Northwest Africa 5958: A weakly altered CM‐related ungrouped chondrite,not a CI3          下载免费PDF全文

Emmanuel Jacquet  Jean‐Alix Barrat  Pierre Beck  Florent Caste  Jérôme Gattacceca  Corinne Sonzogni  Matthieu Gounelle 《Meteoritics & planetary science》2016,51(5):851-869

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Cretaceous–Cenozoic tectonic history of the Jiaojia Fault and gold mineralization in the Jiaodong Peninsula,China: constraints from zircon U–Pb,illite K–Ar,and apatite fission track thermochronometry     

Jun Deng  Changming Wang  Leon Bagas  Emmanuel John M. Carranza  Yongjun Lu 《Mineralium Deposita》2015,50(8):987-1006

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Impact of textural patterns on modeled rock weathering rates and size distribution of weathered grains     

Yoni Israeli  Eyal Salhov  Simon Emmanuel 《地球表面变化过程与地形》2021,46(6):1177-1187

Rock texture has a critical influence on the way rocks weather. The most important textural factors affecting weathering are grain size and the presence of cracks and stylolites. These discontinuities operate as planes of mechanical weakness at which chemical weathering is enhanced. However, it is unclear how different rock textures impact weathering rates and the size of weathered grains. Here, we use a numerical model to simulate weathering of rocks possessing grain boundaries, cracks, and stylolites. We ran simulations with either synthetic or natural patterns of discontinuities. We found that for all patterns, weathering rates increase with discontinuity density. When the density was <~25%, the weathering rate of synthetic patterns followed the order: grid > honeycomb > Voronoi > brick wall. For higher values, all weathering rates were similar. We also found that weathering rates decreased as the tortuosity of the pattern increased. Moreover, we show that textural patterns strongly impact the size distributions of detached grains. Rocks with an initial monomodal grain size distribution produce weathered fragments that are normally distributed. In contrast, rocks with an initial log-normal size distribution produce weathered grains that are log-normally distributed. For the natural patterns, weathering produced lower modality distributions.  相似文献   

The tectono-sedimentary evolution of a hyper-extended rift basin: the example of the Arzacq–Mauléon rift system (Western Pyrenees,SW France)     

Emmanuel Masini  Gianreto Manatschal  Julie Tugend  Geoffroy Mohn  Jean-Marie Flament 《International Journal of Earth Sciences》2014,103(6):1569-1596

In this paper, we present a sedimentary and structural analysis that together with maps, sections and new Ar/Ar data enable to describe the tectono-sedimentary evolution of the Mauléon hyper-extended rift basin exposed in the W-Pyrenees. Hyper-extension processes that ultimately resulted in exhuming mantle rocks are the result of the subsequent development of two diachronous detachment systems related to two evolutional stages of rifting. An initial Late Aptian Early Albian crustal thinning phase is first recorded by the development of a crustal necking zone controlled by the north-vergent Southern Mauléon Detachment system. During a subsequent exhumation phase, active faulting migrates to the north with the emplacement of the Northern Mauléon detachment system that exhumed north section thinned continental crust and mantle rocks. This diachronous crustal thinning and exhumation processes are also recorded by the diachronous deposition of syn-tectonic sedimentary tracts above the two supra-detachment sub-basins. Syn-tectonic sedimentary tracts record the progressive exhumation of footwall rocks along detachment systems. Tectonic migration from the southern to the northern Mauléon Detachment system is recorded by the coeval deposition of “sag” deposits above the necking zone basin and of syn-tectonic tracts above exhumed rocks north section. Located on a hanging-wall situation related to the Mauléon hyper-extension structures, the Arzacq Basin also records a major crustal thinning phase as shown by its subsidence evolution so as by deep seismic images. The absence of major top-basement structures and its overall sag morphology suggest that crustal thinning processes occurred by decoupled extension of lower crustal levels contrasting with the Southern Mauléon Detachment system. Reconciling observations from the Mauléon and Arzacq Basins, we finally propose in this paper that they were the result of one and the same asymmetric crustal thinning and exhumation processes, where extension is accommodated into the upper crust in the Mauléon Basin (lower plate basin) and relayed in ductile lower crust below the Arzacq Basin (upper plate basin).  相似文献   

