Probe and SIMS investigation of clinopyroxene inclusions in chromites from the Troodos chromitites (Cyprus): Implications for dunite–chromitite genesis     

Anna Merlini  Giovanni Grieco  Luisa Ottolini  Valeria Diella 《Ore Geology Reviews》2011,41(1):22-34

Chromite ores formation is still a debated topic and, in this study, detailed analyses of major, minor elements by EMPA and Rare Earth Elements (REE) by SIMS, were performed on silicate inclusions detected in chromite grains of chromitite pods, enveloping dunites and on clinopyroxene of lherzolitic host rock of well known Trodoos chromite ores. Results show the complexity of relationships among lithologies that reflects the subtlety of genetic events and of chromite ore occurrence.Analyses of textural and chemical features have led to a better understanding of the chromite ore genetic process, that is related to a supra-subduction geodynamic setting where partial melting processes were overlapped by metasomatic events.Metasomatism, that marks the general genetic context, is characterized by the presence of a hydrated boninitic melt that favors the precipitation of chromite ores. Chromite ores, typical of ophiolite complexes and usually enveloped by dunite are, in this case, characterized by the presence of two different types of dunites whose geochemical differences are reflected by olivine mineral chemistry and by different REE patterns of analyzed clinopyroxenes. Such geochemical marks, related to different magmatic and metasomatic events, could be a main key for location of fertile or barren dunites in terms of chromite ore occurrence in the field.  相似文献   

Predictive assessment of the asbestos content in the Western Italian Alps: an essential tool for an effective approach to risk analysis and management in tunneling operations and muck reuse     

Davide Labagnara  Mario Patrucco  Piergiorgio Rossetti  Valeria Pellegrino 《Environmental Earth Sciences》2013,70(2):857-868

The modern approach to the design and management of tunnel excavation, and muck reuse, can be influenced to a great extent by the possible presence of rock formations containing asbestos minerals. This situation creates problems concerning the protection of the workers’ health and the expectable environmental criticalities, while a drastic re-consideration of the muck destination is necessary. Since, in the case of carcinogens, corrective action following exposure or dispersion is not acceptable, detailed knowledge of the characteristics of the material to be excavated is all the more essential. Only on this basis it is possible to design the tunneling operations in a prevention through design approach, so that the tunnel driving techniques, fittings and technologies, and special equipment and modus operandi, can grant, where necessary, minimized risk conditions, and make a correct decision on whether, how and when these measures must be fully activated, since such an approach involves a remarkable impact on costs and work organization. In the Western Alps a detailed identification and quantification of the asbestos content in rocks is a difficult task, due to the fact that the asbestos in the host rocks, mainly serpentinite, shows a highly variable distribution, typical of ophiolitic belts throughout the world, as it is mostly associated with joints and shear zones. The possibilities of a predictive assessment of the asbestos content in the formations to be excavated are here discussed, with special reference to the reliability of the achievable results.  相似文献   

Platform margin collapses and sequence stratigraphic organization of carbonate slopes: Cretaceous–Eocene,Gargano Promontory,southern Italy     

Alfonso Bosellini  Claudio Neri  Valeria Luciani 《地学学报》1993,5(3):282-297

We describe the sequence stratigraphic organization and the associated sedimentological characteristics of Cretaceous to Eocene slope and base-of-slope carbonate successions. The study area is located in the Gargano Promontory which belongs to the stable foreland of southern Italy. The succession consists of three superimposed depositional sequences separated by major unconformities. The upper two sequences are clear examples of sequence stratigraphic organization; in fact, they both start with huge megabreccia wedges (LST) followed upward by thin pelagic units (TST) and a thick package of calciturbidites and debrites that alternate with pelagic mudstone (HST). The Cretaceous highstand systems tract is clearly arranged in a number of coarsening-upward cycles while the Eocene one which also comprises a toplap shallow water unit, is not. The Gargano stratigraphic palimpsest and the entire margin of the Apulia Platform show remarkable similarities with present-day carbonate platform margins and slopes where irregular, convex-bankward embayments suggest large-scale failures. It is clear that classic sequence stratigraphic organization can result from simple platform dismantling, having no or little time relation with global sea-level fluctuations. In fact, as the margin failure (LST) interrupts the carbonate production, a period of starvation (TST) along the entire slope and base-of-slope follows necessarily. Finally, when the margin once again becomes active and productive, sediment exportation starts again and the system begins to prograde (HST).  相似文献   

A mechanistic approach reveals non linear effects of climate warming on mussels throughout the Mediterranean sea     

Valeria Montalto  Brian Helmuth  Paolo M Ruti  Alessandro Dell’Aquila  Alessandro Rinaldi  Gianluca Sarà 《Climatic change》2016,139(2):293-306

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Effect of degassing on sulfur contents and δ34S values in Somma-Vesuvius magmas     

Luigi Marini  Valeria Chiappini  Roberto Cioni  G. Cortecci  E. Dinelli  Claudia Principe  Giorgio Ferrara 《Bulletin of Volcanology》1998,60(3):187-194

