Zircon U-Pb Dating and Geological Significance of Late Paleozoic Intrusive Rocks in the Khanbogd-Erdene Area, Southern Mongolia

The Khanbogd-Erdene region in southern Mongolia is a globally important copper–polymetallic metallogenic province, hosting large to super-large deposits, such as Oyu Tolgoi and Tsagaan Suvarga. The area experiences frequent tectonic–magmatic activity, particularly Late Paleozoic subduction-related magmatism, which controls the occurrence of large-scale copper–polymetallic mineralization. This study focuses on the Late Paleozoic granitic intrusive rocks in the Khanbogd-Erdene region of southern Mongolia. Using LA-ICP-MS and SHRIMP dating techniques, precise zircon U–Pb ages were obtained for 10 samples. A total of 209 zircon grains from these 10 intrusive rocks were analyzed, with most cathodoluminescence (CL) images of zircon grains showing distinct oscillatory zoning. Th/U ratios ranging from 0.11 to 2.92 indicate they are magmatic. The younger group of granitic rocks yielded ages between 260.2 ± 1.2 Ma and 286.6 ± 0.9 Ma, indicating an Early Permian geological age. The other seven samples yielded older ages between 315.9 ± 1.8 Ma and 340.9 ± 0.9 Ma, indicating a Carboniferous geological age. These large-scale Carboniferous to Early Permian intrusive rocks in the Khanbogd-Erdene region are products of tectonic–magmatic activity during specific stages of crustal evolution. The findings provide reliable chronological data for regional tectonic–magmatic activity and offer new evidence for constraining the timing of the Variscan orogeny in southern Mongolia.