2-D Joint Inversion of Semi-Airborne CSEM and LOTEM Data in Eastern Thuringia, Germany

Various electromagnetic (EM) techniques have been developed for exploring natural resources. The novel frequency-domain semi-airborne controlled source electromagnetic (semi-AEM) method takes advantages of both ground and airborne techniques. It combines ground-based high-power electrical dipole sources with large scale and spatially densely covered magnetic fields measured via airborne receivers. The method can survey the subsurface down to approximately 1000 m and is particularly sensitive towards conductive bodies (e.g. mineralized bodies) in a more resistive host environment. However, the signal-to-noise ratio of semi-AEM is lower than that of ground-based methods such as long-offset transient electromagnetics (LOTEM), mainly due to the limited stacking time and motion induced noise. As a result, the semi-AEM often has reduced depth of investigation in comparison to LOTEM. One solution to overcome these flaws is to analyse and interpret semi-AEM data together with information from other EM methods using a joint inversion. Since our study shows that LOTEM and semi-AEM data have complementary subsurface resolution capabilities, we present a 2-D joint inversion algorithm to simultaneously interpret frequency-domain semi-AEM data and transient electric fields using extended dipole sources. The algorithm has been applied to the field data acquired in a former mining area in eastern Thuringia, Germany. The 2-D joint inversion combines the complementary information and provides a meaningful 2-D resistivity model. Nevertheless, obvious discrepancies appear between the individual and joint inversion results. Consequent synthetic modelling studies illustrate that the discrepancies occur because of i) differences in lateral and depth resolution between the semi-AEM and LOTEM data caused by different measuring configurations, ii) different measured EM components, and iii) differences in the error weighting of the individual datasets. Additionally, our synthetic study suggests that more flexible land-based configurations with sparse receiver locations are possible in combination with semi-AEM without a significant loss of target resolution, which is promising for accelerating data acquisition and for survey planning and logistics, particularly when measuring in inaccessible areas

Identification of Candida glabrata genes involved in pH modulation and modification of the phagosomal environment in macrophages

notes: PMCID: PMC4006850types: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov'tCandida glabrata currently ranks as the second most frequent cause of invasive candidiasis. Our previous work has shown that C. glabrata is adapted to intracellular survival in macrophages and replicates within non-acidified late endosomal-stage phagosomes. In contrast, heat killed yeasts are found in acidified matured phagosomes. In the present study, we aimed at elucidating the processes leading to inhibition of phagosome acidification and maturation. We show that phagosomes containing viable C. glabrata cells do not fuse with pre-labeled lysosomes and possess low phagosomal hydrolase activity. Inhibition of acidification occurs independent of macrophage type (human/murine), differentiation (M1-/M2-type) or activation status (vitamin D3 stimulation). We observed no differential activation of macrophage MAPK or NFκB signaling cascades downstream of pattern recognition receptors after internalization of viable compared to heat killed yeasts, but Syk activation decayed faster in macrophages containing viable yeasts. Thus, delivery of viable yeasts to non-matured phagosomes is likely not triggered by initial recognition events via MAPK or NFκB signaling, but Syk activation may be involved. Although V-ATPase is abundant in C. glabrata phagosomes, the influence of this proton pump on intracellular survival is low since blocking V-ATPase activity with bafilomycin A1 has no influence on fungal viability. Active pH modulation is one possible fungal strategy to change phagosome pH. In fact, C. glabrata is able to alkalinize its extracellular environment, when growing on amino acids as the sole carbon source in vitro. By screening a C. glabrata mutant library we identified genes important for environmental alkalinization that were further tested for their impact on phagosome pH. We found that the lack of fungal mannosyltransferases resulted in severely reduced alkalinization in vitro and in the delivery of C. glabrata to acidified phagosomes. Therefore, protein mannosylation may play a key role in alterations of phagosomal properties caused by C. glabrata.Deutsche ForschungsgemeinschaftNational Institutes for HealthWellcome TrustBBSR

Progress in Tourism Management: from the geography of tourism to geographies of tourism - A review

