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Ashworth Luisa Kinnaird Judith Ann Nex Paul Andrew Martin Erasmus Rudolph Marthinus Przybyłowicz Wojciech Józef 《Mineralogy and Petrology》2018,112(6):753-765
Mineralogy and Petrology - Mineralized NYF and LCT pegmatites occur throughout the northeast-trending Neoproterozoic Damara Belt, Namibia. Mineralization in the pegmatites varies geographically,... 相似文献
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Fabien Nex Gerhard Schäfer Jean-Marie Côme Timothy M. Vogel 《Comptes Rendus Geoscience》2006,338(5):297-306
The goal of this study was to develop an innovative chloroethene biodegradation module based on biological, thermodynamical and mechanistic concepts. The biodegradation scheme was based on the postulate that in each part of an aquifer only one degradation mechanism is dominant: the one involving the most energetic electron acceptor. Thus, the selection of the active degradation mechanism was a function of the concentration of different electron acceptors. Modified Monod-type kinetics was used in order to take into account the possible influence of some compounds on the biodegradation of a given organic compound. The numerical model developed was applied to a simple test case, whose results are presented here. To cite this article: F. Nex et al., C. R. Geoscience 338 (2006). 相似文献
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Judith A. Kinnaird D. Hutchinson L. Schurmann P. A. M. Nex Renee de Lange 《Mineralium Deposita》2005,40(5):576-597
The Platreef, the putative local analogue of the Merensky Reef, forms the floor to the mafic succession in the northern limb
of the Bushveld Complex. We define the Platreef as ‘the lithologically variable unit, dominated by pyroxenite, which is irregularly
mineralised with PGE, Cu and Ni, between the Transvaal metasedimentary footwall or Archaean basement and the overlying Main
Zone gabbronorite’. We define the mineralisation around calcsilicate xenoliths within the Main Zone in the far north of the
limb as a ‘Platreef-style‘ mineralisation. The Platreef (ss) has a strike extent of ∼30 km, whereas Platreef-style mineralisation
occurs over a strike length of 110 km. The Platreef varies from 400 m thick in the S to <50 m in the N. The overall strike
is NW or N, with dips 40–45°W at surface, shallowing down dip, The overall geometry of the southern Platreef appears to have
been controlled by irregular floor topography. The maximum thickness of the southern Platreef occurs in two sub-basins on
the farms Macalacaskop and Turfspuit. Lithologically, the southern Platreef is heterogeneous and more variable than sectors
further north and, although predominantly pyroxenitic, includes dunites, peridotites and norite cycles with anorthosite in
the mid to upper portion. Zones of intense serpentinisation may occur throughout the package. Faults offset the strike of
the Platreef: a N–S, steeply dipping set is predominant with secondary ENE and ESE sets dipping 50–70°S. The fault architecture
was pre-Bushveld and also locally controlled thickening and thinning of the succession. Country rock xenoliths, <1500 m long,
are common. On Macalacaskop, these are typically quartzites and hornfelsed banded ironstones, shales, mudstones and siltstones
whereas on Turfspruit dolomitic or calcsilicate xenoliths also occur. Sulphides may reach >30 modal% in some intersections.
These are dominated by pyrrhotite, with lesser pentlandite and chalcopyrite, minor pyrite and traces of a wide compositional
range of sulphides. In the southern sector, mineralised zones have Cu grades of 0.1–0.25% and Ni 0.15–0.36%. Massive sulphides
are localised, commonly, but not exclusively towards the contact with footwall metasedimentary rocks. Magmatic sulphides are
disseminated or net-textured ranging from a few microns to 2 cm grains of pyrrhotite and pentlandite with chalcopyrite and
minor pyrite. Much of the sulphide is associated with intergranular plagioclase, or quartz-feldspar symplectites, along the
margins of rounded cumulus orthopyroxenes. The PGEs in the southern sector occur as tellurides, bismuthides, arsenides, antimonides,
bismuthoantimonides and complex bismuthotellurides. PGM are rarely included in the sulphides but occur as micron-sized satellite
grains around interstitial sulphides and within alteration assemblages in serpentinised zones. The Pt:Pd ratio ∼1 and PGE
grade may be decoupled from S and base metal abundance. 相似文献
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ABSTRACT Remote sensing images have long been recognized as useful for the detection of building damages, mainly due to their wide coverage, revisit capabilities and high spatial resolution. The majority of contributions aimed at identifying debris and rubble piles, as the main focus is to assess collapsed and partially collapsed structures. However, these approaches might not be optimal for the image classification of façade damages, where damages might appear in the form of spalling, cracks and collapse of small segments of the façade. A few studies focused their damage detection on the façades using only post-event images. Nonetheless, several studies achieved better performances in damage detection approaches when considering multi-temporal image data. Hence, in this work a multi-temporal façade damage detection is tested. The first objective is to optimally merge pre- and post-event aerial oblique imagery within a supervised classification approach using convolutional neural networks to detect façade damages. The second objective is related to the