The usually medium-grained garnetites form up to several cm thick layers in quartz-magnetite mineralizations of the Desna Unit in the Silesicum. The garnetite mineral assemblage consists of epidote, quartz, garnet, magnetite, biotite, ilmenite, apatite and retrograde chlorite. The mineralogical and petrological results demonstrate that garnetites are metamorphosed submarine exhalites. Garnet from the garnetites has compositions with nearly equal amounts of spessartine and almandine components and can by interpreted as result metamorphic reactions partially consuming of the Mn-rich epidote. Thermobarometric calculations from the garnetites yielded peak amphibolite facie metamorphic conditions ca. 540–600 °C and up to 3 kbar. Chemical composition of fluids estimated for this metamorphic event is H2O = 82 až 95 mol. %, CO2 = 4 až 17 mol %, NaCl = 1 až 2 mol. %. The biotite was partially replaced by chlorite during younger retrograde metamorphic event under greenschist facie.
Neovolcanites from the Uherský Brod area sporadically enclose cm to dm large xenoliths of plutonic rocks. This paper focuses on characterization of xenoliths from the Bučník hill which are enclosed in trachyandesites by using classic petrographic methods. Based on mineral composition and textural features of main rock-forming minerals, the studied xenoliths can be classified as fine- to coarse-grained pyroxenic-amphibolic gabbros or diorites, respectively. They consist mainly of intermediate polysynthetically twinned plagioclase (andesine to labradorite; An44–55) and yellow-brown pleochroic magnesiohastingsite to pargasite (XMg = 0.64–0.75; Si = 6.09–6.29 apfu; Ti = 0.30–0.42 apfu). Relicts of diopside (XMg = 0.70–0.80; Ti = 0.01–0.03 apfu; Na = 0.03–0.04 apfu), brown strongly pleochroic phlogopite leaflets (XMg = 0.58–0.65; Si = 5.51–5.60), apatite columns (predominantly fluorapatite; F = 0.43–0.77 apfu) and K-feldspar (Ab16–17Or82–84An00–01) grains are less frequent. Amphiboles sporadically enclose round or tabular inclusions of labradorite to bytownite (An64–72) and subhedral olivine (Fo64). Xenoliths are similarly to host trachyandesites affected by superimposed hydrothermal alteration. Secondary minerals represent acid plagioclase (An05–10), chlorites (clinochlore; XMg = 0.55–0.67; Si = 3.13–3.29 apfu), carbonates (calcite and siderite), Ti-minerals (ilmenite, rutile and titanite), sulphides (pyrite and chalcopyrite) and less frequently quartz. The genetic affinity of xenoliths and the host neovolcanites is evidenced by the similarity in mineral composition and whole-rock chemistry. Xenoliths can be interpreted either as material from deeper parts of the magma chamber, or more probably as crystal cumulates (i.e. equivalents of cumulate gabbros).
Studied locality is situated in western part of the Silesian Unit of the Outer Western Carpathians. Analcime was found in magmatic rock of the teschenite association which was subject of extensive analcimization. Th e analcime crystals, filling the veins and cavities (amygdules, miaroles), have a size up to 5 mm and composite structure: a milky white core shows irregular shape, up to 1 mm in size, and a vitreous transparent rim showing euhedral crystals. The vitreous transparent analcime from veins forms either euhedral crystals or white-pink spherulitic aggregates (size up to 5 mm). Their composition is not close to stoichiometry, with the SiO 2 /Al 2 O 3 mole ratios from 2.08 to 3.12. Increasing SiO 2 /Al 2 O 3 molar ratios of analcimes are consistent with decreasing crystallization temperatures. Analcime contains abundant primary fluid inclusions, less secondary fluid inclusions. Fluid inclusions are one-phase (L-only) or two-phase (L+V) with essentially constant liquid-vapour ratios (gaseous phase takes ca. 10 vol. %). The homogenization temperatures of two-phase inclusions range between 122 and 180 °C (analcime from veins) and between 219 and 295 °C (analcime from cavities - amygdules, miaroles). Inclusions freeze at temperatures of -38 to -49 °C. The last ice melts at temperatures between -0.6 and -3.7 °C. The eutectic temperature was not possible to measure due to the small size of the inclusions. The hydrothermal analcime formed from fluids causing the pervasive post-magmatic hydrothermal alteration of the host magmatic rock. The parent fluids were low-salinity (0.7 to 3.2 wt. % NaCl equiv.) aqueous solutions that were progressively cooled during mineral precipitation. This mineral phase represents a transitional stage between the high-temperature and low-temperature stages of post-magmatic hydrothermal activity in the study area.
Hydrothermal mineralization sporadically occurs in the western part of Chřiby Hills in a form of thin carbonate veins and veinlets hosted by sedimentary rocks of the Lukov Member of the Soláň Formation. These veins were found in old quarries and slope debris nearby Koryčany, Cetechovice, and Roštín. The mineral filling of studied veins is formed by calcite or rarely calcite and barite. Based on the investigation of fluid inclusions, hydrothermal calcite crystallized from low-temperature (Th = 70–187 °C) and on average low-salinity (0.2–5.6 wt. % NaCl equiv.) hydrothermal solutions. Hydrothermal veins filling crack systems with the direction NNW–SSE or W–E in quarries Holý kopec near Koryčany and Roštín-Chapel are probably post-tectonic. Their origin can be connected to young tectonic events after the termination of main phase of the Alpine Orogeny. Diagenetic origin cannot be excluded in case of calcite vein which fills a bed joint between layers of conglomerate in old quarry 3.5 km south–southeast from the town Koryčany. The source fluids can be derived from mixing of seawater with diagenetic waters. In case of post-tectonic veins, a contribution of meteoric waters is also possible. In addition, UV-fluorescence microscopy reveals a sporadic presence of inclusion with higher hydrocarbons which exhibits strong blue-white fluorescence. These inclusions document a migration activity of higher hydrocarbons in the northwestern part of the Rača Unit in Chřiby Hills.
