The supergene origin of ruthenian hexaferrum in Ni‐laterites          下载免费PDF全文

Thomas Aiglsperger  Joaquín A. Proenza  Salvador Galí  Jordi Rius  Francisco Longo  Cristina Domènech 《地学学报》2017,29(2):106-116

For two decades, the nature of Fe‐rich, oxygen‐bearing, Ru–Os compounds found in the supergene environment has been debated. Ru–Os–Fe‐oxides and nano‐intergrowths of ruthenium with magnetite have been proposed. We applied FE‐SEM, EMPA, μ‐Raman spectroscopy and synchrotron tts‐μXRD to Ru–Os–Fe compounds recovered from Ni‐laterites from the Dominican Republic. The results demonstrate that a significant portion of Fe exists in a common structure with the Ru–Os alloy, that is, ruthenian hexaferrum. This mineral occurs both as nanoparticles and as micrometric patches within a matrix of Fe‐oxide(s). Our data suggest that supergene ruthenian hexaferrum with a (Ru_0.4(Os,Ir)_0.1Fe_0.5)_?1.0 stoichiometry represents the most advanced weathering product of primary laurite within Ni‐laterites from the Dominican Republic.  相似文献   

Incorporating climate change and morphological uncertainty into coastal change hazard assessments     

Heather M. Baron  Peter Ruggiero  Nathan J. Wood  Erica L. Harris  Jonathan Allan  Paul D. Komar  Patrick Corcoran 《Natural Hazards》2015,75(3):2081-2102

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Estimation of flood damage functions for river basin planning: a case study in Bangladesh     

Y. C. Ethan Yang  Patrick A. Ray  Casey M. Brown  Abedalrazq F. Khalil  Winston H. Yu 《Natural Hazards》2015,75(3):2773-2791

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Modeling defects and plasticity in MgSiO3 post-perovskite: Part 1—generalized stacking faults     

Alexandra M. Goryaeva  Philippe Carrez  Patrick Cordier 《Physics and Chemistry of Minerals》2015,42(10):781-792

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Long-term hydrological,biogeochemical, and climatological data from Walker Branch Watershed,East Tennessee,USA     

Natalie A. Griffiths  Patrick J. Mulholland 《水文研究》2021,35(3):e14110

In 1967, the original Walker Branch Watershed (WBW) project was established to study elemental cycling and mass balances in a relatively unimpacted watershed. Over the next 50+ years, findings from additional experimental studies and long-term observations on WBW advanced understanding of catchment hydrology, biogeochemistry, and ecology and established WBW as a seminal site for catchment science. The 97.5-ha WBW is located in East Tennessee, USA, on the U.S. Department of Energy's Oak Ridge Reservation. Vegetation on the watershed is characteristic of an eastern deciduous, second-growth forest. The watershed is divided into two subcatchments: the West Fork (38.4 ha) and the East Fork (59.1 ha). Headwater streams draining these subcatchments are fed by multiple springs, and thus flow is perennial. Stream water is high in base cations due to weathering of dolomite bedrock and nutrient concentrations are low. Long-term observations of climate, hydrology, and biogeochemistry include daily (1969–2014) and 15-min (1994–2014) stream discharge and annual runoff (1969–2014); hourly, daily, and annual rainfall (1969–2012); daily climate and soil temperature (1993–2010); and weekly stream water chemistry (1989–2013). These long-term datasets are publicly available on the WBW website (https://walkerbranch.ornl.gov/long-term-data/ ). While collection of these data has ceased, related long-term measurements continue through the National Ecological Observatory Network (NEON), where WBW is the core terrestrial and aquatic site in the Appalachian and Cumberland Plateau region (NEON's Domain 7) of the United States. These long-term datasets have been and will continue to be important in evaluating the influence of climatic and environmental drivers on catchment processes.  相似文献   

A gridded sea surface salinity data set for the tropical Pacific with sample applications (1950–2008)     

T. Delcroix  G. Alory  S. Cravatte  T. Corrège  M.J. McPhaden 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):38-48

We present a gridded data set of Sea Surface Salinity (SSS) for the tropical Pacific (120°E–70°W; 30°N–30°S), with a grid resolution of 1° longitude, 1° latitude and 1 month, from 1950 to 2008. The product, together with its associated error field, is derived from an objective analysis of about 10 million validated SSS records, with most of the data originating from Voluntary Observing Ships, TAO/TRITON moorings and Argo profilers (during the most recent period). We expect this product to benefit studies in oceanography, meteorology and paleoceanography. As examples of applications, we analyse: (a) the seasonal and ENSO (El Niño Southern Oscillation) modes of observed SSS variability, (b) the ability of 23 coupled models used in the Intergovernmental Panel for Climate Change 4th Assessment Report (IPCC AR4) to simulate the mean SSS and these two time varying modes, and (c) the usefulness of the SSS product and of its associated error field in calibrating and validating the paleo-salinity time series. We anticipate improvements and regular updates to our product, as more SSS data become available from in situ networks and from the ongoing and near-future satellite-derived observations by SMOS (Soil Moisture and Ocean Salinity) and Aquarius.  相似文献   

