Jörn H. Kruhl

Technical University of Munich | TUM · TUM School of Engineering and Design

The occurrence of pseudotachylyte-ultracataclasite veins at the Main Central Thrust (central Nepal) is reported here for the first time. The veins are planar, mm-thin layers concordant to the main foliation and layering of the wallrock. They contain elongate domains with variable amount of glasses and µm to mm-sized angular to sub-angular fragments...

Transmission electron microscopy and 3D focused ion beam/scanning electron microscope nanotomography are applied to grain and phase boundaries between quartz, plagioclase, K-feldspar, clinopyroxene, amphibole, and calcite. The samples come from metamorphic, plutonic and volcanic rocks, and hydrothermal quartz, and experienced cooling and decompress...

During the exhumation of rocks and the associated temperature and pressure decrease, the anisotropic thermoelastic properties of minerals lead to internal stresses on the grain scale, which in turn cause fracturing and opening of grain and phase boundaries. To gain deeper insight into the onset of grain-boundary cracking and the subsequent evolutio...

"Drawing Geological Structures" provides undergraduate as well as graduate and practicing geologists with a thorough, step-by-step practical guide to the art of geological drawing. Beginning with the basics, the book covers thin sections, sample sections, samples, and geological stereograms. The chapters provide examples of how drawings evolve and...

Grain and phase boundaries are one of the most important features of crystalline materials. They affect physical properties of rocks, such as rheology, strength, resistance to cracking and corrosion, and fluid permeability and provide information on their tectonometamorphic history. Based on focused ion beam (FIB) sample preparation, transmission e...

This book addresses earthquakes, with a special focus on the Ghorka earthquake, which struck parts of central Nepal in April 2015. Drawing on this disastrous event, it closely examines various aspects of earthquakes in contributions prepared by international experts. The topics covered include: the geological and geophysical background of seismicit...

Shock-fragmentation of the Ries impact crater forms characteristic and complex fracture patterns from micro- to kilometre-scale. Outside the crater rim, prominent fractures are mainly vertical to sub-vertical, either in radial or tangential orientation to the crater. The traces of radial fractures from various outcrops around the Ries consistently...

Quantification of geological structures is a precondition for obtaining insight into structure-forming processes. Structures generated during rock fragmentation are typically complex and, therefore, difficult to investigate by classical methods of Euclidian geometry and structural geology. However, fractal geometry provides powerful tools for quant...

Impact-induced brittle deformation structures within Malm limestone and lower basement rock in and around the Ries crater are recorded, measured and quantified. Quantifications are mainly done by methods, based on structural geology, classical spatial statistics and fractal geometry. A variety of deformation structures are observed, which include p...

IntroductionChaotic dynamic systems and nonlinear processes, together with the resulting fractals and multifractals, are becoming increasingly fundamental for analyzing data and understanding processes in the Earth and environmental sciences. Many processes and phenomena, poorly known only a few years ago, can now be studied and understood with the...

Silicified fault rocks typically show structures resulting from various stages of fragmentation and quartz crystal-lization. Both processes interact episodically and result in complex structures on various scales, which require a wide spectrum of analysis tools. Based on field and microstructural data, the spatial-temporal connection between deform...

Silicified fault rocks typically show structures resulting from various stages of fragmentation and quartz crystal-lization. Both processes interact episodically and result in complex structures on various scales, which require a wide spectrum of analysis tools. Based on field and microstructural data, the spatial-temporal connection between deform...

Field and microstructural data of the Pfahl shear zone in north-eastern Bavaria (Germany) reveal the intimate spatial-temporal connection between fragmentation, fluid influx and quartz crystallization. These processes and their interaction led to complex-structured quartz units: (i) a dense network of early quartz veins, (ii) two domains of fine-gr...

Numerous quarries in and around the Ries me-teorite crater provide an excellent opportunity to study impact-related deformation features and structures in the basement rocks and their thin sedimentary cover. In this investigation, impact-induced brittle deformation features from Malm Limestone exposures outside the inner crater ring are studied. Sh...

Shock waves of the Ries meteorite impact caused fragmentation of the target rock far beyond the range and style typical for regional brittle deformation (Fig. 1). In horizontal and vertical directions fracture patterns vary systemically with increasing distance from the impact centre. Quantification of fracture patterns with different fractal-geome...

Shock-induced fragmentation structures of basement rocks and their limestone cover in and around the Ries impact crater (Germany) were recorded on outcrop, hand sample, and thin-section scale, and quantified mainly by fractal geometry methods. Quantification was performed by automated procedures and in areas of squarecentimetres to square-decametre...

