A re-evaluation of metal diapir breakup and equilibration in terrestrial magma oceans     

Henri Samuel 《Earth and Planetary Science Letters》2012

Due to mechanisms such as impact heating, early atmospheric thermal blanketing, and radioactive heating, the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable. In such a context, a key question to constrain the early thermo–chemical evolution of the Earth is how much iron diapirs provided by differentiated impactors emulsified during their sinking towards the bottom of an early magma ocean.In the past years, several workers have focused on this question, using however various approaches and making different assumptions. While most studies favor rapid breakup and equilibration of iron bodies during their sinking through the magma ocean, recent work suggests that iron bodies of size comparable or greater than a few tens of kilometers may preserve most of their initial volume as they reach the bottom of a magma ocean, therefore leading to metal–silicate disequilibrium.To clarify the discrepancies and the differences among studies I have conducted a series of numerical simulations and theoretical calculations to derive the conditions and the timing for the breakup of metal diapirs of any size, sinking through a silicate magma ocean, with a large range of plausible viscosity values. The obtained breakup criterion is used to derive stable diapir sizes and their ability to equilibrate with the surrounding silicates. I show that for plausible magma ocean viscosities, diapirs with initial radii smaller than the thickness of a magma ocean rapidly break up into stable diapir sizes smaller than 0.2 m, at which metal–silicate equilibration is rapidly achieved.  相似文献   

Predicting the occurrence of sand banks in the North Sea     

H. Henriët van der Veen  Suzanne M. J. H. Hulscher 《Ocean Dynamics》2009,59(5):689-696

Sand banks have a wavelength between 1 and 10 km, and they are up to several tens of meters high. Also, sand banks may have an impact on large-scale human activities that take place in the North Sea like sand mining, shipping, offshore wind farms, etc. Therefore, it is important to know where sand banks occur and what their natural behavior is. Here, we use an idealized model to predict the occurrence of sand banks in the North Sea. The aim of the paper is to research to what extent the model is able to predict the occurrence of sand banks in the North Sea. We apply a sensitivity analysis to optimize the model results for a North Sea environment. The results show that the model correctly predicts whether or not sand banks occur for two thirds of the North Sea area.  相似文献   

Assessment of water body change and sedimentation rate in Moulay Bousselham wetland,Morocco, using geospatial technologies     

Mounir Karim  Mehdi Maanan  Mohamed Maanan  Hassan Rhinane  Henri Rueff  Lahssen Baidder 《国际泥沙研究》2019,34(1):65-72

Coastal lagoons have significant biodiversity and ecologic and socio-economic interest. Several resident and migratory birds live in coastal lagoons as well as fish and other aquatic biota. Over the years, lagoons worldwide have been subject to considerable sediment deposition coming especially from soil erosion due of agricultural activities, and the lagoon's inflows have resulted in an accelerated sedimentation which can drastically affect the aquatic ecosystem balance. A new, fast, and cost-effective approach was developed, using water surface change as a proxy, to evaluate the sediment deposition rate. In the current research, this methodology was applied in the Moulay Bousselham Lagoon in Morocco, and a combination of Landsat 8 and Landsat 5 imagery acquired at four points in time over 30 years(1985-2015) was used. Following geometric correction and enhancement, the interpretation of the acquired images provided important insight on the current conditions of the water surface change using the Normalized Difference Water Index(NDWI). Several iterations were done to determine a suitable threshold for effective water surface detection. In order to validate the automatically extracted water surface features, many band combinations of Landsat and Sentinel 2 were used as references to run the accuracy assessment. The results show that the Moulay Bousselham Lagoon lost 17.60%(106 ha) of its water surface area, and 530,000 m^3 to 1,060,000 m^3 of its water volume during the last three decades.Converting water surface loss into sedimentation returned a rate of 0.58 cm/yr. These results have been confirmed by previous field work using sedimentological approaches. Proper management should be applied to sustain the vitality of this lagoon environment.  相似文献   

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset II: Land use,hydrology and sediment production monitoring in Houay Pano,northern Lao PDR     

