The great sulfur depletion of Earth’s mantle is not a signature of mantle–core equilibration

The extreme depletion of the Earth’s mantle in sulfur is commonly seen as a signature of metal segregation from Earth’s mantle to Earth’s core. However, in addition to S, the mantle contains other elements as volatile as S that are hardly depleted relative to the lithophile volatility trend although they are potentially as siderophile as sulfur. We report experiments in metal-sulfide–silicate systems to show that the CI normalized abundances of S, Pb, and Sn in Earth’s mantle cannot be reproduced by element partitioning in Fe ± S–silicate systems, neither at low nor at high pressure. Much of the volatile inventory of the Earth’s mantle must have been added late in the accretion history, when metal melt segregation to the core had become largely inactive. The great depletion in S is attributed to the selective segregation of a late sulfide matte from an oxidized and largely crystalline mantle. Apparently, the volatile abundances of Earth’s mantle are not in redox equilibrium with Earth’s core.     

Prediction of blasting-induced fragmentation in Meydook copper mine using empirical,statistical, and mutual information models

One of the most important aims of blasting in open pit mines is to reach desirable size of fragmentation. Prediction of fragmentation has great importance in an attempt to prevent economic drawbacks. In this study, blasting data from Meydook mine were used to study the effect of different parameters on fragmentation; 30 blast cycles performed in Meydook mine were selected to predict fragmentation where six more blast cycles are used to validate the results of developed models. In this research, mutual information (MI) method was employed to predict fragmentation. Ten parameters were considered as primary ones in the model. For the sake of comparison, Kuz-Ram empirical model and statistical modeling were also used. Coefficient of determination (R ²), root mean square error (RMSE), and mean absolute error (MAE) were then used to compare the models. Results show that MI model with values of R ², RMSE, and MAE equals 0.81, 10.71, and 9.02, respectively, is found to have more accuracy with better performance comparing to Kuz-Ram and statistical models.     

Major and trace elements in water from different sources in Jeddah City,KSA

We collected a total of 50 water samples comprising tap water, ground water, and bottled water, from various areas of Jeddah City. We collected tap water samples from 25 districts, groundwater samples from 10 wells, and 15 different brands of bottled water. The levels of 28 elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Water certified reference material (CWW-TM-B) was used to ensure quality assurance. Recoveries ranged from 92 to 104.8% for all measured elements. Levels of major and trace elements in groundwater samples were higher than those in both bottled and tap drinking water. Only four elements (Al, Cs, U, and Zn) were shown to be higher in tap water samples than other samples type. However, their values were far below the guideline values. All mean concentrations of Na, K, Mg, and Ca in well water samples were significantly (p < 0.05) higher than those in both bottled and tap drinking water. In addition, only Al and Zn in tap water samples were significantly (p < 0.05) higher than those in both bottled and well drinking water. Most of the other elements were higher in well water samples compared to other sources. The results from this study will be used to increase public awareness about the safety of drinking water. It will also be useful for increasing awareness of health issues related to drinking water and to water used for other purposes.     

Ontogenetic changes in feeding and food preferences of the dog conch Laevistrombus canarium Linnaeus 1758 (Mollusca: Gastropoda) from Merambong shoal,Malaysia

Laevistrombus canarium is one of the marine gastropod mollusks that have high commercial value,particularly in the aquaculture sector in Malaysia.This study was conducted to determine the feeding and food items of L.canarium at dif ferent ontogenetic stages(juveniles,sub-adults and adults)from Merambong shoals,Malaysia.Field observations on feeding activity were conducted,followed by detailed laboratory analysis on the stomach content.Five-minutes observations on randomly selected individuals were conducted at the fi eld sampling site and their feeding activities were recorded with reference to age stage.Various shell sizes from each ontogenetic stage were randomly collected and quickly anaesthetized with ice and preserved in 10%formalin before being transported to the laboratory for stomach content analyses.Field observations showed that L.canarium mainly grazed on epiphytes occurring on seagrass(46.67%),followed by sediment surface(40%)and epiphytes occurring on macroalgae(13.33%).Stomach content analyses showed a signifi cant dif ference(P0.05)in gastro-somatic index(Gasi)between the juveniles(0.39±0.05),sub-adults(0.68±0.09)and adults(0.70±0.05)(P0.05).Food items found in the conch stomach include diatoms,detritus,foraminifera,seagrass and macroalgae fragments,sand particles and shell fragments.The Index of Relative Importance(%IRI)indicates three main types of food dominated the three ontogenetic stages namely diatoms,sand particles and detritus.However,no signifi cant diff erence(P0.05)was detected between the three main food items(diatoms,sand particles and detritus)among the ontogenetic stages.Therefore,feeding activity revealed the role of the dog conch in the marine food network.While,classifi cation of the types of food consumed by L.canarium through stomach content analysis determines the particular position of the gastropod in the food chain.Further studies are needed to provide a better insight between trophic relationships of L.canarium with marine ecosystem.     

