ACTA MUSEI MORAVIAE - SCIENTIAE GEOLOGICAE 94/2009

Abstract
Buriánek, D., 2009: Petrografie poličského krystalinika – Acta Musei Moraviae, Sci.geol., 94: 3–46

Petrography of the Polička Crystalline Complex

The Polička Crystalline Complex is a metamorphosed volcano-sedimentary complex situated in the E part of the Bohemian Massif. Lithotectonic sequences of the Polička Crystalline Complex can be subdivided on the three subunits.

The basal subunit is composed of medium-grained biotite and two-mica gneisses (±Grt ±Sil) with highly deformed bodies of metagranitoids, amphibolites, marbles, calc-silicate rocks and granulites. Granulites are tectonically incorporated in to Polička Crystalline Complex. Mineral assemblage of metapelites preserved post peak stage evolution granulites (620–680 °C and 6–8 kbars) accompanied with anatexis and intrusion dykes of granitoid.

The middle subunit of Polička Crystalline Complex consists of the monotonous complex of mediumgrained biotite to two-mica paragneisses (±Grt ±Sil) with locally abundant calc-silicate nodules up to 0.5 m thicks. Monotonous rocks complex is interpreted as metagreywackes with intercalations metapelites and rare metaconglomerates. The metapelites from middle subunit Polička Crystalline Complex indicates anticlockwise metamorphic evolution. Relics of the oldest LP–MT metamorphism (M1) are preserved mainly in the northernmost part unit. Somewhat later metamorphosis under P–T conditions 580–680 °C a 5–7 kbar affected major part Polička Crystalline Complex (M2). This metamorphic event is locally related with partial melting of metapelites. During exhumation are K-feldspar and sillimanite in the migmatites partially replaced by muscovite (M3).

The upper subunit is in the eastern part Polička Crystalline Complex, and consists of the mica schist with quartzite and paragneisses intercalations. The two-mica mica schist (±St ±Grt ±Sill ±Pl ±Ky) forms several strips NW–SE orientation along NE margin Polička Crystalline Complex and preserved P–T conditions 630–660 °C and 7–8 kbar.

Variscan magmatic rocks represent characteristic members of Polička Crystalline Complex. The basic, tonalite and granite plutonic suites were distinguished here on the basis of petrology and geochemistry. Basic and tonalite suite intruded predominantly middle subunit Polička Crystalline Complex. Dykes and bodies rocks of granite suite are widely distributed in all subunits Polička Crystalline Complex.

Key words: petrography, lithology, tectonic, P–T conditions, Polička Crystalline Complex, Czech Republic,

David Buriánek, Czech Geological Survey, Leitnerova 23, Brno, e-mail: david.burianek@geology.cz

Abstract
Škoda, R., Klementova, M., .opjakova, R., 2009: Studie zirkonu z alkalickeho syenitu od Nalou.an, moldanubikum. Acta Mus. Moraviae, Sci. geol., 94, 47.59.

Study of zircon from alkali syenite near Nalou.any, Moldanubicum, Czech Republic

The fine-grained part of alkali-feldspar syenite near Nalou.any is extremely enriched in Zr, Th and U. In these parts the zircon content reach 5 %. The zircon forms euhedral crystals 100 do 350 µm in size with uniform typology. Among crystal faces dominate prism (100) and pyramid (101). The prism (110) and pyramids (301), (211), and (121) are less evolved. According Pupins classification studied zircons fall into S24.S25 indicated crystallization temperature about 850 ºC and confirmed high alkalinity. In the BSE four different parts of zircon were observed: i) central part with inclusions of thorite, ii) dark parts propagating along fractures, iii) homogeneous rim, and iv) bright zones between central part and rim. The dark parts contain higher concentrations of Ca, Fe, Al and Ti. Based on the U and Th content the radiation damage was calculated. The highest degree of radiation damage shows bright parts (0.38.0.66 dpa) and the lowest was recorded in the rim (0.07.0.31 dpa). The dark parts exhibit lower damage (0.11.0.38 dpa) than central parts (0.17.0.46 dpa). Metamict state was confirmed by HRTEM. The first percolation point was reached about 0.11 dpa. Low calculated radiation damage in the most altered dark parts suggest loss of U > Th during mineral-fluid interaction.