This Progress in Tourism Management paper seeks to review the development of geographical contributions to the study of tourism over the last decade. Given the limited number of surveys of geography published in academic journals since the 1970s, it is particularly timely to question and debate where the subject has evolved to, the current debates and issues facing those who work within the subject and where the subject will evolve in the next five years. The paper is structured around a number of distinct themes to emerge from the research activity of geographers, which is deliberately selective in its coverage due to the constraints of space, but focuses on: explaining spatialities; tourism planning and places; development and its discontents; tourism as an 'applied' area of research, and future prospects

Denying bogus skepticism in climate change and tourism research

This final response to the two climate change denial papers by Shani and Arad further highlights the inaccuracies, misinformation and errors in their commentaries. The obfuscation of scientific research and the consensus on anthropogenic climate change may have significant long-term negative consequences for better understanding the implications of climate change and climate policy for tourism and create confusion and delay in developing and implementing tourism sector responses

Eigenschaften magnetotellurischer Übertragungsfunktionen - mit einer Fallstudie aus dem Gaxun-Nur Becken in NW-China

Die Eigenschaften der elektromagnetischen Moden und des magnetotellurischen (MT) Impe-danztensors werden im Rahmen von bei der Interpretation magnetotellurischer Daten auftretender Fragestellungen systematisch untersucht, und die methodischen Ergebnisse bei der Auswertung von Felddaten benutzt. Unter Verwendung räumlicher Beziehungen aus der Elektrodynamik können für beliebige Leitfähigkeitsverteilungen nach Moden getrennte Übertragungsfunktionen abgeleitet werden, die dann ausschließlich Felder in der tangential-elektrischen (TE) oder tangential-magnetischen Mode (TM) enthalten. Obwohl räumliche Beziehungen auf praktische Felddaten aufgrund der unzureichenden flächenhaften Überdeckung nicht angewandt werden können, erweisen sich die abgeleiteten Beziehungen als nützlich zur Charakterisierung der Beiträge der einzelnen Moden zu aus Messdaten bestimmbaren Übertragungsfunktion. So sind die für anomale TE und TM Felder ursächlichen Leitfähigkeitsanomalien bei gleicher Periode unter Umständen nicht identisch, was im Falle von 3D Strukturen aufgrund der Überlagerungen beider Moden in jedem Element des Impedanztensors zu einem nicht zerlegbaren Gemisch verschiedener Effekte führt. Bei dem Versuch, MT Daten mit 3D Effekten durch ein zweidimensionales Modell zu erklären, werden insbesondere TM Anteile in der angenommenen E-Polarisation (reine TE Mode) und TE Anteile in der angenommenen B-Polarisation (reine TM Mode) angepasst, was dem physikalischen Hintergrund nicht Rechnung trägt und daher zu fehlerhaften Modellen führen muss. Vor diesem Hintergrund erscheint es vor allem sinnvoll, vertikale magnetische Übertragungsfunktionen (reine TE Mode) zu berücksichtigen sowie vertikale elektrische Übertragungsfunktionen (reine TM Mode), die in der Praxis allerdings nicht direkt aus Messdaten bestimmt werden können. Sogenannte galvanische Verzerrung kann als Grenzfall betrachtet werden, indem an klein-räumigen Anomalien nur anomale TM Felder entstehen, und induktive Effekte vernachlässigt werden können. Das verzerrende elektrische Feld oszilliert dann mit gleicher Phase wie das regionale elektrische Feld, und ändert daher die Phasenlage des elektrischen Feldes nicht. Zur Beschreibung des Verzerrungseffektes empfiehlt sich daher die Betrachtung der Polarisations-zustände des elektromagnetischen Feldes und deren Entsprechung im Impedanztensor. Dieser Ansatz führt auf eine elliptische Parametrisierung der Spalten des Tensors. Die Existenz einer regionalen 2D Struktur kann bei geeigneter Drehung des Tensors in Richtung der Hauptachsen der Struktur aus verschwindenden Elliptizitäten behauptet werden. Die Orientierung der Ellipsen gibt dann die Verzerrungswinkel, d.h. die Richtung des linear polarisierten elektrischen Feldes in Bezug auf die Hauptachsen, an. Da sich alle Ellipsenparameter analytisch aus dem Tensor bestimmen lassen, ist die Implementierung eines Optimierungsalgorithmus zur Bestimmung des Koordinatensystems, das durch minimale Elliptizitäten gekennzeichnet ist, auch unter gleichzeitiger Berücksichtigung vieler Stationen und Frequenzen leicht und äußerst effektiv. Breitbandige MT Daten, die während eines MT Experiments im Gaxun-Nur Becken in NW-China gemessen wurden, wurden einer solchen Elliptizitätsanalyse zur Bestimmung der Dimensionalität des Untergrundes, der Streichrichtung zweidimensionaler Strukturen und der Identifikation galvanischer Verzerrung unterworfen. 