New observations on high‐pressure phases in a shock melt vein in the Villalbeto de la Peña meteorite: Insights into the shock behavior of diopside     

Marina Martinez  Adrian J. Brearley  Josep M. Trigo‐Rodríguez  Jordi Llorca 《Meteoritics & planetary science》2019,54(11):2845-2863

The petrology and mineralogy of shock melt veins in the L6 ordinary chondrite host of Villalbeto de la Peña, a highly shocked, L chondrite polymict breccia, have been investigated in detail using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electron probe microanalysis. Entrained olivine, enstatite, diopside, and plagioclase are transformed into ringwoodite, low‐Ca majorite, high‐Ca majorite, and an assemblage of jadeite‐lingunite, respectively, in several shock melt veins and pockets. We have focused on the shock behavior of diopside in a particularly large shock melt vein (10 mm long and up to 4 mm wide) in order to provide additional insights into its high‐pressure polymorphic phase transformation mechanisms. We report the first evidence of diopside undergoing shock‐induced melting, and the occurrence of natural Ca‐majorite formed by solid‐state transformation from diopside. Magnesiowüstite has also been found as veins injected into diopside in the form of nanocrystalline grains that crystallized from a melt and also occurs interstitially between majorite‐pyrope grains in the melt‐vein matrix. In addition, we have observed compositional zoning in majorite‐pyrope grains in the matrix of the shock‐melt vein, which has not been described previously in any shocked meteorite. Collectively, all these different lines of evidence are suggestive of a major shock event with high cooling rates. The minimum peak shock conditions are difficult to constrain, because of the uncertainties in applying experimentally determined high‐pressure phase equilibria to complex natural systems. However, our results suggest that conditions between 16 and 28 GPa and 2000–2200 °C were reached.  相似文献   

From back-analysis to run-out prediction: a case study in the Western Italian Alps   总被引：3，自引：1，他引：2  

Marina Pirulli  Alessio Colombo  Claudio Scavia 《Landslides》2011,8(2):159-170

Rock avalanches are complex phenomena that occur with a low frequency but which have a high destructive potential. As a consequence, the people who are responsible for the management of a territory are more and more interested in predicting the possible evolutions of well-known potential events. Tackling the above problems from a quantitative point of view, the RASH3D code, based on continuum mechanics concepts, has been here used to predict the evolution of a potential rock avalanche in the Western Italian Alps. A calibration-based approach, in which rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of past events similar to the landslide under investigation, is proposed to set rheological parameter values to be used for prediction purposes. The back-analysis of a 2?10⁶ m³ rock avalanche located in the Divedro Valley, close to the area of the potential event, has then been analysed using both a frictional and a Voellmy rheology. The characteristics of the slope and the dynamics of the event have made the frictional rheology more suitable to come to the correct simulation of the historical case. The back-analysis results have contributed not only in the selection of the rheological parameter values but also in the choice of the type of rheological law to use in the carried out forward-analyses.  相似文献   

An example of karst catchment delineation for prioritizing the protection of an intact natural area     

Vesna Ristić Vakanjac  Zoran Stevanović  Aleksandra Maran Stevanović  Boris Vakanjac  Marina Čokorilo Ilić 《Environmental Earth Sciences》2015,74(12):7643-7653

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Curie Point Depth Estimates and Correlation with Subduction in Mexico   总被引：2，自引：0，他引：2  

