Effect of self-weight consolidation on a hydro-sedimentological model for the Río de la Plata estuary

The effect of the consolidation process on the morphodynamics and fine sediment dynamics of the Río de la Plata estuary is explored through a circulation-wave-sediment transport model. The consolidation model is calibrated based on settling column experimental data. Different simulations are done in order to initialize the mud layer distribution and to investigate the impact of different erosion parameter assumptions on the modeled sediment dynamics. Finally a two-year simulation is done with and without the consolidation process and realistic hydrodynamic forcings. Considering the consolidation process, the model correctly reproduces measured vertical density profiles in the Montevideo Bay access channel. The simulated suspended sediment dynamics behavior in Montevideo Bay with the consolidation process provides a more realistic deposition pattern in regard to the dredging activities.     

NanoSr – A New Carbonate Microanalytical Reference Material for In Situ Strontium Isotope Analysis

The in situ measurement of Sr isotopes in carbonates by MC‐ICP‐MS is limited by the availability of suitable microanalytical reference materials (RMs), which match the samples of interest. Whereas several well‐characterised carbonate reference materials for Sr mass fractions > 1000 µg g^?1 are available, there is a lack of well‐characterised carbonate microanalytical RMs with lower Sr mass fractions. Here, we present a new synthetic carbonate nanopowder RM with a Sr mass fraction of ca. 500 µg g^?1 suitable for microanalytical Sr isotope research (‘NanoSr’). NanoSr was analysed by both solution‐based and in situ techniques. Element mass fractions were determined using EPMA (Ca mass fraction), as well as laser ablation and solution ICP‐MS in different laboratories. The ⁸⁷Sr/⁸⁶Sr ratio was determined by well‐established bulk methods for Sr isotope measurements and is 0.70756 ± 0.00003 (2s). The Sr isotope microhomogeneity of the material was determined by LA‐MC‐ICP‐MS, which resulted in ⁸⁷Sr/⁸⁶Sr ratios of 0.70753 ± 0.00007 (2s) and 0.70757 ± 0.00006 (2s), respectively, in agreement with the solution data within uncertainties. Thus, this new reference material is well suited to monitor and correct microanalytical Sr isotope measurements of low‐Sr, low‐REE carbonate samples. NanoSr is available from the corresponding author.     

Interpretation of dilatometer tests in a heavy oil reservoir

This paper presents a prospective study for identifying selected parameters of the modified Cam‐Clay model representing the behaviour of heavy oil reservoirs. The first part shows that the plastic compressibility, which controls the main recovery mechanism of such reservoirs, can be accurately determined, simultaneously with other parameters, by an inverse analysis of pressure–strain curves. The conditions of the identification procedure mainly involve two tests conducted under different drainage conditions or at different strain rates. The numerical study also establishes the sequence of an original in situ experimental program, in which three dilatometer tests at a relatively great depth (several hundreds of metres) were carried out. The comparison of the experimental data with the numerical computations reveals a significant over‐consolidation ratio which does not allow the plastic compressibility to be determined but supports the findings regarding the geological erosion of the site. Copyright © 2006 John Wiley & Sons, Ltd.     

深海火山堆积期间从海底火山作用到富含硫化物石英脉型金成矿作用的演化

富含硫化物石英脉型金矿是加拿大太古宙金矿类型中重要的一种.关于它的成因仍是个谜.象Copper Rand和Geant Dormant这样一些金矿,其中的富硫化物含金石英脉的形成早于区域韧性变形,因而排除了变质成因的可能.Geant Do rmant金矿尤其适合于阐述金矿成因问题,因为其中的含金石英脉产于一层序关系保存完好的弱形变火山沉积序列中.本文论述了与该矿床有关的火山堆积及其热液系统的演化.从野外、岩相学与地球化学资料确定了火山演变及其形成的水下环境.热液事件则从野外分布特征、硫化物以及蚀变矿物组合和蚀变围岩的质量平衡计算等方面加以讨论.在分析火山与热液事件年代学和几何学关系基础上,认为含金石英脉是在火山成因热液系统的最后阶段形成的,该热液系统包括在深水火山堆积期间从贫金海底火山作用演变成富金矿脉型成矿作用的整个过程.本文探讨了在这种环境中含金石英脉的形成和金的富集机制以及所提出的金矿成因模式在勘探中的意义.     

