Magnetotellurics in the Eger Rift: An overview of subsurface imaging of different tectonic features

2021 ◽  
Author(s):  
Ute Weckmann ◽  
Anna Platz ◽  
Basel Aleid ◽  
Gregor Willkommen ◽  
Johannes Mair ◽  
...  
Keyword(s):  
Lower Crust ◽  
Large Scale ◽  
Rift System ◽  
Earthquake Swarms ◽  
Shallow Subsurface ◽  
Eger Rift ◽  
Continental Lithospheric Mantle ◽  
Tectonic Features ◽  
2D And 3D ◽  
Scoria Cones

<p>The Bohemian Massif represents the easternmost part of the geodynamically active European Cenozoic Rift System. This region hosts the contact between three tectonic units of the Variscan Belt, the NE-SW trending Eger Rift and the NNW-SSE striking Marianské Lázne fault. It is characterised by ongoing magmatic processes in the intra-continental lithospheric mantle, repeated earthquake swarms, extensive CO<sub>2</sub> degassing in mineral springs and mofettes and the presence of Quaternary volcanoes. While the ICDP drilling programme utilizes information gathered within shallow boreholes in the region, we applied the Magnetotelluric (MT) method to obtain site characterizations in the vicinity of the proposed drill sites. The electrical conductivity has proven to be an important parameter to image the above-mentioned tectonic from the lower crust to the shallow subsurface as well as on a regional and a local scale. Here, we present 2D and 3D inversion models of different MT and Radio-MT (RMT) experiments to study e.g. the Hartouŝov mofette fields, the Quaternary scoria cones, the regional faults and their interplay. Thereby the experiments were designed that we can use lower frequency data from MT to support shallow 3D inversions of e.g. the scoria cones in the regions. The most prominent large-scale conductivity features map channels from the lower crust to the surface possibly forming pathways for fluids into the region of earthquake swarms, mofette fields and know spas. However, the locations of the scoria cones seem to be bound to regional fault zones.</p>

Near-surface conductivity structures of quaternary volcanic maars in the Western Bohemian Massif: 3D imaging using the Radio-Magnetotelluric method

2020 ◽  
Author(s):  
Gregor Willkommen ◽  
Radek Klanica ◽  
Světlana Kováčiková ◽  
Jan Mrlina ◽  
Anna Platz ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Fault Zone ◽  
Bohemian Massif ◽  
Rift System ◽  
Earthquake Activity ◽  
Potential Core ◽  
Near Surface ◽  
Eger Rift ◽  
Cheb Basin ◽  
Scoria Cones

<p>As part of the Bohemian Massif, the Cheb Basin is one of the most active areas of the European Cenozoic Rift System. Separated from the ENE-WSW striking Eger Rift to the west by the morphological prominent Mariánské Lázne Fault Zone (MLF), the basin shows presently no active volcanism at the surface. Nonetheless it is characterized by degassing of mantle derived CO<sub>2</sub> in mofettes and mineral springs and by repeated occurrences of swarm earthquakes along the Pocátky-Plesná Zone (PPZ) and MLF near Nový Kostel. All these activities are vivid signs of ongoing magmatic processes in the lithospheric mantle. Over the last 15 years four potential maar diatreme structures were discovered and join the two known scoria cones Komorní hurka and Zelezná hurka in the western part of the Cheb Basin. Unlike scoria cones there are no prominent morphological indications for maar diatreme structures, why only modern approaches in remote sensing and systematic gravimetrical surveys led to the discovery of the Mýtina Maar in 2007 (Mrlina et. al., 2007), the Neualbenreuth Maar in 2017 (Rohrmüller et. al., 2017) and recently the two potentials Ztracený rybník maars close to Libá (Hosek et. al., 2019; Mrlina et. al. 2019). All these quaternary volcanic structures are located very close along the Tachov Fault Zone (TFZ), one of the major NNW-SSE striking fault zones of the Bohemian Massif. Maar volcanoes were formed when rising magma interacts explosively with groundwater. Advancing explosions left a cone-shaped diatreme that has been filled with post-eruptive sediments which could conduce as a climate archive for the last 300.000 years in central Europe. An interdisciplinary Project "Drilling the Eger Rift" within the International Continental Scientific Drilling Program (ICDP) targets the interactions between fluids, deep biosphere, CO<sub>2</sub> degassing and earthquake activity to shed light on the tectonic structure and related geodynamic processes. As a part of this project, Radio-Magnetotelluric (RMT) measurements were applied to image the near-surface electrical conductivity structure of these maar volcanoes. From May 2018 on, we conducted field experiments encompassing six 500 m RMT profiles across the Neualbenreuth maar, three 700 m profiles across Mýtina Maar and finally eight 400 - 1200 m long profiles over both Ztracený rybník maars. Compared with geo-electric resistivity tomography (ERT), our RMT measurements are more sensitive to conductors such as fluids or metallic compounds and were done with an areal coverage for 3D inversion and interpretation. With advanced and statistically robust data processing techniques typically applied to MT data resulted in impedance tensors in a period range of 10 kHz to 250 kHz. This RMT data sets are then modelled using inversion. The resulting 3D electrical conductivity models across the maar diatreme structures show distinct contrasts between the resistive rocks of the diatreme and the rather conductive post-eruptive sediments. The inversion results will be compared and discussed, in particular regarding a position for a potential core drilling in one of the maar structures. </p>

