Key publications
Hrouda, F., Chadima, M., Ježek, J. et al. (2016), "Anisotropy of out-of-phase magnetic susceptibility of rocks as a tool for direct determination of magnetic subfabrics of some minerals: an introductory study"; Geophysical Journal International, Vol. 208 (1) , pp. 385-402 | |||||
Abstract: The magnetic susceptibility measured in alternating field can in general be resolved into a component that is in-phase with the applied field and a component that is out-of-phase. While in non-conductive diamagnetic, paramagnetic and many ferromagnetic materials the phase is effectively zero, in some ferromagnetic minerals, such as pyrrhotite, hematite, titanomagnetite or small magnetically viscous grains of magnetite, it is clearly non-zero. The anisotropy of out-of-phase susceptibility (opAMS) can then be used as a tool for the direct determination of the magnetic subfabrics of the minerals with non-zero phase. The error in determination of out-of-phase susceptibility non-linearly increases with decreasing phase angle. This may result in imprecise determination of the opAMS in specimens with very low phase angle. The degree of opAMS is higher than that of ipAMS, which may in contrast result in slightly increasing precision n the opAMS determination. It is highly recommended to inspect the results of the statistical tests of each specimen and to exclude the specimens whose opAMS is determined with insufficient precision from further processing. In rocks, whose magnetism is dominated by the mineral with non-zero out-of-phase susceptibility, the principal directions of the opAMS and ipAMS are virtually coaxial, while the degree of opAMS is higher than that of ipAMS. In some specific cases, the opAMS provides us with similar data to those provided by anisotropies of low-field dependent susceptibility and frequency-dependent susceptibility. The advantage of the opAMS compared to the other two anisotropies is its simultaneous measurement with the ipAMS during one measuring process, while the other two anisotropies require the AMS measurements in several fields or at least at two operating frequencies. | |||||
BibTeX:
@article{Hrouda2016, author = {Hrouda, František and Chadima, Martin and Ježek, Josef and Pokorný, Jiří}, title = {Anisotropy of out-of-phase magnetic susceptibility of rocks as a tool for direct determination of magnetic subfabrics of some minerals: an introductory study}, journal = {Geophysical Journal International}, year = {2016}, volume = {208}, number = {1}, pages = {385--402}, url = {http://dx.doi.org/10.1093/gji/ggw399} } |
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Hrouda, F. & Ježek, J. (2014), "Frequency-dependent AMS of rocks: A tool for the investigation of the fabric of ultrafine magnetic particles"; Tectonophysics, Vol. 629 , pp. 27-38 | |||||
Abstract: In some geological processes, new very fine-grained magnetic minerals may originate. The variation in content of these minerals is routinely investigated by frequency-dependent magnetic susceptibility, which is traditionally interpreted in terms of the presence of viscous superparamagnetic (SP) particles in addition to stable single domain (SSD) and multidomain (MD) magnetic particles. In addition, the fabric of these grains can be investigated through the frequency-dependent AMS. Through standard AMS measurement at different frequencies, one can evaluate the contribution of SP particles to the whole-rock AMS; appropriate methods were developed. Various rocks, soils and ceramics, showing frequency-dependent magnetic susceptibility, were investigated. Measurable changes of AMS with operating frequency were revealed and attempts are made of their fabric interpretation. | |||||
BibTeX:
@article{Hrouda2014b, author = {Hrouda, František and Ježek, Josef}, title = {Frequency-dependent AMS of rocks: A tool for the investigation of the fabric of ultrafine magnetic particles}, journal = {Tectonophysics}, year = {2014}, volume = {629}, pages = {27--38}, url = {http://www.sciencedirect.com/science/article/pii/S0040195114000882}, doi = {http://dx.doi.org/10.1016/j.tecto.2014.01.040} } |
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Studýnka, J., Chadima, M. & Suza, P. (2014), "Fully automated measurement of anisotropy of magnetic susceptibility using 3D rotator"; Tectonophysics, Vol. 629 , pp. 6-13 | |||||
Abstract: A 3D rotator (for MFK1-FA or MFK1-A Kappabridges) was developed to increase the speed and comfort of anisotropy of magnetic susceptibility (AMS) measurements. The 3D rotator rotates the specimen simultaneously about two axes with different velocities. The two-axis rotation enables the determination of 320 directional susceptibilities during a single anisotropy measurement. These directions are very well distributed on a sphere which makes the measuring design almost rotatable. The actual measurement is fully automated in such a way that, once the specimen is mounted into the rotator, it requires no additional manipulation to measure the full AMS tensor. The approximate duration of one anisotropy measurement is 1.5min. Fundamental ideas of data acquisition and processing, AMS tensor fitting and respective error analysis are described and discussed. Calculation of the anisotropy tensor, respective error analysis and immediate data visualization is provided by Safyr5 software. Examples comparing the 3D rotator data with previously developed systems of AMS determination are presented. | |||||
BibTeX:
@article{Studynka2014, author = {Studýnka, Jan and Chadima, Martin and Suza, Petr}, title = {Fully automated measurement of anisotropy of magnetic susceptibility using 3D rotator}, journal = {Tectonophysics}, year = {2014}, volume = {629}, pages = {6--13}, url = {http://www.sciencedirect.com/science/article/pii/S0040195114001152}, doi = {http://dx.doi.org/10.1016/j.tecto.2014.02.015} } |
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Hrouda, F., Pokorný, J., Ježek, J. et al. (2013), "Out-of-phase magnetic susceptibility of rocks and soils: a rapid tool for magnetic granulometry"; Geophysical Journal International, Vol. 194 (1) , pp. 170-181 | |||||
