Minerals of crandallite group and synchysite were found on base-metal ore veins at historical deposit Zlatý důl near Hlubocky, which is hosted by the Lower Carboniferous flysch sediments of the Moravo-Silesian Culm. Minerals of crandallite group were discovered in a sample which is formed by Fe-rich dolomite, quartz, anatase and ore minerals (primary phases: chalcopyrite, pyrite and galena, secondary phases: chalcocite, covellite, limonite and native copper). The sample is cut by younger calcite vein. Euhedral zoned crystals of minerals of crandallite group, up to 25 µm in size, were found to be enclosed in Fe-rich dolomite. Lighter zones (in BSE image) contained more REE and Sr than darker zones. Four endmembers - crandallite, florencite-(REE), goyazite and gorceixite participate on chemical composition of these minerals, taking 17.4 - 56.5, 14.1 - 53.3, 4.2 - 66.5 and 0.0 - 0.2 mol. %, respectively. Synchysite was found in the same sample and also in a sample, which is formed mostly of quartz and sulphides (chalcopyrite > galena). Synchysite formed isometric or irregular grains, ? 70 µm in size. The presence of synchysite-(Y) and synchysite-(Ce) was revealed from available microprobe compositional data. Both phosphates and carbonates are enriched in LREE, carbonates are also enriched in MREE. Rare-earth elements were probably leached by hydrothermal fluids from REE-rich minerals from host Culmian sediments.
Origin and chemical composition of fluids of hydrothermal ore veins at historical deposit Zlatý důl near Hlubočky (Lower Carboniferous of the Nízký Jeseník Upland) were studied using petrography, microthermometry and crush-leach analysis of fluid inclusions and analysis of stable isotopes of oxygen and carbon in carbonates, oxygen in quartz and sulphur in sulphides. Studied mineralization has epithermal and partly mesothermal character (Th = < 50 to 293 °C). The H2O-NaCl-CaCl2 system is mostly enclosed in the primary fluid inclusions in minerals of post-Variscan ore veins. These fluids had low to medium homogenization temperatures (68 to 293 °C) and moderate to high salinities (19–27 wt. % NaCl eq.). In contrast, low to moderate salinity (0–10 wt. % NaCl eq.) fluids of the system H2O-NaCl-KCl-(MgCl2-FeCl2) with low homogenization temperatures (< 50 to 110 °C) were enclosed in secondary fluid inclusions. The main source of water was probably evaporated seawater for older fluids. The source of carbon was in carbon of the homogenized Earth’s crust and partly in carbon of organic matter. Meteoric water is the main source for younger fluids. Origin of sulphur of sulphides is in the surrounding Lower Carboniferous sediments (shales). The high content of SO4 in fluids hosted by Fe-rich dolomite suggests the origin of the fluids in the evaporated Permian basins. Studied older quartz-galena vein is probably Variscan in age. Genetically similar mineralization can be found also at other localities in the Moravo-Silesian Lower Carboniferous (Culm, siliciclastics of the Lower Carboniferous age).
Ve dvou slichových vzorcich ze sedimentů odebraných v potoce
Zlatý důl, který je pravostranným přitokem řeky Bystřice, byly
studovany těžke mineraly. V těžke frakci byly zastoupeny
zejmena rudni mineraly (pyrit, chalkopyrit, galenit) a take
granaty, akcesoricky pak zirkon, amfibol, epidot, staurolit,
turmalin a monazit. Nalezeno bylo i množstvi fragmentů
antropogenniho původu, sklovite ”sferulky“ a ulomky slitiny
složeni Pb-Sn. Korund byl nalezen jako poloostrohranne zrno
tmavě modre barvy se zonalni stavbou. Chemickou analýzou byly
zjistěny vedle hlavni složky, Al, rovněž stopove obsahy Ti, Fe,
Cr a Ba (≤ 0,56 hm. % jejich oxidů). V korundu jsou uzavirany
nepravidelne inkluze Ti-bohateho magnetitu, který obsahuje 63,0
mol. % magnetitove složky, 36,2 mol. % složky ulvospinelove,
0,4 mol. % coulsonitove, 0,2 mol. % složky chromitove a 0,2
mol. % hercynitove komponenty. Primarni zdrojovou horninou
korundu je pravděpodobně alkalický bazalt nebo lamprofyr,
připadně těžka frakce kulmských drob.
An electron microprobe study of polished sections prepared from a sample of fine-grained sandstone from the locality Slivotín (Ždánice-Hustopeče Formation, Ždánice Unit, Flysch Belt of the Outer Western Carpathians, Czech Republic) allowed to yield in addition to data on chemical composition also the detailed information on in situ textural relationships of individual minerals. During our study, emphasis was given to accessory phases belonging to the translucent heavy mineral fraction. The detrital garnet (Alm36-82Grs2-45Prp2-22Sps0-15) was extensively dissolved and replaced by calcite cement from its margins and along the cracks. Detrital fluorapatite was dissolved in a similar way, however, dissolution episode was followed by growth of authigenic rims composed of carbonate-fluorapatite. Other observed heavy minerals (zircon, chrome spinel, TiO2 phase, monazite, tourmaline) probably remained unaltered by diagenetic processes. The chemical composition of chrome spinels varies mostly between magnesiochromite and chromite, whereas spinel is very rare. The chemical composition of garnets and chrome spinels is comparable with published data from Czech, Polish and Slovak parts of the Flysch Belt of the Western Carpathians, and indicates the primary source of detrital material in rocks of deeper parts of orogen, characterized especially by the presence of catazonal metamorphites and almost lacking volcanic rocks. Redeposition of heavy minerals from older sediments cannot also be ruled out. The pronounced diagenetic alteration of garnet, if not very scarce in the area of Flysch Belt, could help to explain the earlier observations of wide fluctuations of contents of garnet in heavy mineral concentrates.