Study of the Earth's oblateness and rotating atmosphere effects upon an artificial satellite in terms of KS-regular variables

This paper is concerned with an orbit prediction with the KS-regular variables. Perturbations due to the gravitational oblateness of the Earth, and the rotating atmosphere are considered. Application of the method for the perturbed motion are illustrated by numerical and graphical examples for a test case of the orbit.     

Landslide inventory in a rugged forested watershed: a comparison between air-photo and field survey data

Landslide inventories are routinely compiled by means of aerial photo interpretation (API). When examining photo pairs, the forest canopy (notably in old-growth forest) hides a population of “not visible” landslides. In the present study, we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the Capilano basin, coastal British Columbia. API was coupled with intensive fieldwork for identification and measurement of all landslides. A 30-year framework was adopted. We show that “not visible” landslides can represent up to 85% of the total number of failures and account for 30% of the volume of debris mobilised. Such percentages display high sub-basin variability with rates of sediment production varying by one order of magnitude between two sub-basins of the study area. This is explained qualitatively by GIS-based analysis of slope frequency distributions, drainage density, and spatial distribution of surficial materials. Such observations find further support in the definitions of transport-limited and supply-limited basins. As a practical consideration to land managers, we envisage that supplementary fieldwork for landslide identification is mandatory in transport-limited systems only. Fieldwork has demonstrated that gully-related failures have a greater importance than one could expect from API.     

Impact of wastewater discharge on the channel morphology of ephemeral streams

The impact of wastewater flow on the channel bed morphology was evaluated in four ephemeral streams in Israel and the Palestinian Territories: Nahal Og, Nahal Kidron, Nahal Qeult and Nahal Hebron. Channel changes before, during and after the halting of wastewater flow were monitored. The wastewater flow causes a shift from a dry ephemeral channel with intermittent floods to a continuous flow pattern similar to that of humid areas. Within a few months, nutrient‐rich wastewater flow leads to rapid development of vegetation along channel and bars. The colonization of part of the active channel by vegetation increases flow resistance as well as bank and bed stability, and limits sediment availability from bars and other sediment stores along the channels. In some cases the established vegetation covers the entire channel width and halts the transport of bed material along the channel. During low and medium size flood events, bars remain stable and the vegetation intact. Extreme events destroy the vegetation and activate the bars. The wastewater flow results in the development of new small bars, which are usually destroyed by flood flows. Due to the vegetation establishment, the active channel width decreases by up to 700 per cent. The deposition of fine sediment and organic material changed the sediment texture within the stable bar surface and the whole bed surface texture in Nahal Hebron. The recovery of Nahal Og after the halting of the wastewater flow was relatively fast; within two flood seasons the channel almost returned to pre‐wastewater characteristics. The results of the study could be used to indicate what would happen if wastewater flows were introduced along natural desert streams. Also, the results could be used to predict the consequences of vegetation removal as a result of human intervention within the active channel of humid streams. Copyright © 2001 John Wiley & Sons, Ltd.     

On the effects of a bumpy core-mantle interface

Motivated by the high degree of correlation between the variable parts of the magnetic and gravitational potentials of the Earth discovered by Hide and Malin (using a harmonic analysis approach and utilizing the geomagnetic data) when one field is suitably displaced relative to the other, Moffatt and Dillon (1976) studied a simple planar model in an attempt to find a quantitative explanation for the suggestion that this high degree of correlation may be due to the influences produced by bumps on the core-mantle interface. Moffatt and Dillon assumed that the core-mantle interface was z = η(x) where |?η/?χ| ? 1 and such that in the core [z < η(x)] a uniform flow (U₀, 0, 0) prevails in the presence of a uniform ‘toroidal’ field (B₀, 0, 0); (here z is the vertical coordinate and x is the eastward distance). The whole system rotates uniformly about the vertical with angular velocity Ω. The present work extends the model discussed by Moffatt and Dillon to include a horizontal component of angular velocity Ω_H and a uniform small poloidal field B_p. In addition, the uniform toroidal field is here replaced by one which vanishes everywhere in the mantle and increases linearly, from zero on the interface, with z. It is shown that the presence of Ω_H and B_p, together with the present choice of toroidal magnetic field, has a profound effect both on the correlation between the variable parts of the magnetic and gravitational fields of the Earth, and on how far the disturbances caused by the topography of the interface [which is necessarily three-dimensional i.e. z = η(x, y) here] can penetrate into the liquid core. In particular it is found that the highest value of the correlation function is +0.79 which corresponds to a situation in which the magnetic potential is displaced both latitudinally and longitudinally relative to the gravitational potential.     

Discrimination between primary magmatic biotites, reequilibrated biotites and neoformed biotites

The ternary diagram TiO₂–FeO*–MgO (FeO* = FeO + MnO) is proposed as a quantitative objective tool for distinguishing between primary magmatic biotites and those that are more or less reequilibrated, or possibly neoformed, by or within a hydrothermal fluid. The limit of the domains of the primary magmatic biotites, the reequilibrated biotites and the neoformed biotites were determined on the basis of optical, paragenetic and chemical criteria. To cite this article: H. Nachit et al., C. R. Geoscience 337 (2005).