Abstract: The magnetic susceptibility measured in alternating field can be resolved into a component that is in-phase with applied field and a component that is out-of-phase. While the former component is widely used for solving various geophysical, geological and environmental problems, the latter component is paid only minor attention. The theoretical relationship between the frequency-dependent in-phase susceptibility and the out-of-phase susceptibility is described by the $/2 law valid for materials in which the latter is due to presence of magnetic particles on transition between superparamagnetic and stable single-domain states possessing sufficiently wide distribution of relaxation times.To advantageously use the out-of-phase susceptibility, which is measured simultaneously with the in-phase susceptibility during one measuring process, in magnetic granulometry, new parameters, XON and XOD, are proposed approximately converting the out-of-phase susceptibility into the XFN and XFD parameters of the frequency-dependent susceptibility.The validity of the new parameters was tested through mathematical modelling and through investigating samples of various sediments. The correlations found seem to be acceptable from the practical point of view. In addition, simple test is proposed for checking that the out-of-phase susceptibility is solely due to the viscous phenomena and not due to electrical eddy currents or weak field hysteresis.As the out-of-phase susceptibility is measured automatically along the in-phase-susceptibility with some instruments and can be directly interpreted in magnetic granulometry terms, it is to recommend to be routinely investigated in solving various problems of environmental magnetism. | |||||
BibTeX:
@article{Hrouda2013, author = {Hrouda, František and Pokorný, Jiří and Ježek, Josef and Chadima, Martin}, title = {Out-of-phase magnetic susceptibility of rocks and soils: a rapid tool for magnetic granulometry}, journal = {Geophysical Journal International}, year = {2013}, volume = {194}, number = {1}, pages = {170--181}, url = {http://gji.oxfordjournals.org/content/194/1/170.abstract}, doi = {http://dx.doi.org/10.1093/gji/ggt097} } |
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Chadima, M., Pokorný, J. & Dušek, M. (2011), "Rema6W–MSWindows Software for Controlling JR-6 Series Spinner Magnetometers"; , The Earth's Magnetic Interior , pp. 303-309, Springer Netherlands | |||||
BibTeX:
@inbook{Chadima2011, author = {Chadima, Martin and Pokorný, Jiří and Dušek, Miroslav}, title = {Rema6W–MSWindows Software for Controlling JR-6 Series Spinner Magnetometers}, booktitle = {The Earth's Magnetic Interior}, publisher = {Springer Netherlands}, year = {2011}, pages = {303--309}, url = {http://dx.doi.org/10.1007/978-94-007-0323-0_21}, doi = {http://dx.doi.org/10.1007/978-94-007-0323-0_21} } |
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Hrouda, F. (2011), "Models of frequency-dependent susceptibility of rocks and soils revisited and broadened"; Geophysical Journal International, Vol. 187 (3) , pp. 1259-1269, Blackwell Publishing Ltd | |||||
Abstract: Mathematical models of the frequency-dependent susceptibility in rocks, soils and environmental materials have been adapted to measurements performed with multiple operating frequencies (465, 976, 3904, 4650, 15 616, 100 000 and 250 000 Hz) on the basis of log-normal volume distribution of magnetic particles. The XFD parameter depends, in addition to the amount of SP particles, also on the operating frequencies, whose values should be therefore also presented. The model curves of the XFD parameter versus arithmetical mean ($) of the logarithms of grain volume are roughly bell-like shaped. The width and peak position of these curves is controlled by mean and standard deviation of the logarithmic volume distribution. Magnetic susceptibility contributions from paramagnetic minerals, and from ferrimagnetic particles not belonging to a unimodal SP/SD volume distribution, tend to decrease the XFD parameter. Therefore, low XFD values do not therefore necessarily indicate low amount of SP particles, but can also be indicative of the presence of the paramagnetic fraction. A new parameter XR is introduced based on susceptibility measurements at three operating frequencies; it is insensitive to dia- and paramagnetic fractions and helps us to differentiate between wide and narrow size distributions of ferromagnetic particles. A new XFB parameter is introduced that originates through normalizing the XFD parameter by the difference of natural logarithms of operating frequencies and related to the decade difference between the frequencies. It is convenient for comparison of the Bartington MS-2 Susceptibility Meter data with the MFK1-FA Kappabridge data. | |||||
BibTeX:
@article{GJI:GJI5227, author = {Hrouda, František}, title = {Models of frequency-dependent susceptibility of rocks and soils revisited and broadened}, journal = {Geophysical Journal International}, publisher = {Blackwell Publishing Ltd}, year = {2011}, volume = {187}, number = {3}, pages = {1259--1269}, url = {http://dx.doi.org/10.1111/j.1365-246X.2011.05227.x}, doi = {http://dx.doi.org/10.1111/j.1365-246X.2011.05227.x} } |
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Hrouda, F. (2010), "Modelling relationship between bulk susceptibility and AMS in rocks consisting of two magnetic fractions represented by ferromagnetic and paramagnetic minerals — Implications for understanding magnetic fabrics in deformed rocks"; Journal of the Geological Society of India, Vol. 75 (1) , pp. 254-266 | |||||
Abstract: Measurement of Anisotropy of Magnetic Susceptibility (AMS) has become an important tool for Structural Geological analysis in the past few decades. In the past, AMS data have been used for petrofabric analysis of deformed rocks as well as for gauging strain. However, the AMS of some rocks can be carried by both ferromagnetic and paramagnetic minerals. Separating effects of these mineral groups on the rock's AMS is difficult because of expensive and commercially less available instrumentation. On the other hand, instrumentation is available in most rock magnetic and palaeomagnetic laboratories for resolving bulk susceptibility into ferromagnetic and paramagnetic components. Mathematical modelling was made of the relationship between bulk susceptibility and AMS. If the contribution of the ferromagnetic or the paramagnetic fraction to the rock susceptibility is dominant (let us say higher than 80%), the resultant AMS is relatively near to the AMS of the dominating fraction in all aspects, the degree of AMS, shape parameter and orientation of principal susceptibilities. In the interpretation of the AMS of rocks with dominating one fraction, the resolution of the AMS into paramagnetic and ferromagnetic components is not necessary, the resolution of bulk susceptibility into components is sufficient that can be made using the instrumentation available in most rock magnetic and palaeomagnetic laboratories. | |||||
