Volcanic arc of Kamchatka: a province with high-δO magma sources and large-scale O/O depletion of the upper crust     

Ilya N. Bindeman  Vera V. Ponomareva  John W. Valley 《Geochimica et cosmochimica acta》2004,68(4):841-865

We present the results of a regional study of oxygen and Sr-Nd-Pb isotopes of Pleistocene to Recent arc volcanism in the Kamchatka Peninsula and the Kuriles, with emphasis on the largest caldera-forming centers. The δ¹⁸O values of phenocrysts, in combination with numerical crystallization modeling (MELTS) and experimental fractionation factors, are used to derive best estimates of primary values for δ¹⁸O(magma). Magmatic δ¹⁸O values span 3.5‰ and are correlated with whole-rock Sr-Nd-Pb isotopes and major elements. Our data show that Kamchatka is a region of isotopic diversity with high-δ¹⁸O basaltic magmas (sampling mantle to lower crustal high-δ¹⁸O sources), and low-δ¹⁸O silicic volcanism (sampling low-δ¹⁸O upper crust). Among one hundred Holocene and Late Pleistocene eruptive units from 23 volcanic centers, one half represents low-δ¹⁸O magmas (+4 to 5‰). Most low-δ¹⁸O magmas are voluminous silicic ignimbrites related to large >10 km³ caldera-forming eruptions and subsequent intracaldera lavas and domes: Holocene multi-caldera Ksudach volcano, Karymsky and Kurile Lake-Iliinsky calderas, and Late Pleistocene Maly Semyachik, Akademy Nauk, and Uzon calderas. Low-δ¹⁸O magmas are not found among the less voluminous products of stratovolcano eruptions and these volcanoes do not show drastic changes in δ¹⁸O during their evolution. Additionally, high-δ¹⁸O(magma) of +6.0 to 7.5‰ are found among basalts and basaltic andesites of Bezymianny, Shiveluch, Avachinsky, and Koryaksky volcanoes, and dacites and rhyolites of Opala and Khangar volcanoes (7.1-8.0‰). Phenocrysts in volcanic rocks from the adjacent Kurile Islands (ignimbrites and lavas) define normal-δ¹⁸O magmas. The widespread and volumetric abundance of low-δ¹⁸O magmas in the large landmass of Kamchatka is possibly related to a combination of near-surface volcanic processes, the effects of the last glaciation on high-latitude meteoric waters, and extensive geyser and hydrothermal systems that are matched only by Iceland. Sr and Pb isotopic compositions of normal and low-δ¹⁸O, predominantly silicic, volcanic rocks show negative correlation with δ¹⁸O, similar to the trend in Iceland. This indicates that low-δ¹⁸O volcanic rocks are largely produced by remelting of older, more radiogenic, hydrothermally altered crust that suffered δ¹⁸O-depletion during >2 My-long Pleistocene glaciation. The regionally-distributed high-δ¹⁸O values for basic volcanism (ca. + 6 to +7.5‰) in Kamchatka cannot be solely explained by high-δ¹⁸O slab fluid or melt (± sediment) addition in the mantle, or local subduction of hydrated OIB-type crust of the Hawaii-Emperor chain. Overall, Nd-Pb isotope systematics are MORB-like. Voluminous basic volcanism (in the Central Kamchatka Depression in particular) requires regional, though perhaps patchy, remobilization of thick (30-45 km) Mesozoic-Miocene arc roots, possibly resulting from interaction with hot (ca. 1300°C), wedge-derived normal-δ¹⁸O, low-⁸⁷Sr/⁸⁶Sr basalts and from dehydration melting of lower crustal metabasalts, variably high in δ¹⁸O and ⁸⁷Sr/⁸⁶Sr.  相似文献   

Spatial loyalty and territorial embeddedness in the multi-sector clustering of the Berguedà region in Catalonia (Spain)     

Montserrat Pallares-Barbera  Antoni F. Tulla  Ana Vera 《Geoforum》2004,35(5):635-649

The development of clusters of local growth is supported by different processes. Endogenous economic development produced by small and medium-sized enterprises (SMEs) is based on family firms in which local market characteristics influence the sectorial diversification that emerges within certain regions. In the Berguedà region (Catalonia, Spain), the formation of a successful network of SMEs in three main sectors (food, textile and machinery) in the 1990s demonstrated the importance of grass-roots prerequisites, including industrial tradition, social networks and a sense of spatial loyalty, one of the main concepts studied in this paper. The aim of this paper is to study how institutions, local economic networks and collective social agents generate a propitious economic space that constitutes favourable embedding in Berguedà. However, the key element in this industrial system is the loyalty that entrepreneurs and workers feel towards their industrial region. These two processes, territorial embeddedness and spatial loyalty, appear to be two of the major forces behind the economic dynamism of the region and have led to the formation of a new cluster of firms.  相似文献   

Boundary assessment under uncertainty: A case study     

Vera Pawlowsky  Ricardo A. Olea  John C. Davis 《Mathematical Geology》1993,25(8):1075-1076

  相似文献   

Analysis of the pipe depth development in small-scale backward erosion piping experiments     

Vandenboer  Kristine  van Beek  Vera M.  Bezuijen  Adam 《Acta Geotechnica》2019,14(2):477-486

Acta Geotechnica - Backward erosion piping is an important failure mechanism for water-retaining structures. It results in the formation of shallow pipes at the interface of a sandy or silty...  相似文献   

Shakemaps uncertainties and their effects in the post-seismic actions for the 2012 Emilia (Italy) earthquakes     

