Papers by Marta Chlupáčová
Journal of GEOsciences, 2012
Mafic and silicic dyke rocks, which occur in the Ag-U ore district of Jáchymov (Joachimsthal) in ... more Mafic and silicic dyke rocks, which occur in the Ag-U ore district of Jáchymov (Joachimsthal) in the Krušné hory (Erzgebirge) belong to kersantites, diorite porphyries, and granite porphyries, subordinately to spessartites. Dykes of minettes are located outside the district and penetrate the Nejdek-Eibenstock granitic massif. Mafic and silicic dykes exhibit diverse cross-cutting relationships and form in places composite dykes. Lamprophyres correspond to shoshonitic magmas with high abundances of compatible (Cr, Ni) and incompatible elements (Rb, Ba, P). All mafic dykes were affected by a postmagmatic alteration manifested by replacement of primary olivine and pyroxenes by amphibole, biotite and chlorite. Granite porphyries crystallized from leucocratic, weakly peraluminous, low-P magmas with moderate enrichments in Rb and depletions in Ca, Sr and Zr. By contrast, diorite porphyries are intermediate rocks containing 62-65 wt. % SiO 2 whose geological occurrence and major-element composition suggest origin by magma mixing involving lamprophyric and silicic melts, with simultaneous fractionation of biotite. The Th/U ratios in all dyke rocks correspond to chondritic and crustal values and demonstrate that whole-rock uranium contents were neither significantly increased nor affected by contemporaneous mineralization events. The stable isotope composition has been determined for whole rocks (O, C, S) and carbonate minerals (C, O). Wholerock δ 18 O values range between 1.6 to 7.8 ‰ SMOW and do not show any systematic variations with the rock types. The isotopic composition of carbonates is represented by the following values: δ 18 O = 19.6 to 25.0 ‰ SMOW and δ 13 C = -5.7 to -9.0 ‰ PDB. The high positive values of δ 18 O of carbonates are in a remarkable contrast to compositions of primary magmatic carbonates and indicate the carbonate formation during low-temperature hydrothermal event(s). Sulphides in kersantites and diorite porphyries yielded δ 34 S = 0.5 to 6.6 ‰ CDT, which document crustal in addition to mantle source of sulphur consistent with average value in the Saxothuringian crust (~ 5 ‰ CDT). Bulk magnetic susceptibility of dyke rocks shows a general decrease from mafic to silicic magmas in a sequence as follows: kersantites -500, minettes -350, diorite porphyries -350 and granite porphyries -50•10 -6 [SI]. Local increases up to 5000•10 -6 [SI] are due to accessory pyrrhotite in kersantites and diorite porphyries. Mafic dykes in the Western Krušné hory (Erzgebirge) are preferentially found within the Jáchymov-Gera tectonic zone and demonstrate spatial focusing of ascending mantle-derived melts. Such pathways may have served for transfer of ore-forming elements on the crustal scale by fluids of diverse origin.
Journal of Geodynamics, 2003
P-Wave velocity of metamorphic and magmatic rocks from the West Bohemian Saxothuringian (e.g. phy... more P-Wave velocity of metamorphic and magmatic rocks from the West Bohemian Saxothuringian (e.g. phyllites, quartzites, metabasites, mica schists, orthogneisses, granites and young volcanics) was measured using an acoustic method. The specimens were saturated with water in order to avoid the influence of open microcracks and porous space. Anisotropy coefficients were calculated from measurements in three perpendicular directions. Phycodes phyllitic slates
Studia Geophysica et Geodaetica, 2010
Magnetic susceptibility of 72 cambisol profiles from the vicinity of the Vír dam, NW Moravia was ... more Magnetic susceptibility of 72 cambisol profiles from the vicinity of the Vír dam, NW Moravia was measured. The enhanced susceptibility of topsoil, particularly of the horizon O, was assessed from the aspect of vegetation setting and magnetic mineralogy. Magnetic susceptibility variations with field and temperature as well as frequency dependent susceptibility were applied to indicate magnetic carriers. It was found that the enhanced magnetic susceptibility is caused very likely by the presence of maghemite and magnetite of various grain sizes. Magnetic minerals are pedogenic in origin in all three horizons, while in the O and A horizons they are mostly anthropogenic in origin. Magnetic susceptibility was correlated with contents of trace elements Mo, Cu, Pb, Zn, Ag, As, Cd, Sb, Bi, Hg, Se, furthermore with TOT/C, TOT/S, and 137 C. The close association of susceptibility with Pb, Sb and Hg, or also with Mo, As, Se and their similar depth variations suggest a slight anthropogenic input in soils from a long-distant source. The same is valid for 137 C, its strong correlation with magnetic susceptibility has been found.
