Alteration of detrital titanite in the Drahany Upland

Titanite is a common accessory mineral of magmatic rocks, low- and medium-grade metamorphic rocks and it occurs as a detrital mineral in clastic sediments. Our paper deals with titanite alterations as a result of interaction of diagenetic fluids with detrital titanite during deep burial of sedimentary rocks of Drahany Upland, Protivanov Formation. Detrital titanites and their alteration products were examined by electron microprobe. Titanite dissolution was observed from the rim and along the cracks, accompanied by the formation of an authigenic calcite, TiO2 phase, synchysite-(Ce), and rarely chlorite. With an increasing degree of alteration, detrital titanite occurs as small irregular relics inside a mixture of authigenic minerals. Based on the composition of authigenic minerals, we can suppose diagenetic fluid rich in CO2, F and Ca responsible for alteration of detrital titanite. The maximum temperatures in this area during deep burial of sedimentary rocks reached 250–300 °C, corresponding to the conditions of very low-grademetamorphism. Contents of REE (0.67–3.55 wt. % REE2O3) in detrital titanite are rather high and vary significantly. Authigenic synchysite-(Ce) compared with detrital titanite strongly prefers LREE over HREE, indicating that LREE released during dissolution of detrital titanite were preferentially incorporated into the structure of synchysite-(Ce), whereas HREE were mobilized and removed away by diagenetic fluids.Titanite is a common accessory mineral of magmatic rocks, low- and medium-grade metamorphic rocks and it occurs as a detrital mineral in clastic sediments. Our paper deals with titanite alterations as a result of interaction of diagenetic fluids with detrital titanite during deep burial of sedimentary rocks of Drahany Upland, Protivanov Formation. Detrital titanites and their alteration products were examined by electron microprobe. Titanite dissolution was observed from the rim and along the cracks, accompanied by the formation of an authigenic calcite, TiO2 phase, synchysite-(Ce), and rarely chlorite. With an increasing degree of alteration, detrital titanite occurs as small irregular relics inside a mixture of authigenic minerals. Based on the composition of authigenic minerals, we can suppose diagenetic fluid rich in CO2, F and Ca responsible for alteration of detrital titanite. The maximum temperatures in this area during deep burial of sedimentary rocks reached 250–300 °C, corresponding to the conditions of very low-grademetamorphism. Contents of REE (0.67–3.55 wt. % REE2O3) in detrital titanite are rather high and vary significantly. Authigenic synchysite-(Ce) compared with detrital titanite strongly prefers LREE over HREE, indicating that LREE released during dissolution of detrital titanite were preferentially incorporated into the structure of synchysite-(Ce), whereas HREE were mobilized and removed away by diagenetic fluids

NEOBVYKLÁ SN-MINERALIZACE Z NYF PEGMATITU U KLUČOVA; TŘEBÍČSKÝ MASIV, MOLDANUBIKUM

Sn-mineralisation was found in the NYF pegmatite near Klučov, in the Třebíč Massif. It fills small veinlets in albitized graphic or blocky K-feldspar zone. Two different mineral assemblages were distinguished: herzenbergite-varlamoffite-stokesite-cassiterite and cassiterite-varlamoffite-tinzenite. Lathy herzenbergite I crystals up to 2 mm were formed during primary crystallization from late hydrothermal fluids and their chemical composition correspond to SnS with small amount of Cu and Fe. Varlamoffite and stokesite form fine grained aggregates and their textural relationships suggest replacement of herzenbergite

PRACOVIŠTĚ ELEKTRONOVÉ MIKROSKOPIE A MIKROANALÝZY: VYTVÁŘENÍ SPOLEČNÝCH PRACOVIŠŤ – CESTA K INTEGRACI VÝZKUMU, VÝUKY A PRAXE

The article describes the analytical capabilities of a new microanalytical facility, established jointly by the Masaryk University in Brno and the Czech Geological Service. The core instrument of the Centre of Electron Microscopy and Microanalysis is an electron microprobe CAMECA SX100, equipped with 5 WD spectrometers (two of them with large LIF and PET crystals, three with layered crystals for light element analysis), an ED analysis system PGT, SE, BSE detectors, CL camera, and a built-in optical polarizing microscope)

SROVNÁNÍ CHEMISMU DETRITICKÝCH PYROP-ALMANDINŮ LULEČSKÝCH SLEPENCŮ S CHEMISMEM GRANÁTŮ VYBRANÝCH GRANULITŮ ČESKÉHO MASIVU

The paper presents the comparison of major oxides (microprobe) and trace elements (LA-ICP-MS) chemistry of the detrital pyropealmandines from Luleč Conglomerates with pyrop-almandines of selected granulites of the Czech Massif for the purpose of provenance of the Culm sediments. Chemical compositions of pyrope-almandines from Luleč quarry are in a good correlation with chemical compositions of granulite garnets from Miroslav Crystalline Unit and small granulite bodies W of Jihlava. Pyropealmandines from leptynites of the Polička Crystalline Unit and Náměšť Granulite Massif show great differences in REE patterns. The results seem to indicate the source areas of granulites might have been changing from the older to the younger horizons of the Luleč Conglomerates

STUDIUM OPTICKÝCH ANOMÁLIÍ V GRANÁTECH Z CA-SKARNŮ BRNĚNSKÉHO, ŠUMPERSKÉHO A ŽULOVSKÉHO MASIVU

Optical anisotropy commonly occurs in grossular-andradite garnets from different types of Ca-skarns. The difference between the crystal chemistry of isotropic and non-isotropic lamellae is discussed. It is assumed that the substitution of OH groups and fluorine for oxygen or entire SiO4 tetrahedra is the main cause of the occurrence of optical anomalies in the studied samples, rather than Fe3+/Al3+ordering on the positions of trivalent cations, as some previous authors suggest

Chemical composition of ceramic tumblers from Loštice

The paper summarizes results of geochemical examination of the Loštice pottery. A clay nodule found during archaeological works was used for a part of tumbler replicas´ production as a plastic raw material. At the temperature over 1 200 °C, the replicas made of loess collapsed. The affect of garnets on formation of “blebs” was experimentally verified. The results showed that the ceramic tumblers of the (010) and (020) groups were made of clay soil with the addition of almandine garnet as non-plastics. The “blebs” form by thermal decomposition of almandine. The firing temperature must exceed 1 200 °C. Cordierite (sekaninaite, possibly ossumilite) crystallizes from the melt. Another part of replicas was made of local loess.The paper summarizes results of geochemical examination of the Loštice pottery. A clay nodule found during archaeological works was used for a part of tumbler replicas´ production as a plastic raw material. At the temperature over 1 200 °C, the replicas made of loess collapsed. The affect of garnets on formation of “blebs” was experimentally verified. The results showed that the ceramic tumblers of the (010) and (020) groups were made of clay soil with the addition of almandine garnet as non-plastics. The “blebs” form by thermal decomposition of almandine. The firing temperature must exceed 1 200 °C. Cordierite (sekaninaite, possibly ossumilite) crystallizes from the melt. Another part of replicas was made of local loess