Marina Manea  Vlad C. Manea 《Pure and Applied Geophysics》2011,168(8-9):1489-1499

We investigate the regional thermal structure of the crust in Mexico using Curie Point Depth (CPD) estimates. The top and bottom of the magnetized crust were calculated using the power-density spectra of the total magnetic field from the freely available ??Magnetic Anomaly Map of North America??. We applied this method to estimate the regional crustal thermal structure in overlapping square windows of 2°?×?2°. The CPD estimates range between 10 and 40?km and show several regions of relatively shallow and deep magnetic sources, with a general inverse correlation with measured heat flow. A deep CPD region (20?C30?km) is located in the fore-arc area where the subducting Cocos plate has a flat-slab geometry. This deep region is bound to the NW and SE by shallow CPD areas beneath the states of Michoacan (CPD?=?12?C16?km) and Oaxaca (CPD?=?~16?km), respectively. There is a good spatial correlation between this deep CPD area and two main fracture zones located on the incoming Cocos plate (Orozco and O??Gorman fracture zones), suggesting that subduction plays an important role in setting apart different CPD provinces along the Mexican coast. Another deep CPD (16?C32?km) area corresponds to the region where the Rivera plate subducts beneath Jalisco block. The Trans-Mexican Volcanic Belt is characterized by a decrease in Curie depths from west (16?C20?km) to east (10?C12?km). Finally, several deep CPD areas are situated in the back-arc region where old Mesozoic terrains are present. Our results suggest that the main control on the crust??s regional thermal structure in the fore-arc and volcanic arc regions is due to the subduction of the Cocos and Rivera plates beneath Mexico.  相似文献   

High‐temperature gold‐copper extraction with chloride flux in lava tubes of Tolbachik volcano (Kamchatka)     

Vadim S. Kamenetsky  Alexander Belousov  Victor V. Sharygin  Liudmila M. Zhitova  Kathy Ehrig  Michael E. Zelenski  Ilya Chaplygin  Marina A. Yudovskaya  Pavel N. Nesterenko  Sergey M. Zakharov 《地学学报》2019,31(6):511-517

Subvolcanic environments in supra‐subduction zones are renowned for hosting epithermal deposits that often contain electrum and native gold, including bonanza examples. This study examined mineral assemblages and processes occurring in shallow‐crust volcanic settings using recent eruption (2012–2013) of the basaltic Tolbachik volcano in the Kamchatka arc. The Tolbachik eruptive system is characterized by an extensive system of lava tubes. After cessation of magma input, the tubes maintained the flow of hot oxidized gases that episodically interacted with the lava surfaces and sulphate‐chloride precipitates from volcanic gases on these surfaces. The gas‐rock interaction had strong pyrometamorphic effects that resulted in the formation of molten salt, oxidized (tenorite, hematite, Cu‐rich magnesioferrite) and skarn‐like silicate mineral assemblages. By analogy with experimental studies, we propose that a combination of these processes was responsible for extraction of metals from the basaltic wall rocks and deposition of Cu‐, Fe‐ and Cu‐Fe‐oxides and native gold.  相似文献   

Biotechnology of Metal Removal from Industrial Wastewater: Zinc Case Study     

Inga Zinicovscaia  Gheorghe Duca  Liliana Cepoi  Tatiana Chiriac  Ludmila Rudi  Tatiana Mitina  Marina V. Frontasyeva  Sergey Pavlov  Svetlana F. Gundorina 《洁净——土壤、空气、水》2015,43(1):112-117

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Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review     

Charykova  Marina V.  Krivovichev  Vladimir G. 《Mineralogy and Petrology》2017,111(1):121-134

Mineralogy and Petrology - Contemporary mineralogy and geochemistry are concerned with understanding and deciphering processes that occur near the surface of the Earth. These processes are...  相似文献   

Effect of agrochemicals on macroinvertebrate assemblages in Pampasic streams,Buenos Aires,Argentina     

Marina Solis  Hernán Mugni  Silvia Fanelli  Carlos Bonetto 《Environmental Earth Sciences》2017,76(4):180

Agricultural practices have been intensified in recent decades in Argentina. The Pampa plain is the main agricultural region of the country. The effect of increased application of agrochemicals on the invertebrate fauna of the Pampasic streams remains unreported. In the present study, we compared the abundance and composition of invertebrate assemblages in seven Pampasic streams with contrasting soil use in their basins. Two streams run through intensively cropped plots, two drain basins with livestock fields, while the other three are located within a biosphere Reserve. Higher nutrient and insecticide concentrations were measured in the streams draining cropped basins, related with pesticide applications and crop fertilization. The invertebrate assemblage composition of the cropped streams differed significantly from the others and between the two. Present evidence suggests that the impact of agrochemicals results in a change in composition with decreased abundance or absence of sensitive species such as Hyalellidae, Caenidae, Baetidae and Curculionidae and increased abundance of more tolerant taxa: Ostracoda, Glossiphoniidae (Hirudinea), Ancylidae (Gundlanchia), Ampullariidae (Pomacea canaliculata), Sphaeriidae and Dugesiidae. Available information suggests that macrophyte cover and composition also influence the invertebrate assemblages of the Pampasic streams.  相似文献   