Keywords: zircon, typology, radiation damage, metamictisation, fluid interaction.

Radek Škoda, Renata Čopjakova, Institute of Geological Science, Faculty of Science, Masaryk University, Kotlařska 2, 611 37 Brno, e-mail: rskoda@sci.muni.cz

Mariana Klementova, Institute of Inorganic Chemistry, Academy of Science, Řež 1001, 250 68

Abstract

Houzar, S., Hrazdil, V. 2009: Nordenskioldin CaSnB₂O₆ z Kozlova u Nedvedice, novy vzacny akcesoricky mineral pro nedvedicke mramory. - Acta Musei Moraviae, Sci. geol., 94, 61.66.

Nordenskioldine CaSnB₂O₆ from the locality Kozlov near Nedvedice, new rare accessoric mineral for Nedvedice marbles

Very rare mineral of Europe - nordenskioldine CaSnB₂O₆ - was found in Sn-rich calc-silicate assemblage (tin skarn) of Nedvedice marbles near Kozlov (4 km N from Nedvedice, western Moravia). It forms rare euhedral grains approx. 3.10 µm in size enclosed in calcite. Nordenskioldine was identified using an electron microprobe, its chemical composition (Ca_0.965-1.020 Mg_0.003-0.007 Fe_00.005 Mn_0-0.003) Sn_0.990-1.013 (B₂ F_0-0.039) O₆ corresponds to the theoretical formula. Besides calcite the mineral assemblage contains vesuvianite, Sn-andradite, malayaite, fluorapatite, cassiterite and stokesite. Nordenskioldine crystallized as primary Sn-B skarn mineral under conditions enriched especially in B₂O₃ and poor in SiO₂ and CO₂.

Key words: nordenskioldine, electron microprobe, boron, tin skarn, Nedv.dice marbles, Czech Republic.

Stanislav Houzar, Vladimir Hrazdil: Department of Mineralogy and Petrography, Moravian Museum, Zelny trh 6, 659 37 Brno, Czech Republic, shouzar@mzm.cz; vhrazdil@mzm.cz.

Abstract

Copjakova, R., Houzar, S. (2008): Zirkonolit v mramoru u Krahulova a sta.i HT/LP metamorfozy moldanubika v kontaktni aureole trebicskeho plutonu. - Acta Mus. Moraviae, Sci. geol., 94, 67-76.

Zirconolite in marble at Krahulov and age of HT/LP metamorphism in the contact aureole of the Trebic Pluton (Moldanubian zone)

Regional-scale contact metamorphism of the Trebic Pluton led to the formation of distinct zoning manifested typically in dolomite marbles. Inside part of metamorphic aureole appears rare zirconolite as an accessory mineral in clinohumite-spinel-forsterite marble. The zirconolite-bearing assemblage contains calcite, dolomite, hydroxylclinohumite, spinel, forsterite, chlorite, phlogopite, fluorapatite, baddeleyite and ilmenite-geikielite. Zirconolite grains (<200 µm in size) sporadic overgrowth of baddeleyite or comprise its common relic. The chemical composition of zirconolite varies due to complex zoning of Hf (0.67-1.09 wt. % HfO₂), Th (0.38-12.76 wt. % ThO₂), U (0.11-9.57 wt. % UO₂), Fe (0.64-2.88 wt. % Fe₂O₃), Mg (0.20-1.92 wt. % MgO), Nb (0.56-1.01 wt. % Nb₂O₅), W (0.38-1.11 wt. % WO₃), and Y (0.15-0.84 wt. % Y₂O₃). The CHIME zirconolite dating yields average age 331 ±11 Ma corresponding to post-peak HT/LP metamorphic phase in marbles and is in good agreement with the age of emplacement of the T.ebi. Pluton.

Key words: zirconolite, baddeleyite, marble, metamorphism, CHIME dating, Moldanubicum, Czech Republic

Renata Copjakova, Czech Geological Survey, Leitnerova 23, 658 69 Brno; and Masaryk University, Kotlarska 2, 611 37 Brno, e-mail: copjakova@sci.muni.cz

Stanislav Houzar, Department of Mineralogy and Petrography, Moravian Museum, Zelny trh 6, 659 37 Brno, Czech Republic, shouzar@mzm.cz

Abstract

Kocourková, E., Hrazdil, V., 2009: Scorodite FeAsO₄·2H₂O from Jezdovice near Třešť. – Acta Musei Moraviae, Sci. geol., 94, 77–81.