Uncertainty Analysis of Geochemical Anomaly by Combining Sequential Indicator Co-simulation and Local Singularity Analysis     

Liu  Yue  Carranza  Emmanuel John M. 《Natural Resources Research》2022,31(4):1889-1908

Natural Resources Research - Accurate characterization of geochemical anomaly related to metal mineralization and quantification of uncertainty propagation in space prediction are important for...  相似文献   

Spatial and temporal analysis of observed trends in extreme precipitation events in different climatic zones of Nigeria     

Ogolo  Emmanuel O.  Matthew  Olaniran J. 《Theoretical and Applied Climatology》2022,148(3-4):1335-1351

Theoretical and Applied Climatology - The purpose of this study is to assess spatial and temporal changes in extreme precipitation events from 1983 to 2017 over different climatic regions of...  相似文献   

Vulnerability of water resources in northern Cameroon in the context of climate change     

Ambe Emmanuel Cheo  Hans-Jürgen Voigt  Roy Lyonga Mbua 《Environmental Earth Sciences》2013,70(3):1211-1217

Water resources in northern Cameroon have continuously been reducing over the past years. Many studies have suggested two principal causes: (1) human activities such as poor farming practices, unsustainable use of water resources, increased demand of water, deforestation, land-use change, etc., (2) human-induced climate change. Northern Cameroon in this study includes: the Adamawa, North and Far North regions located closer to the Sahel regions of Africa. These regions are already water stressed because of their location and any further change in climate with rising temperature would impact water resource either positively or negatively. Time series analysis and a 12-month standardized precipitation index (SPI12) with digital data between 1957 and 2006 were used to investigate the variation of water resources in northern Cameroon. Results obtained varies between the different regions with an increased annual trend in temperature and precipitation for Ngaoundere (Adamawa region) and Garoua (north region), whereas Maroua (far north region) had a decreased annual trend in both precipitation and temperature. Further variability results obtained from a SPI12 show that wetter period out number drought period in all three regions. The study concluded that water resources vary with the changing climatic condition and the severity of the impact varies from region to region. Furthermore, water deficiency in northern Cameroon might not be due to climate change. The reasons might be a combination of poor water management and other factors such population growth, the environmental condition, etc.  相似文献   

Io’s atmosphere: Constraints on sublimation support from density variations on seasonal timescales using NASA IRTF/TEXES observations from 2001 to 2010     

Constantine C.C. Tsang  John R. Spencer  Emmanuel Lellouch  Miguel A. López-Valverde  Matthew J. Richter  Thomas K. Greathouse 《Icarus》2012,217(1):277-296

