摘要
The aim of this article is to study and reveal the mineralogical composition of dune sands from the Bouarfa Figuiget region(eastern Morocco)and to find the potential source of these dune sands.The mineralogical study was made by combining field studies to collect samples and determine the facies of the surrounding area with labortory studies,including geochemical analysis(DRX analysis),morphoscopic study of the sands under a binocular magnifying glass according to the fractions making up these sands,heavy mineral extraction and analysis under a microscope,and calcimetric analysis.The results revealed two main categories of minerals in sandy deposits:light and heavy minerals.These include quartz,plagioclase feldspar,calcite platelets,and fragments of greyish,greenish,and whitish rock.Quartz was the dominant mineral.Heavy minerals include dark(opaque)minerals such as garnet,tourmaline,epidote,zircon,rutile,and rock fragments.This composition is the result of erosion,transport,and deposition processes in the crystalline sandstone and sedimentary formations of the eastern High Atlas,which feed the study area via aeolian pathways,including winds from ERG CHBI.The quartz grains in the dune sands of the eastern region,accumulated by wind action,are mainly round,matte grains of aeolian origin.The mineral associations observed show the presence of two types of sandy deposits:(1)Sand dominated by matte,round quartz grains(fraction 225μm),associated with accessory minerals(garnet,tourmaline,zircon,rutile,kyanite,and epidote),oxides(magnetite and ilmenite),and rock fragments of mixed mineral,crystalline,and sedimentary origin.(2)Totally dominant matte round quartz sand associated with iron oxides and a few rock fragments(fractions 142μm,180μm and 357μm).Sand with fraction 225μm consists almost entirely of quartz(8%)with garnets and a few rock fragments.These results suggest that the variation in the composition of the dune sands in the study area depends on the nature of the granulometric fraction studied,and therefore on the variety of sources feeding the sands studied(Chott Tigri,crystalline and sedimentary formations of the Eastern High Atlas).
基金
supported by the Académie Hassan Ⅱ des Sciences et Techniques(Rabat,Morocco)as part of the AP-2018 project.
