quantitative mapping of clay minerals using airborne imaging spectroscopy new data on mugello italy from sim ga prototypal sensor

AbstractThe possibility of using high spectral and spatial resolution remote sensing technologies is becoming increasingly important in the monitoring of soil degradation processes. A high spatial resolution hyperspectral dataset was acquired with the airborne Hyper SIM-GA sensor from Selex Galileo, simultaneously with ground soil spectral signatures and samples collection. A complete mapping procedure was developed using the 2000–2450 nm spectral region, demonstrating that the 2200 absorption band allows the obtainment of reliable maps of the clay content. The correlation achieved between the observed and the predicted values is encouraging for the extensive application of this technique in soil conservation planning and protection actions

Corsica ophiolites: geochemistry and petrogenesis of basaltic and metabasaltic rocks

This paper presents a systematic geochemical characterization of the basaltic and metabasaltic rocks from the Alpine Corsica ophiolites. The various ophiolitic units of Alpine Corsica can basically be subdivided into two main types: (1) high-pressure/low-temperature, metamorphic ophiolites belonging to the Lower Schistes Lustrés (LSL) and Upper Schistes Lustrés (USL) Complexes and (2) the non-metamorphic, upper ophiolitic units. Basaltic and metabasaltic rocks from all these units display many common geochemical characteristics, which indicate a common genesis in a mid-ocean ridge setting. However, on the bases of their high field strength element (HFSE) and rare earth element (REE) distribution, two main geochemical types can be recognized. One type has normal MORB-type (N-MORB) geochemical features, being characterized by flat N-MORB normalized HFSE patterns, slight depletion in Th, U, Ta and variable depletion of light REE (LREE) with respect to medium REE (MREE). This type is volumetrically prevalent and is found in metabasalts from the LSL and USL, as well as in basalts from the upper ophiolitic units. The other type has transitional MORB-type (T-MORB) geochemical features, as it shows slightly enriched N-MORB normalized HFSE patterns, slight enrichment in Th, U, Ta and LREE enrichment with respect to MREE. This type is observed in metabasaltic rocks from the Santo Pietro di Tenda Unit (USL) and in basalts from the Nebbio and from the bottom of the Balagne units. A distinguishing geochemical feature of basaltic and metabasaltic rocks from the Alpine Corsica ophiolites is a marked heavy REE (HREE) fractionation with respect to MREE. The (Sm/Yb)N ratios range from 1.1 to 2.6, but in most cases are > 1.5. This feature is interpreted as a garnet signature, which can be related to the melting of a heterogeneous mantle source characterized by garnet-bearing mafic/ultramafic layers. Semi-quantitative modelling of the REE data for the N-MORBs indicates that these rocks may have derived from small-degree (< 8%) partial melting of a depleted MORB-type peridotitic source bearing small volumes of garnet-pyroxenite relics. The differential degree of partial melting of this source can explain the significant range of variation of LREE/MREE ratios, as well as the high (Sm/Yb)N ratios observed in the studied N-MORB rocks. In addition, the N-MORB rocks most likely derived from compositionally similar mantle sources and much of the internal chemical variation in these rocks is more likely due to differential partial melting rather than different enrichments of their mantle sources. Semi-quantitative modelling of the REE data for the T-MORBs indicates that these rocks may have been derived from small-degree (< 5%) partial melting of a lithospheric mantle source bearing garnet-pyroxenite relics. They could represent products extruded in the ocean-continent transition zone during the initial stage of oceanic opening, whereas N-MORBs may represent volcanic sequences formed in more internal paleo-oceanic positions after the onset of the oceanic spreading

Potential Use of Remote Sensing Techniques for Exploration of Iron Deposits in Western Sahara and Southwest of Algeria

At present, Western Sahara is politically one of the most sensitive areas of the World. Its economic development could be achieved through the exploitation of mineral resources that can be found in the almost unexplored area administrated by the Saharawi Arab Democratic Republic. In this paper, we describe applications of known and cost-effective remote sensing techniques to detect and map areas containing mineral deposits, through the enhancement of Landsat ETM+ imageries. Several image processing techniques (false color composite, band ratioing, and principal component analysis) were used to highlight the presence of iron deposits. Two test areas were selected, one in Western Sahara and another one in Algeria. The occurrence of iron deposits in these test areas was assured using literature data for the Algerian test site and through a field campaign for the Western Sahara. There is good agreement between the ground truth data and the results obtained by the enhancements of the satellite images. Landsat images can be downloaded free of charge and their enhancements does not need expensive hardware or software tools. Therefore this technology could be transferred to the Saharawi technicians, enabling them to explore and manage the mineral resources of their own country independently. © 2013 International Association for Mathematical Geology