The Menilite Formation is an important lithostratigraphic member of the Krosno-menilite Unit in the Carpathian Flysch Belt. The rocks of the Menilite Formation occur as small bodies also within Sub-Silesian Unit on the geological map sheet 25-13 Přerov. In this paper, we present new occurrence of chert layers of the Menilite Formation at ground elevation 275 which is situated 1.2 km easternlyof the village Dřevohostice. The rock body is formed of layers of laminated gray-white to gray-brown menilite chert interlayered by thin interpositions of weathered gray-green non-calcareous claystones. The menilite cherts consist of brownish-yellow and gray opal laminae with limonite and chalcedony streaks. Opal laminae have thickness mostly in range of 1–10 mm. Rock matrix is cut by numerous veins formed by opal and chalcedony which originated during at least two diff erent events. Menilite cherts sporadicallyenclose small siliceous chalcedony geodes. Claystones have pelitic texture with a clotted inner structure and contain siliceous sponge spicules and other non-specified microfossils (probably planktonic diatoms). The cherty layers documented in a dug probe have WNW–ESE direction with inclination to SSW under the angle of 25°. The sediments were folded during the overthrust of the Sub-Silesian Nappe on the Carpathian Foredeep in the Karpatian and during subsequent late-tectonic rotations towards NW.
The Sn-W ore deposits in the Krupka surroundings are associated with greisens, which occur in the upper parts of Late Variscan granitoid intrusions. Fluid inclusions were studied in samples of quartz, cassiterite, apatite, fluorite, and topaz in greisenized granites, greisens, and hydrothermal veins with Sn-W mineralization. The greisenization process took place at temperatures 370–490 °C and pressures 155–371 bars, and associated fluids had predominantly low salinity and a low gas (CO2, N2 and CH4) content. The post-greisenization stage was connected with the formation of (i) low-salinity (0–8 wt. % NaCl eq.) fluid inclusions with homogenization temperatures <120–295 °C and (ii) high-salinity (18 to >35 wt. % NaCl eq.) fluid inclusions with homogenization temperatures 140–370 °C, often containing trapped crystals of quartz, topaz, and sulfides, or daughter crystals of salts and carbonates, which were identified by microthermometric measurements, electron microprobe analysis, and Raman spectroscopy. Analyses of fluid inclusion leachates have shown that Na and Ca chlorides predominate in fluids. According to hydrogen stable isotopes, the source of greisenizing and post-greisenizing fluids was not only magmatogenic but also meteoric water or fluids derived from sedimentary rocks.
Abstract Fluorcaphite [SrCaCa 3 (PO 4 ) 3 F] is a rare strontium-calcium member of the apatite supergroup which was previously known only from the Khibiny and Lovozero alkaline complexes. This paper presents evidence of a third fluorcaphite occurrence. It was found in hydrothermally altered Lower Cretaceous teschenite, which forms an intrusive body (probably a sill) in the Lower Cretaceous siliciclastic flysch sediments at Tichá near Frenštát pod Radhoštěm, Silesian Unit, Outer Western Carpathians (Czech Republic). Fluorcaphite occurs as an accessory mineral in hydrothermal veins and in an adjacent alteration zone within the host teschenite. Vein-hosted fluorcaphite forms euhedral crystals and skeletal crusts enclosed in analcime while the teschenite-hosted fluorcaphite forms small overgrowths on older phenocrysts of magmatic apatite. Fluorcaphite from Tichá contains 0.50–1.97 Sr apfu, 2.96–4.49 Ca apfu, 0.59–1.09 F apfu and significantly lower Na (0.01–0.05 apfu) and LREE contents (up to 0.07 apfu). Fluorcaphite formed under hydrothermal conditions after solidification of the host teschenite during post-magmatic hydrothermal activity at temperatures probably between ∼150 and 300°C. The initial 87 Sr/ 86 Sr ratio of vein-hosted analcime +fluorcaphite (0.7063) is significantly higher than those of the host teschenite (0.7041). We therefore suggest a mix of strontium sources in the vein analcime+fluorcaphite: (1) from the host teschenite plus (2) from external source(s) including the Lower Cretaceous seawater and/or surrounding sedimentary rocks of the Silesian Unit. These data indicate an open-system fluid regime and the participation of various fluid sources during the alteration event giving rise to fluorcaphite.
The Obřany Hill is situated in the Hostýn Hills which are formed by the Raea Unit of the Magura Nappe. Local sedimentary rocks (sandstone, conglomerate, shale, rare limestones) have been characterized petrographically and geochemically in this paper. Quartz sandstones dominate at the Hill. Detrital plagioclase occurring within sandstone is pure albite. The first investigated limestone was according to Dunham classification determined as a lime mudstone. Geochemically, it is rich in SiO2. The second limestone sample was determined as chemically very pure packstone. It is probably a boulder from local conglomerates. Clay (i.e., weathered claystone) is of various colour, exhibits high contents of Al2O3 and Fe2O3 and contains concretions of pelosiderite.
