干旱区生态环境知识资源中心

The present article is concerned with the geochemistry of red-pink granites in the Late Orogenic Plutonites and their relationship with uranium content in order to discriminate the fertile from non-fertile types. Chemical analysis has been carried out, including the major oxides, trace elements and REE, to determine their geotectonic affinity, and the relationship between U and major oxides, trace elements and rare earth elements.

Geotectonically, the study revealed that the post orogenic red-pink granites are either within-plate granites or volcanic are granites. Chemically the granites are subalkaline and peraluminous to metaluminous. Also, the younger granites occur in three phases. The highly differentiated phase is the fertile type which is characterized by high silica content, with respect to alumina, impoverished in calcium, as well as in ferromagnesian elements (Fe2O3+MgO) and is enriched in alkali elements (Na2O+K2O). Moreover, the fertile type is characterized by high Rb and low Sr. Also, direct relation between SiO2 and Rb is obtained, while with Ba and Sr do not correlated well. The REE illustrate that the fertile granites possess high negative Eu value relative to the normal type.

The relationship between U and La, Ce, Sm, Pb, Rb, Zr, F and Mo was found to be direct relation, while Co, Sr, Eu, and Ba was found to be a weak correlation.