Studia Geophysica et Geodaetica, 2010
Magnetic properties as well as the magnetomineralogy were investigated in rocks underlying a 7 km... more Magnetic properties as well as the magnetomineralogy were investigated in rocks underlying a 7 km long aeromagnetic anomaly situated in the Moldanubian crystalline unit of the Bohemian Massif. The anomaly is caused by highly magnetic cordierite gneiss forming a stripe of NE -SW direction east of the town of Humpolec, eastern Bohemia. Magnetic susceptibility and its anisotropy (AMS), natural remanent magnetization, field and temperature variations of susceptibility were measured. Optical study of thin sections, electron microprobe and Mössbauer studies were also used to reveal the carrier of the high susceptibility and the high NRM. There appear to be two major generations of Fe-Ti oxides: older hematite with ilmenite exsolutions (Ti-hematite) which is the dominant remanence phase, and younger magnetite, the dominant susceptibility phase, usually associated with rutile. This indicates a reaction Hematite + Ilmenite → Magnetite + + Rutile; the trace elements in magnetite, as well as texture and morphology of the oxide grains support this assertion. An additional minor portion of maghemite is revealed by Mössbauer and thermomagnetic results. The Ti-hematite belongs to the oldest mineral assemblage in the rock, despite its anhedral morphology. Inclusions in Ti-hematite, among which corundum and abundant paragonite occur, record a strongly peraluminous and probably disequilibrium association during the crystallization of the Ti-hematite. K e y w o r d s : aeromagnetic anomaly, cordierite gneiss, magnetic properties, thermomagnetic analysis, Ti-hematite, ilmenite exsolutions, magnetite, maghemite, rutile V. Procházka et al. 96 Stud. Geophys. Geod., 54 (2010)
Studia Geophysica et Geodaetica, 2006
Low-field variation of magnetic susceptibility was investigated on a collection of several hundre... more Low-field variation of magnetic susceptibility was investigated on a collection of several hundreds specimens of various minerals and rocks using the KLY-4S Kappabridge. The measurement is fully automated, being executed in 21 distinct fields ranging from 2 to 450 A/m (in one frequency of 875 Hz). The measurement is rapid, 7 min per specimen, so that large collections of specimens can be investigated. The results can be processed both graphically and mathematically. For the latter processing, parameters of two kinds were introduced. One characterizes the susceptibility change with field, the other one characterizes the field in which the susceptibility no longer obeys the Rayleigh law and starts becoming more complex.
Lithos, 2009
Serpentinized peridotiteclinopyroxenite, approximately 11 × 5 m in size, enclosed in high-pressu... more Serpentinized peridotiteclinopyroxenite, approximately 11 × 5 m in size, enclosed in high-pressure felsic granulite, occurs in a quarry near the village of Bory (Gföhl Unit of the Moldanubian Zone of Western Moravia, Czech Republic). The anisotropy of magnetic susceptibility (AMS) ...