1D und 2D Inversionrechnungen konnten nur für den kurzperiodischen Anteil durchgeführt werden. Bei längeren Perioden treten 3D Effekte auf, die zumindest für die magnetischen Übertragungsfunktionen mit 3D Modellrechnungen simuliert werden können. Aus den Leitfähigkeitsmodellen kann im Zusammenhang mit geologischen Geländeuntersuchungen und Satellitenbildinterpretationen eine geologisches Modell abgeleitet werden, das sich in den regionalen geologischen Kontext widerspruchsfrei einfügt. Aufgrund der Ergebnisse wird die Anlage zumindest von Teilen des heutigen Gaxun-Nur Beckens in das mittlere Mesozoikum gestellt, aus dem großräumige Krustenextension in Zentralasien bekannt ist, und auch im Untersuchungsgebiet zur Entwicklung tektonischer Gräben geführt hat. Eine spätere Reaktivierung mesozoischer Störungssysteme sowie dazu synthetisch angelegte Sekundärstörungen definieren im Känozoikum den südöstlichen Beckenrandbereich. Diese ebenfalls extensionellen Bewegungen scheinen bis heute aktiv zu sein, und haben wesentlichen Einfluss auf rezente Sedimentation und die hydrogeologische Situation im Untersuchungsgebiet.The properties of the electromagnetic modes and the magnetotelluric(MT) impedance tensor are systematically investigated in the course of MT data interpretation and the results are used for the analysis of actual field data. Using spatial relations of electrodynamic theory, response functions separated into tangential-electric (TE) and tangential-magnetic modes (TM) are constructed for arbitrary conductivity models. Though the theory is at present only applicable in synthetic model studies due to insufficient spatial coverage of MT sites in practical measurements, it serves to a deeper understanding of MT transfer functions. The results of a synthetic model study prohibit a 2D inversion of impedance data which are not strictly 2D, since the modes, carrying information about structures at different depth, may in general not be separated by rotation or tensor decomposition, and TE- and TM-mode fields are attempted to be fitted in B-Polarization (pure TM-mode) and E-Polarization (pure TE-mode), respectively. In contrast, the purely TE-mode vertical magnetic transfer function is free of TM-mode distortion, and therefore more reliable in terms of 2D inversion. The purely TM-mode vertical electric transfer function would be a suitable measure of TM-mode fields, but it can not be determined in practice. A limiting case of distorting TM-mode fields arising from shallow anomalies is commonly described in terms of galvanic distortion. Based upon the polarization states of principal electric and magnetic fields in presence of a regional 2D structure, a novel ellipse parameterization of the MT impedance tensor is developed, which reduces to the standard galvanic distortion model if applicable. The presence of a regional 2D structure is judged from vanishing ellipticities of the telluric vectors representing the polarization state of the principal electric field, and the presence of galvanic distortion is inferred from the orientation of ellipses representing the telluric vectors. Based upon the ellipse parameterization, multi-site multi-period strike and dimensionality analysis is easily implemented and proved to be stable even when using noisy data. During a MT field experiment in the Gaxun-Nur basin in NW-China, performed in conjunction with geological field investigations and satellite remote sensing data interpretation, broad-band MT-data were collected at 36 sites. Impedance data were subjected to dimensionality, distortion and strike analysis using the novel ellipticity analysis and to 1D and 2D inversion where adequate. 3D modeling could explain 3D effects of vertical magnetic transfer functions at intermediate periods, but fails to fit impedance data in the same period range. The final conductivity models of the upper crust suggest, that the Gaxun-Nur basin occupies a Mesozoic extensional region, where tectonic basins have evolved and Mesozoic sediments are trapped in more than 1300m deep structures. This scenario fits into a regional extensional event reported from other regions of central Asia. Cenozoic extension and related deformation is aligned along reactivated SW-NE-trending Mesozoic fault zones or along synthetically arranged N-S-trending faults. The latter appear to be active in the southeastern part of the Gaxun-Nur basin, and influence present sedimentation and the hydrogeological situation

Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

Crustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust ( 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung http://dx.doi.org/10.13039/501100001711Westfälische Wilhelms-Universität Münster (1056

Imaging the Whole-Lithosphere Architecture of a Mineral System-Geophysical Signatures of the Sources and Pathways of Ore-Forming Fluids

Mineral systems can be thought of as a combination of several critical elements, including the whole-lithosphere architecture, favorable geodynamic/tectonic events, and fertility. Because they are driven by processes across various scales, exploration benefits from a scale-integrated approach. There are open questions regarding the source of ore-forming fluids, the depth of genesis, and their transportation through the upper crust to discrete emplacement locations. In this study, we investigate an Au-Cu metal belt located at the margin of an Archean-Paleoproterozoic microcontinent. We explore the geophysical signatures by analyzing three-dimensional models of the electrical resistivity and shear-wave velocity throughout the lithosphere. Directly beneath the metal belt, narrow, vertical, finger-like low-resistivity features are imaged within the resistive upper-middle crust and are connected to a large low-resistivity zone in the lower crust. A broad low-resistivity zone is imaged in the lithospheric mantle, which is well aligned with a zone of low shear-wave velocity, examined with a correlation analysis. In the upper-middle crust, the resistivity signatures give evidence for ancient pathways of fluids, constrained by a structure along a tectonic boundary. In the lower lithosphere, the resistivity and velocity signatures are interpreted to represent a fossil fluid source region. We propose that these signatures were caused by a combination of factors related to refertilization and metasomatism of the lithospheric mantle by long-lived subduction at the craton margin, possibly including iron enrichment, F-rich phlogopite, and metallic sulfides. The whole-lithosphere architecture controls the genesis, evolution, and transport of ore-forming fluids and thus the development of the mineral system.ISSN:1525-202

Geodynamic Modeling of Lithospheric Removal and Surface Deformation: Application to Intraplate Uplift in Central Mongolia

Intraplate surface deformation is enigmatic and the underlying mechanisms responsible are not fully understood. We use thermo‐mechanical numerical modeling to explore the conditions under which lithospheric removal processes can occur and investigate the timing and amplitude of consequent surface deformation. We allow lithospheric removal to develop dynamically and self‐consistently by applying a phase transition and density jump that is hypothesized to be a consequence of metamorphic eclogitization in a thickened crust, rather than simply imposing an initial dense block. By systematically varying parameters, we test their influence and control on lithospheric removal. We confirm that a weak and dense lower crust, a hot crust‐mantle boundary, and a convergent regime are critical requirements for delamination‐style removal. We apply these results to central Mongolia, which is an ideal natural laboratory for studying intraplate surface uplift because of its high topography and location in the continental interior. We determine that the physical parameters and structure inferred in this region match the conditions for delamination. Thus, model outputs are evaluated against the available observational evidence. We find that the removal of the lithosphere by delamination can explain: the dome‐shaped topographic pattern and elevated surface; the thin lithosphere and its structure; the elevated temperature at the crust‐mantle boundary. Additionally, it is hypothesized that delamination leads to magmatism due to mantle decompression melting, consistent with intraplate volcanism. Ultimately, the results suggest that lithospheric removal by delamination is a physically plausible mechanism and a potential explanation for intraplate uplift.Key Points: Conditions for lithospheric removal‐induced surface deformation are investigated and applied to intraplate uplift in central Mongolia A weak and dense lower crust (modeled with a phase transition to eclogite) and convergent motion are required for removal by delamination Model outputs—topography, lithospheric structure, timing—match observational evidence, suggesting a physically plausible mechanismDeutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/50110000165

Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

Crustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust ( 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.ISSN:1343-8832ISSN:1880-598