Sulfur contents and δ³⁴S values of Somma-Vesuvius magmas are consistent with syneruptive, open-system degassing at temperatures of 800–850°C for Plinian pumices and 1100–1200°C for lavas. The extent of degassing appears to be greater in lavas than in pumices. The key parameter controlling the ³⁴S/³²S ratio of Somma-Vesuvius volcanics is the average magma oxidation state, which generally varies from 0.85 to 1.20 Δ NNO units for lavas and from 1.20 to 1.40 Δ NNO units for pumices. Consequently, S contents and δ³⁴S values of magmas constitute a potentially valuable tool in estimating their average redox conditions. The results of this study may help in risk mitigation when the Vesuvius magmatic system evolves toward eruptive conditions. Received: 20 January 1998 / Accepted: 5 May 1998  相似文献   

On the potential of an RST-based analysis of the MODIS-derived chl-a product over Condor seamount and surrounding areas (Azores,NE Atlantic)     

Emanuele Ciancia  Clara Magalhães Loureiro  Ana Mendonça  Irina Coviello  Carmine Di Polito  Teodosio Lacava  Nicola Pergola  Valeria Satriano  Valerio Tramutoli  Ana Martins 《Ocean Dynamics》2016,66(9):1165-1180

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Assessing the progress of desertification of the southern edge of Chihuahuan Desert: A case study of San Luis Potosi Plateau     

Cristina Noyola-Medrano  Valeria Abigaíl Martínez-Sías 《地理学报(英文版)》2017,27(4):420-438

The aim of this study is to establish if the San Luis Potosi Plateau (SLPP), which is part of the southern edge of the Chihuahuan Desert, is generating desertification processes, indicating a progression of the desert toward the central part of Mexico. Therefore, we analyzed the temporal evolution of four environmental indicators of desertification: Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Iron Oxides Index (IO) and Surface Temperature (ST). Landsat TM images are used to cover a period from 1990 to 2011. A new equation of total balance is proposed to generate an image of the overall evolution of each factor which is applied to get a probability map of desertification. The evolution of NDVI, NDWI and IO shows a behavior almost stable over the time. In contrast, the ST shows a slight increase. The outcomes of this study confirm periods of vegetation re-greening and 8.80% of the SLPP has the highest probability to develop desertification. The most affected area is the portion west of the region, and the east and south are the least affected areas. The results suggest a slight advance of the desert, although most of the area doesn’t have the necessary conditions to develop desertification.  相似文献   

Albian high-resolution biostratigraphy and isotope stratigraphy: The Coppa della Nuvola pelagic succession of the Gargano Promontory (Southern Italy)   总被引：1，自引：0，他引：1  

Valeria Luciani  Miriam Cobianchi  Hugh C. Jenkyns 《Eclogae Geologicae Helvetiae》2004,97(1):77-92

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Temporal correlation of magmatic-tectonic events in the lower and upper crust in north-east Australia     

Valeria Murgulov  William L. Griffin  Suzanne Y. O’Reilly 《International Journal of Earth Sciences》2012,101(5):1091-1109

Hf model ages yielded by rutiles in a garnet-rich lower-crustal granulite xenolith from the McBride Province and whole-rock Nd and Hf model ages for the plagioclase- and garnet-rich Chudleigh and McBride granulites overlap with the well-defined U–Pb ages for detrital zircons and zircons in granitoids (Murgulov et al. Chem Geol 245:198–218, 2007; Mineral Petrol 95:17–45, 2009), suggesting temporal correlation of magmatic-tectonic events in the lower and upper crust in the north-east Australian craton. Intrusion of basaltic magmas into and below the lower crust beneath the Chudleigh Province around 1.4, 1.7 and 2.3?Ga and beneath the McBride Province around 1.5, 1.7, 2.3 and 2.5?Ga provided heat for remelting and supplied magmas with juvenile mantle isotope signatures to the upper crust. Similar magmas provided enough heat to cause melting in the lower crust beneath the Chudleigh Province around 0.12 and 0.8–0.9?Ga and beneath the McBride Province around 0.42, 0.8–0.9?Ga, 1.1 and 1.3?Ga but were not sufficient to cause significant melting in the upper crust. A wide range in initial ¹⁷⁶Hf/¹⁷⁷Hf values and a ~1.55?Ga Hf model age yielded by rutiles in the McBride granulite provide a link to the genesis of ~420?Ma granitoids. The data for a plagioclase-rich granulite from the Atherton Province are similar to those for the Chudleigh and McBride granulites. However, additional samples are required to test whether the lower crust of the Tasman orogenic belt is lithologically and isotopically similar to the lower crust of the craton.  相似文献   

Discovery of marine Late Cretaceous carbonates and evaporites in the Kufra Basin (Libya) redefines the southern limit of the Late Cretaceous transgression     

Sebastian Lüning  Kai-Uwe Grfe  Dan Bosence  Valeria Luciani  Jonathan Craig 《Cretaceous Research》2000,21(6):721

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