scholarly journals Neoarchean Mantle-derived Magmatism within the Repulse Bay Block, Melville Peninsula, Nunavut: Implications for Archean Crustal Extraction and Cratonization

2015 ◽  
Vol 42 (3) ◽  
pp. 305 ◽  
Author(s):  
Crystal LaFlamme ◽  
Christopher R.M. McFarlane ◽  
David Corrigan
Keyword(s):  
Lower Crust ◽  
Large Scale ◽  
Nous Proposons ◽  
Granitic Gneiss ◽  
Geochemical Properties ◽  
Lree Content ◽  
Continental Lithospheric Mantle ◽  
Granitoid Intrusions ◽  
Oceanic Slab ◽  
Metasomatized Mantle

SUMMARYThe Repulse Bay block (RBb) of the southern Melville Peninsula, Nunavut, lies within the Rae craton and exposes a large (50,000 km2) area of middle to lower crust. The block is composed of ca. 2.86 Ga and 2.73–2.71 Ga tonalite-trondhjemite-granodiorite (TTG) and granitic gneiss that was derived from an older 3.25 and 3.10 Ga crustal substrate. This period of crustal generation was followed by the emplacement of ca. 2.69–2.66 Ga enderbite, charnockite, and granitoid intrusions with entrained websterite xenoliths. These voluminous batholith-scale bodies (dehydrated and hydrated intrusions), and the associated websterite xenoliths, have similar whole rock geochemical properties, including fractionated light rare earth element (LREE)–heavy (H)REE whole rock patterns and negative Nb, Ti, and Ta anomalies. Dehydrated intrusions and websterite xenoliths also contain similar mineralogy (two pyroxene, biotite, interstitial amphibole) and similar pyroxene trace element compositions. Based on geochemical and mineralogical properties, the two lithologies are interpreted to be related by fractional crystallization, and to be the product of a magmatic cumulate processes. Reworking of the crust in a ca. 2.72 Ga subduction zone setting was followed by ca. 2.69 Ga upwelling of the asthenospheric mantle and the intrusion of massif-type granitoid plutons. Based on a dramatic increase in FeO, Zr, Hf, and LREE content of the most evolved granitoid components from the 2.69–2.66 Ga cumulate intrusion, we propose that those granitoid plutons were in part derived from a metasomatized mantle source enriched by fluids from the subducting oceanic slab that underwent further hybridization (via assimilation) with the crust. Large-scale, mantle-derived Neoarchean sanukitoid-type magmatism played a role in the development of a depleted lower crust and residual sub-continental lithospheric mantle, a crucial element in the preservation of the RBb.RÉSUMÉLe bloc de Repulse Bay (RBb) dans le sud de la péninsule de Melville, au Nunavut, est situé dans le craton de Rae et expose une large zone (50 000 km2) de croûte moyenne à inférieur. Ce bloc est composé de tonalite-trondhjémite-granodiorite (TTG) daté à ca. 2,86 Ga et 2,73–2,71 Ga, et de gneiss granitique dérivé d’un substrat crustal plus ancien daté à 3,25 Ga et 3,10 Ga. Cette période de croissance crustale a été suivie par la mise en place entre ca. 2,69 et 2,66 Ga d’intrusions d’enderbite, charnockite et de granitoïde incluant des xénolites d’entraînement de websterite. Ces intrusions de taille batholitique (intrusions déshydratées et hydratées) ainsi que les xénolites d’entraînement de websterite associés, ont des propriétés géochimiques sur roche totale semblables notamment leurs profils de fractionnement des terres rares légers (LREE) et des terres rares lourds (HREE) ainsi que leurs anomalies négatives en Nb, Ti et Ta. Les intrusions déshydratées et les xénolites de websterite ont aussi des minéralogies similaires (deux pyroxènes, biotite, amphibole interstitielle) ainsi que des compositions semblables en éléments traces de leurs pyroxènes. Étant donné leurs propriétés géochimiques et minéralogiques, ces deux lithologies sont interprétées comme provenant d’une cristallisation fractionnée, et comme étant le produit de processus d'accumulations magmatiques. Le remaniement de la croûte dans un contexte de subduction vers ca. 2,72 Ga, a été suivi vers ca. 2,69 Ga d’une remontée du manteau asthénosphérique et de l’intrusion de granitoïdes de type massif. D'après l’importante augmentation en FeO, Zr, Hf et LREE dans les granitoïdes les plus évolués du magmatisme ayant pris place entre ca. 2,69 Ga et 2,66 Ga, nous proposons que ces plutons aient été en partie dérivés d’une source mantélique métasomatisée enrichies par des fluides d’une plaque océanique en subduction et qui a subi une hybridation supplémentaire (par assimilation) avec la croûte. Le magmatisme néo-archéen de type sanukitoïde, dérivé du manteau et de grande échelle, a joué un rôle dans le développement d’une croûte inférieure et d’un manteau lithosphérique continental résiduel appauvri, un élément déterminant pour la préservation du RBb.

