Abstract

To study and identify soil minerals in the arid regions of Iraq, a transect of seven pedons distributed in Pripj region, which forms the largest trough in the southern desert of Muthanna province, was selected, the pedons were morphologically described and obtained disturbed soil samples from every horizon for the purpose of conducting some mineralogical analysis. Results of mineralogical analysis of the very fine sand showed supremacy of the light minerals, which formed more than 93% in comparison with the heavy minerals. The light minerals showed the supremacy of quartz in all the studied pedions horizons, followed by Feldspar and gypsum respectively, also the presence of fragments of different rocks types was noticed, especially carbonates, chert and mudstone rocks. Weathering index for light minerals by soil quartz content over feldspars mineral showed values ranged between 11.6-33.1, the results of this index showed higher values in the high topographic regions, in comparison with the pedons in the low regions of the trough which were characterized with a different pattern of the other pedons. Whereas the percentage of the heavy minerals ranged between 2.09-7.55% with an average of 4.99%, with a clear increase in the registered values of the low regions pedons in comparison with the high regions pedons, the results also showed that one of the most important identified minerals in the studied pedons is the opaque's minerals' group which showed the highest percents in the heavy minerals group, with similarity in the quality of the heavy minerals and difference in the quantity of the studied pedons soils, which indicates that these soils are resedimented. To study the weathering intensity of the heavy minerals (easily weathered minerals/resistant minerals to weathering), the ratio between(Carnet+ Tourmaline/ Amp bole + Pyroxene) was used as a weathering index. The results showed weak differences in the weathering index percents of the heavy minerals for all the studied soils. Also we counted the index minerals percent which included the sum of resistant minerals( Carnet + Rutile + Zircon + Tourmaline) this percent was corresponding with preceding percent, and showed raising in the surface horizons.