Scorodite FeAsO₄·2H₂O from Jezdovice near Třešť

In the Jezdovice area (Jihlava ore district) the silver ores were exploited from the mid- 13^th century up to the 18^th century. The locality is hosted by cordierite-biotite gneisses of Moldanubian zone. The deposit is formed by hydrothermal mineralization, including quartz veins with Fe-sphalerite, galena, pyrite, arsenopyrite, pyrrhotite and chalcopyrite. Scorodite was found on old dumps near Jezdovice-Práchovna. The mineral was identified by X-ray powder diffraction, refined unit-cell parameters of scorodite correspond to the published values. The occurrence of scorodite in Jezdovice is the first in the Jihlava mining district.

Key words: scorodite, X-ray powder diffraction, Jihlava ore district, Ag–Pb–Zn ore deposit, Czech Republic.

Eva Kocourková: Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic, retty@centrum.cz.

Vladimír Hrazdil: Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic, vhrazdil@mzm.cz.

Abstract

Buriánek, D., Čech, S., Abrahám, M., 2009: Chemické složení těžkých minerálů jako indikátor zdrojových oblastí pro křídové sedimenty na jižním okraji vysokomýtské synklinály (jv. okraj české křídové pánve) – Acta Musei Moraviae, Sci. geol., 94, 83–96.

Chemical composition of heavy minerals as indicators of source areas for Cretaceous sediments in the south margin Vysoké Mýto syncline (SE. Margin Czech Cretaceous Basin)

Heavy minerals as garnet, amphibole, tourmaline and staurolite are useful indicators of source areas of sedimentary basins. The observed chemical variation of heavy minerals from Cretaceous marine sediments in south margin Vysoké Mýto syncline indicate uniform source region during formation cenomanian to turonian sediments. The detrital materials, seems to have come from the neighbouring crystalline units in the west and southwest direction as Polička and Svratka Crystalline Complexes. On the other hand evidence for transport directions from southern and southeastern crystalline units (moravicum) is absent. These results probably reflect morphology of pre-cenomanian drainage pattern.

Key words: heavy minerals, chemical composition, Czech Cretaceous Basin,

Česká geologická služba, Leitnerova 22, 658 59, Brno; david.burianek@cgu.cz

Abstract

Dolnicek Z., Polach M. (2009): Hydrotermalni mineralizace v piskovcich pestrych godulskych vrstev na lokalit. Bystry potok (Moravskoslezske Beskydy). - Acta Mus. Moraviae, Sci. geol., 94: 97.110. Brno.

Hydrothermal mineralization in sandstones of Variegated Godula Member at the locality Bystry potok (Moravskoslezske Beskydy Mts.)

Tiny hydrothermal veinlets hosted by Upper Cretaceous siliciclastic flysch sediments of the Variegated Godula Member (Godula Development, Silesian Unit, Outer West Carpathians) have been studied from mineralogical, fluid inclusion and stable isotope points of view. The occurrence of mineralization composed of quartz, and three populations of calcite containing isolated grains and aggregates of galena and chlorite (chamosite) is restricted only to sandstone beds. Fluid inclusions hosted by quartz trapped a heterogeneous mixture of aqueous solution and vapour phase at temperature of ~120 ºC, whereas calcitehosted fluid inclusions enclosed homogeneously trapped aqueous fluids (Th = 111.155 ºC). The salinities are generally low, between 1.1 and 2.6 wt. % NaCl eq. The highly positive fluid δ¹⁸O values (+6.2 to +9.5 ‰ SMOW) and variable fluid δ¹³C values (-4.3 to -9.5 ‰ PDB) have been found. The origin of the hydrothermal minerals is interpreted to be in �gdiagenetic�h fluids that have been probably generated during deeper burial and/or subsequent tectonic deformations of the host clay-rich sedimentary rocks.