Lithos, 2011
This paper presents new structural, anisotropy of magnetic susceptibility (AMS), petrological, an... more This paper presents new structural, anisotropy of magnetic susceptibility (AMS), petrological, and geochronological data to examine the link between LP-HT metamorphism and S-type granite formation in the Moldanubian unit, Bohemian Massif. We first describe the intrusive relationships of an S-type granite to its host cordierite-bearing migmatites, superbly exposed in the Rácov locality, northeastern Moldanubian batholith. The knife-sharp contacts and rectangular stoped blocks establish that the migmatites cooled and were exhumed above the brittle-ductile transition prior to the granite emplacement. The U-Pb monazite geochronology combined with P-T estimations constrain the age and depth of migmatization at~329 Ma and~21 km (T ≈ 730°C). The migmatite complex was then exhumed at a rate of 6-7 mm y −1 to a depth of b 9 km where it was intruded by the granite at~327 Ma. These data indicate that the hot fertile metapelitic middle crust in this part of the Moldanubian unit, newly defined as the Pelhřimov complex, underwent rapid isothermal decompression at~329-327 Ma, giving rise to biotite melting and generation of large volumes of S-type granite magma. We propose that the rapid~329-327 Ma exhumation of the Pelhřimov complex may have been partly assisted by the crustal-scale Přibyslav mylonite zone, which delineates the underlying western edge of the Brunia microplate underthrust beneath the eastern half of the Moldanubian unit during the early Carboniferous. The front edge of Brunia thus acted as a rigid backstop at depth, localizing the exhumation of the Pelhřimov complex and separating the hot fertile middle crust to the west from the already cooled overthrust complexes to the east. The magnetic fabric of the granite around the migmatite blocks further reveals that the Pelhřimov complex was shortened vertically and extended in the~WNW-ESE direction during and after its exhumation, implying that the SSE-directed underthrusting of Brunia along the eastern margin of the Bohemian Massif was replaced by vertical thinning and~WNW-ESE stretching of the Moldanubian crust. As a general conclusion, we suggest that even for extremely rapid crustal exhumation, S-type granite magmas can be formed at greater depths by isothermal decompression of the metapelitic host, and then ascend almost instantaneously to the already exhumed (and cooled) shallow parts of the same metamorphic core complex. This model may explain the short time spans for the extensive migmatization and associated S-type granite formation, crustal exhumation, and granite emplacement, as well as the presence of "cold", discordant granite-migmatite contacts in once "hot" migmatite terrains.
International Journal of Earth Sciences, 2008
In the Jizera granite of the Krkonoše–Jizera Plutonic Complex, northern Bohemian Massif, contrast... more In the Jizera granite of the Krkonoše–Jizera Plutonic Complex, northern Bohemian Massif, contrasting patterns of magmatic K-feldspar fabrics and brittle fractures characterize different structural levels of the pluton. The uppermost exposed level at ∼800–1,100 m above sea level is dominated by flat foliation that overprints two steep foliations. In contrast, K-feldspar shape-fabric in an underground tunnel (∼660 m above sea level) shows complex variations in orientation and intensity. Magnetic fabric carried by coaxial contributions of biotite, magnetite, and maghemite is homogeneous along the examined section of the tunnel, and is decoupled from the K-feldspar fabric. The Jizera granite is crosscut by two regional sets of subvertical fractures (∼NE–SW and ∼NW–SE) and by near-surface exfoliation joints. The multiple fabrics are inferred to reflect a complex magmatic strain history at different structural levels of the pluton, bearing little or no relationship to the fracture network. In contrast to the original concept of Hans Cloos (“granite tectonics”), we conclude that no simple genetic relationship exists between fabrics and fractures in plutons. An alternative classification of fractures in plutons thus should avoid relationships to magmatic fabrics and should instead consist of cooling, syntectonic, uplift, and post-uplift fractures.
Journal of Geosciences, 2008
Mafic and silicic dyke rocks, which occur in the Ag-U ore district of Jáchymov (Joachimsthal) in ... more Mafic and silicic dyke rocks, which occur in the Ag-U ore district of Jáchymov (Joachimsthal) in the Krušné hory (Erzgebirge) belong to kersantites, diorite porphyries, and granite porphyries, subordinately to spessartites. Dykes of minettes are located outside the district and penetrate the Nejdek-Eibenstock granitic massif. Mafic and silicic dykes exhibit diverse cross-cutting relationships and form in places composite dykes. Lamprophyres correspond to shoshonitic magmas with high abundances of compatible (Cr, Ni) and incompatible elements (Rb, Ba, P). All mafic dykes were affected by a postmagmatic alteration manifested by replacement of primary olivine and pyroxenes by amphibole, biotite and chlorite. Granite porphyries crystallized from leucocratic, weakly peraluminous, low-P magmas with moderate enrichments in Rb and depletions in Ca, Sr and Zr. By contrast, diorite porphyries are intermediate rocks containing 62-65 wt. % SiO 2 whose geological occurrence and major-element composition suggest origin by magma mixing involving lamprophyric and silicic melts, with simultaneous fractionation of biotite. The Th/U ratios in all dyke rocks correspond to chondritic and crustal values and demonstrate that whole-rock uranium contents were neither significantly increased nor affected by contemporaneous mineralization events. The stable isotope composition has been determined for whole rocks (O, C, S) and carbonate minerals (C, O). Wholerock δ 18 O values range between 1.6 to 7.8 ‰ SMOW and do not show any systematic variations with the rock types. The isotopic composition of carbonates is represented by the following values: δ 18 O = 19.6 to 25.0 ‰ SMOW and δ 13 C = -5.7 to -9.0 ‰ PDB. The high positive values of δ 18 O of carbonates are in a remarkable contrast to compositions of primary magmatic carbonates and indicate the carbonate formation during low-temperature hydrothermal event(s). Sulphides in kersantites and diorite porphyries yielded δ 34 S = 0.5 to 6.6 ‰ CDT, which document crustal in addition to mantle source of sulphur consistent with average value in the Saxothuringian crust (~ 5 ‰ CDT). Bulk magnetic susceptibility of dyke rocks shows a general decrease from mafic to silicic magmas in a sequence as follows: kersantites -500, minettes -350, diorite porphyries -350 and granite porphyries -50•10 -6 [SI]. Local increases up to 5000•10 -6 [SI] are due to accessory pyrrhotite in kersantites and diorite porphyries. Mafic dykes in the Western Krušné hory (Erzgebirge) are preferentially found within the Jáchymov-Gera tectonic zone and demonstrate spatial focusing of ascending mantle-derived melts. Such pathways may have served for transfer of ore-forming elements on the crustal scale by fluids of diverse origin.
