Rare earth element (REE) enrichment in Algerian phosphorites has been evoked recently by a number of authors and are considered among the richest Paleocene-Eocene phosphorites worldwide. The Bled El ...Hadba deposit belongs to the giant Djebel Onk phosphorite complex in northeast Algeria. The deposit was subject to many geological studies that were focused on P2O5 contents for commercial purposes. The upper Thanetian phosphorite layer is about 30 m thick, and subdivided into three sub-layers (lower, main and upper sub-layer), based on P2O5 contents, where the main sub-layer is considered to be the richest. Despite this, few detailed geochemical investigations were carried out on this deposit thus far. In this work, major, trace and REE analyses were conducted on phosphate particles (pellets, coprolites and glauconites) using ‘in situ’ LA-ICP MS, and on whole-rock samples using XRF technique. The results show that the main sub-layer displays the highest whole-rock P2O5 contents, varying between 19.65 and 21.32 wt% compared to the lower (10.47–16.87 wt%) and upper (9.43–13.87 wt%) sub-layers. Among the phosphate particles, glauconites display the lowest P2O5 contents in the three sub-layers (17.45–19.35 wt%) compared to pellets (21.14–24.33 wt%) and coprolites (21.75–24.12 wt%), and largely the highest Al2O3, SiO2, MgO and Fe2O3(t). Glauconites also show higher ΣREE contents (764–2050 ppm) compared to pellets (221–910 ppm) and coprolites (214–909 ppm). Within the glauconite particles, the ΣREE, along with Al2O3, SiO2, MgO, and Fe2O3(t) contents, increase from core to the rim, whereas P2O5 contents decrease, which suggests that glauconitization postdates phosphatization processes. Also, the glauconitization process increase from the lower to the upper sub-layer; this is shown by the positive correlations between Al2O3 contents and those of MgO and SiO2 in one hand, and negative correlations between Al2O3 and P2O5 on the other hand. Ce, Eu, Y anomalies, along with La/Nd ratios and Nd contents, all point towards phosphatization under oxic conditions as a result of warm water upwelling, whereas glauconitization started under more reduced (sub-oxic) conditions; i.e., during early diagenesis, the peak of REE uptake from porewater, and under slow sedimentation rates.
Despite their relatively low P2O5 concentrations, the ΣREE contents of the Bled El Hadba phosphate particles record the highest concentrations in all Algerian and north African phosphorites. The main sub-layer is considered to be the most glauconite-rich phosphorite in Algeria. Therefore, more extensive REE analyses are recommended to better evaluate its economic potential in terms of critical raw materials.
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•The REE-enriched Bled El Hadba deposit belongs to the Dj. Onk phosphorite complex.•Phosphate particles were in situ LA-ICP-MS analyzed for their chemistry.•Glauconite particles are very enriched in REE compared to pellets and coprolites.•Phosphatization predates glauconitization processes.
An extensible viscoelastic plate equation with a nonlinear time-varying delay feedback and nonlinear source term is considered. Under suitable assumptions on relaxation function, nonlinear internal ...delay feedback, and source term, we establish a general decay of energy by using the multiplier method if the weight of weak dissipation and the delay satisfy
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Ringing of yellow-legged gulls Larus michahellis michahellis begun in Algeria in 2009, the first scheme of its kind in North Africa. Ringing of chicks was initiated at Skikda and extended a year ...later to four other colonies located along the Algerian coast. Preliminary analysis of observations of ringed yellow-legged gulls from Algerian colonies indicates that juveniles dispersed in a northwesterly direction to the Balearic Sea and the Bay of Biscay, and westwards to the Alborán Sea and the Iberian Atlantic coast from Cadiz Bay to Galicia. Preliminary results suggested two distinct routes: gulls from the eastern Algerian colonies moved N/NW to eastern Spain and overland to the Bay of Biscay, a pattern of dispersal previously reported for birds from Spanish and French western Mediterranean colonies. Juveniles from western colonies seemed to move N/NW to the Alborán Sea and Cádiz Bay. In Spain, to where most dispersal occurred, the data suggests that Algerian gulls summered at coastal areas before returning to North Africa in late autumn and winter.
In this paper, by establishing a new characterization of the notion of upper semi-continuity of multi-valued mappings in generalized Banach spaces, we prove some Perov type fixed point theorems for ...multi-valued mappings with closed graphs. Moreover, we derive some Krasnoselskii's fixe point results for multi-valued mappings in generalized Banach spaces. Our results are applied to a large class of nonlinear inclusions systems.
For one spatial variable, a new kind of nonlinear wave equation for Emden-Fowler type is considered with boundary value null and initial values. Under certain conditions on the initial data and the ...exponent p, we exhibit that the visco-elastic term leads our problem to be dissipative and the global solutions still non-exist in L2 at given finite time.
