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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. [ABSTRACT FROM AUTHOR]

Calc‐alkaline granitoid intrusions with abundant mafic microgranular enclaves (MMEs) are widespread in the East Kunlun orogenic belt (EKOB). Here, we present petrological observations, zircon U–Pb ages, whole‐rock geochemical, and Sr–Nd–Hf isotopic data for quartz diorites and the MMEs in the Asiha gold ore deposit in the EKOB, to constrain their petrogenesis and tectonic setting. The laser ablation inductively coupled plasma mass spectrometer 206Pb–238U ages of zircons indicate that the host quartz diorites and their MMEs from the Asiha gold deposit crystallized at 228.4 ± 1.7 Ma and 229.0 ± 1.7 Ma, respectively, which is similar to the gold mineralization age. Whole‐rock geochemical data indicate that the quartz diorites are I‐type granites. The MMEs have εHf(t) values of −7.6 to −0.2, −2.1 on average, whereas those of the quartz diorites range from −3.2 to −0.8, with a mean value of −2.1, which is identical within analytical uncertainty. Moreover, the host quartz diorites and their MMEs have relatively homogeneous Sr–Nd isotopic compositions, with high initial 87Sr/86Sr ratios and low εNd(t) values ranging from 0.70914 to 0.70963 and from −5.9 to −5.5, respectively. In summary, the MMEs and host quartz diorites have similar geochemical characteristics, indistinguishable Sr–Nd–Hf isotopic composition, and almost simultaneous crystallization age. Geochemical evidence shows that they formed due to the mixing of crust‐ and mantle‐derived magmas. Combined with our new results and published geological, geochronological, and geochemical data, this paper proposes that the EKOB had evolved into a post‐collisional environment at about 230–228 Ma, and the host quartz diorites and their MMEs from the Asiha complex formed in the transitional stage from the syn‐collisional to the post‐collisional setting. [ABSTRACT FROM AUTHOR]

The East Kunlun orogenic belt (EKOB) is located in the northeastern part of the Qinghai-Tibetan Plateau, China. Voluminous Silurian-Devonian granitoids were formed during the Proto-Tethys Ocean subduction and collision process. In this study, zircon U-Pb age dating, in-situ Hf isotope analyses, and whole rock major and trace element analyses have been carried out on granitoids from the central to eastern EKOB. The formation ages of granodiorite in the Bairiqili area, the granodiorite in the Wulonggou area are 410 ± 2 Ma and 396 ± 1 Ma, respectively, and the granodiorites show I-type features. The Wulonggou syenogranite with a formation age of 398 ± 2 Ma has a high differentiation index (D.I. = 89.59–92.43), and may belong to the high fractionated I-type granite. The Lalangmai tonalite with a formation age of 423 ± 2 Ma has high Sr (339–590 µg/g), εHf(t) (1.5–7.3), and low Y (3.45–6.33 µg/g), which are similar to modern adakites. The Lalangmai tonalite is the latest adakite record during the Proto-Tethys evolution in EKOB. Combined with previous studies, it is concluded that the granitoids from Cambrian to Devonian divided into four episodes. The first episode (515–436 Ma) mainly consists of I-type island arc granites and adakite, which are formed in a subduction environment. The second episode (436–427 Ma) is characterized by the S-type granites related to the collision. The third episode (427–420 Ma) is the transition period between the collision and the post-collision environment. In the fourth episodes (420–385 Ma), granitoids were formed in post-collision extensional environment, which is characterized by I-type and A-type granites. The upwelling of asthenosphere material is likely caused by the collapse of the orogenic belt. After 420 Ma, I-type and A-type granites formed at different depths but in the same environment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Reshui porphyry Mo deposit is located in the East Kunlun orogenic belt (EKOB). Molybdenum mineralization is distributed in monzogranite and porphyritic monzogranite rocks, mainly presenting as various types of hydrothermal veinlets in altered wall rocks, and the orebodies are controlled by three groups of fractures. In this paper, we present the results of fluid-inclusion and isotopic (S and Pb) investigations of the Reshui Mo deposit. The ore-forming process of the deposit can be divided into three stages: an early disseminated molybdenite stage (stage 1), a middle quartz–molybdenite stage (stage 2) and a late quartz–polymetallic sulfide stage (stage 3). The alteration was mainly potassic and silicic in stage 1, silicic in stage 2, and sericitic and silicic in stage 3. Five types of fluid inclusions (FIs) can be distinguished in quartz phenocrysts and quartz veins, namely W, PL (pure liquid inclusions), PV (pure gas inclusions), C (CO2 three-phase inclusions), and S (daughter mineral-bearing inclusions). The homogenization temperatures of fluid inclusions belonging to stages 1 to 3 are 282.3–378 °C, 238.7–312.6 °C and 198.3–228 °C, respectively. The fluid salinities at stages 1 to 3 are 4.65–8.14% NaCl eq., 4.34–42.64% NaCl eq., and 3.55–4.65% NaCl eq., respectively. The fluids of this deposit were generally moderate–high temperature and moderate–low salinity and belong to the H2O–NaCl–CO2 ± CH4 system. The temperature and pressure changed considerably between stage 2 (high–medium-temperature) and stage 3 (low-temperature). The evidence for ore-forming fluids containing different types of coexisting inclusions in stage 2 and a decrease in the fluid temperature from stage 2 to stage 3 indicate that fluid boiling and fluid mixing were the main mechanisms of ore precipitation. The sulfide 34SV-CDT values range from 4.90‰ to 5.80‰, which is characteristic of magmatic sulfur. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the ore minerals are 18.210–18.786, 15.589–15.723, and 38.298–39.126, respectively. These lead isotopic compositions suggest that the ores were mainly sourced from crustally derived magmas, with minor input from the mantle. The fluid inclusions and S–Pb isotopes provide important information on the genesis of the Reshui porphyry Mo deposit and indicate that the Triassic has high metallogenic porphyry potential in the EKOB. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magmatism and mineralization in the Duolongqiarou Mo deposit occurred at 236–238 Ma. • The magma source is derived from partial melting lower crust involving mantle materials. • Mo deposit is linked to fractionated I-type granite in collision tectonic setting. • Two generations of porphyry Mo-(Cu) mineralization exist in the EKOB Paleo-Tethys. The Mo deposits in the Kunlun-Qinling-Dabie orogen are mainly associated with porphyry or porphyry-skarn mineralisation in a collision or post-collision setting. However, collision-type Mo deposits that are related to granite and mineralization produced in magmatic systems remain poorly constrained. To better define the genetic relationship between the intrusions and Mo mineralization in collision setting, the geochronology, geochemistry, and Sr-Nd-Hf isotopes of the granodiorite and monzogranite in Duolongqiarou Mo deposit, East Kunlun Orogenic Belt (EKOB), NW China, are presented. Zircon U-Pb dating shows granodiorite and monzogranite ages of 237.6 ± 1.5 Ma and 236.8 ± 1.8 Ma, respectively, which is consistent with the molybdenite Re-Os weighted mean model age of 235.9 ± 1.4 Ma. This suggests that the granitic magma related to Mo mineralization at the Duolongqiarou formed during the Triassic (ca. 236 Ma). The ore-bearing monzogranites with high SiO 2 contents (76.84–77.92 wt%) are peraluminous high-K calc-alkalic rocks, while the ore-barren granodiorites with low SiO 2 contents (66.89–69.90 wt%) are metaluminous Na-rich calc-alkalic rocks. Both are enriched in large ion lithophile elements and light rare earth elements but depleted in high-field strength elements, which is characteristic of I-type granites. Ore-bearing and barren granites have similar εNd(t), εHf(t), and T DM2 age, indicating a similar magma source derived from partial melting of ancient Mesoproterozoic lower crustal components with involvement of mantle materials. The amphiboles of monzogranite show higher values of calculated pressures (average 122 MPa) and melt H 2 O content (average 5.7 wt%) than granodiorites, suggesting that monzogranites and granodiorites crystallized at different depths of the same magma chamber. Ore-bearing monzogranites show much lower contents of transition metals (e.g., Sc, V, and Cr), negative Eu anomalies (δEu = 0.32–0.46), and higher differentiation index values (94.52–96.92) compared to barren granodiorites. This suggests that high differentiation and fractionation promote Mo metal enrichment during magmatic evolution and subsequent formation of the magmatic-hydrothermal Duolongqiarou Mo deposit. The Duolongqiarou Mo deposit was formed in a collisional setting in response to the slab break-off of the EKOB Paleo-Tethys ocean. The results of this study combined with published data suggest that at least two generations of Mo polymetallic metallogenic events were observed in the Paleo-Tethys of the EKOB. This is very helpful to target porphyry Mo mineralization and guide regional exploration. [ABSTRACT FROM AUTHOR]

