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《Geoforum》2016
This article continues and expands the conversation initiated by Jørgensen on the need to rethink rewilding, which elicited a response from Prior and Ward. To spur further conversation, my response to both papers argues for two modes of discourse expansion: geographical and disciplinary. Although both articles gesture toward global rewilding sites, their discussions remain focused on European geographies. I offer James Feldman’s environmental history of the Apostle Islands to extend a geographical purview beyond European contexts. Secondly, I take up these papers’ implicit call for humanities scholars to join this conversation, and I argue for the relevance and importance of fictional writings to a debate regarding rewilding. I briefly introduce two recent fictional works and argue for their place in rewilding conversations based on the ability of imaginary writings to develop empathy. 相似文献
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The Neoarchean (ca. 2.75 Ga) Luanga Complex, located in the Carajás Mineral Province in Brazil, is a medium-size layered intrusion consisting, from base to top, of ultramafic cumulates (Ultramafic Zone), interlayered ultramafic and mafic cumulates (Transition Zone) and mafic cumulates (Mafic Zone). Chromitite layers in the Luanga Complex occur in the upper portion of interlayered harzburgite and orthopyroxenite of the Transition Zone and associated with the lowermost norites of the Mafic Zone. The stratigraphic interval that hosts chromitites (∼150 meters thick) consists of several cyclic units interpreted as the result of successive influxes of primitive parental magma. The compositions of chromite in chromitites from the Transition Zone (Lower Group Chromitites) have distinctively higher Cr# (100Cr/(Cr + Al + Fe3+)) compared with chromite in chromitites from the Mafic Zone (Upper Group Chromitites). Chromitites hosted by noritic rocks are preceded by a thin layer of harzburgite located 15–20 cm below each chromitite layer. Lower Cr# in chromitites hosted by noritic rocks are interpreted as the result of increased Al2O3 activity caused by new magma influxes. Electron microprobe analyses on line transverses through 35 chromite crystals indicate that they are rimmed and/or extensively zoned. The composition of chromite in chromitites changes abruptly in the outer rim, becoming enriched in Fe3+ and Fe2+ at the expense of Mg, Cr, Al, thus moving toward the magnetite apex on the spinel prism. This outer rim, characterized by higher reflectance, is probably related to the metamorphic replacement of the primary mineralogy of the Luanga Complex. Zoned chromite crystals indicate an extensive exchange between divalent (Mg, Fe2+) cations and minor to none exchange between trivalent cations (Cr3+, Al3+ and Fe3+). This Mg-Fe zoning is interpreted as the result of subsolidus exchange of Fe2+ and Mg between chromite and coexisting silicates during slow cooling of the intrusion. A remarkable feature of chromitites from Luanga Complex is the occurrence of abundant silicate inclusions within chromite crystals. These inclusions show an adjacent inner rim with higher Cr# and lower Mg# (100 Mg/(Mg + Fe2+)) and Al# (100Al/(Cr + Al + Fe3+)). This compositional shift is possibly due to crystallization from a progressively more fractionated liquid trapped in the chromite crystal. Significant modification of primary cumulus composition of chromite, as indicated in our study for the Luanga Complex, is likely to be common in non-massive chromitites and the rule for disseminated chromites in mafic intrusions. 相似文献
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《Geoforum》2017
This paper explores the circulation of images and words about fish that has been certified or endorsed as ‘sustainable seafood’. Specifically, our discourse analysis – of data collected from online, magazine, and television media sources targeted at North Americans – interrogates the constitution of sustainable seafood as a tenable solution to fisheries limits. We reveal three narratives populated by different messages and personalities that describe spaces of fish harvest, crisis, and consumption. By exploring the multifaceted ways that prominent organization National Geographic mediates sustainable seafood, we also show that the narratives rest easily with each other, and when taken together, present what seems like a cohesive set of cultural instructions for viewers and readers. Throughout, we question what is not present in the narratives and highlight how sustainable seafood as a cultural phenomenon opens up new material and political-economic opportunities for some. In sum, we trace a cultural politics that constitutes sustainable seafood as a tenable solution to fisheries limits, obscures the complexities of industrial fisheries, and generates new opportunities for accumulation. Our analysis and discussion pushes research regarding the contemporary cultural politics of sustainability towards an array of media organizations and formats and encourages further consideration of intimate identity politics. 相似文献