BibTeX:
@article{Hrouda2010, author = {Hrouda, František}, title = {Modelling relationship between bulk susceptibility and AMS in rocks consisting of two magnetic fractions represented by ferromagnetic and paramagnetic minerals — Implications for understanding magnetic fabrics in deformed rocks}, journal = {Journal of the Geological Society of India}, year = {2010}, volume = {75}, number = {1}, pages = {254--266}, url = {http://link.springer.com/10.1007/s12594-010-0013-0}, doi = {http://dx.doi.org/10.1007/s12594-010-0013-0} } |
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Chadima, M., Cajz, V. & Týcová, P. (2009), "On the interpretation of normal and inverse magnetic fabric in dikes: Examples from the Eger Graben, NW Bohemian Massif"; Tectonophysics, Vol. 466 (1-2) , pp. 47-63 | |||||
Abstract: Recent studies of igneous rocks indicate that the predominant occurrence of normal/inverse fabric in dikes may either reflect the presence of multi-domain (MD)/single-domain (SD) grains or it may result from different orientation mechanisms of magnetic minerals in magmas of different viscosities. The ambiguity in physical vs. geological cause of normal/inverse magnetic fabric must be answered before any successful geological interpretation of magnetic fabric can be made. In order to address this problem, we studied magnetic fabric of selected dikes associated with the SW–NE trending Eger Graben (NW Bohemian Massif). The studied area offered very extensive collection of rock types: basanite, bostonite, camptonite, tinguaite, and trachybasalt. Magnetic susceptibility varies according to rock type and reflects the relative contents of magnetic minerals. In most cases, titanomagnetite with variable Ti content was identified as main magnetic carrier. The degree of anisotropy is relatively low, in most cases less than 10%, the shape of anisotropy ellipsoid ranges from slightly prolate to neutral and oblate. Several different types of magnetic fabric (using anisotropy of low-field magnetic susceptibility, AMS) were observed in studied dikes: so-called normal and inverse magnetic fabrics and anomalous magnetic fabric. Comparing all studied sites it seems that the type of magnetic fabric is lithology-dependent. Normal magnetic fabric with magnetic foliations and subhorizontal magnetic lineations both parallel to the dike margins was found in bostonite and trachybasalt dikes. Inverse magnetic fabric with magnetic lineations and magnetic foliations perpendicular to the dike margins was found in camptonite dikes. Anisotropy of anhysteretic remanent magnetization (AMR) indicate that the observed inverse magnetic fabric may be caused by the presence of SD magnetic grains; AMR fabric being normal with respect to dike margins. In contrast to that no single-domain particles were revealed using frequency dependence and anhysteretic susceptibility measurements. The AMS measured in variable weak magnetic fields is field dependent for camptonite dike and field independent for other rock types, i.e. bostonite, basanite, tinguaite, and trachybasalt. For further flow direction and tectonic interpretations of magnetic fabric in dikes it is suggested to use preferably the AMR fabric (at least for dikes which demonstrate significant field dependence of AMS) as it reflects the ‘true' rock fabric more accurately than AMS fabric. | |||||
BibTeX:
@article{Chadima2009, author = {Chadima, Martin and Cajz, Vladimír and Týcová, Patricie}, title = {On the interpretation of normal and inverse magnetic fabric in dikes: Examples from the Eger Graben, NW Bohemian Massif}, journal = {Tectonophysics}, year = {2009}, volume = {466}, number = {1-2}, pages = {47--63}, url = {http://www.sciencedirect.com/science/article/pii/S0040195108004290}, doi = {http://dx.doi.org/10.1016/j.tecto.2008.09.005} } |
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Hrouda, F. (2009), "Determination of field-independent and field-dependent components of anisotropy of susceptibility through standard AMS measurement in variable low fields I: Theory"; Tectonophysics, Vol. 466 (1-2) , pp. 114-122 | |||||
Abstract: Three methods were developed for simultaneous determination of the field-independent susceptibility tensor and the initial susceptibility tensor of MD ferromagnetic fraction, all based on standard measurement of the AMS in variable fields within the Rayleigh Law range. The former tensor reflects possible effects of diamagnetic and paramagnetic minerals, pure magnetite, SD ferromagnetic minerals, and initial susceptibility of MD ferromagnetic minerals. The initial susceptibility tensor of MD ferromagnetic fraction does not however reflect the effect of the entire fraction, because the effect of the SD sub-fraction contributes to the field-independent susceptibility tensor. The differences in the degree of AMS of the field-independent susceptibility tensor and that of the initial susceptibility tensor of MD ferromagnetic fraction may be useful in magnetic granulometry. | |||||
BibTeX:
@article{Hrouda2009c, author = {Hrouda, František}, title = {Determination of field-independent and field-dependent components of anisotropy of susceptibility through standard AMS measurement in variable low fields I: Theory}, journal = {Tectonophysics}, year = {2009}, volume = {466}, number = {1-2}, pages = {114--122}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0040195108002564}, doi = {http://dx.doi.org/10.1016/j.tecto.2008.05.026} } |
