Selection of Less Biased Threshold Angles for SAM Classification Using the Real Value–Area Fractal Technique

The accuracy of classification of the Spectral Angle Mapping (SAM) is warranted by choosing the appropriate threshold angles, which are normally defined by the user. Trial‐and‐error and statistical methods are commonly applied to determine threshold angles. In this paper, we discuss a real value–area (RV–A) technique based on the established concentration–area (C–A) fractal model to determine less biased threshold angles for SAM classification of multispectral images. Short wave infrared (SWIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used over and around the Sar Cheshmeh porphyry Cu deposit and Seridune porphyry Cu prospect. Reference spectra from the known hydrothermal alteration zones in each study area were chosen for producing respective rule images. Segmentation of each rule image resulted in a RV–A curve. Hydrothermal alteration mapping based on threshold values of each RV–A curve showed that the first break in each curve is practical for selection of optimum threshold angles. The hydrothermal alteration maps of the study areas were evaluated by field and laboratory studies including X–ray diffraction analysis, spectral analysis, and thin section study of rock samples. The accuracy of the SAM classification was evaluated by using an error matrix. Overall accuracies of 80.62% and 75.45% were acquired in the Sar Cheshmeh and Seridune areas, respectively. We also used different threshold angles obtained by some statistical techniques to evaluate the efficiency of the proposed RV–A technique. Threshold angles provided by statistical techniques could not enhance the hydrothermal alteration zones around the known deposits, as good as threshold angles obtained by the RV–A technique. Since no arbitrary parameter is defined by the user in the application of the RV‐A technique, its application prevents introduction of human bias to the selection of optimum threshold angle for SAM classification.     

Carbonatite diversity in the Central Andes: the Ayopaya alkaline province,Bolivia

The Ayopaya province in the eastern Andes of Bolivia, 100 km NW of Cochabamba, hosts a Cretaceous alkaline rock series within a Palaeozoic sedimentary sequence. The alkaline rock association comprises nepheline-syenitic/foyaitic to ijolitic intrusions, carbonatite, kimberlite, melilititic, nephelinitic to basanitic dykes and diatremes, and a variety of alkaline dykes. The carbonatites display a wide petrographic and geochemical spectrum. The Cerro Sapo area hosts a small calciocarbonatite intrusion and a multitude of ferrocarbonatitic dykes and lenses in association with a nepheline-syenitic stock. The stock is crosscut by a spectacular REE-Sr-Th-rich sodalite-ankerite-baryte dyke system. The nearby Chiaracke complex represents a magnesiocarbonatite intrusion with no evidence for a relationship to igneous silicate rocks. The magnesiocarbonatite ( REE up to 1.3 wt%) shows strong HREE depletion, i.e. unusually high La/Yb ratios (520–1,500). Calciocarbonatites ( REE up to 0.5 wt%) have a flatter REE distribution pattern (La/Yb 95–160) and higher Nb and Zr contents. The sodalite-ankerite-baryte dyke system shows geochemical enrichment features, particularly in Na, Ba, Cl, Sr, REE, which are similar to the unusual natrocarbonatitic lavas of the recent volcano of Oldoinyo Lengai, Tanzania. The Cerro Sapo complex may be regarded as an intrusive equivalent of natrocarbonatitic volcanism, and provides an example for carbonatite genesis by late-stage crystal fractionation and liquid immiscibility. The magnesiocarbonatite intrusion of Chiaracke, on the other hand, appears to result from a primary carbonatitic mantle melt. Deep seated mantle magmatism/metasomatism is also expressed by the occurrence of a kimberlite dyke. Neodymium and strontium isotope data (_Nd 1.4–5.4, ⁸⁷Sr/⁸⁶ Sr<Bulk Earth) indicate a depleted mantle source for the alkaline magmatism. The magmatism of the Ayopaya region is attributed to failed rifting of western South America during the Mesozoic and represents the only occurrence of carbonatite and kimberlite rocks in the Andes.     

Role of southeastern Sanandaj–Sirjan Zone in the tectonic evolution of Zagros Orogenic Belt,Iran

