic Foreland region include up to five gold-bearing horizons associated with preglacial and Quaternary fluvial sediments. The largest placer potential lies in the preglacial (Eopleistocene?) drainage system, primarily in palaeochannels of the Biała Głuchołaska River. The White Gravel series is the richest gold-bearing horizon. It contains between 0.37 g/m3 Au near the base and <0.10 g/m3 Au in its upper part.Maximumgold grade occurs in the first 1–2mabove the contact with the bedrock. Gold concentration in this area was controlled by the ability of streams to aggradation and the development of sedimentologic traps, where gold was accumulated during the preglacial valley erosion. Oblique orientation of the palaeo-Biała Głuchołaska valley and its tributaries to the regional ice-flow direction probably prevented the glaciers fromeroding deeply into the palaeochannels. From the exploration prospective, study of palaeochannel systems in the vicinity of Otmuchów–Prudnik could identify other buried placer gold occurrences. Gold-bearing sediments, correlated stratigraphically with the Biała Głuchołaska palaeochannel White Gravels occur in several other areas, including the Nysa Kłodzka, Kwisa and Kaczawa valleys.