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Hrouda, F. (2007), "Anisotropy of magnetic susceptibility of rocks in the Rayleigh Law region: Modelling errors arising from linear fit to non-linear data"; Studia Geophysica et Geodaetica, Vol. 51 (3) , pp. 423-438 | |||||
Abstract: The anisotropy of magnetic susceptibility (AMS) within the Rayleigh Law range was investigated theoretically, using mathematical modelling. It was revealed that the orientations of the principal susceptibilities and the shape parameter vary with field so weakly that these variations can be regarded as negligible from the practical point of view. The degree of AMS increases with field according to the degree of anisotropy of the initial susceptibility used and according to the intensity of susceptibility change with field of the mineral considered. The degree of AMS calculated using linear theory is very near to the degree of AMS following from the analysis of AMS within the Rayleigh Law range. If it is desirable to correct the field-dependent degree of AMS, a simple technique is suggested based on measurement of the AMS in two fields. | |||||
BibTeX:
@article{Hrouda2007, author = {Hrouda, František}, title = {Anisotropy of magnetic susceptibility of rocks in the Rayleigh Law region: Modelling errors arising from linear fit to non-linear data}, journal = {Studia Geophysica et Geodaetica}, year = {2007}, volume = {51}, number = {3}, pages = {423--438}, url = {http://link.springer.com/10.1007/s11200-007-0024-5}, doi = {http://dx.doi.org/10.1007/s11200-007-0024-5} } |
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Jezek, J. & Hrouda, F. (2007), "A program for magnetic susceptibility-equivalent pore conversion"; Geochemistry, Geophysics, Geosystems, Vol. 8 (10) , pp. n/a-n/a | |||||
Abstract: Pore magnetic anisotropy can be used to estimate the average geometry of void spaces in rocks in the form of the equivalent pore (EP) ellipsoid. Direct computation of EP from measured magnetic susceptibility is impossible. We present a method and a Matlab program for automatic magnetic susceptibility–equivalent pore conversion. Input data are the magnetic parameters (P and T, or L and F) representing the bulk magnetic anisotropy, and the intrinsic susceptibility of the fluid used in the measurement. EP is estimated iteratively by a repeated look-up table procedure using P and T values computed in a coarse grid of EP axial ratios. The program may be downloaded from the EarthRef.org Digital Archive. | |||||
BibTeX:
@article{Jezek2007, author = {Jezek, J. and Hrouda, František}, title = {A program for magnetic susceptibility-equivalent pore conversion}, journal = {Geochemistry, Geophysics, Geosystems}, year = {2007}, volume = {8}, number = {10}, pages = {n/a--n/a}, url = {http://doi.wiley.com/10.1029/2007GC001709}, doi = {http://dx.doi.org/10.1029/2007GC001709} } |
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Ježek, J. & Hrouda, F. (2007), "SUSIE: A program for inverse strain estimation from magnetic susceptibility"; Computers & Geosciences, Vol. 33 (6) , pp. 749-759 | |||||
Abstract: SUsceptibility–Strain Inverse Estimation (SUSIE) is a Matlab program for the inversion of magnetic susceptibility to irrotational strain. Input data are the bulk susceptibility principal values or their equivalent (magnetic parameters P and T), parameters of magnetic grains (shape, magnetic susceptibility, initial orientation, and rotational response to deformation). SUSIE estimates strain corresponding to input AMS data iteratively, by a repeated look-up table procedure that uses the map of P and T values computed in a coarse strain grid. Usually not more than two or three iterations are needed to obtain the strain estimate that satisfy up to two decimal places of the input P and T values. An example of the use of the program is given. | |||||
BibTeX:
@article{Jezek2007a, author = {Ježek, Josef and Hrouda, František}, title = {SUSIE: A program for inverse strain estimation from magnetic susceptibility}, journal = {Computers & Geosciences}, year = {2007}, volume = {33}, number = {6}, pages = {749--759}, url = {http://www.sciencedirect.com/science/article/pii/S0098300407000222}, doi = {http://dx.doi.org/10.1016/j.cageo.2006.11.002} } |
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Hrouda, F., Chlupáčová, M. & Mrázová, Š. (2006), "Low-field variation of magnetic susceptibility as a tool for magnetic mineralogy of rocks"; Physics of the Earth and Planetary Interiors, Vol. 154 (3-4) , pp. 323-336 | |||||
Abstract: 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 450A/m (in one frequency of 875Hz). The measurement is rapid, 7min 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. The results were evaluated statistically. Remarkable differences were revealed between individual minerals and between some rock types. For example, the field variation of susceptibility of pyrrhotite is in general an order of magnitude larger than that of titanomagnetite. The susceptibility increase in pyrrhotite starts at the field an order of magnitude lower than that of titanomagnetite. Low-field variation of susceptibility then appears as an interesting phenomeon that helps in the identification of magnetic minerals and in some cases also in assessing the compositional variation of them. | |||||
BibTeX:
@article{Hrouda2006, author = {Hrouda, František and Chlupáčová, Marta and Mrázová, Štěpánka}, title = {Low-field variation of magnetic susceptibility as a tool for magnetic mineralogy of rocks}, journal = {Physics of the Earth and Planetary Interiors}, year = {2006}, volume = {154}, number = {3-4}, pages = {323--336}, url = {http://www.sciencedirect.com/science/article/pii/S0031920105002657}, doi = {http://dx.doi.org/10.1016/j.pepi.2005.09.013} } |
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Kratinová, Z., Závada, P., Hrouda, F. et al. (2006), "Non-scaled analogue modelling of AMS development during viscous flow: A simulation on diapir-like structures"; Tectonophysics, Vol. 418 (1-2) , pp. 51-61 | |||||