Geological studies indicate that the southeastern Sanandaj–Sirjan Zone, located in the southeastern Zagros Orogenic Belt, is subdivided transversally into the Esfahan–Sirjan Block with typical Central Iranian stratigraphic features and the Shahrekord–Dehsard Terrane consisting of Paleozoic and Lower Mesozoic metamorphic rocks. The Main Deep Fault (Abadeh Fault) is a major lithospheric fault separating the two parts. The purpose of this paper is to clarify the role of the southeastern Sanandaj–Sirjan Zone in the tectonic evolution of the southeastern Zagros Orogenic Belt on the basis of geological evidence. The new model implies that Neo‐Tethys 1 came into being when the Central Iran Microcontinent split from the northeastern margin of Gondwana during the Late Carboniferous to Early Permian. During the Late Triassic a new spreading ridge, Neo‐Tethys 2, was created to separate the Shahrekord–Dehsard Terrane from Afro–Arabian Plate. The Zagros sedimentary basin was formed on a continental passive margin, southwest of Neo‐Tethys 2. The two ophiolitic belts of Naien–Shahrebabak–Baft and Neyriz were developed to the northeast of Neo‐Tethys 1 and southwest of Neo‐Tethys 2 respectively, related to the sinking of the lithosphere of the Neo‐Tethys 1 in the Late Cretaceous. It can be concluded that deposition of the Paleocene conglomerate on the Central Iran Microcontinent and Pliocene conglomerate in the Zagros Sedimentary Basin is directly linked to the uplift generated by collision.     

Cavity effect on Rayleigh wave dispersion and P-wave refraction

Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.     

Predictive value of Keetch-Byram Drought Index for cereal yields in a semi-arid environment

The study examines the potential of urban roofs to reduce the urban heat island (UHI) effect by changing their reflectivity and implementing vegetation (green roofs) using the example of the City of Vienna. The urban modelling simulations are performed based on high-resolution orography and land use data, climatological observations, surface albedo values from satellite imagery and registry of the green roof potential in Vienna. The modelling results show that a moderate increase in reflectivity of roofs (up to 0.45) reduces the mean summer temperatures in the densely built-up environment by approximately 0.25 °C. Applying high reflectivity materials (roof albedo up to 0.7) leads to average cooling in densely built-up area of approximately 0.5 °C. The green roofs yield a heat load reduction in similar order of magnitude as the high reflectivity materials. However, only 45 % of roof area in Vienna is suitable for greening and the green roof potential mostly applies to industrial areas in city outskirts and is therefore not sufficient for substantial reduction of the UHI effect, particularly in the city centre which has the highest heat load. The strongest cooling effect can be achieved by combining the green roofs with high reflectivity materials. In this case, using 50 or 100 % of the green roof potential and applying high reflectivity materials on the remaining surfaces have a similar cooling effect.     

Investigation of the atmospheric mesoscale circulation patterns and their simulation with WRF-CHEM model of the dust storm occurrence over the southern coast of the Caspian Sea

For the very first time, the mesoscale circulation patterns and synoptic-dynamic structure of the atmospheric systems that led to the dust emission to the south coast region of Caspian Sea (SCRCS) were identified and classified using the region synoptic stations’ observations of 2005–2013. Satellite measurements and images, NCEP/NCAR reanalysis data, and Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-CHEM) model products were also used in this study. Results showed that in 49 % of cases, cyclonic circulations over the Middle East deserts were the main transporter of dust particles into the atmosphere where then transferred to the SCRCS by southerly winds over the Alborz mountains in the lower troposphere and by westerly waves in the middle and upper troposphere. During the warm seasons, the surface heating lead to the development of mesoscale thermal low pressures over the hot deserts on the eastern regions of the Caspian Sea, like Turkmenistan and Qura Qum. Those heat lows were responsible for the 38 % of the occurred events. Turbulence and instabilities in the lower troposphere were identified as the second important dust emitter to the atmosphere where those dust particles transported to the SCRCS with the strong northeasterly wind. The third pattern by 13 % of cases was belonging to the mesoscale thermal low pressure that was developed over the arid regions of Iran like Dasht-é-Kavir. Because of the nature of the turbulence in the lower troposphere and heat lows, the ascent of dust particles by these two mechanisms was limited to a shallow layer in the troposphere. The results of simulation with the WRF-CHEM model, analysis of moderate resolution imaging spectroradiometer (MODIS) images, and spatial zoning of atmospheric optical depth (AOD) confirmed the results of the synoptic study.     

Microlensing by halo MACHOs with a spatially varying mass function

The main aim of microlensing experiments is to evaluate the mean mass of massive compact halo objects (MACHOs) and the mass fraction of the Galactic halo made by this type of dark matter. Statistical analysis shows that by considering a Dirac-Delta mass function (MF) for the MACHOs, their mean mass is about that of a white dwarf star. This result is, however, in discrepancy with other observations such as those of non-observed expected white dwarfs in the Galactic halo which give rise to metal abundance, polluting the interstellar medium by their evolution. Here we use the hypothesis of the spatially varying MF of MACHOs, proposed by Kerins and Evans to interpret microlensing events. In this model, massive lenses with a lower population contribute to the microlensing events more frequently than do dominant brown dwarfs. This effect causes the mean mass of the observed lenses to be larger than the mean mass of all the lenses. A likelihood analysis is performed to find the best parameters of the spatially varying MF that are compatible with the duration distribution of Large Magellanic Cloud microlensing candidates of the MACHO experiment.