Geological research (in Moravia and Silesia)

Corkit z ložiska Zlaté Hory-Východ

Tomáš Pek — Po, 11 lis 2024 00:00:00 +0100

Corkite, a Pb-Fe dominant member of the alunite supergroup, was found in the oxidation zone of the stratiform base metal deposit Zlaté Hory-Východ (Silesia, Czech Republic). It forms yellow-green coatings composed of microscopic botryoidal and globular aggregates in association with anglesite, cerusite, roentgenamorphic Mn-Pb oxides and plumbojarosite (which forms the cores of corkite aggregates but also occurs separatelly as cinnamon-brown coatings composed of microscopic rhomboedric crystals) in the cavities of quartz-limonite material. These aggregates are in polished section strongly zonal with a core made up of plumbojarosite with approx. 14 mol. % of (PO₄)^3- anion at structural position T and the peripheral parts made up of corkite. The chemical composition of corkite, determined by WDX microanalyses, is in relativelly good agreement with its theoretical formula, the anion sites are equally occupied by (SO₄)^2- and (PO₄)^3- groups or (SO₄)^2- slightly predominates. The arsenate anion is present only in trace amounts (below 0,01 apfu) which corresponds to the practical absence of As minerals in the primary ores of Zlaté Hory ore district. Problematic is the presence of silicium in all analyses which could be attributed either to anisomineral admixture or to the presence of (SiO₄)^4- at the anionic site of corkite structure. Analyses recalculated on the basis of two anion groups show excess of cations at both cation sites which could be due to the presence of unanalysed components at the anion site (probably (CO₃)^2- group. Structural position D is occupied virtually only by Pb with only subordinate amount of K. Substitution of Fe by Al at G site is very limited, Al together with Cu and Zn content is only minor. X-ray powder diffraction patterns (major lines 3.060 Å (100); 5.918 Å (75); 2.250 Å (47); 2.528 Å (34)) and calculated unit cell parameters of studied corkite are in good agreement with published data (Giuseppetti and Tadini 1987; Sato et al. 2009).

Listvenit s výskytem minerálu gersdorffit-kobaltinové řady v lomu Dřínová u Tišnova (Morava)

Pavla Hršelová, Jiří Toman, David Buriánek, Dalibor Všianský — Po, 11 lis 2024 00:00:00 +0100

Chromian illite-magnesite-dolomite-quartz rock (listvenite-like) containing Ni-Co mineralization was found in the Svratka orthogneisses from the Dřínová quarry. The main rock-forming minerals are Fe-rich magnesite, Fe-rich dolomite, Cr-illite and quartz, less frequently calcite. Accessory minerals include chromite (with 0.841–0.886 apfu Fe²⁺ and 1.642–1.742 apfu Cr), gersdorffite-cobaltite (Ni_0.45-0.92Fe_0.01-0.34Co_0.01-0.34As_0.83-1.02Sb_0.00-0.03S₁), sulfides (pyrite, sphalerite), and apatite. The illite from the Dřínová quarry contains up to 3 wt. % of Cr₂O₃. Presence of the Cr-illite, accesory chromite, and Ni-Co sulfoarsenides represents origin from ultrabasic protolith, reflecting transformation to phyllosilicatecarbonate-
quartz listvenite.

Revize paleontologických nálezů z lokality Úsobrno

Taťána Fidlerová, Tomáš Turek, Nela Doláková — Po, 11 lis 2024 00:00:00 +0100

The Úsobrno locality is known on the basis of fossil fauna findings, which were documented and published by Vašíček (1941). Field research has not been able to find the original locality yet. In this reason paleontological material which is deposited in the collections of ÚGV PřF MU was researched. We identified a total of 573 species which belonged mainly to the classes Gastropoda, Bivalvia, Anthozoa and Scaphopoda and compared with the original findings mentioned by Vašíček (1941). The age of the samples was determined to be the Lower Badenian.
Based on the findings, especially hermatypal corals, it can be assumed that the sea was warm (above 20 °C), well oxygenated with a soft and hard bottom and mostly shallow. Some findings of fauna from deeper marine areas (Ranella fragment, ahermatypal corals) indicate mixing or postmortem transport during sedimentation.