Electrochemical gold precipitation to explain extensive vertical and lateral mineralization in the world‐class Poderosa‐Pataz district,Peru

The world‐class Poderosa‐Pataz district is famous for its gold endowment in vertically and laterally extensive quartz‐sulphide veins. Precipitating mechanisms are investigated to determine why gold is so laterally and vertically distributed. Micro‐XRF and LA‐ICP‐MS element mapping of pyrites surrounding gold grains reveals systematic enrichment of As around or near visible gold accumulations. These As‐enriched zones define discordant rims and corridors overprinting pyrites. LA‐ICP‐MS spot analyses performed within and outside the As enrichment zones indicate that As is enriched on average by two orders of magnitude in association with gold. Secondary pyrite transformation by hydrothermal fluids with elevated As‐Au induced a change in the semiconducting properties of pyrite grains, resulting in the precipitation of visible gold particles at the interfaces of As‐enriched zones. The electrochemical precipitation mechanism acted as a filter to extract gold in solution regardless of variations in pressure and temperature, hence explaining the vertically and laterally extensive gold mineralization.     

High resolution spectra of galaxies

We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the stellar content and the kinematics simultaneously. These techniques use new synthetic high resolution spectra produced by PéGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region of spiral galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Predicting water flow in fully and partially saturated porous media: a new fractal-based permeability model

Hydrogeology Journal - Predicting the permeability of porous media in saturated and partially saturated conditions is of crucial importance in many geo-engineering areas, from water resources to...     

Evolutionary history of hoofed mammals during the Oligocene–Miocene transition in Western Europe

The biostratigraphy and diversity patterns of terrestrial, hoofed mammals help to understand the transition between the Palaeogene and the Neogene in Western Europe. Three phases are highlighted: (1) the beginning of the Arvernian (Late Oligocene, MP25-27) was characterised by a “stable” faunal composition including the last occurrences of taxa inherited from the Grande Coupure and of newly emerged ones; (2) the latest Arvernian (Late Oligocene, MP28-30) and the Agenian (Early Miocene, MN1-2) saw gradual immigrations leading to progressive replacement of the Arvernian, hoofed mammals towards the establishment of the “classical” Agenian fauna; (3) the beginning of the Orleanian (Early Miocene, MN3-4) coincided with the African-Eurasian faunal interchanges of the Proboscidean Datum Events and led to complete renewal of the Agenian taxa and total disappearance of the last Oligocene survivors. Faunal balances, poly-cohorts and particularly cluster analyses emphasise these three periods and define a temporally well-framed Oligocene–Miocene transition between MP28 and MN2. This transition started in MP28 with a major immigration event, linked to the arrival in Europe of new ungulate taxa, notably a stem group of “Eupecora” and the small anthracothere Microbunodon. Due to its high significance in the reorganisation of European, hoofed-mammal communities, we propose to name it the Microbunodon Event. This first step was followed by a phase of extinctions (MP29-30) and later by a phase of regional speciation and diversification (MN1-2). The Oligocene–Miocene faunal transition ended right before the two-phased turnover linked to the Proboscidean Datum Events (MN3-4). Locomotion types of rhinocerotids and ruminants provide new data on the evolution of environments during the Oligocene–Miocene transition and help understand the factors controlling these different phases. Indeed, it appears that the faunal turnovers were primarily directed by migrations, whereas the Agenian transitional phase mainly witnessed speciations.     

Sinkhole hazards prediction at Ghor Al Haditha, Dead Sea, Jordan: “Salt Edge” and “Tectonic” models contribution—a rebuttal to “Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan, by: Ezersky, M.G., Eppelbaum, L.V., Al-Zoubi,A.3, Keydar S., Abueladas, A-R., Akkawi E., and Medvedev, B.”

Mikhail Ezersky et al. have published the article “Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan” (February 2013) in which the paper “Salt karst and tectonics: sinkholes development along tension cracks between parallel strike-slip faults, Dead Sea, Jordan” published by Closson D, Abou Karaki N, Hallot F in 2009 (Earth Surface Processes and Landforms, 34(10), 1408–1421) is questioned. In this short paper, we propose some clarifications and discuss the criticisms of these authors.     

Soil and bedrock distribution estimated from gully form and frequency: A GIS-based decision-tree model for Lebanon

Torrential rainfall and relatively sparse vegetation in the Mediterranean region result in the development of gully systems and land degradation, notably on lands with specific types of soil and bedrock. This paper proposes a decision-tree model to predict the distribution of soil and bedrock susceptible to gully erosion (white Rendzinas and marly rocks) from the form and frequency of gullies. The study area is located in Lebanon and the model is linked to GIS. V-fold cross-validation of the pruned model indicates that gully features including cross-section size and shape, network frequency, types of meandering, and catchment area can explain 80% of variance in soil/rock properties. The overall accuracy of the soil/rock map was estimated to be ca. 87%. The proposed model is relatively simple, and may also be applied to other areas. It is particularly useful when information about soil and rock obtained from conventional field surveys is limited.