Key words: Silesian Unit, hydrothermal mineralization, sandstone, calcite, chlorite, fluid inclusions, stable isotopes

Zdenek Dolnicek, Martin Polach, Department of Geology, Faculty of Science, Palacky University, tr. Svobody 26, 771 46 Olomouc, e-mail: dolnicek@prfnw.upol.cz, Giraffe@seznam.cz

Abstract

Buriánek, D., 2009: Metamorfní vývoj svorů a jejich tektonická pozice v poličském krystaliniku, Acta Mus. Moraviae, Sci. geol., 94, 111–128.

Metamorphic evolution of mica-schists and their tectonic position in the Polička Crystalline Complex

The Polička Crystalline Complex is situated in the eastern part of the Bohemian Massif. This metamorphosed volcano-sedimentary complex is composed mainly of biotite to two mica gneisses. Micaschists are present only as small lenses or bodies within gneisses, which represent typical rocks of the Polička Crystalline Complex. Based on the geological position, two types of mica-schists were recognized: (i) Mica-schists with mineral assemblage Qtz+Ms+Bt+Grt±Pl±Sill are situated along the contact with the Svratka Crystalline Complex (W boundary Polička Crystalline Complex). These mica-schists yield PT conditions of 642 ±124 °C and 8 ±2 kbar. (ii) Mica-schists with mineral assemblage Qtz+Ms+Bt±Pl±St ±Grt±Pl±Ky form several N-S oriented stripes between villages Stašov, Hamry and Jedlová on NE margin of the Polička Crystalline Complex. Mica-schists in this part of the Polička Crystalline Complex indicate peak P–T conditions of ~650 °C and ~8 kbar and younger decrease of pressure to about 7 kbar and 660 °C, related to thrusting of the Letovice Crystalline Complex over the Polička Crystalline Complex. According theirs mineralogy and geological position can be the mica schists interpreted as tectonic slice rocks from surrounding units (Svratka and Letovice Crystalline Complex) incorporated into the volcano-sedimentary complex of the Polička Crystalline Complex during Variscan orogeny.

Key words: metamorphism, mineralogy, mica-schist, Polička Crystalline Complex, Bohemian Massif.

David Buriánek, Czech Geological Survey, Leitnerova 23, Brno, e-mail: david.burianek@geology.cz

Abstract

Fojt B., Houzar S., Novák, M. (2009): Příspěvek k poznání provenience valounů ve slepencích svrchnoviséského stáří na Drahanské vrchovině: VI. – skarnoid. – Acta Musei Moraviae, Sci. geol., 94: 129–139.

Contribution to the knowledge of provenance of pebbles from the Upper Viséean conglomerates in the Drahany Hights: VI. – Skarnoid.

The pebble of leucocratic biotite migmatite (plagioclase >> K-feldspar) with a small nodule of skarnoid rock (garnet+amphibole+magnetite+quartz) was found at locality Račice, Luleč conglomerates, Drahany Hights. Minerals from both rocks were studied in detail using electron microprobe and polarizing microscope. Thin transitional zone with An-enriched plagioclase (Ab_56–57 An₄₃ Or_0–1) is developed between skarnoid and migmatite. The mineral assemblages and chemical composition of minerals in skarnoid (almandine Alm_73–74Grs_14–16Prp₆Sps_2–3Adr_2–3, grunerite X_Fe = 0.63–0.64, ferri-ferrohornblende X_Fe = 0.74–75) and in host migmatite (plagioclase Ab_68–72 An_25–29 Or_1–4), are similar with those from the localities of magnetite-rich amphibolites from the Polička Unit or border facie of magnetite skarn in the Pernštejn area, Svratka Unit, respectively.

Key words: skarnoid, grunerite, magnetite, almandine, Luleč Conglomerate, provenance, Drahany Culm.

Bohuslav Fojt, Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: fojt@sci.muni.cz

Stanislav Houzar, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic, e-mail: shouzar@mzm.cz

Milan Novák, Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: mnovak@sci.muni.cz

Abstract

Poul, I., Janečka, J. and Melichar, R.: The structural position of the Upper Jurassic limestone “klippen” and breccia horizons in Jasenice village surroundings: a part of the Ždánice-Subsilesian or the Silesian Unit?. — Acta Mus. Morav., Sci. geol, 94, 141–150 (with English summary)

The structural position of the Upper Jurassic limestone “klippen” and breccia horizons in Jasenice village surroundings: a part of the Ždánice-Subsilesian or the Silesian Unit?