Giovanna Cultrera  Licia Faenza  Carlo Meletti  Vera D’Amico  Alberto Michelini  Alessandro Amato 《Bulletin of Earthquake Engineering》2014,12(5):2147-2164

The May 20, 2012, Emilia Ml 5.9 earthquake was followed by some major aftershocks, well recorded by a large number of temporary stations that were installed to monitor the sequence. These additional recordings allowed us a thorough testing of the performance of the ShakeMap—a procedure designed to provide rapid information on the experienced ground motion. We found that the shakemaps for the May 29, 2012, Ml 5.8 earthquake, obtained using the permanent stations only, underestimate significantly the ground motion computed with the highest station density, especially for PSA at long periods (T \(=\) 3.0 s). This low-frequency motion is controlled primarily by the surface waves recorded in the Po plain: the observed site effects are likely not accounted properly by the site correction coefficient based on Vs30 as implemented in the ShakeMap procedure. The shakemaps determined during the seismic sequence have been included in an Italian national law that was passed after the 2012 earthquake. According to this law, the factories safety verifications were bound to the comparison between the shakemaps and the design acceleration required by the current national seismic code. We then decide to appraise the impact of the shakemap accuracy on the law provisions. Following the law recommendations, we have estimated the possible errors resulting from the incomplete evaluation of the ground shaking: our results show that, if the complete dataset were available at the time of the law approval, the number of buildings for which the safety check was required would have been significantly smaller.  相似文献   

The Alpine Seed Conservation and Research Network–a new initiative to conserve valuable plant species in the European Alps     

Jonas V. Müller  Christian Berg  Jacqueline Détraz-Méroz  Brigitta Erschbamer  Noémie Fort  Catherine Lambelet-Haueter  Vera Margreiter  Florian Mombrial  Andrea Mondoni  Konrad Pagitz  Francesco Porro  Graziano Rossi  Patrick Schwager  Elinor Breman 《山地科学学报》2017,14(4):806-810

Safeguarding plants as seeds in ex situ collections is a cost effective element in an integrated plant conservation approach. The European Alps are a regional centre of plant diversity. Six institutions have established a regional network covering the European Alps which will conserve at least 500 priority plant species and which will improve the conservation status of plant species in grassland communities in the subalpine, alpine and nival altitudinal belts. Targeted research will expand the knowledge of the ecology of target species. Public engagement activities will raise the awareness for the importance of specific conservation actions in the European Alps.  相似文献   

Reproductive seasonality of the fish fauna and limnoecology of semi-arid Brazilian reservoirs   总被引：1，自引：1，他引：0  

Sathyabama Chellappa  Regina M.X. Bueno  Thiago Chellappa  Naithirithi T. Chellappa  Vera Maria Fonseca Almeida e Val 《Limnologica》2009,39(4):325-329

The native fish fauna commonly found in the drainage basins of rivers and reservoirs of Latin America, including those of the semi-arid Northeastern Brazil, are representatives of the Neotropical region. This work reports on the reproductive ecology of five commercially important and consumable native fish species, in relation to rainfall and hydrological variables of the semi-arid reservoirs in Brazil. Pluviometric precipitation, temperature, pH, dissolved oxygen and electrical conductivity of the water were registered, and maturation of fish gonads was assessed on a monthly basis. This region is characterized with short spells of rain interspersed with long dry season and rainfall seems to be the main environmental factor which modulates the timing of the spawning period of fish. Construction of reservoirs without adequate facilities for fish migration has an adverse impact on the migratory fish species which are of commercial and ecological importance to semi-arid Northeastern Brazil.  相似文献   

A WebGis tool for seismic hazard scenarios and risk analysis     

Vera Pessina  Fabrizio Meroni 《Soil Dynamics and Earthquake Engineering》2009

The WebGis development represents a natural answer to the growing requests for dissemination and use of geographical information data. WebGis originates from a combination of web technology and the Geographical Information System, which is a recognised technology that is mainly composed of data handling tools for storage, recovery, management and analysis of spatial data. Here, we illustrate two examples of seismic hazard and risk analysis through the WebGis system in terms of architecture and content. The first presents ground shaking scenarios associated with the repetition of the earthquake that struck the Lake of Garda area (northern Italy) in 2004. The second shows data and results of a more extensive analysis of seismic risk in the western part of the Liguria region (north-western Italy) for residential buildings, strategic structures and historic architecture. The adoption of a freeware application (ALOV Map) assures easy exportability of the WebGis structures for projects dealing with natural hazard evaluation.  相似文献   

A latent class MDS model with spatial constraints for non-stationary spatial covariance estimation   总被引：3，自引：3，他引：0  

J. F. Vera  R. Macías  J. M. Angulo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(6):769-779

Multidimensional scaling (MDS) has played an important role in non-stationary spatial covariance structure estimation and in analyzing the spatiotemporal processes underlying environmental studies. A combined cluster-MDS model, including geographical spatial constraints, has been previously proposed by the authors to address the estimation problem in oversampled domains in a least squares framework. In this paper is formulated a general latent class model with spatial constraints that, in a maximum likelihood framework, allows to partition the sample stations into classes and simultaneously to represent the cluster centers in a low-dimensional space, while the stations and clusters retain their spatial relationships. A model selection strategy is proposed to determine the number of latent classes and the dimensionality of the problem. Real and artificial data sets are analyzed to test the performance of the model.  相似文献   

Editorial: Clean Soil Air Water 1/2009     

Vera Köster 《洁净——土壤、空气、水》2009,37(1):9-10

  相似文献