Depletion, metasomatism and refertilisation in the Sub-Continental Lithospheric Mantle beneath northern Victoria Land (Antarctica): a review

2021 ◽  
Author(s):  
Massimo Coltorti ◽  
Costanza Bonadiman ◽  
Federico Casetta ◽  
Barbara Faccini ◽  
Pier Paolo Giacomoni ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Large Scale ◽  
Ross Sea ◽  
Mantle Xenoliths ◽  
Rift System ◽  
Stability Field ◽  
Alkaline Magmatism ◽  
Metasomatic Process ◽  
Victoria Land ◽  
Continental Lithospheric Mantle

<p>Assessing the nature and evolution of the Sub-Continental Lithospheric Mantle (SCLM) is crucial to understand the dynamics of Earth’s interior and the global scale tectono-magmatic processes. The study of ultramafic xenoliths brought to the surface in specific context, such as northern Victoria Land (Antarctica), is a key to investigate how the SCLM bear witness of large-scale geodynamic episodes. Indeed, the Antarctica lithosphere was involved into three main tectono-magmatic episodes since Paleozoic, i.e. the 550-110 Ma Ross subduction, the Jurassic (~182 Ma) Ferrar magmatism and the Cenozoic alkaline magmatism responsible for the opening of the West Antarctic Rift System (WARS).</p><p>In this study, a review of the petrological and geochemical features of >200 mantle-derived and cumulate xenoliths brought to the surface at Baker Rocks, Greene Point, Handler Ridge, Harrow Peaks, Browning Pass and Mount Overlord enabled us to reconstruct the main depletion and enrichment processes that took place in the Antarctica SCLM. Strong depletion is recorded by Greene Point lherzolites and harzburgites (18-21%), which likely began melting in the garnet facies and terminated in the spinel facies (Perinelli et al. 2006), whereas mild melt extraction in the spinel stability field was hypothesized at Baker Rocks and Handler Ridge (12-16% and 7-13% melting, respectively). The onset of the Jurassic Ferrar large magmatic event is testified by both the refertilisation in Greene Point-Baker Rocks peridotites and the appearance of cumulate orthopyroxenites/olivine-websterites at Harrow Peaks and Baker Rocks. Late enrichment process/es took place in concomitance with the Cenozoic alkaline magmatism of the WARS, resulting in both cryptic and modal metasomatism and overprinting earlier chemical modifications. This metasomatism was particularly effective at Baker Rocks, as shown by the increase of clinopyroxene abundance, its trace element enrichment and the formation of amphibole disseminated and in veins. Clinopyroxene composition in Cenozoic cumulate rocks matches the enrichment path observed in the peridotites, supporting the link between the last metasomatic process and the recent alkaline magmatism.</p><p>Among mantle xenoliths populations, Greene Point record the highest T-P (870-1059 °C; 0.8-1.6 GPa) and the least oxidized conditions (fO<sub>2</sub> down to -2/-3 ΔFMQ). Cumulate rocks yield the highest fO<sub>2</sub> (up to +1.5 ΔFMQ), at T varying between 900 and 1150°C, approximating the conditions of crystallizing melts. No discrepancies in fO<sub>2</sub> emerged between amphibole-bearing and amphibole-free peridotites, ruling out a strict correlation between amphibole stability, H<sub>2</sub>O activity and fO<sub>2</sub>. Nevertheless, the alkaline metasomatic event, which led to amphibole formation, caused a remarkable increase in the H<sub>2</sub>O content of the system. In fact, anhydrous peridotites preserve bulk H<sub>2</sub>O contents ≤128 ppm, while lherzolites with disseminated amphibole and hornblendites have H<sub>2</sub>O contents as up to 354-1120 ppm and 1.42 wt%, respectively.</p><p> </p><p>Perinelli, C., et al. 2006. Geochemical and O-isotope constraints on the evolution of lithospheric mantle in the Ross Sea rift area (Antarctica). Contributions to Mineralogy and Petrology, 151(3), 245-266.</p>

