Effects of Hydrothermal Alteration on Geochemical Characteristics of the El Sukkari Granite, Central Eastern Desert, Egypt

Abstract

The El Sukkari granite is predominantly peraluminous and classified as intrusive in a syn-collisional setting. Geochemical evidence suggests that this granite was generated by partial melting of metagraywackes at ˜800°C as deduced from zircon saturation temperatures. The El Sukkari granite underwent multistage hydrothermal processes accompanying gold mineralization. Intensive hydrothermal alteration of the granite occurred along brittle structures that are mostly filled by dikes and quartz veins. Sodic and potassic metasomatism are the major alteration effects. Hydrothermal alteration is indicated by depletion of both light and heavy REE and Eu-enrichment. Eu-enrichment is due largely to chemical contribution from hydrothermal fluids. Other major and trace elements were enriched or depleted during one of the main alteration stages. Rb, Zn, Nb, Zr, T, Y, and Ga show depletion. Ba and Sr display enrichments, whereas Co, Li, and Cr underwent insignificant changes. Ground gamma-ray spectrometry measurements indicate that radioactive element concentrations are generally low in the altered granite. Correlations between eU, eTh, and eU/eTh of the altered granite and the plot of chemically measured U against corresponding Th values for both fresh and altered granites reflect the geochemical coherence of uranium and thorium during magma crystallization. Both elements are mainly hosted in accessory phases and were not disturbed by the hydrothermal alteration.