Laurie Boithias  Yves Auda  Stéphane Audry  Jean-Pierre Bricquet  Alounsavath Chanhphengxay  Vincent Chaplot  Anneke de Rouw  Thierry Henry des Tureaux  Sylvain Huon  Jean-Louis Janeau  Keooudone Latsachack  Yann Le Troquer  Guillaume Lestrelin  Jean-Luc Maeght  Pierre Marchand  Pierre Moreau  Andrew Noble  Anne Pando-Bahuon  Kongkeo Phachomphon  Khambai Phanthavong  Alain Pierret  Olivier Ribolzi  Jean Riotte  Henri Robain  Emma Rochelle-Newall  Saysongkham Sayavong  Oloth Sengtaheuanghoung  Norbert Silvera  Nivong Sipaseuth  Bounsamay Soulileuth  Xaysatith Souliyavongsa  Phapvilay Sounyaphong  Sengkeo Tasaketh  Chanthamousone Thammahacksa  Jean-Pierre Thiebaux  Christian Valentin  Olga Vigiak  Marion Viguier  Khampaseuth Xayyathip 《水文研究》2021,35(5):e14126

Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m²) and small catchment (0.6 km²) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to, for example, assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g., contaminants other than faecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment.  相似文献   

The Imaclim-R model: infrastructures, technical inertia and the costs of low carbon futures under imperfect foresight   总被引：2，自引：2，他引：0  

Henri Waisman  Céline Guivarch  Fabio Grazi  Jean Charles Hourcade 《Climatic change》2012,114(1):101-120

This paper analyzes the transition costs of moving towards a low carbon society when the second-best nature of the economy is accounted for. We emphasize the consequences on mitigation costs of considering the interplay between a) technical systems inertia, including slow infrastructure turnover in transportation and construction; and b) imperfect foresight influencing investment decisions. To this end, the hybrid general equilibrium modeling framework Imaclim-R is employed as it allows for transitory partial adjustments of the economy and captures their impact on the dynamics of economic growth. The modeling exercise quantitatively emphasizes the a) specific risks that the interplay between inertia and imperfect foresight leads to high macroeconomic costs of carbon abatement measures; b) opportunities of co-benefits from climate policies permitted by the correction of sub-optimalities in the reference scenarios. The article draws insights for the framing of future climate architectures by studying the role of measures that act complementarily to carbon pricing in the transport sector. In particular, reallocating public investment towards low-carbon transport infrastructure significantly reduces the overall macroeconomic costs of a given GHG stabilization target and even creates the room for long-term net economic benefits from climate policies.  相似文献   

Characteristic features of air ions at Mace Head on the west coast of Ireland     

Marko Vana  Mikael Ehn  Tuukka Petj  Henri Vuollekoski  Pasi Aalto  Gerrit de Leeuw  Darius Ceburnis  Colin D. O'Dowd  Markku Kulmala 《Atmospheric Research》2008,90(2-4):278-ICNAA07

Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm³. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm^− 3 for the negative ions and 423 cm^− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm²V^− 1s^− 1 and 1.49 cm²V^− 1s^− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.  相似文献   

A multiscale electrical survey of a lateritic soil system in the rain forest of Cameroon     

Henri Robain  Marc Descloitres  Michel Ritz  Quantin Yene Atangana 《Journal of Applied Geophysics》1996,34(4):237-253

Resistivity investigations were carried out on an elementary watershed in SW Cameroon, firstly to assess the applicability of direct-current (DC) resistivity methods to solve various pedological problems in intertropical regions, and subsequently to determine the relationships between electrical resistivities and pedological properties of lateritic soil systems. The survey included measurements in pits with a small Wenner fixed-spacing array (SWA), vertical electrical soundings (VES) and vertical electrical “quick soundings” (VEQS) both using the Schlumberger configuration. The VES data were interpreted using a conventional multilayer inversion program to obtain best-fit models. Constraints to the interpretation of these data were provided by SWA and pedological information from existing observation pits. The results of the interpretation reveal five distinct geoelectrical layers overlying a resistive bedrock. The first is a thin organo-mineral upper layer with low resistivities in the range 250–450 Ωm. The second layer corresponds to micro-aggregated clayey materials and is more resistive (1300–1800 Ωm). The third represents the main part of ferruginous materials and is even more resistive (2000–4500 Ωm). The fourth corresponds to unsaturated saprolite and the last to saturated saprolite (ground water) with resistivities ranging from 800 to 1500 Ωm and from 150 to 250 Ωm, respectively. Estimates of soil volumes for the entire study area were obtained from VEQS interpretations. Most of the soil cover corresponds to saprolite (74%, being saturated by ground water), while topsoil and ferruginous materials represent 14 and 12%, respectively. Finally, geophysical results based upon 1-D inversion provide a satisfactory approximation of the various lateritic components' 3-D geometry over the watershed. The study provides original quantitative results concerning the behaviour of intertropical soil systems as well as some geomorphological keys for soil mapping at a regional scale.  相似文献   