fact that façades are normally depicted in several views in aerial manned photogrammetric surveys; hence, different procedures combining these multi-view image data are also proposed and embedded in the image classification approach. Six multi-temporal approaches are compared against 3 mono-temporal ones. The results indicate the superiority of multi-temporal approaches (up to ~25% in f1-score) when compared to the mono-temporal ones. The best performing multi-temporal approach takes as input sextuples (3 views per epoch, per façade) within a late fusion approach to perform the image classification of façade damages. However, the detection of small damages, such as smaller cracks or smaller areas of spalling, remains challenging in this approach, mainly due to the low resolution (~0.14 m ground sampling distance) of the dataset used. 相似文献
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The Goanikontes area lies within the southern Central Zone of the northeast trending branch of the Damara Orogen. The cover succession around Goanikontes, which comprises Etusis to Chuos Formation metasediments, is in tectonic contact with older pre-Damaran basement rocks. The area can be divided into three structural domains with basement in the east, a northeast-plunging anticline of Damaran metasediments to the west and a high strain zone up to 1 km wide that separates them and truncates the anticline. The high strain zone has provided an important focus for the emplacement of sheeted granites adjacent to the basement-cover contact. Goanikontes is also one of several significant uranium anomalies within the Damaran Orogen, and the excellent 3D exposure of the Swakop river has provided evidence for an interpretation of the tectono-metamorphic setting of magmatism and mineralisation. The granitoids have been divided into equigranular granites and sheeted leucogranites. The sequence of emplacement of the equigranular granites is from red syenogranite (534±7 Ma) to later grey monzogranite (517±7 Ma) with foliated basement-hosted granite of probable time equivalence to the syenogranites. Each type can be distinguished on major- and trace-element geochemistry. The later sheeted leucogranites, which are volumetrically the most important, intrude both basement and cover rocks. These have been divided into six distinct types based on field characteristics and structural setting backed by geochemical data and fluid extraction analyses. The earliest type A are irregular in form, boudinaged and folded by D3, and geochemically distinct with notably low HFSE; type B's are white, weakly foliated, folded by D3, garnetiferous and highly peraluminous; type C are tourmaline-bearing, occasionally boudinaged and exhibit the typical sheet-form within the cover rocks. Of the post-D3 sheets, type D, which is restricted to the high strain zone is characterised by smoky quartz, high radioactivity and often by visible betafite or beta-uranophane; type E, the dominant type within the high strain zone contains prominent oxidation haloes and type F is red in colour, coarsely pegmatitic and has the highest concentration of alkalis. The uranium-mineralised type D sheets have consistently higher fluid and CO2 content than other sheeted leucogranites. The close correlation between sheet type and uranium abundance, supported by linear trends on LIL plots suggests that the distribution of radiogenic elements is primarily magmatic with more recent meteoric re-distribution, rather than due to substantial hydrothermal modification 相似文献
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ABSTRACT Geospatial information acquired with Unmanned Aerial Vehicles (UAV) provides valuable decision-making support in many different domains, and technological advances coincide with a demand for ever more sophisticated data products. One consequence is a research and development focus on more accurately referenced images and derivatives, which has long been a weakness especially of low to medium cost UAV systems equipped with relatively inexpensive inertial measurement unit (IMU) and Global Navigation Satellite System (GNSS) receivers. This research evaluates the positional accuracy of the real-time kinematics (RTK) GNSS on the DJI Matrice 600 Pro, one of the first available and widely used UAVs with potentially surveying-grade performance. Although a very high positional accuracy of the drone itself of 2 to 3 cm is claimed by DJI, the actual accuracy of the drone RTK for positioning the images and for using it for mapping purposes without additional ground control is not known. To begin with, the actual GNSS RTK position of reference center (the physical point on the antenna) on the drone is not indicated, and uncertainty regarding this also exists among the professional user community. In this study the reference center was determined through a set of experiments using the dual frequency static Leica GNSS with RTK capability. The RTK positioning data from the drone were then used for direct georeferencing, and its results were evaluated. Test flights were carried out over a 70 x 70 m area with an altitude of 40 m above the ground, with a ground sampling distance of 1.3 cm. Evaluated against ground control points, the planimetric accuracy of direct georeferencing for the photogrammetric product ranged between 30 and 60 cm. Analysis of direct georeferencing results showed a time delay of up to 0.28 seconds between the drone GNSS RTK and camera image acquisition affecting direct georeferencing results. 相似文献
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