Supergénny jarosit v metalydite na lokalite Betliar-Turecká (Slovenská republika)

Peter Ružička — Ne, 10 lis 2024 00:00:00 +0100

Jarosite was identified for the first time in the metalydite of the Bystrý potok Formation of
the Gelnica Group in the Southern Gemeric Unit of the Western Carpathians (Slovakia) at
the locality Betliar-Turecká. In metalydite, jarosite forms granular aggregates with small
tabular to pseudocubic crystals, occurring as pseudomorphs after pyrite or as crystals
within muscovite interlayers. Pyrite was not preserved in the studied metalydite as it was
completely replaced by secondary jarosite. Pyrite is present as an accessory mineral in the
accompanying graphitic-muscovite phyllites, locally in the metalydite. The sulphur necessary
for jarosite formation comes from the breakdown of pyrite, while the source of potassium
is muscovite. During the supergene process, low pH fluids attack muscovite, releasing K⁺
needed for jarosite formation. Chemical composition investigated by EPMA and based on
the Raman spectroscopy showed that, jarosite is typical with dominant Fe³⁺ in the interval
of 2.86–2.97 apfu and K⁺ in the range of 0.76–0.94 apfu. It contains minor amounts of Na⁺
up to 0.13 apfu, H₃O⁺ up to 0.11 apfu, As⁵⁺ up to 0.08 apfu and Pb²⁺ up to 0.01 apfu. The
source of sodium in the jarosite is probably derived from muscovite, as no feldspars or clay
minerals have been identified in the metalydite. The arsenic in the jarosite is probably sourced
from arsenic-rich pyrite, while the source of lead may be attributed to galena, related
to hydrothermal processes within nearby metamorphic manganese mineralization. The
phosphorus in the jarosite likely originates from accessory apatite, which is found within
the surrounding acidic metavolcanoclastics and phyllites that host the metalydite horizons.

Paleoekologické vyhodnotenie fosiliferných vrstiev vrchného bádenu na lokalite Dubová (severozápadná časť Dunajskej panvy)

Čt, 12 pro 2024 00:00:00 +0100

Miocénne sedimenty na úpätí Malých Karpát bývajú častokrát veľmi bohaté na fosílie,
napriek tomu dočasné odkryvy často nebývajú zdokumentované. V práci predstavujeme
výsledky získané zo záchranných prác z už nejestvujúceho odkryvu jz. od obce Dubová,
ktorý vznikol vďaka stavebnej činnosti. Veľmi podrobne sme zdokumentovali faunu a flóru
marginálnych morských sedimentov vrchného bádenu (spodný seraval) nanoplanktónovej
zóny NN6 a ekobiozóny Ammonia beccarii, ktorá je laterálnym ekvivalentom zóny
bulimino/bolivínovej. Na základe diverzifikovanej asociácie vápnitého nanoplanktónu,
dierkavcov, koralov, mäkkýšov a machoviek interpretujeme zmeny paleoprostredia počas
sedimentácie. Aj v krátkom časovom úseku, ktorý reprezentoval profil s hrúbkou 2,5 m, sme
odhalili rôzne typy paleoekologického prostredia, ktoré boli ovplyvnené zmenami salinity,
prínosom živín a dynamikou vodného prostredia. V celom profile predpokladáme veľmi
plytkovodné prostredie, maximálne do 40 m, striedanie epizód s nízkym obsahom kyslíka
(prevaha zástupcov rodu Ammonia), ktoré vznikali pravdepodobne v závislosti od energie
prostredia. Salinita sa počas sedimentácie menila postupne od morskej, dokumentovanej
schránkami dierkavcov (Elphidium, Borelis) a machoviek Cupuladria a Reusirella, po
hyposalínnu dokumentovanú mäkkýšmi rodov Vitta a Pustulosia smerom do nadložia.
Vodný stĺpec dokumentuje príbrežné prostredie vonkajšieho šelfu, vysoká abundancia redepozitov
vápnitého nanoplanktónu kriedového a paleogénneho veku umožňuje uvažovať
o riečnych prínosoch paleo-Váhu.

Kyselé metavulkanity z okolí Táborských skal ve zlatohorském rudním revíru

Tomáš Pek — Pá, 20 pro 2024 00:00:00 +0100

Acidic metavolcanites from vicinity of Táborské skály in Zlaté Hory Ore District (Silesia,
Czech Republic) were identified as metamorhosed equivalents of rhyolites or alkali-rhyolites,
based on their modal composition and also on major and trace element analyses. Major
elements composition of so-called „problematic“ siliceous rocks, accompanying acidic
metavolcanites resembles more closely chemistry of sedimentary rocks, but their trace element
pattern is virtually identical with investigated metarhyolites; they probably represent
strongly altered volcanogenic (probably pyroclastic) rocks. Trace element distribution in
acidic metavolcanites is comparable with A-type granites. Based on A-type affinity of studied
rocks and position of their analyses in geotectonic discrimination plots after Pearce et al.
(1984), confinement of volcanism to divergent geotectonic environment is the most probable.