We present an analysis of 19 μm spectra of Io’s SO₂ atmosphere from the TEXES mid-infrared high spectral resolution spectrograph on NASA’s Infrared Telescope Facility, incorporating new data taken between January 2005 and June 2010 and a re-analysis of earlier data taken from November 2001 to January 2004. This is the longest set of contiguous observations of Io’s atmosphere using the same instrument and technique thus far. We have fitted all 16 detected blended absorption lines of the ν₂ SO₂ vibrational band to retrieve the subsolar values of SO₂ column abundance and the gas kinetic temperature. By incorporating an existing model of Io’s surface temperatures and atmosphere, we retrieve sub-solar column densities from the disk-integrated data. Spectra from all years are best fit by atmospheric temperatures <150 K. Best-fit gas kinetic temperatures on the anti-Jupiter hemisphere, where SO₂ gas abundance is highest, are low and stable, with a mean of 108 (±18) K. The sub-solar SO₂ column density between longitudes of 90–220° varies from a low of 0.61 (±0.145) × 10^?17 cm^?2, near aphelion in 2004, to a high of 1.51 (±0.215) × 10¹⁷ cm^?2 in 2010 when Jupiter was approaching its early 2011 perihelion. No correlation in the gas temperature was seen with the increasing SO₂ column densities outside the errors.Assuming that any volcanic component of the atmosphere is constant with time, the correlation of increasing SO₂ abundance with decreasing heliocentric distance provides good evidence that the atmosphere is at least partially supported by frost sublimation. The SO₂ frost thermal inertias and albedos that fit the variation in atmospheric density best are between 150–1250 W m^?2 s^?1/2 K^?1 and 0.613–0.425 respectively. Photometric evidence favors albedos near the upper end of this range, corresponding to thermal inertias near the lower end. This relatively low frost thermal inertia produces larger amplitude seasonal variations than are observed, which in turn implies a substantial additional volcanic atmospheric component to moderate the amplitude of the seasonal variations of the total atmosphere on the anti-Jupiter hemisphere. The seasonal thermal inertia we measure is unique both because it refers exclusively to the SO₂ frost surface component, and also because it refers to relatively deep subsurface layers (few meters) due to the timescales of many years, while previous studies have determined thermal inertias at shallower levels (few centimeters), relevant for timescales of ～2 h (eclipse) or ～2 days (diurnal curves).  相似文献   

Vertical profiling of SO2 and SO above Venus’ clouds by SPICAV/SOIR solar occultations     

Denis A. Belyaev  Franck Montmessin  Jean-Loup Bertaux  Arnaud Mahieux  Anna A. Fedorova  Oleg I. Korablev  Emmanuel Marcq  Yuk L. Yung  Xi Zhang 《Icarus》2012,217(2):740-751

New measurements of sulfur dioxide (SO₂) and monoxide (SO) in the atmosphere of Venus by SPICAV/SOIR instrument onboard Venus Express orbiter provide ample statistics to study the behavior of these gases above Venus’ clouds. The instrument (a set of three spectrometers) is capable to sound atmospheric structure above the clouds in several observation modes (nadir, solar and stellar occultations) either in the UV or in the near IR spectral ranges. We present the results from solar occultations in the absorption ranges of SO₂ (190–230 nm, and at 4 μm) and SO (190–230 nm). The dioxide was detected by the SOIR spectrometer at the altitudes of 65–80 km in the IR and by the SPICAV spectrometer at 85–105 km in the UV. The monoxide’s absorption was measured only by SPICAV at 85–105 km. We analyzed 39 sessions of solar occultation, where boresights of both spectrometers are oriented identically, to provide complete vertical profiling of SO₂ of the Venus’ mesosphere (65–105 km). Here we report the first firm detection and measurements of two SO₂ layers. In the lower layer SO₂ mixing ratio is within 0.02–0.5 ppmv. The upper layer, also conceivable from microwave measurements by Sandor et al. (Sandor, B.J., Todd Clancy, R., Moriarty-Schieven, G., Mills, F.P. [2010]. Icarus 208, 49–60) is characterized by SO₂ increasing with the altitude from 0.05 to 2 ppmv, and the [SO₂]/[SO] ratio varying from 1 to 5. The presence of the high-altitude SO_x species could be explained by H₂SO₄ photodissociation under somewhat warmer temperature conditions in Venus mesosphere. At 90–100 km the content of the sulfur dioxide correlates with temperature increasing from 0.1 ppmv at 165–170 K to 0.5–1 ppmv at 190–192 K. It supports the hypothesis of SO₂ production by the evaporation of H₂SO₄ from droplets and its subsequent photolysis at around 100 km.  相似文献   

An empirical line list for methane in the 1.26–1.71 μm region for planetary investigations (T = 80–300 K). Application to Titan     

Alain Campargue  Le Wang  Didier Mondelain  Samir Kassi  Bruno Bézard  Emmanuel Lellouch  Athena Coustenis  Catherine de Bergh  Mathieu Hirtzig  Pierre Drossart 《Icarus》2012,219(1):110-128

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