Generative Adversarial Network Applied to Ore Type Modeling in Complex Geological Environments     

Jordão  Helga  Azevedo  Leonardo  Sousa  António Jorge  Soares  Amílcar 《Mathematical Geosciences》2022,54(7):1165-1182

Mathematical Geosciences - In complex geological environments, the spatial domain characterization of different ore types has been one of the most important challenges in the assessment of mineral...  相似文献   

Monazite CHIME/EPMA dating of Erinpura granitoid deformation: Implications for Neoproterozoic tectono-thermal evolution of NW India     

Jana Just  Bernhard Schulz  Helga de Wall  Fred Jourdan  Manoj K. Pandit 《Gondwana Research》2011,19(2):402-412

The in-situ “chemical” Th–U–Pb dating of monazite with the electron microprobe is used to unravel the Neoproterozoic tectono-thermal history of the “Erinpura Granite” terrane in the foreland of the Delhi Fold Belt (DFB) in the NW Indian craton. These granitoids are variably deformed and show effects of shearing activity. Monazites from the Erinpura granitoids recorded two main events; (1) protolith crystallization at 863 ± 23 Ma and (2) recrystallization and formation of new Th-poor monazite at 775 ± 26 Ma during shear overprint. Some components of the Erinpura granitoids, such as the Siyawa Granite and granites exposed near Sirohi town, show evidence of migmatization. This migmatization event is documented by anatexis and associated monazite crystallization at 779 ± 16 Ma. The age data indicate an overlap in timing between anatectic event and ductile shear deformation. The end of the tectono-thermal event in the Sirohi area is constrained by a 736 ± 6 Ma Ar–Ar muscovite age data from the ductile shear zone.  相似文献   

Influence of low ozone episodes on erythemal UV-B radiation in Austria     

Schwarz  Matthias  Baumgartner  Dietmar J.  Pietsch  Helga  Blumthaler  Mario  Weihs  Philipp  Rieder  Harald E. 《Theoretical and Applied Climatology》2018,133(1-2):319-329

This study investigates the influence of low ozone episodes on UV-B radiation in Austria during the period 1999 to 2015. To this aim observations of total column ozone (TCO) in the Greater Alpine Region (Arosa, Switzerland; Hohenpeissenberg, Germany; Hradec Kralove, Czech Republic; Sonnblick, Austria), and erythemal UV-B radiation, available from 12 sites of the Austrian UV-B monitoring network, are analyzed. As previous definitions for low ozone episodes are not particularly suited to investigate effects on UV radiation, a novel threshold approach—considering anomalies—is developed to provide a joint framework for the analysis of extremes. TCO and UV extremes are negatively correlated, although modulating effects of sunshine duration impact the robustness of the statistical relationship. Therefore, information on relative sunshine duration (SD_rel), available at (or nearby) UV-B monitoring sites, is included as explanatory variable in the analysis. The joint analysis of anomalies of both UV index (UVI) and total ozone (∆UVI, ∆TCO) and SD_rel across sites shows that more than 65% of observations with strongly negative ozone anomalies (∆TCO < −1) led to positive UVI anomalies. Considering only days with strongly positive UVI anomaly (∆UVI > 1), we find (across all sites) that about 90% correspond to negative ∆TCO. The remaining 10% of days occurred during fair weather conditions (SD_rel ≥ 80%) explaining the appearance of ∆UVI > 1 despite positive TCO anomalies. Further, we introduce an anomaly amplification factor (AAF), which quantifies the expected change of the ∆UVI for a given change in ∆TCO.

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Assimilation of time-averaged observations in a quasi-geostrophic atmospheric jet model     

Helga S. Huntley  Gregory J. Hakim 《Climate Dynamics》2010,35(6):995-1009

The problem of reconstructing past climates from a sparse network of noisy time-averaged observations is considered with a novel ensemble Kalman filter approach. Results for a sparse network of 100 idealized observations for a quasi-geostrophic model of a jet interacting with a mountain reveal that, for a wide range of observation averaging times, analysis errors are reduced by about 50% relative to the control case without assimilation. Results are robust to changes to observational error, the number of observations, and an imperfect model. Specifically, analysis errors are reduced relative to the control case for observations having errors up to three times the climatological variance for a fixed 100-station network, and for networks consisting of ten or more stations when observational errors are fixed at one-third the climatological variance. In the limit of small numbers of observations, station location becomes critically important, motivating an optimally determined network. A network of fifteen optimally determined observations reduces analysis errors by 30% relative to the control, as compared to 50% for a randomly chosen network of 100 observations.  相似文献   

Migration of Synthetic Seismograms For Crustal Structures With Random Heterogeneities     

H. Emmerich  J. Zwielich  G. Müller 《Geophysical Journal International》1993,113(1):225-238

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Gondwana break-up and the northern margin of the Saxothuringian belt (Variscides of Central Europe)     

Helga Kemnitz  Rolf L. Romer  Onno Oncken 《International Journal of Earth Sciences》2002,91(2):246-259

