Namkha Norbu

The East Kunlun orogenic belt (EKOB), located in the northeastern part of the Qinghai‐Tibet Plateau, is a significant Cu‐Ni mineralization region associated with the geological evolution of the Paleo‐Tethys and Proto‐Tethys stages. Orogenic environments in this region exhibit considerable metallogenic potential, with two distinct metallogenic models: the subduction‐related island arc model and the post‐collisional extensional model. This study investigates the petrology, zircon U–Pb chronology, and geochemistry of ore‐bearing intrusions in the Langmuri Cu‐Ni deposit. The results reveal that the wehrlite yields a zircon U–Pb age of 420.0 ± 1.4 Ma, with an average ε _Hf ( t ) value of −5.5 and significant Nb‐Ta negative anomalies. These features suggest that the parental magma was likely derived from the partial melting of a metasomatized continental lithospheric mantle. Additionally, crustal contamination during magma ascent triggered significant crustal sulfur assimilation. The Langmuri deposit represents a mineralization event formed during the final tectonic stage of the Proto‐Tethys Ocean in a post‐collisional extensional setting. Slab breakoff released hydrous fluids and melts that metasomatically enriched the lithospheric mantle, thereby providing the material basis for magmatic sulfide segregation.

The East Kunlun Orogenic Belt is considered as one of the important gold mineralization regions in the Tethys tectonic domain. These orogenic gold deposits are related to intermediate-acid intrusions formed at the end of Paleo-Tethys evolution, but the petrogenesis is controversial. This paper presents a new study on the geochemistry of zircon U-Pb, O, S, and Pb isotopic compositions of Asiha quartz diorite, granite porphyry, and sulfides. The geochemical features of quartz diorite and granite porphyry are consistent with the modern adakite, with high content of Sr but low content of Y, Yb, and MgO. Magmatic zircons from these two types of intrusion yielded U-Pb ages of 238.4 ± 1.4 Ma and 240 ± 1.7 Ma, respectively. The high O isotopic composition of Asiha complex may reflect that crust or crustal derivates were incorporated into the magmatic melt, and the Pb isotope characteristics indicates a lower crust origin. The δ³⁴S values of pyrites range from 4.9‰ to 11.6‰. This study infers that the Asiha complex perhaps formed by partial melting of the Paleo-Tethys subducted oceanic crust with seafloor sediments and is markedly different from the traditional adakite. Asiha deposit is an orogenic gold deposit related to adakite-like rocks, which formed in Triassic in the East Kunlun Orogenic Belt.

The Gayahedonggou magmatic Cu-Ni sulfide deposit was recently discovered in the East Kunlun orogenic belt (Northern Tibetan Plateau, China). The mineralization in this region is associated with mafic–ultramafic intrusions. To date, the formation age and metallogenic model of these ore-bearing intrusions have not been studied systematically. In this paper, the petrology, zircon U-Pb chronology, and geochemistry of ore-bearing wehrlite and quartz diorite are investigated. The results show that the zircon U-Pb isotopic age of wehrlite is 419.9 ± 1.5 Ma with an average εHf(t) value of 3.0, indicating that wehrlite originated from a depleted mantle or the asthenosphere. The (La/Yb)_N, (La/Sm)_N, (Gd/Yb)_N, Nb/U, and Ce/Pb ratios of wehrlite are between 3.01–7.14, 1.69–3.91, 1.36–1.51, 2.07–2.93, and 0.55–1.42, respectively, indicating that the parent magma of the wehrlite had been contaminated by the upper crust. The zircon U-Pb isotopic age of quartz diorite is 410.2 ± 3.5 Ma with an average εHf(t) value of 8.0, and the A/CNK and A/NK ratio of quartz diorites ranges from 1.02 to 1.04 and from 2.13 to 2.23, respectively. These features are similar to those of the type I granite, and the quartz diorite was likely derived from the lower crust. Combined with the regional geological evolution, the Gayahedonggou complex formed in a post-collision extensional environment. The pyroxene in the Gayahedonggou complex is mainly clinopyroxene, which is enriched in the CaO content, indicating that the CaO content of the parent magma of the Gayahedonggou complex is high or that the complex has been contaminated by Ca-rich surrounding rocks, which hinders Cu-Ni mineralization.