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Paul William Kojo Yankson Alex Barimah Owusu George Owusu John Boakye-Danquah Jacob Doku Tetteh 《Natural Hazards》2017,85(2):691-707
In this paper, the extent to which the potentially transit-dependent portion of the population is vulnerable to the effects of a hurricane is estimated. The vulnerability of an area is defined as a composite measure of the proportion of disadvantaged persons, distance to transit, and flooding potential of people within an area. Unlike past studies which have focused on the vulnerability of the population in relatively large geographic areas, this study estimates the vulnerability of the population in 30 m × 30 m areas as defined in the National Land Cover Database. Population estimates from the national census at block level are disaggregated to the 30 m × 30 m units using a modified dasymetric mapping method in ArcGIS. The modified mapping method assigns population to each small areal unit using weights estimated by regressing the area of each land use in a census block against the population in that block. The coefficients in the regression analysis are “weights” associating population with each land use, and are used to distribute the population in each census block to the small geographic units based on their land use. In a case study of New Orleans, the results show that some areas are not well served by the existing transit pickup locations, as evidenced by their high vulnerability scores. Reassignment of pickup point locations to cover higher vulnerability score areas was investigated using integer linear programming. The results show that the optimally located pickup points serve areas with a larger average vulnerability score than the current pickup points in the study area. The method appears to be helpful in identifying vulnerable areas that, subsequently, could receive improved hurricane evacuation service in the future. 相似文献
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In arid and semi-arid countries worldwide, conflicts between human development activities and conservation of groundwater resources are widespread and attract many public debates. This research aims to propose groundwater management alternatives for a coastal aquifer by studying its vulnerability and in particularly the risk of seawater intrusion. An additional objective is to propose some agricultural policies aimed to conserve groundwater resources in Mahdia and Ksour Essaf. Intensive groundwater mining, for irrigation and for water drinking, has caused an overexploitation of the water resources. In addition, the degradation of water quality, caused by septic tanks and intensive agricultural activities, has given rise to notable crucial state of the groundwater resources. With the aim of tackling the groundwater degradation problem, integration into a common platform of vulnerability assessment, seawater intrusion modelling and hydrochemical analysis is proposed. This platform can considerably reflect the water resources state in order to propose some solutions reducing the contamination of the Mahdia–Ksour Essaf aquifer. The groundwater management alternatives, proposed in this study, were prepared within a geographical information system. 相似文献
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《Applied Geochemistry》1993,8(4):339-356
The abundant data available on the geochemistry and mineralogy of the Herynian gold deposit of Le Chaˆtelet (Massif Central, France) formed the basis for an analysis of the complex signature of a gold deposit and its hydrothermal alteration haloes. This study describes the deposit and its environment at various scales.The sulfide paragenesis of the Le Chaˆtelet deposit resulted from several stages, one of which was an event responsible for the deposition of Au-bearing arsenopyrite quartz veins; the Au is contained within the arsenopyrite lattice. Hydrothermal activity associated with these veins produced two superimposed alteration haloes: an outer halo of kaolinite + tosudite + siderite alteration that developed at the expense of the plagioclase minerals, and an inner halo of illite±siderite alteration that affected all the minerals. The hydrothermal alteration was followed by silicification of the wall rocks and then deposition of the Au-bearing arsenopyrite.The hydrothermal alteration related to the event also generated geochemical signatures such as Li, B, LREE, As, Sb, Au and W anomalies. Mineralogical studies and geochemical analyses of the hydrothermal facies show that: (1) the anomalous Li is trapped mainly in the tosudite lattice and to a lesser degree in the illite lattice; and (2) the B is probably located in tosudite and illite lattices. Arsenic, Sb and Au are contained in the arsenopyrite lattice.During weathering, the lithochemical signatures (determined by the analytical techniques used in this study) lose some of their specific characteristics, depending on the original concentrations. At deposit scale (0.25–1.0 km2), B and Li in the soill profiles indicate zones of hydrothermal alteration, whereas As and Au indicate zones of mineralization. At a regional scale, the association of Au, Li and B in stream sediments is characteristics of this type of mineralization. Therefore, in the hydrothermal setting described at Le Chaˆtelet, Au, As, Li and B appear, at all scales, to be dependable pathfinders for Au-bearing hydrothermal systems of possible economic interest. 相似文献
