Geochemical signatures and tectonic setting of monzogranites in the Lawu ore deposit, Damxung, Xizang

The Lawu ore deposit is located in the eastern part of the Gangdise Cu-Pb-Zn polymetallic metallogenic belt in Damxung, Xizang. The geochemical signatures have revealed that the monzogranites outcropped in the Lawu ore deposit are rich in SiO₂(65.40%-74.43%), Al₂O₃ and CaO, and poor in Fe and Na₂O. The A/CNK ratios range between 1.41 and 2.20, suggesting the highly peraluminous granites. The ΣREE values vary between 5.08×10^-6 and 80.38×10^-6. The La_N/Yb_N ratios range between 2.43 and 5.65. The ΣLREE/ΣHREE ratios range from 1.63 to 3.64. The REE distribution patterns display the right-leaning curves, and negative Eu anomalies. The high field strength elements such as Nb, Ti, Zr and Ce as well as Ba are markedly depleted while the large ion lithophile elements such as K, Rb and Sr are markedly enriched. It follows that the monzogranites in the Lawu ore deposit were derived from the upper crust, and the source rocks are represented by mudstones. The peraluminous granites cited above are interpreted to be formed in the syn-collisional tectonic settings during crustal thickening.