Two GUIs-based analysis tool for spectroradiometer data pre-processing

A new graphical user interface (GUI) for pre-processing reflectance spectra, built using MATLAB and expressly designed for the ASD FieldSpec® spectroradiometer, was developed to solve problems that generally affect experimental ASD data. The GUI is characterised by an easily readable, graphic visualisation of spectra, from which the absorption band depth (ABD) can be obtained for a selected wavelength. The output format of the ASD data is a binary file with an .asd extension. The binary file, that provides a single spectrum, can be processed using a software functionality, by means of a GUI, that allows to select one or more binary files to produce a spectral library in a unique .txt file. The spectral reflectance is re-calibrated with the "convex-hull" methodology to eliminate the convex shape, which is typical of reflectance spectra. Different examples of the use of the new GUI are provided. © 2013 Springer-Verlag Berlin Heidelberg

Remote sensing techniques using Landsat ETM+ applied to the detection of iron ore deposits in Western Africa

Remote sensing methods enable the rapid and inexpensive mapping of surface geological and mineralogical features. This capability proves highly useful when working on isolated or inaccessible areas. In this study, several enhancements of Landsat Enhanced Thematic Mapper plus (i.e. band ratios, false colour composites and principal component analysis) were used and evaluated to obtain the best possible visualisation of iron deposits hosted in the Devonian sedimentary rocks of northwestern Africa. In particular, two test sites were chosen: southern Algeria (Djebilet area), where the literature mineralogical and geological data on iron mine fields were already available, and the Western Sahara (the southern flank of Tindouf Basin), which was investigated during a field campaign and was where the occurrence of an analogous sedimentary succession led us to hypothesise the possible presence of exploitable iron deposits. This work demonstrates the usefulness of multispectral imagery in the detection of iron-rich areas and establishes a full remote sensing procedure, which can be profitably applied to a wider region of Western Sahara and can provide interesting perspectives on the possibility of detecting new exploitable iron ore deposits in arid environments. © 2012 Saudi Society for Geosciences

Clay content mapping through integration of geophysical proximal and remote sensing data

Soil sustainable exploitation planning and land resource evaluation require up-to-date and accurate maps of soil properties. In that respect, geophysical techniques present particular interests given their non-invasiveness and their fast data acquisition capacity, which permit to characterize large areas with fine spatial and/or temporal resolutions. We investigated the relevancy of combining data from airborne hyperspectral (Hs), electromagnetic induction (EMI) and far-field ground-penetrating radar (GPR) for mapping soil properties, in particular soil clay content, at the field scale. Data from the three techniques were acquired at a test site in Mugello (Italy) characterized by relatively strong spatial variations of soil texture. Soil samples were collected for determining actual clay contents. For the frequencies used in this study (200-2000 MHz), the GPR surface reflection is mainly determined by soil dielectric permittivity, itself primarily influenced by soil moisture. In contrast, EMI is mostly sensitive to soil electrical conductivity, which integrates several soil properties including in particular soil moisture and clay content. Taking advantage of the complementary information provided by the two instruments, the GPR and EMI data were combined and correlated to local ground-truth measurements of clay content to provide high-resolution clay content maps over the entire field area. Besides, a relationship was also observed between Hs data and clay content measurements, which permitted to produce a Hs-derived clay content map. EMI-GPR and Hs maps showed close spatial patterns and a relatively high correlation was observed between both clay content estimates, as well as between clay content estimates and ground-truth clay content measurements. Future analyses will entail more advanced Bayesian data fusion techniques for combining EMI-GPR and Hs information. These results demonstrated great promise for integrated, digital soil mapping applications

3-D geomechanical rock mass characterization for the evaluation of rockslide susceptibility scenarios

An integrated methodology based on traditional field and remote surveys such as terrestrial laser scanning and terrestrial infrared thermography is proposed, with the aim of defining susceptibility scenarios connected to rock slopes affected by instability processes. The proposed methodology was applied to a rock slope threatening a coastal panoramic roadway located in western Elba Island (Livorno district, central Italy). The final aim of the methodology was to obtain an accurate three-dimensional rock mass characterization in order to detect the potentially more hazardous rock mass portions, calculate their volume, and collect all the required geomechanical and geometrical parameters to perform a detailed stability analysis. The proposed approach proved to be an effective tool in the field of engineering geology and emergency management, when it is often urgently necessary to minimize survey time when operating in dangerous environments and gather all the required information as fast as possible