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Doklady Earth Sciences - An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X22340037 相似文献
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The Bastar craton in central India, surrounded by cratonic blocks and Paleoproterozoic to Neoproterozoic orogenic belts, is a window to investigate the Archean-Paleoproterozoic crustal evolution and tectonic processes. Here we propose a new tectonic classification of the craton into the Western Bastar Craton (WBC), Eastern Bastar Craton (EBC), and the intervening Central Bastar Orogen (CBO). We present petrologic, geochemical and zircon U-Pb, REE and Lu-Hf data from a suite of rocks from the CBO and along the eastern margin of the WBC Including: (1) volcanic successions comprising meta-andesite and fine-grained amphibolite, representing arc-related volcanics along a convergent margin; (2) ferruginous sandstone, in association with rhyolite, representing a volcano-sedimentary succession, deposited in an active trench; and (3) metamorphosed mafic-ultramafic suite including gabbro, pyroxenite and dunite invaded by trondhjemite representing the section of sub-arc mantle and arc root adjacent to a long-lasting subduction system. Petrologic studies indicate that the mafic-ultramafic suite crystallized from an island arc tholeiitic parental magma in a suprasubduction zone environment. The chondrite-normalized and primitive mantle normalized diagrams of the mafic and ultramafic rocks suggest derivation from MORB magma. The mixed characters from N-MORB to E-MORB of the studied samples are consistent with subduction modification of a MORB related magma, involving partial melting of the metasomatized mantle wedge. Our zircon U-Pb age data suggest that the cratonic nuclei was constructed as early as Paleoarchean. We present evidence for active subduction and arc magmatism through Mesoarchean to Neoarchean and early Paleoproterozoic, with the trench remaining open until at least 2.3 Ga. Two major crust building events are recognized in the Bastar craton: during Mesoarchean (recycled Paleoarchean subduction-related as well as juvenile/depleted mantle components) and Neoarchean (accretion of juvenile oceanic crust, arc magmatism including granite batholiths and related porphyry mineralization). The final cratonization occurred during latest Paleoproterozoic, followed by collisional assembly of the craton and its incorporation within the Peninsular Indian mosaic during Mesoproterozoic. In the global supercontinent context, the craton preserves the history of Ur, the earliest supercontinent, followed by the Paleo-Mesoproterozoic Columbia, as well as minor thermal imprints of the Neoproterozoic Rodinia and associated Grenvillian orogeny. 相似文献
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Heather M. Murphy Morgan D. Prioleau Mark A. Borchardt Paul D. Hynds 《Hydrogeology Journal》2017,25(4):981-1001
Globally, approximately 2.2 billion people rely on groundwater for daily consumption. It is widely accepted that groundwater is more pristine than surface water but while this assumption is frequently the case, groundwater is not ubiquitously free of contaminants; accordingly, this presumption can result in an unfounded and potentially hazardous sense of security among owners, operators and users. The current paper presents a review of published literature providing epidemiological evidence of the contribution of groundwater to global human enteric infection. An emphasis is placed on enteric pathogens transmitted via the faecal-oral route, and specifically those associated with acute gastrointestinal illness (AGI). The review identified 649 published groundwater outbreaks globally between 1948 and 2013 and several epidemiological studies that show there is an increased risk of AGI associated with the consumption of untreated groundwater. The review identified that the following five pathogens were responsible for most outbreaks: norovirus, Campylobacter, Shigella, Hepatitis A and Giardia. Crudely, the authors estimate that between 35.2 and 59.4 million cases of AGI per year globally could be attributable to the consumption of groundwater. Although groundwater is frequently presumed to be a microbiologically safe source of water for consumption, this review demonstrates that consumers served by an untreated groundwater supply remain at risk to enteric disease. The authors conclude that collaboration between microbiologists, hydrogeologists and epidemiologists is needed to better understand pathogen occurrence, persistence, detection and transport in groundwater as well as build stronger epidemiological evidence documenting the true magnitude of disease associated with groundwater globally. 相似文献