Journal of Volcanology and Geothermal Research, 2002
Vertical variations in magnetic fabric and paragenesis of the ferrimagnetic minerals for a virtua... more Vertical variations in magnetic fabric and paragenesis of the ferrimagnetic minerals for a virtually upright dyke of the Altenberg syenogranite porphyry were investigated using profile data of borehole E-16 to a depth of 922.7 m (Eastern Krušné hory Mts., NW Bohemia). It was revealed that this dyke likely consists of two magma pulses indicated both by magnetic fabric and by
Tectonophysics
A large ultramafic body (garnet clinopyroxenite and garnet peridotite) embedded in felsic granuli... more A large ultramafic body (garnet clinopyroxenite and garnet peridotite) embedded in felsic granulite at Bory (Moldanubian Zone of Western Moravia, Czech Republic) contains multiple carrier of susceptibility. Low-field variation of anisotropy of magnetic susceptibility (AMS) enables the separation of the field independent and low-field dependent AMS components to be made. In granulite, the former is carried by paramagnetic minerals and a subordinate admixture of magnetite, while the latter is due to pyrrhotite. In the ultramafite, the field-independent component is carried by pure magnetite formed by serpentinization, while the field-dependent component is due to pyrrhotite and subordinate paramagnetic minerals. Despite small differences, all AMS components are roughly coaxial both within granulite and within ultramafite, but very different between granulite and ultramafite. The difference indicates that the forces that imposed the later granulite fabric were not strong enough to obli...
About 11 x 5 m large body of serpentinized peridotite-clinopyroxenite, enclosed in felsic granuli... more About 11 x 5 m large body of serpentinized peridotite-clinopyroxenite, enclosed in felsic granulite, occurs in a quarry near the village of Bory (Moldanubian Zone of Western Moravia). The granulite is characterized by the presence of lighter quartz and feldspar-rich bands-layers (up to 10 cm width) alternating with gray stripes consisting of feldspars, quartz, garnet and kyanite. The presence of biotite and sillimanite, that together with quartz ribbons and relic kyanite define the foliation, depends on the degree of retrogression in amphibolite facies conditions. The ultramafic rocks show various degree of serpentinization of olivine and orthopyroxene and of amphibolization of clinopyroxene. The high-temperature textural modification of the clinopyroxenite is characterized by formation of exsolution lamellae of orthopyroxene and garnet in clinopyroxene or recrystallization of large (up 10 mm) clinopyroxene crystals into fine-grained matrix with garnet. The anisotropy of magnetic su...
Journal of Structural Geology, 2014
European Journal of Mineralogy, 2005
... Vladimír Á EK 1 ,* , Roman SKÁLA 1 , Marta CHLUPÁ OVÁ 2 and Zden k DVO ÁK 3. ... The authors ... more ... Vladimír Á EK 1 ,* , Roman SKÁLA 1 , Marta CHLUPÁ OVÁ 2 and Zden k DVO ÁK 3. ... The authors thank I. Vav ín (Czech Geological Survey) for electron microprobe analyses and F. Hrouda (Agico Ltd., Brno) for data on magnetic susceptibility. ...
