In this work, we investigated a 3 ha sulphide-bearing waste-rock dump (Libiola Mine, Italy) using mineralogical, geochemical,
and geostatistical analyses. The dumped materials were highly heterogeneous in grain size and lithology and varied both laterally
and vertically. Other than the host rock of the ore, basalts and serpentinites, the dumped materials contained high amounts
of low-grade chalcopyrite- and pyrite-rich mineralisations. Due to these characteristics and to the absence of minerals able
to neutralise acidity, this waste-rock dump can be classified as an acid mine drainage (AMD) producer. The study confirms
that AMD is still active and, in the best scenario, can persist for up to 6.17 × 103 years. The consequences of this process are of serious environmental concern as it involves strong acidification of the circulating
waters, the release of potentially toxic metals into the soil, streams and rivers and the precipitation of huge quantities
of secondary Fe-oxides and Fe-oxyhydroxides. 相似文献
The effects of low-temperature on the crystal structure of a natural epidote [Ca1.925Fe0.745Al2.265Ti0.004Si3.037O12(OH), a = 8.8924(7), b = 5.6214(3), c = 10.1547(6)? and β = 115.396(8)° at room conditions, Sp. Gr. P21/m] have been investigated with a series of structure refinements down to 100 K on the basis of X-ray single-crystal diffraction
data. The reflection conditions confirm that the space group is maintained within the T-range investigated. Structural refinements at all temperatures show the presence of Fe3+ at the octahedral M(3) site only [%Fe(M3) = 70.6(4)% at 295 K]. Only one independent proton site was located and two possible
H-bonds occur, with O(10) as donor and O(4) and O(2) as acceptors. The H-bonding scheme is maintained down to 100 K and is
supported by single crystal room-T polarised FTIR data. FTIR Spectra over the region 4,000–2,500 cm−1 are dominated by the presence of a strongly pleochroic absorption feature which can be assigned to protonation of O(10)–O(4).
Previously unobserved splitting of this absorption features is consistent with a NNN influence due to the presence of Al and
Fe3+ on the nearby M(3) site. An additional relatively minor absorption feature in FTIR spectra can be tentatively assigned to
protonation of O(10)–O(2). Low-T does not affect significantly the tetrahedral and octahedral bond distances and angles, even when distances are corrected
for “rigid body motions”. A more significant effect is observed for the bond distances of the distorted Ca(1)- and Ca(2)-polyhedra,
especially when corrected for “non-correlated motion”. The main low-T effect is observed on the vibrational regime of the atomic sites, and in particular for the two Ca-sites. A significant reduction
of the magnitude of the thermal displacement ellipsoids, with a variation of Ueq (defined as one-third of the trace of the orthogonalised Uij tensor) by ~40% is observed for the Ca-sites between 295 and 100 K. Within the same T-range, the Ueq of the octahedral and oxygen sites decrease similarly by ~35%, whereas those of the tetrahedral cations by ~22%. 相似文献
Since Holocene time, above-mean precipitations recorded during the El Niño warm ENSO phase have been linked to the occurrence of severe debris flows in the arid Central Andes. The 2015–2016 El Niño, for its unusual strength, began driving huge and dangerous landslides in the Central Andes (32°) in the recent South Hemisphere summer. The resulting damages negatively impacted the regional economy. Despite this, causes of these dangerous events were ambiguously reported. For this reason, a multidisciplinary study was carried out in the Mendoza River valley. Firstly, a geomorphological analysis of affected basins was conducted, estimating morphometric parameters of recorded events such as velocity, stream flow, and volume. Atmospheric conditions during such events were analyzed, considering precipitations, snow cover, temperature range, and the elevation of the zero isotherm. Based on our findings, the role of El Niño on the slope instability in the Central Andes is more complex in the climate change scenario. Even though some events were effectively triggered by intense summer rainstorm following expectations, the most dangerous events were caused by the progressive uplifting of the zero isotherm in smaller basins where headwaters are occupied by debris rock glaciers. Our research findings give light to the dynamic coupled system ENSO–climate change–landslides (ECCL) at least in this particular case study of the Mendoza River valley. Landslide activity in this Andean region is driven by wetter conditions linked to the ENSO warm phase, but also to progressive warming since the twentieth century in the region. This fact emphasizes the future impact of the natural hazards on Andean mountain communities. 相似文献
In this contribution, we present a virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical
simulations with the aim to highlight the power of 3D representations in the understanding of this geological phenomenon.
In particular, samples of mixed juveniles from Salina island (Southern Italy) are reconstructed in 3D by serial lapping and
digital montage and numerical simulations are performed by using a 3D chaotic dynamical system. Natural and simulated magma
mixing structures are visualized by using several multimedia tools including animations and “virtual reality” models. It is
shown that magma interaction processes can generate large spatial and temporal compositional heterogeneities in magmatic systems.
