Geochemistry and Metallogenic Characteristics of Ultramafic Volcanic Rocks in Southern Qinling Tectonic Belt

This study integrates multi-disciplinary methods such as field geology, petrography, mineralogy and geochemistry to investigate the ultrabasic volcanic rocks within the Southern Qinling Orogenic belt. The aim is to provide constraints for the geochemistry of the ultrabasic volcanic rocks in this area and their ore-bearing characteristics. The research results are of great significance for the search of primary diamond deposits in the Southern Qinling orogenic belt. The research results show that the ultrabasic rocks in the Langao area of the Southern Qinling Mountains are mostly irregular tubular, cylindrical and lens-shaped in the wild. The main rock types are altered Kimberly breccia and gravelly tuxaceous kimberly, etc. The average content of SiO₂ in the samples was 40.36%, that of MgO was 11.09%, that of CaO was 9.7%, that of TFe2O3 was 13.63%, that of Al₃O₂ was 9.67%, and that of TiO₂ was 3.84%. The average ratio of CaO/Al₂O₃ is 1.00, and the average ratio of CaO/TiO₂ is 2.69. Overall, it is enriched with large-ion lithophilic elements and light rare earth elements, significantly deficient in elements such as K, Ba, and Sr, and enriched with high-field elements such as U, Nb, Zr, and Sm. The average Nb/U ratio is 37.59. The average total amount of rare earth elements (∑REE) is 271.833×10^-6. The average contents of light and heavy rare earths (LREE) were 248.602×10^-6 and 23.231×10^-6 respectively. The average ratio of light and heavy rare earth elements (LREE/HREE) is 10.61. In this study, both basic and ultrabasic components were used to jointly constrain the ore-bearing properties of the samples. The diagrams of the samples show that the mineralization effect is not good, and the empirical discriminant also indicates that kimberlite belongs to the poor ore type. It is suggested that further research be conducted on its ore-bearing property from other perspectives such as structural analysis and mineralogy.