Ultrahigh-pressure (UHP) metamorphic conditions are defined by the stability of coesite and allocated rocks formed in convergent tectonic settings at depth > 90 km. Jadeite-quartzite and eclogite samples from the Shuanghe UHP slab of the Dabie Shan (central China) were investigated. The rocks underwent UHP metamorphism at c. 220-230 Ma due to a N-s...

Fault zones serve as pathways for large quantities of hot fluids that may change rock composition and structure, generating ore deposits and geothermal fields. This typically leads to quartz precipitation reflecting cyclicity of deformation and fluid-flow. The dextral strike-slip Pfahl shear zone (Germany) represents a fault zone with frequent puls...

1] TEM and SEM/FIB sequential imaging of quartz grain boundaries from contact and regional metamorphic rocks show that most of the grain boundaries are open on the nanometer scale. Three types of voids occur. (i) Roughly 40–500 nm wide open zones parallel to the grain boundaries. They are suggested to be caused by general volume reduction as a resu...

Fractal-geometry techniques are widely applied to the quantification of complex rock structures. Important properties of such structures are (i) different scaling behaviour on different scales, (ii) inhomogeneity, and (iii) anisotropy. The current paper presents a special view on the quantification of these properties by classical and newly develop...

Ultrahigh-pressure (UHP) metamorphic rocks form in convergent tectonic settings at depths > 90 km. In general, UHP conditions are defined by the stability of coesite. Coesite inclusions in various host minerals are a common feature in UHP rocks. We present data of typical quartz microfabrics, which resulted from the transformation of coesite to qua...

The Bavarian Pfahl shear zone is a WNW-ESE trending dextral strike-slip shear zone at the SW margin of the Bohemian Massif (Central Europe). It was discontinuously active during decreasing PT-conditions, i.e. from ductile to brittle, from the late-Carboniferous to the late-Cretaceous – Paleocene times. Triassic hydrothermal activity produced a 150...

Porphyritic dykes, formed in an active strike-slip shear zone, represent a laboratory of fabric development at high temperature, high cooling rates and variable strain and provide insight into processes during rapid magma ascent related to volcanism in a continent collision zone. 640 – 675 °C hot tonalitic magma injected the SE-margin of the Wester...

Porphyric dykes, formed in an active shear zone, represent a laboratory of fabric development at high T, high cooling rates and variable strain. ~ 640-675°C hot tonalitic magma injected the SE -margin of the W estern Alps at ~ 10 km depth and rapidly cooled t o the wall-rock temperature of ~ 480 -510°C. Locally increased stress at grain contacts du...

Quartz grain boundaries from metamorphic and igneous rocks may emphasize a complex geometry, characterized by self-similarity over one to two orders of magnitude. Their fractal analysis highlights scaling sub-domains, i.e. scale intervals with a particularly good correlation. Given the importance of these aspects for the deciphering of geological m...

a b s t r a c t Syntectonic plutons may record short-lived geological events related to crustal melting and deformation of the continental crust. Therefore, interpretation of microstructure and orientation of fabrics is critical in order to constrain space/time/temperature/deformation relationships during pluton crystallization. Here we describe th...

Vein patterns and quartz crystallization in the Pfahl shear zone (Bavarian Forest, Germany): clues to understanding interaction of tectonics and fluid flow in a fossil hydrothermal system Giacomo Prosser (1), Jörn Kruhl (2), Domenico Liotta (3), Tim Yilmaz (2), and Sabine Volland (2) The Pfahl shear zone represents a NW-SE trending dextral strike-s...

Magmatic mineral distribution patterns in a syntectonic syenite pluton have been recorded at high resolution over several square metres on quarried faces. The anisotropy and inhomogeneity of K-feldspar and mafic mineral distribution patterns have been quantified using two methods originally based on fractal geometry. (1) Map-counting, based on box-...

The Santa Lucia Shear Zone (SLSZ, Corsica) is a granulite-facies Permian shear zone that developed after the emplacement of a deep-seated gabbroic intrusion. New structural data shows that the SLSZ results from the juxtaposition of three spatially distinct mylonite belts, which are the product of the interaction between magmatism, metamorphism and...

Fractal-geometry-based analysis techniques offer simple and efficient ways for analyzing magmatic fabrics that are otherwise difficult to describe quantitatively. This study shows an application of two different methods on flow patterns observed in a syntectonic magmatic body injected into the lower crust. XZ and YZ rock cuts are scanned, and the s...

