Prediction of sediment yield at storm period in Northwest Algeria

This paper studies the hydrodynamics and variability of stream flow and sediment yield in Wadi El Hammam, located in the semi-arid region of Algeria. In this location, hysteresis effects are obvious especially during high discharge periods. The sediment concentration and load maxima go several months before discharge maxima, while decreased sediment concentrations are noticed during the discharge peaks. In order to explain these phenomena, we have adopted a methodology that consists of finding a simple regression model capable of explaining the sediment load as a function of the water discharge measured at gauging stations of three rivers at various scales, e.g., annual and seasonal. Suspended sediment concentrations are measured during a 22-year period (1986/1987–2007/2008). The results have shown that the power model explains the greatest part of the variance (80%). The changes in sediment availability result in so-called hysteresis effects. In this work, we have described different loops: clockwise or positive hysteresis loops and anti- or counter-clockwise hysteresis loops. The analysis of the seasonal sediment yields has shown that the autumn season contributes a large proportion of the annual sediment yield (62%).     

A reconnaissance study of platinum group elements (PGE) contents from sulfide mineralization in pyroxenites in Faryab ophiolite of Iran

Platinum group elements (PGE) enrichment occurs in Zn–Cu and Ni-rich ophiolities in a number of geological settings. Platinum group elements (PGE) mineralization in Pyroxenite from the Faryab ophiolities of Zagros belt in south Iran was studied. The ophiolite rocks represent blocks of Tethyan oceanic crust that were emplaced on the continental margin during the late Cretaceous period. Much of lower ophiolitic section is composed of homogeneous harzburgite, while upper sections harzburgite interlayer with dunite and pyroxenite are included. This study focused on pyroxenite that includes most of sulfide mineralization in Faryab. More than 500 samples were investigated from polished thin sections; that cover all area of Faryab. The sulfide phases include pyrrhotite, pentlandite, millerite, violarite, smythite, and heazlewoodite. The results show that in almost all the samples Os is below the 2 ppb detection limit, Platinum values vary from <5 to 91 ppb and the light PGE (Ru, Rh, and Pd) relative to the heavy PGE (Os, Ir, and Pt) are more concentrated. Calculation showed that in pyroxenites Pd–Pt is occurring with orthopyroxenite and Rh–Os is occurring in clinopyroxenite. Ni/Pd ratios in Faryab vary between 7 and 356 and Pd/Ir ratio is 0.1–27. This indicates that in Faryab area partial melt of mantle occurred. Pd/Rh ratio in Faryab is 0.1–11, and Pd/Pt varies between 0.2 and 1.5. Pd/Ir ratio in Faryab decreases and shows that PGE in Faryab occurred.