Line length balancing to evaluate multi-phase submarine landslide development: an example from the Storegga Slide, Norway

2019 ◽  
Vol 500 (1) ◽  
pp. 531-549 ◽  
Author(s):  
Suzanne Bull ◽  
Joseph A. Cartwright
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Line Length ◽  
Proximal Region ◽  
Submarine Landslide ◽  
Landslide Development ◽  
Multi Phase ◽  
Storegga Slide ◽  
2D And 3D ◽  
3D Seismic Data

AbstractThis study shows how simple structural restoration of a discrete submarine landslide lobe can be applied to large-scale, multi-phase examples to identify different phases of slide-lobe development and evaluate their mode of emplacement. We present the most detailed analysis performed to date on a zone of intense contractional deformation, historically referred to as the compression zone, from the giant, multi-phase Storegga Slide, offshore Norway. 2D and 3D seismic data and bathymetry data show that the zone of large-scale (>650 m thick) contractional deformation can be genetically linked updip with a zone of intense depletion across a distance of 135 km. Quantification of depletion and accumulation along a representative dip-section reveals that significant depletion in the proximal region is not accommodated in the relatively mild amount (c. 5%) of downdip shortening. Dip-section restoration indicates a later, separate stage of deformation may have involved removal of a significant volume of material as part of the final stages of the Storegga Slide, as opposed to the minor volumes reported in previous studies.

scholarly journals The Role of Dimensionality in Understanding Granuloma Formation

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 58 ◽  
Author(s):  
Simeone Marino ◽  
Caitlin Hult ◽  
Paul Wolberg ◽  
Jennifer Linderman ◽  
Denise Kirschner
Keyword(s):  
Experimental Data ◽  
Large Scale ◽  
Bacterial Load ◽  
Computational Cost ◽  
Granuloma Formation ◽  
In Silico Studies ◽  
Cellular Recruitment ◽  
2D And 3D

Within the first 2–3 months of a Mycobacterium tuberculosis (Mtb) infection, 2–4 mm spherical structures called granulomas develop in the lungs of the infected hosts. These are the hallmark of tuberculosis (TB) infection in humans and non-human primates. A cascade of immunological events occurs in the first 3 months of granuloma formation that likely shapes the outcome of the infection. Understanding the main mechanisms driving granuloma development and function is key to generating treatments and vaccines. In vitro, in vivo, and in silico studies have been performed in the past decades to address the complexity of granuloma dynamics. This study builds on our previous 2D spatio-temporal hybrid computational model of granuloma formation in TB (GranSim) and presents for the first time a more realistic 3D implementation. We use uncertainty and sensitivity analysis techniques to calibrate the new 3D resolution to non-human primate (NHP) experimental data on bacterial levels per granuloma during the first 100 days post infection. Due to the large computational cost associated with running a 3D agent-based model, our major goal is to assess to what extent 2D and 3D simulations differ in predictions for TB granulomas and what can be learned in the context of 3D that is missed in 2D. Our findings suggest that in terms of major mechanisms driving bacterial burden, 2D and 3D models return very similar results. For example, Mtb growth rates and molecular regulation mechanisms are very important both in 2D and 3D, as are cellular movement and modulation of cell recruitment. The main difference we found was that the 3D model is less affected by crowding when cellular recruitment and movement of cells are increased. Overall, we conclude that the use of a 2D resolution in GranSim is warranted when large scale pilot runs are to be performed and if the goal is to determine major mechanisms driving infection outcome (e.g., bacterial load). To comprehensively compare the roles of model dimensionality, further tests and experimental data will be needed to expand our conclusions to molecular scale dynamics and multi-scale resolutions.