The structure and geological origin of the Jurassic-Cretaceous limestones in northern Moravia (Valašské Meziříčí and Štramberk towns vicinity) is still under discussion. The limestone “blocks” in Jasenice village are marked as “klippen” or olistoliths and they are a part of flysch nappes in Outer Western Carpathians. While the limestone body at Jasenice is considered to be a part of the Silesian Nappe in published geological maps, the breccias surrounding the limestone are supposed to be a part of the Ždánice- Subsilesian Nappe. According to new geological research, the Jasenice limestone body is a olistolith accompanied with a coarse limestone conglomerates representing olistostrome deposits (gravity slump) situated at the base of the Silesian Nappe.

Key words: Jurassic, klippe, tectonics, Ždánice-Subsilesian Unit, Silesian Unit, olistolith, breccia, olistostrome

Ivan Poul, 1 – Czech Geological Survey, office Brno, Leitnerova 22, 658 69 Brno, Czech Republic, e-mail: ivan.poul@geology.cz; 2 – Institute of Geotechnics, Faculty of Civil Engineering, Brno University of Technology, Veveří 331/95, 602 00 Brno, Czech Republic; 3 – Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic

Jiří Janečka, Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: wilgefortz@yahoo.com

Rostislav Melichar, Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: melda@sci.muni.cz

Abstract

Musil R., 2009: Deposition and erosion stages in the Moravian Karst. – Acta Mus. Morav., Sci. geol., 94, 151–165 (with English summary).

Deposition and erosion stages in the Moravian Karst

Moravian Karst represents the largest and the most important karst territory in the Czech Republic, with regard to its long scientific research and the excellent development of broad spectrum of surface and underground karst phenomena, including a number of active stream sinks and karst springs. Between Jurassic and Quaternary, the area underwent significant changes, different on the karstic surface and within the karst valleys and connected cave floors. Separate development of northern, central and southern part of Moravian Karst is under discussion. This publication reviews the complicated development of this region and its changes from Jurassic to the Quaternary (river valleys, open air and cave sediments and their periodical deposition and erosion).
The substantial part of karst formation took place before the Badenian transgression. The sedimentary record demonstrates repeated sediment deposition and erosion, especially within surface river valleys and cave corridors. Cave chimneys played the key role in processes of accumulation and subsequent erosion of loam sediments in cave corridors. Major part of the remaining, so far not eroded loam sediments originated during the last stage of accumulation, i.e. in the Late Last Glacial. Correspondingly, we must expect that similar repeated stages of accumulation and erosion of variable intensity took place in previous glacials and interglacials. These processes, well recognizable in the Last Glacial and Holocene, must have been characteristic for the whole Quaternary.

Key words: Czech Republic, Moravian Karst, Mesozoic and Cenozoic times, main karsology changes, denudation and erosion stages of sediments.

Rudolf Musil, Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic. E-mail: rudolf@sci.muni. cz

Abstract:

Cempírek, J., Houzar, S. (2009): Přelud známý jako „Český kráter“ (recenze knihy). – Acta Mus. Moraviae, Sci. geol., 94, 167–173.

Illusion known as „Czech Crater“ (book review)

The book “Czech Crater” from Petr Rajlich represents a new manipulative and highly speculative type of geological literature in Czech Republic. Without any real evidence, the author presents imaginary Proterozoic impact producing “Czech Crater” of 290×240 km in diameter. The book commonly ignores or misinterprets modern studies in fields of structural geology, petrology, geochemistry and geochronology. Alleged “recrystallized pseudotachylites” are actually ordinary garnet migmatites, deformed quartz grains are nothing but tectonically fractured quartz in pegmatites and metamorphic boudins, putative “shocked” garnets originated during Variscan migmatization. In case of Saidenbach microdiamonds author simply ignores or misinterprets all scientific studies that were written about the locality. The concept of “Czech crater” represents a clearly mistaken, publicity-searching speculation which was fully accepted only by its author.

Key words: Czech Impact Crater, speculation, false evidence, Bohemian Massif, Czech Republic

Jan Cempírek, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic, jcempirek@mzm.cz

Stanislav Houzar, Department of Mineralogy and Petrography, Moravian Museum, Zelný trh 6, 659 37 Brno, Czech Republic, shouzar@mzm.cz