• The granites and Sn mineralization in the Xiaowolong deposit formed at ca. 260 Ma. • The porphyry monzogranite was unfractionated I-type granite and derived from partial melting of ancient crust. • The Xiaowolong deposit occurred in a subduction geodynamic setting. Abundant granitoids are exposed along the East Kunlun orogenic belt (EKOB), and many skarn deposits occur at the contacts between intrusions and strata. One such is the Xiaowolong deposit, a skarn-type tin polymetallic deposit that is temporally and spatially associated with porphyry monzogranite. Tin mineralization is mainly hosted by the skarn. In this study, we reported zircon and cassiterite U–Pb ages, whole-rock geochemistry, and Sr–Nd–Hf isotopic data, and used these to constrain the timing of intrusion and mineralization in the Xiaowolong deposit and identify the origin of the ore-related granites and the link between Sn mineralization and granitic magmatism. Age determinations by LA-ICP-MS U–Pb zircon dating indicated that the porphyry monzogranite formed at 260.0 ± 0.7 Ma. Cassiterite from the ore-bearing skarn yielded a Tera-Wasserburg U–Pb lower intercept age of 258.0 ± 3.7 Ma. These ages suggested that both granitic intrusion and related Sn mineralization in the Xiaowolong deposit were initiated during the Permian (ca. 260 Ma). The porphyry monzogranites had high SiO 2 (71.26–73.13 wt%) and Al 2 O 3 (13.84–14.46 wt%) contents, were alkali-enriched (K 2 O + Na 2 O = 7.08–7.69 wt%), had A/CNK values that ranged from 1.01 to 1.05, were enriched in light REEs and large ion lithophile elements such as Rb, Th, U and K, were depleted in high field strength elements, and had relatively low Zr, Nb, Y and Ce contents. They thus exhibited the geochemical characteristics of I-type granite. The porphyry monzogranite had consistent negative whole rock ɛNd(t) (−6.8 to −7.1) and magmatic zircon ɛHf(t) values ranging from −7.4 to −1.6, and two-stage Hf model ages ranging from 1393 Ma to 1758 Ma. Detailed elemental and isotopic data demonstrated that the porphyry monzogranite were derived from partial melting of ancient crustal source, and emplacement in a subduction tectonic setting. The Xiaowolong tin mineralization event indicated that the EKOB has great potential for exploration focusing on Permian-Triassic Sn skarn deposits. [ABSTRACT FROM AUTHOR]