Detrital provenance of the Grenvillian Oaxacan Complex,southern Mexico: a zircon perspective     

Luigi A. Solari  Fernando Ortega-Gutiérrez  Mariano Elías-Herrera  Carlos Ortega-Obregón  Consuelo Macías-Romo  Margarita Reyes-Salas 《International Journal of Earth Sciences》2014,103(5):1301-1315

The Oaxacan Complex is the largest exposure of Grenvillian-age rocks in Mexico, constituting the backbone of the Oaxaquia microcontinent. Whereas the main rock-forming events were previously established at 1,150–1,200 Ma (charnockite–syenite–gabbros), 1,020 Ma (AMCG suite), 990 Ma (granulite-facies metamorphism), and ca. 970 Ma post-tectonic pegmatites, no data are yet available to establish provenance links with other Grenville-age terranes. In this work, we studied detrital zircons belonging to 12 samples, all metamorphosed under granulite facies but variably affected by retrogression. Laser ablation inductively coupled plasma mass spectrometry U–Pb geochronology was employed on selected zircons to determine their crystallization age and geochemistry. The results of the analysis of about 100 crystals per sample show that the studied zircons range between ca. 940 and 1,400 Ma, with only three samples having zircons between 1,400 and 1,600 Ma, and only one showing older zircons up to ca. 1,775 Ma. Whereas some of the slightly discordant (1–5 %) zircons in several samples show ages younger than the granulite metamorphism (probably as a result of Pb loss), and thus a disturbed geochemical pattern (abnormal enrichment in LREE, decreasing HREE), a few metamorphic zircons show flat and depleted HREE patterns, contrasting with the igneous pattern of older zircons (positive Ce anomaly, negative Eu anomaly, enriched HREE pattern). The main distributions observed using the kernel density estimator diagrams fall in the range 975–995 Ma (six samples), 1,100 Ma (four samples) and 1,120–1,170 Ma (six samples). Only the southernmost sample shows a marked peak at ca. 1,400 Ma. The application of the Kolmogorov–Smirnov (K–S) statistical test to the studied samples and particularly the comparison of obtained P values yield interesting similarities. Overall, two sample groups show internal similarities, i.e., they may belong to the same source area, whereas only one sample is dissimilar, failing to pass the K–S test. Comparison of these data with the timing of comparable events in the Sveconorwegian orogens, the Sunsas and Rondonia-San Ignacio belts of Amazonia, and some of the Precambrian massifs cropping out in the Andes help to constrain possible Mesoproterozoic conjugate margins of Oaxaquia.  相似文献   

Accurate 3D surface measurement of mountain slopes through a fully automated image-based technique   总被引：1，自引：1，他引：0  

Mattia Previtali  Luigi Barazzetti  Marco Scaioni 《Earth Science Informatics》2014,7(2):109-122

In this paper an automated procedure for surface reconstruction that can be used for surveying and monitoring rock and ground slopes is presented. This method has been developed for geological and engineering applications, where accuracy and completeness are factors of primary importance for the final 3D model, which must provide a detailed metric survey and not only a visual reconstruction of the scene. The proposed procedure integrates two image matching techniques. The first one is used to automatically extract a set of tie points that are needed for computing the exterior orientation parameters of all images through a photogrammetric bundle adjustment. Such tie oints are also exploited to obtain a preliminary seed model that is then enriched based on Multi-photo Least Squares Matching. During this second stage, the surface model is improved in terms of point density and accuracy. Different strategies were implemented to successfully combine both techniques, along with some new improvements. The presented procedure has been tested in two different applications: geometric modelling of rock cliffs and evaluation of weathering of a ground slope. In both cases the obtained results presented accuracy sufficient for geological investigation. Moreover, outcomes were comparable to the ones from laser scanning surveying and other photogrammetric implementations.  相似文献   

Geometric and kinematic characterization of landslides affecting urban areas: the Lungro case study (Calabria,Southern Italy)     

Giovanni Gullà  Dario Peduto  Luigi Borrelli  Loredana Antronico  Gianfranco Fornaro 《Landslides》2017,14(1):171-188

The geometric and kinematic characterization of landslides affecting urban areas is a challenging goal that is routinely pursued via geological/geomorphological method and monitoring of ground displacements achieved by geotechnical and, more recently, advanced differential interferometric synthetic aperture radar (A-DInSAR) data. Although the integration of all the above-mentioned methods should be planned a priori to be more effective, datasets resulting from the independent use of these different methods are commonly available, thus making crucial the need for their standardized a posteriori integration. In this regard, the present paper aims to provide a contribution by introducing a procedure that, taking into account the specific limits of geological/geomorphological analyses and deep/surface ground displacement monitoring via geotechnical and A-DInSAR data, allows the a posteriori integration of the results by exploiting their complementarity for landslide characterization. The approach was tested in the urban area of Lungro village (Calabria region, southern Italy), which is characterized by complex geological/geomorphological settings, widespread landslides and peculiar urban fabric. In spite of the different level of information preliminarily available for each landslide as result of the independent use of the three methods, the implementation of the proposed procedure allowed a better understanding and typifying of the geometry and kinematics of 50 landslides. This provided part of the essential background for geotechnical landslide models to be used for slope stability analysis within landslide risk mitigation strategies.  相似文献   

Petrophysical and mechanical properties of Euganean trachyte and implications for dimension stone decay and durability performance     

Luigi Germinario  Siegfried Siegesmund  Lara Maritan  Claudio Mazzoli 《Environmental Earth Sciences》2017,76(21):739

Euganean trachyte is a subvolcanic porphyritic rock extracted in northern Italy with an age-old tradition of use as dimension stone, historically linked, in particular, to the fervent building activity brought by the Roman Empire and, later on, the Republic of Venice Serenissima. The results of a comprehensive petrophysical and mechanical characterization of Euganean trachyte from the most representative quarries are discussed here, involving the following properties: density, porosity, water absorption, capillary water uptake, hygroscopic water adsorption, hydric/hygric dilatation, water vapor diffusion, thermal expansion, and resistance to salt attack and abrasion. The different trachyte varieties, although belonging to the same quarry basin, exhibit a relatively wide array of technical performances, which are strongly dependent on pore volume, size, size distribution, shape, and degree of interconnection, controlling modes and rates of water transport and retention. Therefore, indications are provided for evaluating durability performance of the stone, with stress on water-driven weathering. Complementary information is finally given on the possible criteria followed in the antiquity for properly selecting the trachyte quarries to be exploited, and by a comparison with the properties of the most important trachytes extracted in Europe.  相似文献