The same topological structures are observed in both 3D reconstructed rock samples and chaotic numerical simulations, indicating
that the mixing of magmas is governed by chaotic dynamics. The use of 3D multimedia models gives the opportunity to penetrate
into magma mixing structures and to understand their significance in the context of magma dynamics. Such an approach is very
powerful since multimedia tools can strongly capture the attention of the reader bringing him/her into an interactive and
memorable geological experience.
Electronic supplementary material enclosed: 相似文献
The Concón Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Paleozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (5–12 m) and a late group of thin dikes (0.5–3 m). Two new amphibole 40Ar/39Ar dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field observations, AMS studies and petrographic data, we conclude that the emplacement of the CMDS was syntectonic with the Jurassic arc extension and associated with sinistral displacements along the NW-trending structures that host the CMDS. The common occurrence of already deformed and rotated xenoliths in the dikes indicates that deformation in the granitoids started previously.The early thick dikes and country rocks appear to have been remagnetized during the exhumation of deep-seated coastal rocks in the Early Cretaceous (around 100 Ma). The remanent magnetization in late thin dikes is mainly retained by small amounts of low-Ti magnetite at high temperature and pyrrhotite at low temperature. The magnetization in these dikes appears to be primary in origin. Paleomagnetic results from the thin dikes also indicate that the whole area was tilted 23° to the NNW during cooling of the CMDS.The NNW–SSE extension vectors deduced from the paleomagnetic data and internal fabric of dikes are different with respect to extension direction deduced for the Middle–Late Jurassic of northern Chile, pointing to major heterogeneities along the margin of the overriding plate during the Mesozoic or differences in the mechanisms driving extension during such period. 相似文献
Classical depth-integrated smoothed particle hydrodynamics (SPH) models for avalanches are extended in the present work to include a μ(I)− rheological model enriched with a fragmentation law. With this improvement, the basal friction becomes grain distribution dependent. Rock avalanches, where grain distribution tends to change with time while propagating, are the appropriate type of landslide to apply the new numerical proposal. The μ(I)− rheological models considered in the present work are those of Hatano and Gray, combined with two different fragmentation laws, a hyperbolic and a fractal-based law. As an application, Frank avalanche, which took place in Canada in 1903, is analyzed under the scope of the present approach, focusing in the influence of the rheological and fragmentation laws in the evolution of the avalanche. 相似文献
The aim of this contribution is to describe a femur (MCRS 199) assigned to Nothrotheriops sp. from the Late Pleistocene of Santa Fe Province (Argentina), and discuss the implications of this find in the context of the dispersal of ground sloths during the Great American Biotic Interchange. The specimen MCRS 199 is smaller than the femora referred to the North American species Nothrotheriops texanus and Nothrotheriops shastensis but shares several features with these species: (i) shape and position of the greater trochanter, (ii) development of the lesser trochanter, (iii) presence of connection between the third trochanter and the ectepicondyle, (iv) distal third of the femur wider, with ML/DW index of 1.93, and (v) location and relationship of the distal condyles. These similarities allow us to assign MCRS 199 to Nothrotheriops sp. The record of Nothrotheriops sp. from Santa Fe Province chronologically coincides with the earliest records of Nothrotheriops shastensis suggesting a broad geographical distribution of Nothrotheriops during the Late Pleistocene, ranging from 33–36°N (e.g. states of California and Arizona, USA) to 31°S (northern Salado River, Santa Fe Province, Argentina). Thus, Nothrotheriops have dispersed from North America (where Nothrotheriops has early records, Calabrian–Middle Pleistocene) to South America where localities bearing Nothrotheriops are Late Pleistocene in age. In addition, once in South America and probably during the Middle Pleistocene, Nothrotheriops probably gave rise to its sister taxon, Nothrotherium, with records from the Middle Pleistocene (e.g. 223 ka BP, northeastern Brazil) to the Late Pleistocene (e.g. 15 ka BP). 相似文献
Optical fibre–based sensors have now established their place in the field of geohazard monitoring due to their sensitivity to strain and temperature changes. Progressive development in the technology leads to the availability of novel, accurate and durable sensors at a relatively limited cost. This creates room for original monitoring applications that have been, so far, impeded by the shortcomings of conventional monitoring tools. In this work, we explore the applicability of an interferometric optical fibre sensor as a vibration sensing tool at laboratory scale. We tested the ability of the sensor to identify precursors of instability in a downscaled model of a rainfall-induced landslide composed of granular material. We carried out four experimental tests which involved different sensor deployments and soil mixtures. The recorded signals were processed by means of a time–frequency analysis and we identified two frequency-domain parameters—the spectral centroid and band power—that could provide information on the development of instability. Their ratio yielded a unique parameter through which a precursory stage could be outlined by defining a threshold value based on the data collected at the beginning of the experiment. In our lab tests, precursors of instability were detected 2–3 min before a crack was observed at the surface. This may upscale to a lead time of about 20–30 min or more in the field, classifying our monitoring approach in between an alarm and a warning system. The work presented here can be considered a first promising step towards an innovative monitoring system and shows the potential of optical fibre sensing as a shallow landslide monitoring technique, encouraging further testing, especially in real-case studies.