Abstract: Development of magnetic fabric within a diapirically ascending columnar body was investigated using non-scaled analogue model made of plaster of Paris containing small amount of fine-grained homogeneously mixed magnetite. The apparatus for the modelling consists of a manual squeezer with calibrated spring and a Perspex container. Set of weak coloured layers at the bottom of the container was forced to intrude overlying fine-grained sand through a hole in a board attached to the squeezer. The development of AMS fabric is correlated with complex flow pattern indicated by coloured and originally horizontal plaster layers. Strongly constrictional and vertical fabric in the base and in the lower domain of the diapir resulting from convergent and upwards flows is overprinted by subhorizontal oblate fabrics due to vertical flattening and initial divergent flow in the apical parts. The measured AMS fabrics are compared with natural examples of magmatic stocks and dykes. | |||||
BibTeX:
@article{Kratinova2006, author = {Kratinová, Zuzana and Závada, Prokop and Hrouda, František and Schulmann, Karel}, title = {Non-scaled analogue modelling of AMS development during viscous flow: A simulation on diapir-like structures}, journal = {Tectonophysics}, year = {2006}, volume = {418}, number = {1-2}, pages = {51--61}, url = {http://www.sciencedirect.com/science/article/pii/S0040195106000485}, doi = {http://dx.doi.org/10.1016/j.tecto.2005.12.013} } |
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Chadima, M., Hansen, A., Hirt, A. M. et al. (2004), "Phyllosilicate preferred orientation as a control of magnetic fabric: evidence from neutron texture goniometry and low and high-field magnetic anisotropy (SE Rhenohercynian Zone of Bohemian Massif)"; Geological Society, London, Special Publications, Vol. 238 (1) , pp. 361-380 | |||||
Abstract: The low- and high-field magnetic anisotropy (AMS, HFA) of the Rhenohercynian mudstones and greywackes is compared to the theoretical anisotropy calculated from neutron texture goniometry measurements. The magnetic anisotropy is predominantly carried by the paramagnetic phyllosilicates in the form of chlorite/mica stacks and the ferromagnetic contribution is insignificant. The respective principal directions of the theoretical anisotropy and the AMS and HFA are sub-parallel; magnetic foliation reflects the orientation of the maximal concentration of phyllosilicate basal planes, magnetic lineation is subparallel to the intersection axis of those planes. For the purpose of quantitative comparison, the infrequently used standard deviatoric susceptibility as a measure of the HFA degree is employed. A very good linear correlation of the degree of theoretical anisotropy and the measured AMS and HFA is found. The prolate and oblate shapes of the respective fabric ellipsoids are reasonably well correlated. Neutron texture goniometry justifies the use of the conventional magnetic anisotropy technique for the assessment of the mineral fabric of studied rocks. When compared with other works relating the magnetic anisotropy to the mineral preferred orientation (examined by e.g. U-stage or X-ray texture goniometry) neutron texture goniometry seems to be a preferable and very precise method fabric analysis. | |||||
BibTeX:
@article{Chadima2004, author = {Chadima, Martin and Hansen, Anke and Hirt, Ann M and Hrouda, František and Siemes, Heinrich}, title = {Phyllosilicate preferred orientation as a control of magnetic fabric: evidence from neutron texture goniometry and low and high-field magnetic anisotropy (SE Rhenohercynian Zone of Bohemian Massif)}, journal = {Geological Society, London, Special Publications}, year = {2004}, volume = {238}, number = {1}, pages = {361--380}, url = {http://sp.lyellcollection.org/cgi/doi/10.1144/GSL.SP.2004.238.01.19}, doi = {http://dx.doi.org/10.1144/GSL.SP.2004.238.01.19} } |
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Hrouda, F. (2002), "Low-field variation of magnetic susceptibility and its effect on the anisotropy of magnetic susceptibility of rocks"; Geophysical Journal International, Vol. 150 (3) , pp. 715-723, Blackwell Science Ltd | |||||
Abstract: The theory of the low-field anisotropy of magnetic susceptibility (AMS) assumes a linear relationship between magnetization and the magnetizing field. This assumption is precisely valid in diamagnetic and paramagnetic minerals by definition, while in ferrimagnetic and antiferromagnetic minerals this relationship is in general non-linear (represented by a hysteresis loop), being linear only with very weak fields in which the initial susceptibility is measured. Recently, it has been shown that, in using common measuring fields, the field-independent susceptibility is measured in magnetite, while in pyrrhotite, haematite and titanomagnetite it may often be outside the initial susceptibility range. The problem can be solved in three ways. The simplest way is using very weak measuring fields (less than 10 A m−1), but this can result in significant lowering of sensitivity and precision. The second way is to respect the non-linearity and measure the susceptibility in so many directions that contour diagram of directional susceptibilities can be presented instead of a susceptibility ellipsoid. The third way is to measure the AMS within the Rayleigh law range and calculate the initial directional susceptibilities from which the AMS can be correctly determined using linear theory. | |||||
BibTeX:
@article{GJI:GJI1731, author = {Hrouda, František}, title = {Low-field variation of magnetic susceptibility and its effect on the anisotropy of magnetic susceptibility of rocks}, journal = {Geophysical Journal International}, publisher = {Blackwell Science Ltd}, year = {2002}, volume = {150}, number = {3}, pages = {715--723}, url = {http://doi.wiley.com/10.1046/j.1365-246X.2002.01731.x}, doi = {http://dx.doi.org/10.1046/j.1365-246X.2002.01731.x} } |
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Hrouda, F. (2002), "The use of the anisotropy of magnetic remanence in the resolution of the anisotropy of magnetic susceptibility into its ferromagnetic and paramagnetic components"; Tectonophysics, Vol. 347 (4) , pp. 269-281 | |||||