In the northeastern Dom Feliciano Belt, Santa Catarina/Brazil, Paleoproterozoic rocks (mainly the Camboriú Complex) and Neoproterozoic granitoids – with the older Itapema Granite and the younger Corre-mar, Rio Pequeno and Serra dos Macacos granites – experienced a deformation history from magmatic to greenschist facies temperatures, under different...

This study analyses the possibility of accurate quantification of automatically digitized mineral-phase distribution patterns in igneous rocks. Based on their colour contrast, different minerals were manually and automatically digitized on micro to macro scales. Depending on the digitized mineral phase, the accuracy of the automated digitizing proc...

The software tool AMOCADO is presented here. It is designed for quantifying pattern anisotropy. This automated method, based on a modified Cantor-dust method, is applied to various artificial and natural 2D patterns. The results illustrate different applications for the software tool. The automation, results in a high data density and in a precisio...

The calc-alcaline granitoids of the Hercynian Corsica Batholith show a large-scale magmatic flow pattern, outlined by the alignment of large (mm-cm) euhedral feldspar crystals. The trend of the steep magmatic foliation is generally N-S in the northern part of the island, swings to approximately E-W orientation in the central part of the Batholith a...

Macro- and microstructures of syntectonic granitoids provide numerous information about (i) crystallization, deformation and rheology history of these rocks, (ii) development of fabric anisotropy and heterogeneity during flow processes, and (iii) relationships between local and regional kinematics. The Piquiri Syenite Massif (611+-3 Ma) is part of...

In recent years, considerable progress has been made in increasing the spatial resolution in Neutron Computed Tomography (N-CT), now achieving a resolution of 20-30 μm. This is a level comparable with standard X-ray CT methods. Unlike X-rays, cold neutrons provide good contrast for light elements and are capable of penetrating thicker layers of hea...

Syntectonic magmatic rocks, namely syntectonic granitoids, provide important information about large-scale crustal processes, such as formation of large-scale and deep-rooted faults and thrusts, and the compositional and structural re-organization of the continental crust in general. However, emplacement and crystallization of granitoid melts in re...

Magmatic processes such as magma emplacement and deformation-cooling histories leave visible traces in fabrics of magmatic rocks on all scales from µm to m. Together with the mostly diffuse and irregular nature of the patterns, this large scale range greatly impedes comprehensive analyses of the rock's fabrics. While such fabric patterns have been...

The quantitative analysis of patterns as a geometric arrangement of material domains with specific geometric or crystallographic properties such as shape, size or crystallographic orientation has been shown to be a valuable tool with a wide field of applications in geo- and material sciences. We have developed a collection of automated methods that...

X-ray computed tomography is a well-established method for fabric analysis in many fields of science. Neutron Computed Tomography has very recently achieved high resolution comparable to X-ray CT, and has already proven to be a very powerful tool in geologic texture determination. While X-rays show attenuation monotonously rising with the atomic nu...

Syn-tectonic late-Hercynian granitoids, emplaced at mid-crustal level through multiple dyke injections, are well-exposed in a ∼1 km-long section, in the southern Sila Massif (Calabria, Italy). The fieldwork study permitted us to reconstruct the following order of emplacement: (i) granodiorites with euhedral Kfs megacrystals (Grd1, in the main text)...

Volcanic dome-building episodes commonly exhibit acceleration in both effusive discharge rate and seismicity before explosive eruptions. This should enable the application of material failure forecasting methods to eruption forecasting. To date, such methods have been based exclusively on the seismicity of the country rock. It is clear, however, th...

Fabrics of syntectonic magmatic rocks provide important information on melt emplacement and crystallization conditions and, consequently, information on state and development of certain parts of the continental crust. Therefore, detailed studies on magmatic fabrics and, specifically, their quantification is a necessary prerequisite for any more det...

During the last decade, studies on magmatic fabrics on different scale have been made for analyzing kinematics of melt emplacement and deformation as well as cooling histories of magmatic bodies and their host rocks (Brown 2001). The problem arises for comparing data from structural analysis in thin-sections and fabrics in outcrop scale. Magmatic f...

During the last decade, studies on magmatic fabrics on different scale have been made for analyzing kinematics of melt emplacement and deformation as well as cooling histories of magmatic bodies and their host rocks (Brown 2001). The problem arises for comparing data from structural analysis in thin-sections and fabrics in outcrop scale. Magmatic f...

Volcanic activity, which often includes a complex interplay between different factors such as magmatic processes, changes in crustal stress, earthquake events, etc., may lead to remarkable challenges regarding the identification of practically useful hazard patterns. These patterns may change over time at variable speed and in ways that are difficu...