Comparing landslide susceptibility models in the Río El Estado watershed on the SW flank of Pico de Orizaba volcano,Mexico     

Gabriel Legorreta Paulín  Solène Pouget  Marcus Bursik  Fernando Aceves Quesada  Trevor Contreras 《Natural Hazards》2016,80(1):127-139

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Intra-interstadial environmental changes in Last Glacial loess revealed by molluscan assemblages from the Upper Palaeolithic site of Amiens-Renancourt 1 (Somme,France)     

Olivier Moine  Pierre Antoine  Sylvie Coutard  Gilles Guérin  Christine Hatté  Clément Paris  Ségolène Saulnier-Copard 《第四纪科学杂志》2021,36(8):1322-1340

The Amiens-Renancourt 1 site recently yielded one of the most important Upper Palaeolithic human occupations of northern France by the number of flint artefacts and especially by the presence of Venus figurines. All the material comes from a single archaeological layer located in a tundra gley bracketed by loess units. A multi-proxy study combining a detailed stratigraphy, luminescence and radiocarbon datings and high-resolution (5 cm per sample) grain size and molluscan analyses was therefore carried out to reconstruct and date the associated environmental changes and to determine the exact context of the human occupation. The chronological frame thus established supports the correlations of the archaeology-bearing tundra gley and of an underlying arctic brown soil with Greenland interstadials GI-4 and GI-3. Composition changes in the molluscan population enabled the identification of transitional and optimum phases and sub-phases within these two pedogenetic horizons. A conceptual correlation model linking molluscan phases with millennial-scale variations of Greenland ice-core and Sieben Hengste speleothem climate records is proposed. The Human occupation appears contemporaneous to the end of the stadial–interstadial transition of GI-3. Synchronous in Amiens-Renancourt 1 and Nussloch, subsequent micro-gleys may also result from a regional/global forcing. Such a level of detail is unprecedented in a loess sequence.  相似文献   

A CO2-rich gas trigger of explosive paroxysms at Stromboli basaltic volcano,Italy     

Patrick Allard 《Journal of Volcanology and Geothermal Research》2010,189(3-4):363-374

In addition to rhythmic slug-driven Strombolian activity, Stromboli volcano occasionally produces discrete explosive paroxysms (2 per year on average for the most frequent ones) that constitute a major hazard and whose origin remains poorly elucidated. Partial extrusion of the volatile-rich feeding basalt as aphyric pumice during these events has led to consider their triggering by the fast ascent of primitive magma blobs from possibly great depth. Here I examine and discuss the alternative hypothesis that most of the paroxysms could be triggered and driven by the fast upraise of CO₂-rich gas pockets generated by bubble foam growth and collapse in the sub-volcano plumbing system. Data for the SO₂ and CO₂ crater plume emissions are used to show that Stromboli's feeding magma may originally contain as much as 2 wt.% of carbon dioxide and early coexists with an abundant CO₂-rich gas phase with high CO₂/SO₂ molar ratio (≥ 60 at 10 km depth below the vents, compared to ～ 7 in time-averaged crater emissions). Pressure-related modelling indicates that the time-averaged crater gas composition and output are well accounted for by closed system decompression of the basalt–gas mixture until the volcano–crust interface (～ 3 km depth), followed by open degassing and crystallization in the volcano conduits. However, both the low viscosity and high vesicularity of the basaltic magma permit bubble segregation and bubble foam growth at deep sill-like feeder discontinuities and at shallower physical boundaries (such as the volcano–crust interface) where the gas-rich aphyric basalt interacts with the unerupted crystal-rich and viscous magma drained back from the volcano conduits. Gas pressure build-up and bubble foam collapse at these boundaries will intermittently trigger the sudden upraise of CO₂-rich gas blobs that constitute the main driving force of the paroxysms. Deeper-sourced gas blobs, driving the most powerful explosions, will be the richest in CO₂ and have highest CO₂/SO₂ ratios. This mechanism is shown to account well for the dynamic, seismic and petrologic features of Stromboli's paroxysms and, hence, to provide a potential alternative interpretation for their genesis and their forecasting. Enhanced bubble foam leakage prior to a paroxysm, or foam emptying in several steps, should lead indeed to precursory upstream of CO₂-rich gas and increasing CO₂/SO₂ ratio in crater plume emissions. The recent detection of such signals prior to two explosions in December 2006 and March 2007 strongly supports this expectation and the model proposed in this study.  相似文献   

Subalpine fires: the roles of vegetation,climate and,ultimately, land uses     

Bérangère Leys  Christopher Carcaillet 《Climatic change》2016,135(3-4):683-697

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