Classification of volcanic rocks is a fundamental task in the geologic studies. Volcanic rocks are igneous rocks that cooled rapidly above the surface of the Earth's crust. They are classified according to their oxide chemical content. Furthermore, volcanic rocks can also be classified numerically by statistical means. But these methods are mostly dependent on human expert decision making and have a high cost. In this paper, a novel approach in the classification of volcanic rocks is proposed. This method is based on the rough set mathematical theory. The continuous data of the information system are firstly discretized using the information loss method. Secondly, the discretized decision table is reduced and the decision rule sets are extracted. The results are consistent with previous methods and show that the proposed method reduces time and calculation costs.

<p>Wadi El Reddah representing a semi-closed basin, extends in the N-S direction. It has only one outlet at the northern tip while the wadi collects floodwater from internal tributaries along wall rocks. The present study discusses the relationship between geology and geochemistry data to detect anomalous radioactive locations. The geochemical maps show the mineralization areas with abnormal rare metal contents. This led to two uranium occurrences (GXXIII and GXXIV) at Gabal Gattar in the perthitic leucogranite. At Wadi El Reddah, high contents of pathfinder elements (REE, Y, Zn, Nb and As) were discovered at the southern and eastern boundaries. This may be attributed to the presence of alkali feldspar granite at Gabal Gattar at the upstream of Wadi El Reddah and also to the sharp contact between Gabal Gattar and Hammamat Sedimentary rocks. A strong positive correlation coefficient between Fe₂O^t and or Al₂O₃ with Zr, Hf, Nb, Ta, REE, U, Rb, and Th reflects their association with thematization processes.</p>

This study deals with petrology and radioactivity of Gabal Al-Aglab younger granite, central Eastern desert, Egypt. Geologically the area consists of ophiolotic Mélange and younger granite. The study reveals that the younger granite are post orogenic granites, characterized by high differential index, which in turn represents the latest stage of the successive younger granite intrusions. Microscopically, Gabal Al-Aglab younger granites is holocrystalline, medium to coarse grained, characterized by the predominance of perthite over plagioclase, quartz and biotite. Zircon, apatite, titanite, allanite, and opaque minerals are the accessory and secondary minerals. The pegmatites occur as lenticular and circular pockets at the periphery of the younger granites. Geochemically, the younger granites show mainly peraluminous to metaluminous character and originated from subalkaline magma in within plate tectonic setting (crustal thickness > 30 km) at water vapour pressure varying from 0.5 to 3 kb with crystallization temperature between 670º to 800º C. Field survey together with the complied total count aeroradiometric map reveal that the pegmatites of Gabal Al-Aglab younger granite is significantly highly radioactive compared to the surrounding rocks. The uranium content varies between 3 to 12 ppm with an average of 7.1 ppm and thorium from 11 to 35 ppm with an average of 20 ppm and an average ratio (Th/U) 2.8.The pegmatites show higher U contents relative to their hosted younger granites as identified by microscopic investigation, scanning electron microscopy and confirmed by XRD.

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