Tectonics, 2013
ABSTRACT [1] Field relationships combined with new U-Pb zircon geochronology suggest that the sha... more ABSTRACT [1] Field relationships combined with new U-Pb zircon geochronology suggest that the shallow-level Krkonoše-Jizera plutonic complex, northern Bohemian Massif, was assembled successively from bottom to top, starting with emplacement of the separately evolved S-type Tanvald granite (317.3 ± 2.1 Ma), followed by at least two voluminous batches of the I-type porphyritic Liberec (319.5 ± 2.3 Ma) and Jizera (320.1 ± 3.0 Ma and 319.3 ± 3.7 Ma) granites. The intrusive sequence was completed by uppermost, minor intrusions of the equigranular Harrachov (315.0 ± 2.7 Ma) and Krkonoše granites. The I-type granites exhibit an unusually complex pattern of superposed feldspar phenocryst and magnetic fabrics as revealed from the anisotropy of magnetic susceptibility (AMS). The outer Liberec granite preserves margin-parallel foliations and lineations, interpreted to record emplacement-related strain captured by cooling from the pluton floor and walls. In contrast, the inner Jizera, Harrachov, and Krkonoše granites were overprinted by synmagmatic strain resulting from dextral movements along regional strike-slip faults cutting the opposite ends of the plutonic complex. Late-stage felsic dikes in the Liberec and Jizera granites reorient from horizontal to vertical (lineation-perpendicular) attitude in response to changing the least principal stress direction, whereas mafic schlieren do not do so, representing only randomly oriented small-scale thermal-mechanical instabilities in the phenocryst framework. In general, this case example challenges the common approach of inferring pluton-wide magma flow from interpolated foliation, lineation, and schlieren patterns. More likely, magmatic fabrics in large plutons record complex temporal succession of superposed strains resulting from diverse processes at multiple scales.
Studia Geophysica et Geodaetica, 2010
Magnetic properties as well as the magnetomineralogy were investigated in rocks underlying a 7 km... more Magnetic properties as well as the magnetomineralogy were investigated in rocks underlying a 7 km long aeromagnetic anomaly situated in the Moldanubian crystalline unit of the Bohemian Massif. The anomaly is caused by highly magnetic cordierite gneiss forming a stripe of NE -SW direction east of the town of Humpolec, eastern Bohemia. Magnetic susceptibility and its anisotropy (AMS), natural remanent magnetization, field and temperature variations of susceptibility were measured. Optical study of thin sections, electron microprobe and Mössbauer studies were also used to reveal the carrier of the high susceptibility and the high NRM. There appear to be two major generations of Fe-Ti oxides: older hematite with ilmenite exsolutions (Ti-hematite) which is the dominant remanence phase, and younger magnetite, the dominant susceptibility phase, usually associated with rutile. This indicates a reaction Hematite + Ilmenite → Magnetite + + Rutile; the trace elements in magnetite, as well as texture and morphology of the oxide grains support this assertion. An additional minor portion of maghemite is revealed by Mössbauer and thermomagnetic results. The Ti-hematite belongs to the oldest mineral assemblage in the rock, despite its anhedral morphology. Inclusions in Ti-hematite, among which corundum and abundant paragonite occur, record a strongly peraluminous and probably disequilibrium association during the crystallization of the Ti-hematite. K e y w o r d s : aeromagnetic anomaly, cordierite gneiss, magnetic properties, thermomagnetic analysis, Ti-hematite, ilmenite exsolutions, magnetite, maghemite, rutile V. Procházka et al. 96 Stud. Geophys. Geod., 54 (2010)
Studia Geophysica et Geodaetica, 2006
The KLY-4S Kappabridge and KLF-4A Magnetic Susceptibility Meter enable automated measurement of s... more The KLY-4S Kappabridge and KLF-4A Magnetic Susceptibility Meter enable automated measurement of susceptibility variation with field in the ranges of 2−450 A/m and 5−300 A/m (in effective values), respectively. Unfortunately, the measurement accuracy decreases with decreasing field and it is not easy to decide whether the susceptibility variation at the lowest fields is natural phenomenon or results from measuring errors. To overcome this problem, the accuracies of both the above instruments were investigated experimentally using artificial specimens (mixture of pure magnetite and plaster of Paris) with variable susceptibilities ranging from 1 × 10 −5 to 5 × 10 −2 . The complete curve of the field variation of susceptibility of each specimen was measured 10 times and the relative error was calculated for each field.
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Papers by Marta Chlupáčová