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.
Secondary bornite occurs within quartz-carbonate ore vein in dump material at historical deposit of Zlatý důl near Hlubocky. This mineral was characterized using ore microscopy and electron microprobe analyses. The studied sample was formed by quartz, which occurs in the centre of the ore vein, carbonate of the dolomite-ankerite series, which formed bands on the edge of the ore vein and the unspecified beige coloured carbonate. The ore minerals were represented by primary chalcopyrite and secondary chalcocite, covellite and galena (the layer of galena grows on chalcocite on the edge of the altered chalcopyrite aggregate). The studied sample was partly weather-worn and especially carbonate of the dolomite-ankerite series was altered to iron oxyhydroxides. Bornite lamellae up to 100 × 40 μm were found along cracks of the chalcopyrite aggregate (where chalcopyrite is altered to chalcocite). Lamellar bornite occurs also in secondary chalcocite. Bornite contained only trace amount of Pb, other elements (Zn, Co, Ni, Mn, Cd, Hg, As, Ag, Bi, Sb, Se and Cl) were bellow the detection limits. Bornite is probably a secondary mineral, which was formed at the expense of chalcopyrite. Bornite from historical deposit of Zlatý důl represents the first occurrence of this mineral in the Bystřice Ore District and also in the whole Moravo-Silesian Culm.
An in situ electron microprobe study of detrital minerals yielded important insights into the diagenetic history of the Cretaceous-to-Paleogene flysch sandstones from the Chvalčov site, Rača Unit, Flysch Belt of the Outer Western Carpathians. Detrital titanite and a Fe-Ti mineral (probably ilmenite) were almost completely altered to TiO2 minerals, which also newly crystallized in intergranular spaces of sandstone. Brookite, anatase, and, exceptionally, rutile were identified by Raman spectroscopy. Authigenic TiO2 phases show complex composition with occasionally elevated contents of Fe, Nb, Zr, V, Sc, Cr, Al, Y, and/or P, which were likely sourced from altered neighboring heavy minerals. In addition, rare authigenic LREE- and Y-enriched apatite rims were observed on detrital apatite. The remobilization of REE, Y, and HFSE was likely mediated by acidic early diagenetic fluids enriched in fluoride and sulfate anions. The superimposed formation of calcite cement was associated with the dissolution of detrital garnet, feldspars, and quartz. The compositions of detrital apatite and garnet (Alm60-82Prp4-30Sps0-24Grs0-19) are comparable with those from adjacent parts of the Flysch Belt. Detrital rutile is enriched in Nb, V, Cr, and Zr. Our study illustrates the intensity of diagenetic alteration of detrital minerals in flysch sandstones as well as the usefulness of in-situ electron-microprobe investigations for the recognition of processes influencing heavy minerals in diagenetically altered sediments.
Prace se zabýva mineralogii a podminkami vzniku rudnich žil na vybraných lokalitach v jihozapadni casti kulmu Nizkeho Jeseniku. Dostupnými metodami (polarizacni mikroskopie, WDX a EDX analýzy, mikrotermometrie a analýzy výluhů fluidnich inkluzi, izotopicke složeni S, C, O, stopove prvky v karbonatech a hornině, katodova luminiscence karbonatů, Ramanova spektroskopie a izotopicke složeni Pb) byly studovany vzorky žiloviny. Mineralni asociaci na žilach tvoři křemen-dolomitický karbonat-kalcit-(baryt) a sulfidicke mineraly (pyrit, chalkopyrit, galenit, sfalerit). Na lokalitach Hrabůvka, Olsovec a Zlatý důl byl prokazan vicefazový vznik mineralizace. Studovana mineralizace ma epitermalni až mezotermalni charakter (Th = <50 až 290 °C). Fluidni system H2O-NaCl-CaCl2 je nejcastěji uzaviran v primarnich fluidnich inkluzich mineralů povariských žil, tato fluida jsou niže až středně teplotni (48 až 295 °C), středně až vysokosalinni (15 - 27 hm. % NaCl ekv.). V sekundarnich inkluzich byly zjistěny nizkoteplotni (<50 až 122 °C) a nizkosalinni (0 - 10 hm. % NaCl ekv.) fluida systemu H2O-NaCl-KCl-(MgCl2-FeCl2). Původ siry sulfidických mineralů je v okolnich kulmských sedimentech (droba, jilova břidlice). Zdrojem uhliku karbonatů je uhlik homogenizovane zemske kůry a castecně i uhlik oxidovane organicke hmoty. Hlavnim zdrojem vody starsich fluid je evaporovana mořska voda, u mladsich fluid se významně uplatnila voda meteoricka. Nově zjistěne REE mineraly na žilach ve Zlatem dole dokladaji mobilitu REE v nizkoteplotnich, výsesalinnich roztocich. Vysoký obsah SO4 ve fluidech Fe-bohateho dolomitu ze Zlateho dolu ukazuje na původ fluid v permských evaporovaných jezerech. Zdrojem Pb galenitů jsou kulmske sedimenty.
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