Abstract: The anisotropy of magnetic susceptibility (AMS) is often controlled by both ferromagnetic (sensu lato) and paramagnetic minerals. The anisotropy of magnetic remanence (AMR) is solely controlled by ferromagnetic minerals. Jelı́nek (Trav. Geophys. 37 (1993)) introduced a tensor derived from the isothermal AMR whose normalized form equals the normalized susceptibility tensor provided that the ferromagnetic fraction is represented by multi-domain magnetite. The present paper shows the close correlation between these tensors for a collection of strongly magnetic specimens containing multi-domain magnetite. In addition, acceptable correlation between the tensors was also found for a collection of specimens containing single-domain magnetite. A new method is developed for the AMS resolution into ferromagnetic and paramagnetic components using the AMR. Some examples are presented of this resolution in mafic microgranular enclaves in granodiorite and in gneisses of the KTB borehole. | |||||
BibTeX:
@article{Hrouda2002, author = {Hrouda, František}, title = {The use of the anisotropy of magnetic remanence in the resolution of the anisotropy of magnetic susceptibility into its ferromagnetic and paramagnetic components}, journal = {Tectonophysics}, year = {2002}, volume = {347}, number = {4}, pages = {269--281}, url = {http://www.sciencedirect.com/science/article/pii/S0040195102000756}, doi = {http://dx.doi.org/10.1016/S0040-1951(02)00075-6} } |
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Ježek, J. & Hrouda, F. (2002), "Software for modeling the magnetic anisotropy of strained rocks"; Computers & Geosciences, Vol. 28 (9) , pp. 1061-1068 | |||||
Abstract: The anisotropy of magnetic susceptibility is controlled by the preferred orientation of magnetic minerals in rocks and may be significantly influenced by deformation. This allows us to replace difficult estimation of strain parameters by indirect anisotropy of magnetic susceptibility (AMS) measurements. The interpretation of AMS is based on observation experience and modeling the AMS to strain relationship. The modeling is complex due to the large number of input parameters: different carriers of magnetism and their magnetic properties, their initial orientation distribution, the manner in which the deformation influences the reorientation of magnetic carriers, the character and duration of deformation. These parameters are taken into account in the presented package of Matlab functions for modeling AMS of strained rocks. The functions can be freely combined by the user to cover all basic types of homogeneous deformation (simple shear, pure shear, plane strain, coaxial deformation, transpression). A procedure is presented to treat the example of inhomogeneous deformation. textcopyright 2002 Elsevier Science Ltd. All rights reserved. | |||||
BibTeX:
@article{Jezek2002b, author = {Ježek, Josef and Hrouda, František}, title = {Software for modeling the magnetic anisotropy of strained rocks}, journal = {Computers & Geosciences}, year = {2002}, volume = {28}, number = {9}, pages = {1061--1068}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0036871022&partnerID=tZOtx3y1}, doi = {http://dx.doi.org/10.1016/S0098-3004(02)00023-7} } |
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Hrouda, F. (1994), "A technique for the measurement of thermal changes of magnetic susceptibility of weakly magnetic rocks by the CS-2 apparatus and KLY-2 Kappabridge"; Geophysical Journal International, Vol. 118 (3) , pp. 604-612, Blackwell Publishing Ltd | |||||
Abstract: Techniques for the correction of the effect of the furnace signal on the data measured in the investigation of thermal changes of magnetic susceptibility of weakly magnetic rocks using the CS-2 apparatus and KLY-2 Kappabridge are described. A new method is developed for separating the ferromagnetic and paramagnetic room temperature susceptibility components even for the case in which new magnetite forms during heating. | |||||
BibTeX:
@article{GJI:GJI604, author = {Hrouda, František}, title = {A technique for the measurement of thermal changes of magnetic susceptibility of weakly magnetic rocks by the CS-2 apparatus and KLY-2 Kappabridge}, journal = {Geophysical Journal International}, publisher = {Blackwell Publishing Ltd}, year = {1994}, volume = {118}, number = {3}, pages = {604--612}, url = {http://dx.doi.org/10.1111/j.1365-246X.1994.tb03987.x http://gji.oxfordjournals.org/cgi/doi/10.1111/j.1365-246X.1994.tb03987.x}, doi = {http://dx.doi.org/10.1111/j.1365-246X.1994.tb03987.x} } |
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Hrouda, F. (1993), "Theoretical models of magnetic anisotropy to strain relationship revisited"; Physics of the Earth and Planetary Interiors, Vol. 77 (3-4) , pp. 237-249 | |||||
Abstract: Mathematical modelling of the relationships between the low-field magnetic anisotropy and strain are redeveloped, and the calculated data are compared with the degree of anisotropy for various rock types. It is found that the degree of anisotropy for realistic strain magnitudes is unrealistically high in the ‘passive' model. The ‘ductile' model, for which the degree of anisotropy depends on the magnetic grain the matrix viscosity ratio, becomes realistic at high viscosity contrasts. In the ‘line/plane' model, the theoretical degree of anisotropy corresponds well to the natural degree of anisotropy for rocks in which the carrier of magnetic anisotropy is either magnetite or phyllosilicate minerals; by contrast, in the case of haematite and pyrrhotite, the modelled degree of anisotropy is much higher than the natural values. In the ‘viscous' model, the calculated degree of anisotropy corresponds well to that measured in sedimentary and volcanic rocks. In the models imposing pure shear strain, the natural logarithm of the degree of anisotropy to natural strain relationship can be approximately represented by a straight line, at least for low to intermediate strains; the proportionality constant varies according to the specific model and the specific carrier of the anisotropy of magnetic susceptibility. | |||||
BibTeX:
@article{Hrouda1993, author = {Hrouda, František}, title = {Theoretical models of magnetic anisotropy to strain relationship revisited}, journal = {Physics of the Earth and Planetary Interiors}, year = {1993}, volume = {77}, number = {3-4}, pages = {237--249}, url = {http://www.sciencedirect.com/science/article/pii/003192019390101E http://linkinghub.elsevier.com/retrieve/pii/003192019390101E}, doi = {http://dx.doi.org/10.1016/0031-9201(93)90101-E} } |