In this study electrical properties of a graphite-rich quartzite from the former lower crust exposed in the Serre San Bruno, Calabria (southern Italy) have been analysed by means of complex electrical conductivity measurements in the frequency range 10−3 to 106 Hz on plug samples of 25 mm in diameter and 22 mm high. The samples were identified as a...

The crystallographic orientations of two sets of 3144 and 1660 straight segments of sutured quartz grain boundaries, formed during dynamic recrystallization and subsequent annealing at lower greenschist and lower amphibolite-facies conditions respectively, have been studied by combined universal-stage and electron backscatter diffraction measuremen...

Abstract At the basement-cover boundary of the north-eastern Tauern Window (Eastern Alps), the following Alpine P-T-d development has been reconstructed on the basis of macro- and micro-structures as well as preferred crystallographic orientations, mineral parageneses and compositions. During increasing P-T conditions in the greenschist facies a fi...

Brittle and ductile microfabrics in cordierite from a migmatite were studied by universal-stage method and electron probe micro-analysis. The microfabrics record crystal fracturing and ductile deformation of one deformation event at ∼570°C and ∼380MPa, but at variable strain rates. The cordierite microfabrics evolve in four stages. (1) At strain ra...

The quantitative analysis of patterns as a geometric arrangement of material domains with specific geometric or crystallographic properties such as shape, size or crystallographic orientation has been shown to be a valuable tool with a wide field of applications in geo- and material sciences. Pattern quantification allows an unbiased comparison of...

Fabrics and their anisotropy and inhomogeneity are fundamental properties of igneous rocks and fabric quantification is a necessary pre-requisite for studying the structure and development of igneous rocks during different stages of their history. Even if the combination of classical geometrical (e.g. grain geometry, grain size distribution) and no...

Grain and phase boundaries in polycrystalline material control fundamental material properties, such as strength, alteration resistance or deformation behavior, and provide important information about the material history. In addition, the technical treatment of boundaries represents a powerful tool for governing properties of technical material (g...

The crystallography and geometry of high-angle grain boundaries from dynamically recrystallized quartz have been studied. On the basis of combined electron backscatter diffraction and universal stage measurements, the complete crystallographic orientation of the grain boundaries could be calculated. The u-stage rotation of the grain boundaries to a...

Shearing of regional extent, involving granitoids and underlying mid-crustal rocks of the Sila massif (Calabria, Italy), is analysed in this paper. The deformed granitoids are affected by a wide NNW-SSE oriented deformation zone, stretching for about 60 km, from the neighbourhood of Cecita Lake to Cropani village. Meso- and micro-structures in gran...

Quantification of pattern anisotropy gives insight into pattern forming processes and facilitates comparison between nature, experiments and simulations. For efficient analyses, automated procedures for these operations are required. AMOCADO, a MATLAB-based implementation of the modified Cantor dust method which allows for a time-efficient analysis...

The Monte'e Senes intrusive complex in northeastern Sardinia represents a good example of a syntectonic tonalitic sheet-complex. Its history consists of at least three intrusive events involving tonalitic magma and one subsequent intrusive event involving leucogranitic magma. The tonalites form numerous cm- to m-thick layers subparallel to the main...

Three different fractal geometry methods for pattern analysis are applied on a quartz-filled late-Hercynian fracture zone in NW Sardinia. Fragment–size distribution analysis and the box-counting method offer the possibility to (i) detect self-similarity of patterns and, therefore, argue for a specific pattern forming process, and (ii) allow the qua...

In order to better understand the nature of deep crustal high electrical conductivity, we studied the electrical properties of a tilted section of a former lower continental crust exposed in the Calabrian arc of the Alpine–Apennine mountain system. Geoelectric field measurements and impedance measurements on rock samples showed that these high-grad...

The Rhodope Massif, as part of the Alpine-Himalayan orogenic system, experienced several phases of continental subduction, collision, thrusting, extension and a widespread granitoid magmatism in Cretaceous and Tertiary times. On the basis of (i) the intimate interfingering of the multiple granitoid intrusions and the country rocks, (ii) the paralle...

Magmatic mineral distribution patterns in a syntectonic syenite pluton have been recorded at high resolution over several square metres on quarried faces. The anisotropy and inhomogeneity of K-feldspar and mafic mineral distribution patterns have been quantified using two methods originally based on fractal geometry. (1) Map-counting, based on box-...

