In this study, pumice is used as a novel natural heterogeneous catalyst for the synthesis of 3,4-dihydropyrimidine-2-(1H)-ones/thiones via the one-pot multi-component condensation of aromatic aldehydes, urea/thiourea, and ethyl acetoacetate or acetylacetone in excellent yields (up to 98%). The physical and chemical properties of the catalyst were studied. Their geochemical analysis revealed a basaltic composition. Furthermore, X-ray diffraction showed that it is composed of amorphous materials with clinoptilolite and heulandites zeolite minerals in its pores. Moreover, pumice has a porosity range from 78.2–83.9% (by volume) and is characterized by a mesoporous structure (pore size range from 21.1 to 64.5 nm). Additionally, it has a pore volume between 0.00531 and 0.00781 m2/g and a surface area between 0.053 and 1.47 m2/g. The latter facilitated the reaction to proceed in a short time frame as well as in excellent yields. It is worth noting that our strategy tolerates the use of readily available, cheap, non-toxic, and thermally stable pumice catalyst. The reactions proceeded smoothly under solvent-free conditions, and products were isolated without tedious workup procedures in good yields and high purity. Indeed, pumice can be reused for at least five reuse cycles without affecting its activity.

Mineralization in the Wadi Hammad area is represented by polymetallic vein-type and occurs in four modes, they are mineralized main quartz vein, silicified shear zone, associated hydrothermal alterations, and breccia zones. They mainly occur in the contact between Dokhanvolcanics and Younger granites and are confined to and controlled by the Wadi Hammad shear zone. The study revealed that Dokhan volcanics have adakitic nature and are formed by slab melt. Accordingly, these rocks are favorable sites for the formation of Au-(Cu)deposits. Hammad granite rocks are characterized bymetaluminous to weakly peraluminous, span the boundary between the ilmenite-magnetite series, transitional between moderately and strongly oxidized granites, situated a relatively shallow to moderate depths (20 to 30 km), and started to crystallize at temperatures around 800 °C. It is suggested that mineralization in WadiHammad formed due to intrusion of the strongly oxidizing, water-and volatile-rich, and alkaline to alkaliecalcic magma into the adakiticDokhan volcanic leads to circulation of these fluids in the latter leaching the available metals (Au and base metals). The leached metals are deposited in preexisting open fissures at the cold end of convective cells near the surface form Au (Cu)-rich quartz veins.

Gold mineralization in Wadi Hammad is one of few gold occurrences located in the North Eastern Desert of Egypt, occurring at the boundary between the post-tectonic Younger granite and Dokhan volcanics along a north-south (N-S) trending shear zone between them. The main mineral assemblages include arsenopyrite-pyrite-chalcopyrite-galena-sphalerite and sphaleritegold-covellite-cerussite-pseudomorphic iron oxides. Mineralogical and geochemical studies indicate that the mineralization is of the low sulphidation epithermal gold type, with Pb-Cu type base-metal sulfides. The hydrothermal solutions forming the mineralization have temperatures between 200 and 300 °C. The mineralization formed in three main stages; the first one includes the intrusion of younger granite into the Dokhan volcanics coeval with the initial shearing along the contact between them and responsible for the formation of the main milky white quartz-polymetallic sulfide vein. The second stage is related to later (third and fourth) deformational events responsible for the formation of the grey-colored quartz hosting sphaleriteII-gold-covellitecerussite-pseudomorphic iron oxides and connected with the basic dolerite dykes and related hydrothermal solutions. This stage includes the release of gold from their main sulfide hosts and re-precipitation in the fractures in quartz vein and alteration zones. The results of this study reveal the existence of promising gold deposits in the North Eastern Desert (NED) of Egypt, which changes the stereotype and may set the stage for future exploration of gold in the NED. Moreover, this study unveiled the nature of the intrusion-related type of mineralization and their characteristic features which can be used in the exploration of similar types in the surrounding areas.

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