At the northwestern edge of the Hercynian Bohemian Massif (Saxothuringian belt) new U-Pb zircon age data from rift-related magmatic rocks indicate that the initiation of Gondwana break-up in this area started during the Middle to Upper Cambrian. Magmatic rocks from a bimodal, MORB- to within-plate volcanic sequence in the Vesser area are dated between ca. 517 and 501 Ma. The volcaniclastic sequences analysed exhibit basal layers of conglomerates and mature sandstones, which can be correlated with a widespread Gondwana-derived onlap horizon of an uppermost Cambrian/Tremadocian age that links the Vesser area with the Saxothuringian continental basin. The association of the Vesser rocks with the Saxothuringian terrane as part of the Armorican terrane assemblage is further demonstrated by a coeval magmatic development and by identical detrital components which are derived from a common Cadomian basement (white mica with a ca. 539 Ma K-Ar minimum age and inherited zircon signatures). The Vesser unit, situated between the NW margin of the Saxothuringian zone and the Mid-German Crystalline Zone, probably represents a N-facing remnant of an ocean-continent transition of the, or within the, Armorican terrane assemblage and involves sections of the early break-up process at the peri-Gondwanan shelf south of the Rheic ocean.  相似文献   

Temporal distribution of heavy metal concentrations in oysters Crassostrea rhizophorae from the central Venezuelan coast     

Juan A. Alfonso  Helga Handt  Abrahan Mora  Yaneth Vásquez  José Azocar  Eunice Marcano 《Marine pollution bulletin》2013

The oyster Crassostrea rhizophorae is a bivalve abundant in Venezuelan estuaries and consumed by local populations. No known values have been reported on trace metals in oysters from the central Venezuelan coast. We report the concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn in the soft parts of C. rhizophorae, which were collected bimonthly between March 2008 and March 2009, at two sampling areas from the Central Venezuelan Coast: Buche estuary and Mochima estuary. Our results show that for each metal there is a similar temporal variation pattern. The concentrations of the heavy metals reported in this work are useful as reliable baselines and can be used for comparison in future environment studies. Concentrations in C. rhizophorae from the Buche estuary can be interpreted to be high on a global scale for Cd, Cu, Ni and Mn, indicating atypically raised bioavailabilities.  相似文献   

Assembling insurgent citizenship: immigrant advocacy struggles in the Washington DC metropolitan area     

Helga Leitner  Christopher Strunk 《Urban geography》2013,34(7):943-964

This article examines the political and spatial registers of struggles against exclusionary local immigration policies and for more welcoming policies in the Washington DC metropolitan area, one of the hotspots for both local anti-immigration policies and immigrant advocacy in the United States. We conceptualize immigrant advocacy not simply as an alliance, but instead as an assemblage that brings together a diverse set of differently positioned actors and nonhuman actants. The assemblage enacts a diverse politics that deploys different forms of activism, while engaging different publics (e.g., religious communities, unions, the larger public sphere in public spaces, etc.) and the state in complex ways. From acting outside the state to engaging in claims-making towards the state, immigrant advocates are making claims and actions that challenge and go beyond dominant conceptions of citizenship rights and liberal democratic politics. The spatial register is similarly diverse. The immigrant advocacy assemblage is confronted with and enacts a different politics of place in central cities and inner- and outer-ring suburbs. Contestations of exclusionary local policies, however, are not simply about a local politics of place. To the contrary, some actors and actants in the assemblage are actively involved in extra-local networking, collaborating across jurisdictional boundaries—between central cities and inner-and outer-ring suburbs within the Washington DC metropolitan area and across the United States. The complexities of these contestations call into question post-political narratives of “proper” politics, underscoring the need for an empirically grounded critical theory of democracy. This article contributes to this task by providing a geographically and historically sensitive analysis of the immigrant advocacy assemblage.  相似文献   

Rocks,fabrics and magnetic anisotropy: an introduction to the issue in honour of František Hrouda     

Manish A. Mamtani  Martin Chadima  Helga de Wall  Reinhard O. Greiling 《International Journal of Earth Sciences》2012,101(3):605-607

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Continental rift-setting and evolution of Neoproterozoic Sindreth Basin in NW-India     

Stefan Schöbel  Kamal K Sharma  Thorsten Hörbrand  Theresa Böhm  Ines Donhauser  Helga de Wall 《Journal of Earth System Science》2017,126(6):90

The Neoproterozoic Sindreth Basin, NW India, and its surrounding area represent a half graben structure situated between the undeformed Malani Igneous Suite (MIS) in the west and a corridor of coeval Cryogenian ductile deformation, anatexis and granite intrusion in the east. The main lithologies observed in the basin are conglomerate, fanglomerate, debris flow and lake deposits derived from a nearby continental provenance, intercalated with concurrent mafic and felsic lava flows. Based on geological traverses across the strike of the basin, we propose a three-fold classification comprising Lower Clastic Unit and an Upper Clastic Unit and a Bimodal (basalt–rhyolite) Volcanic Unit separating the two. Tilting due to basin inversion and faulting has been observed; however, the rocks are unmetamorphosed and show undisturbed primary sedimentary features. The stratigraphic record of the basin is characteristic for deposition and magmatism in a fault-related continental setting. Implications of the findings have been discussed in the context of Neoproterozoic crustal dynamics in NW India. This study provides conclusive evidence for a continental setting for Sindreth Basin evolution and contests the recent models of active subduction setting (either back-arc basin or accretionary sediments over a subduction zone).  相似文献