The Carmo and Cindacta plutons (SE Brazil) represent syntectonic intrusions during the late-Proterozoic Brasiliano orogeny (700–500 Ma) in the southern Ribeira belt. A first magma pulse (the Carmo pluton) intruded as a thin lenticular body along a low-angle WSW-directed overthrust plane, which probably formed during the collision of the Congo and S...

Dynamically recrystallized and sutured quartz grains from metamorphic rocks with different strain intensities and temperature conditions ranging from ca. 350°C to ca. 700°C have been studied. Universal-stage measurements on quartz–quartz high-angle grain boundaries show that they are never curved but always consist of straight segments which prefer...

The shape, pattern and crystallographic orientation of grain boundaries represent important characteristics of crystalline material and contain information about its deformation and annealing history. The present study includes measurements of grain boundaries from experimentally annealed analogue material as well as natural foam texture of quartz...

Four well-established techniques were applied to determine the mineral textures of a muscovite-bearing quartzite: (1) directional measurements on an optical U-stage; (2) X-ray; (3) neutron; and (4) electron diffraction (EBSD). Techniques (1) and (4) are of the ‘single grain’ type and techniques (2) and (3) of the ‘statistical’ or ‘volume’ type. Exp...

Concepts and methods of fractal geometry penetrate various branches of human knowledge to an increasing degree. This tendency is particularly striking in the geosciences, because many processes occurring in and on the Earth result in time dependences and spatial patterns that have a fractal character. The contributions in this volume arose from the...

Empirical data on quartz subgrain patterns from various metamorphic rocks show that, at least up to 10 kbar in the stability field of low-quartz, prismatic subgrain boundaries are dominant whereas basal subgrain boundaries are not developed. In the high-quartz stability field, both prismatic and basal subgrain boundaries occur and form typical rect...

A characteristic feature of the Moldanubian part of the central European Variscides is late-orogenic high-T/low-P metamorphism. Its past history and the possible reasons for this metamorphism are highlighted by the tectonometamorphic development at the south– eastern margin of the Bohemian massif. During the Variscan orogeny, at ca. 340 Ma, two dif...

In a paper entitled “Ductility of garnet as an indicator of extremely high temperature deformation”, Ji & Martignole (1994) argue that garnets were flattened substantially by dislocation creep in the Morin shear zone (Grenville Province, Quebec, Canada) and that the temperature during deformation must therefore have exceeded 900°C. Ji & Martignole...

Along grain boundaries of quartz from metamorphic and igneous rocks complex interfingering (sutures) may occur. Under the light microscope the lengths of the sutures range from approximately 10–1000 m. The sutured grain boundaries are statistically self-similar over one to two orders of magnitude. They represent fractals. Their mathematical counter...

The brittle widening of rocks during regional extension follows a power—law relationship and, therefore, is scale—invariant. The development of extensional veins during this process is best described by the Cantor—dust model with a fractal dimension 0.955 < D < 0.970. D is independent of the rock types, their anisotropics, the amount of widening, t...

Exposed crystalline basement of the Serre Mountains in Calabria presents a tilted block of a nearly complete section of the Hercynian continental lower crust (HCLC). In addition to petrological and structural data from surface mapping, and petrophysical data from the laboratory, a seismic reflection-refraction experiment was conducted in May 1990....

Zusammenfassung In der nördlichen Serre (Süditalien) ist ein zusammenhängender Bereich einer ehemaligen kontinentalen Unterkruste aufgeschlossen (Schenk 1984, 1985). Diese granulitfaziellen Gesteine sind bei ihrem Aufstieg in höhere Krustenbereiche nicht durchgreifend überprägt worden. Deshalb läßt sich an ihnen noch der strukturelle Zustand der eh...

Average elastic data for lower crustal rocks have been calculated on the basis of crystallographic plagioclase orientations from greenschist to granulite facies rocks and the respective single crystal elastic constants. The anisotropy of the P-wave velocity caused by different plagioclase textures is between 2% and 8%, whereas the highest differenc...

Preferred lattice orientations of plagioclase, measured by the universal stage, from deformed amphibolite and greenschist facies rocks near the Insubric Line (Western Alps), reflect the type and orientation of the strain system: either (001) or (010) are oriented parallel or subparallel to the schistosity and form more or less complete girdles arou...

Fortran IV subroutines are presented for the manipulation of U-stage measurements on plagioclase. On the basis of two measured indicatrix axes and one crystallographic plane (either (001) or (010)), additional crystallographic planes and directions, and the Au content, are determined; inverse pole figures may also be produced. The influences of ina...