Evaluation of hydrogeochemical processes and groundwater quality for suitability of drinking and irrigation purposes: a case study in the Aosta Valley region,Italy     

Ashwani Kumar Tiwari  Raffaella Ghione  Marina De Maio  Muriel Lavy 《Arabian Journal of Geosciences》2017,10(12):264

The present study aims to discuss the hydrogeochemical processes in the Aosta Valley region and assess the quality of its groundwater for suitability of drinking and irrigation purposes. One hundred twenty-two samples were collected from the Aosta Valley region in the years 2007 and 2008 (61 per year), and analysed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, major cations and anions. The pH of the samples in both years indicated a near-neutral to alkaline nature of the groundwater. The cation and anion chemistry showed the general ionic abundance as: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and HCO₃ ^?>SO₄ ^2?>Cl^?>NO₃ ^?>F^? in both years. Ca²⁺-Mg²⁺-HCO₃ ^? and Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2? were the dominant hydrogeochemical facies. The computed saturation indices demonstrated that the groundwater was supersaturated with respect to dolomite and calcite in both years. The groundwater chemistry of the study area was mainly controlled by the dissolution of carbonate, sulphate and silicate minerals, as well as ion exchange processes. A comparison of the groundwater quality in relation to drinking water standards showed that most of the water samples were suitable for drinking and domestic uses. The computed water quality index (WQI) values of the study area groundwater ranged from 24 to 84 in the year 2007 and from 22 to 82 in the year 2008, and all the location fell under the Excellent to Good category. Quality assessment for irrigation uses revealed that the groundwater was good to permissible quality for irrigation; however, locally higher salinity, residual sodium carbonate (RSC) and magnesium hazard (MH) restricted its suitability for irrigation at a few sites. These results will be useful in implementing future measures in groundwater resource management at regional and national level.  相似文献   

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage          下载免费PDF全文

Maria Abarca  Paula Guerra  Guillermo Arce  Mauricio Montecinos  Cristian Escauriaza  Marina Coquery  Pablo Pastén 《水文研究》2017,31(2):296-307

Acid drainage is an important water quality issue in Andean watersheds, affecting the sustainability of urban, agricultural, and industrial activities. Mixing zones receiving acid drainage are critical sites where changes in pH and chemical environment promote the formation and dissolution of iron and aluminum oxy/hydroxides. These particles can significantly change the speciation of toxic metals and metalloids throughout drainage networks via sorption, desorption, and settling processes. However, little is known about the behavior of particle size distributions (PSDs) in streams affected by acid drainage and their relationship to metal speciation. This work studied: (a) the PSDs for a wide range of mixing ratios found at a fluvial confluence affected by acid drainage, and (b) the response of PSDs and arsenic speciation to environmental changes found when the particles approach complete mixing conditions. The confluence between the Azufre River (pH ~ 2, high concentration of dissolved metals) and Caracarani River (pH = 8.6, low concentration of dissolved metals) was used as a representative model for study. Field measurements show a bimodal PSD with modal diameters of ~50 and 300 μm. At shorter distances from the junction, the smaller modes with smaller particle volumes were dominant across the stream cross‐sections. A systematic shift towards larger particle sizes and larger particle volumes occurred downstream. The analysis of laboratory PSDs for Azufre/Caracarani mixing ratios between 0.01 and 0.5 (pH from 6.2 to 2.3) showed a bimodal trend with ~15 and 50 μm characteristic diameters; larger particles formed at pH>4. When particle suspensions were transferred in laboratory experiments from very low pH to full mixing conditions (pH ~ 2.8 and mixing ratio ~ 0.25) particle sizes varied, and the dissolved arsenic concentration decreased. The observed reaction kinetics were slow compared to the time scale of advective transport, creating opportunities for engineered controls for arsenic. This work contributes to a better understanding of the chemical‐hydrodynamic interactions in watersheds affected by mining, and identifying opportunities to improve water quality at points of use.  相似文献