Temporal Coherence: A Model for Non-stationarity in Natural and Simulated Wind Records     

Jennifer M. Rinker  Henri P. Gavin  Andrew Clifton  Paul S. Veers  Levi F. Kilcher 《Boundary-Layer Meteorology》2016,159(2):373-389

  相似文献   

Tectonics of the Monte Rosa and surrounding nappes (Switzerland and Italy): Tertiary phases of subduction,thrusting and folding in the Pennine Alps     

Albrecht Steck  Henri Masson  Martin Robyr 《Swiss Journal of Geoscience》2015,108(1):3-34

  相似文献   

Systematique U-Pb et Evolution du Gisement d'Uranium de Lodève (France)     

Joël R. Lancelot  Bruno de Saint André  Henri de la Boisse 《Mineralium Deposita》1984,19(1):44-53

Résumé Considérée comme syngénétique ou diagénétique précoce, la minéralisation uranifère de la couche 0 de l'Autunien du bassin de Lodève a été étudiée par la méthode U-Pb sur roches totales. Les données U-Pb démontrent l'existence de perte en radon, principalement dans la chaine de désintégration de ²³⁸U, et l'intérêt de l'utilisation du couple ²⁰⁷Pb-²³⁵U pour la détermination des âges de cristallisation des concentrations uranifères. Pour la couche 0, deux phases de remobilisation de l'uranium et du plomb ont pu être déterminées respectivement à 173±6 Ma et 108±5 Ma. La plus ancienne de ces deux phases est la plus marquée dans les échantillons étudiés, dont les systèmes U-Pb ne montrent pas la mémoire d'une concentration uranifère permienne. La première mobilisation de l'uranium et du plomb s'est faite lors d'une phase de distension à 160–170 Ma, affectant la croûte continentale du Sud du Massif Central. Cette phase a provoqué la circulation de fluides minéralisés et est marquée par une recristallisation des illites des pélites permiennes entre 100 et 200 °C (du fait de l'élévation du gradient géothermique) et par la mise en place d'un volcanisme d'origine mantellique daté à 155±6 Ma. La composition isotopique en plomb d'une galène de l'Autunien du Lodévois, est analogue à celles des feldspaths des granitoïdes du Massif Central français et à celles des galènes des minéralisations stratiformes de Pb-Zn des Causses, ce qui fournit un argument pour faire dériver au moins une partie des métaux en traces dans les pélites autuniennes de l'altération de la croûte continentale hercynienne environnante.

---

In the Lodeve basin, the uraniferous mineralization associated with the autunian pelitic layer 0 is usually considered as syngenetic or early diagenetic. U-Pb isotopic data performed on U bearing whole rocks demonstrate occurrence of radon losses, mainly in the ²³⁸U decay series; the ²⁰⁷Pb-²³⁵U geochronometer is particularly suitable to date U-Pb systems disturbed by such radon losses. For the autunian layer 0, two U-Pb mobilization phases have been respectively recognized at 173±6 Ma and 108±5 Ma. The oldest phase is the most clearly expressed in the studied samples, no memory of a permian age could be recognized in the U-Pb systems. The first U-Pb mobilization occurred 170 Ma ago, during a distension phase of the continental crust. This phase induced circulations of mineralized fluids, illite recristallization in the permian pelites at temperatures ranging from 100 to 200 °C and emplacement of a mantellic volcanism recently dated at 155±6 Ma. A galena from the Autunian of the Lodeve basin, the feldspars of the surrounding variscan granitoïds and galenas of mesozoïc stratiform deposits in the Causses, present similar Pb isotopic composition, which is in agreement with the hypothesis that some metals of the autunian pelites originated in the surrounding weathered variscan continental crust.

  相似文献