scholarly journals Spheroid Trapping and Calcium Spike Estimation Techniques toward Automation of 3D Culture

2020 ◽  
pp. 247263032093831
Author(s):  
Kenneth Ndyabawe ◽  
Mark Haidekker ◽  
Amish Asthana ◽  
William S. Kisaalita
Keyword(s):  
Calcium Imaging ◽  
Large Scale ◽  
3D Culture ◽  
Tissue Cell ◽  
Cell Recognition ◽  
Temporal Data ◽  
Spike Detection ◽  
Fluorescent Intensity ◽  
Imaging Artifacts ◽  
2D And 3D

We present a spheroid trapping device, compatible with traditional tissue culture plates, to confine microtissues in a small area and allow suspension cultures to be treated like adherent cultures with minimal loss of spheroids due to aspiration. We also illustrate an automated morphology-independent procedure for cell recognition, segmentation, and a calcium spike detection technique for high-throughput analysis in 3D cultured tissue. Our cell recognition technique uses a maximum intensity projection of spatial-temporal data to create a binary mask, which delineates individual cell boundaries and extracts mean fluorescent data for each cell through a series of intensity thresholding and cluster labeling operations. The temporal data are subject to sorting for imaging artifacts, baseline correction, smoothing, and spike detection algorithms. We validated this procedure through analysis of calcium data from 2D and 3D SHSY-5Y cell cultures. Using this approach, we rapidly created regions of interest (ROIs) and extracted fluorescent intensity data from hundreds of cells in the field of view with superior data fidelity over hand-drawn ROIs even in dense (3D tissue) cell populations. We sorted data from cells with imaging artifacts (such as photo bleaching and dye saturation), classified nonfiring and firing cells, estimated the number of spikes in each cell, and documented the results, facilitating large-scale calcium imaging analysis in both 2D and 3D cultures. Since our recognition and segmentation technique is independent of morphology, our protocol provides a versatile platform for the analysis of large confocal calcium imaging data from neuronal cells, glial cells, and other cell types.

scholarly journals Collaborative visual analytics of radio surveys in the Big Data era

2016 ◽  
Vol 12 (S325) ◽  
pp. 311-315 ◽  
Author(s):  
Dany Vohl ◽  
Christopher J. Fluke ◽  
Amr H. Hassan ◽  
David G. Barnes ◽  
Virginia A. Kilborn
Keyword(s):  
Visual Analytics ◽  
Large Scale ◽  
Research Process ◽  
Multidimensional Data ◽  
Asynchronous Collaboration ◽  
Parallel Data ◽  
Display Ecology ◽  
Data Inquiry ◽  
Large Survey ◽  
2D And 3D

AbstractRadio survey datasets comprise an increasing number of individual observations stored as sets of multidimensional data. In large survey projects, astronomers commonly face limitations regarding: 1) interactive visual analytics of sufficiently large subsets of data; 2) synchronous and asynchronous collaboration; and 3) documentation of the discovery workflow. To support collaborative data inquiry, we present encube, a large-scale comparative visual analytics framework. encube can utilise advanced visualization environments such as the CAVE2 (a hybrid 2D and 3D virtual reality environment powered with a 100 Tflop/s GPU-based supercomputer and 84 million pixels) for collaborative analysis of large subsets of data from radio surveys. It can also run on standard desktops, providing a capable visual analytics experience across the display ecology. encube is composed of four primary units enabling compute-intensive processing, advanced visualisation, dynamic interaction, parallel data query, along with data management. Its modularity will make it simple to incorporate astronomical analysis packages and Virtual Observatory capabilities developed within our community. We discuss how encube builds a bridge between high-end display systems (such as CAVE2) and the classical desktop, preserving all traces of the work completed on either platform – allowing the research process to continue wherever you are.

scholarly journals Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an International Continental Drilling Program (ICDP) monitoring site to image fluid-related structures

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 1951-1969 ◽  
Author(s):  
Tobias Nickschick ◽  
Christina Flechsig ◽  
Jan Mrlina ◽  
Frank Oppermann ◽  
Felix Löbig ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Fault Zone ◽  
Large Scale ◽  
Monitoring Site ◽  
Earthquake Activity ◽  
Resistivity Tomography ◽  
Scientific Drilling ◽  
Eger Rift ◽  
Geophysical Surveys ◽  
Cheb Basin

Abstract. The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project “Drilling the Eger Rift” in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it. As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole–dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 and 150 m dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. −9 mGal marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as CO2. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.

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