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Hrouda, F. (1992), "Separation of a component of tectonic deformation from a complex magnetic fabric"; Journal of Structural Geology, Vol. 14 (1) , pp. 65-71 | |||||
Abstract: A method has been developed for separation of the deformational component from a complex rock fabric. For the separation, data on the final (measured) fabric and the primary (pre-deformational) fabric are necessary as input. The primary fabric data are obtained either from measurements in terrains where gradual transitions from primary to deformational fabrics occur or, in the case of magnetic anisotropy, this may be obtained from data in the literature on individual rock types. Examples of the use of the method are presented for rocks from the Nízký Jeseník Mountains of the NE Bohemian massif. | |||||
BibTeX:
@article{Hrouda1992, author = {Hrouda, František}, title = {Separation of a component of tectonic deformation from a complex magnetic fabric}, journal = {Journal of Structural Geology}, year = {1992}, volume = {14}, number = {1}, pages = {65--71}, url = {http://www.sciencedirect.com/science/article/pii/019181419290145M}, doi = {http://dx.doi.org/10.1016/0191-8141(92)90145-M} } |
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Hrouda, F. & Schulmann, K. (1990), "Conversion of the magnetic susceptibility tensor into the orientation tensor in some rocks"; Physics of the Earth and Planetary Interiors, Vol. 63 (1-2) , pp. 71-77 | |||||
Abstract: The preferred orientation of minerals in a rock with a structural or sedimentary fabric can be referred to by the orientation tensor. This paper describes the determination of the orientation tensor of the crystallographic c′-axes from the rock magnetic anisotropy and the mineral anisotropy degree, in rocks in which the magnetic anisotropy is dominantly carried by one mineral with uniaxial magnetic anisotropy (e.g. phyllosilicates, pyrrhotite, hematite). The orientation tensor of biotite c′-axes in four samples of the Bíteš orthogneiss determined in this way is similar to that determined independently through the universal stage measurement of biotite leaves in thin sections and is obtained much more rapidly by the magnetic method. | |||||
BibTeX:
@article{Hrouda1990, author = {Hrouda, František and Schulmann, Karel}, title = {Conversion of the magnetic susceptibility tensor into the orientation tensor in some rocks}, journal = {Physics of the Earth and Planetary Interiors}, year = {1990}, volume = {63}, number = {1-2}, pages = {71--77}, url = {http://www.sciencedirect.com/science/article/pii/0031920190900612}, doi = {http://dx.doi.org/10.1016/0031-9201(90)90061-2} } |
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Hrouda, F. & Kapička, A. (1986), "The effect of quartz on the magnetic anisotropy of quartzite"; Studia Geophysica et Geodaetica, Vol. 30 (1) , pp. 39-45 | |||||
Abstract: The magnetic susceptibility of quartz single crystals is diamagnetic (−14texttimes10 −6 in SI units) and exhibits only very small anisotropy (mostly less than 1%); thus the susceptibility of the quartz matrix in quartzite can be regarded as virtually isotropic. Owing to the influence of the negative and isotropic susceptibility of the quartz matrix, the degree of anisotropy of quartzite, as inferred from model calculations, is higher than that of the ferrimagnetic fraction. This influence is very strong if the mean susceptibility of quartzite is in the vicinity of zero. | |||||
BibTeX:
@article{Hrouda1986, author = {Hrouda, František and Kapička, Aleš}, title = {The effect of quartz on the magnetic anisotropy of quartzite}, journal = {Studia Geophysica et Geodaetica}, year = {1986}, volume = {30}, number = {1}, pages = {39--45}, url = {http://link.springer.com/10.1007/BF01630853}, doi = {http://dx.doi.org/10.1007/BF01630853} } |
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Hrouda, F., Siemes, H., Herres, N. et al. (1985), "The relationship between the magnetic anisotropy and the c-axis fabric in a massive hematite ore."; , Vol. 56 (3)Journal of Geophysics - Zeitschrift fur Geophysik , pp. 174-182 | |||||
Abstract: Preferred orientation of hematite ore from Minas Gerais, Brazil, was investigated by reflected-light microscopy, X-ray structural goniometry and magnetic anisotropy. A close relationship was found between c-axis fabrics determined by magnetic and non-magnetic methods; experiments confirmed the results of the theoretical treatment. For routine work it is advantageous to use both types of methods, profiting from rapidity of measurement of magnetic anisotropy and from detailed c-axis pole figures of pilot specimens provided by X-ray goniometry. (Authors' abstract)-R.A.H. | |||||
BibTeX:
@misc{Hrouda1985b, author = {Hrouda, František and Siemes, Heinrich and Herres, N and Hennig-Michaeli, C}, title = {The relationship between the magnetic anisotropy and the c-axis fabric in a massive hematite ore.}, booktitle = {Journal of Geophysics - Zeitschrift fur Geophysik}, year = {1985}, volume = {56}, number = {3}, pages = {174--182}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-0022266728&partnerID=tZOtx3y1} } |
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Hrouda, F., Stephenson, A. & Woltär, L. (1983), "On the standardization of measurements of the anisotropy of magnetic susceptibility"; Physics of the Earth and Planetary Interiors, Vol. 32 (3) , pp. 203-208 | |||||
Abstract: The magnetic anisotropy of several artificially constructed samples has been measured with different types of instruments in several laboratories. Susceptibility bridge determinations have given consistent results, but the magnitude of the anisotropy determined by the Digico anisotropy delineator is incorrect. For future measurements with this instrument it is necessary to make either a simple calibration change or to make a minor change in the associated computer program. A set of equations for correcting the old published data is given. | |||||
BibTeX:
@article{Hrouda1983, author = {Hrouda, František and Stephenson, Alan and Woltär, Leo}, title = {On the standardization of measurements of the anisotropy of magnetic susceptibility}, journal = {Physics of the Earth and Planetary Interiors}, year = {1983}, volume = {32}, number = {3}, pages = {203--208}, url = {http://www.sciencedirect.com/science/article/pii/0031920183901255}, doi = {http://dx.doi.org/10.1016/0031-9201(83)90125-5} } |
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Hrouda, F. (1982), "Magnetic anisotropy of rocks and its application in geology and geophysics"; Geophysical Surveys, Vol. 5 (1) , pp. 37-82 | |||||
Abstract: Magnetic anisotropy in sedimentary rocks is controlled by the processes of deposition and compaction, in volcanic rocks by the lava flow and in metamorphic and plutonic rocks by ductile deformation and mimetic crystallization. In massive ore it is due to processes associated with emplacement and consolidation of an ore body as well as to ductile deformation. Hence, it can be used as a tool of structural analysis for almost all rock types. Moreover, it can influence considerably the orientation of the remanent magnetization vector as well as the configuration of a magnetic anomaly over a magnetized body. For these reasons it should be investigated in palaeomagnetism and applied geophysics as well. | |||||
BibTeX:
@article{Hrouda1982b, author = {Hrouda, František}, title = {Magnetic anisotropy of rocks and its application in geology and geophysics}, journal = {Geophysical Surveys}, year = {1982}, volume = {5}, number = {1}, pages = {37--82}, doi = {http://dx.doi.org/10.1007/BF01450244} } |
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Jelínek, V. (1981), "Characterization of the magnetic fabric of rocks"; Tectonophysics, Vol. 79 (3-4) , pp. T63-T67 | |||||
Abstract: An inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks. The system involves three newly devised factors: the corrected anisotropy degree, the shape factor and the difference shape factor. The first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree. The shape factor characterizes the quality of anisotropy i.e. the shape of the susceptibility ellipsoid, in a convenient way; its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid. The difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown. | |||||
BibTeX:
@article{Jelinek1981, author = {Jelínek, V}, title = {Characterization of the magnetic fabric of rocks}, journal = {Tectonophysics}, year = {1981}, volume = {79}, number = {3-4}, pages = {T63--T67}, url = {http://www.sciencedirect.com/science/article/pii/0040195181901104}, doi = {http://dx.doi.org/10.1016/0040-1951(81)90110-4} } |
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Hrouda, F. (1980), "Magnetocrystalline anisotropy of rocks and massive ores: A mathematical model study and its fabric implications"; Journal of Structural Geology, Vol. 2 (4) , pp. 459-462 | |||||
Abstract: A simple mathematical model has been used to evaluate the influence of grain magnetocrystalline anisotropy and the scatter of crystallographic axes of grains on the magnetic anisotropy of rocks and massive ores whose carrier of magnetism is a magnetically uniaxial mineral of the type of pyrrhotite or hematite. The variation in magnetic anisotropy of rocks and ores whose carrier of magnetism displays the magnetocrystalline anisotropy greater than 100 is due to the variation in the preferred orientations of crystallographic axes, while the influence of the variation in the grain anisotropy on the rock (ore) anisotropy can be neglected. | |||||
BibTeX:
@article{Hrouda1980, author = {Hrouda, František}, title = {Magnetocrystalline anisotropy of rocks and massive ores: A mathematical model study and its fabric implications}, journal = {Journal of Structural Geology}, year = {1980}, volume = {2}, number = {4}, pages = {459--462}, url = {http://www.sciencedirect.com/science/article/pii/0191814180900073}, doi = {http://dx.doi.org/10.1016/0191-8141(80)90007-3} } |
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Hrouda, F. (1979),
"The strain interpretation of magnetic anisotropy in rocks of the Nizky Jesenik Mountains (Czechoslovakia)"; Sbor. geol. Věd, řada UG, Vol. 16
, pp. 27-62
[BibTeX] |
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BibTeX:
@article{Hrouda1979, author = {Hrouda, František}, title = {The strain interpretation of magnetic anisotropy in rocks of the Nizky Jesenik Mountains (Czechoslovakia)}, journal = {Sbor. geol. Věd, řada UG}, year = {1979}, volume = {16}, pages = {27--62} } |
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Jelínek, V. & Kropáček, V. (1978), "Statistical processing of anisotropy of magnetic susceptibility measured on groups of specimens"; Studia Geophysica et Geodaetica, Vol. 22 (1) , pp. 50-62 | |||||
Abstract: The theory of multivariate statistical processing of the anisotropy of magnetic susceptibility, measured on a group of specimens, originating from a single geological body (outcrop, locality, etc.), is described. The result of the processing is an estimate of the mean normalized tensor and the estimates of the principal susceptibilities, derived from it, together with the respective intervals of confidence, and the estimates of the principal directions with the respective regions of confidence. An anisotropy test for a group of specimens is proposed. The function of the ANS21 computer program employed is briefly described and an example of its output plot is presented. | |||||
BibTeX:
@article{ref1, author = {Jelínek, V and Kropáček, V}, title = {Statistical processing of anisotropy of magnetic susceptibility measured on groups of specimens}, journal = {Studia Geophysica et Geodaetica}, year = {1978}, volume = {22}, number = {1}, pages = {50--62}, url = {http://link.springer.com/10.1007/BF01613632}, doi = {http://dx.doi.org/10.1007/BF01613632} } |
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Jelínek, V. (1977), "The statistical theory of measuring anisotropy of magnetic susceptibility of rocks and its application"; , , Geofyzika, s.p., Brno | |||||
BibTeX:
@book{Jelinek1977, author = {Jelínek, V}, title = {The statistical theory of measuring anisotropy of magnetic susceptibility of rocks and its application}, publisher = {Geofyzika, s.p., Brno}, year = {1977}, url = {http://www.agico.com/downloads/documents/agicoprints/statistical_theory.pdf} } |