Jiuda Sun’s research while affiliated with Jilin University and other places

The Zhaojinggou Nb–Ta deposit is one of large rare metal deposits newly discovered in the northern margin of the North China Craton in recent years. This paper reports petrography, petrochemistry, columbite‐group minerals U–Pb chronology study of the amazonite granitic pegmatite (AGP) exposed in this deposit, and composition of columbite‐group minerals and biotite are obtained by electron probe microanalyzer and LA‐ICP‐MS. Eighteen analyses of columbite‐group minerals yielded weighted mean 206Pb/238U age of 116.9 ± 1.4 Ma. The crystallization temperature of biotite is 630–650°C, and the oxygen fugacity is 10−17–10−18 bars. The biotite has low MgO contents and high Rb, Rb/Sr, and FeOT/(FeOT + MgO) ratios. The AGP has extremely low MgO, Cr, Co and Ni contents, with Nb/Ta ratios range from 1.63 to 9.05 and Rb/Sr ratios range from 303.30 to 648.90, and obvious ‘M’ type tetrad effect of rare earth element indicating that the formation of the AGP is related to crust‐derived magma. The contents of Nb2O5 and FeO decrease, while the Ta2O5 and WO3 contents, Mn# and Ta# values increase gradually from the core to the rim of columbite‐group minerals. Some columbite‐group minerals have unobvious oscillatory zoning, and some have a clear bright zoing with high Ta contents on the rim, indicating that the genesis of Zhaojinggou Nb–Ta deposit is mainly magmatic crystallization differentiation, accompanied by hydrothermal autometasomatism in the late stage. The deposit was formed in an extensional tectonic background in the late Yanshanian, magma was formed by partial melting of Nb–Ta‐rich lower crust, undergoing high evolution. Mineralization is crystallization differentiation and hydrothermal self‐metasomatism

The Haobugao Zn-Fe-Sn skarn deposit in the Southern Great Xing’an Range of NE China contains three generations of garnets that were distinguished using petrography. This paper discusses skarn formation and hydrothermal fluid evolution in the Zn-Fe-Sn skarn system based on the interpretation of diverse textures and compositions of garnets. Crystals of first-generation garnet (Grt 1) from the proximal exoskarn are red-brown, coarse-grained garnets that are subhedral and optically isotropic. They are dominantly grossular (Adr49-18Grs51-82) and have the highest REE contents of the garnets at Haobugao. They are LREE-depleted, HREE-enriched, with negative Eu anomalies, and they formed under low water/rock (W/R) ratios and neutral pH conditions. Crystals of second-generation garnet (Grt 2) from the central exoskarn are yellow-green and andradite dominated (Adr63-97Grs2-36). They have relatively isotropic cores with chaotic anisotropism (Grt 2a) or oscillatory zoned rims (Grt 2b). The Grt 2 cores have low REE contents, are LREE-enriched, HREE-depleted, with positive Eu anomalies, and formed under high W/R ratios and acidic conditions. The Grt 2 rims have higher REE contents, are LREE-depleted, HREE-enriched, with weak negative Eu anomalies, and formed under low W/R ratios and acidic condition. Crystals of third-generation garnet (Grt 3) coexist with pyroxene and are light yellow-brown, zoned or optically homogeneous. They are relatively Fe-rich grossular (Adr49-51Grs48-50), compared with Grt 1. They have the lowest REE contents of the garnets at Haobugao, and a REE pattern similar to that of the Grt 1, which indicates they formed under low W/R ratios, reduced to oxidized and neutral pH conditions. The REE content and fractionation of garnets indicate periodic fluctuations in fluid composition occurred in the Haobugao Zn-Fe-Sn skarn system, likely caused by the joint effects of magmatic and meteoric water. Diverse mechanisms contributed to the ΣREE variation in garnets.

The Haobugao Pb–Zn deposit located in the southern Great Xing’an Range (SGXR) is one of the most important deposits within the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt. Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite are present in the ore area and are assumed to be closely related to the mineralization. In this study, a new isotopic dating technique, zircon U–Pb laser ablation inductively coupled plasma mass spectrometer analysis, was applied to the granites; the analyses indicate that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite were emplaced at 143.9 ± 1.1 Ma and 151.3 ± 1.4 Ma, respectively. Geochemically, these A-type granites are characterized by relatively high SiO2 and K2O contents, low Al2O3 content, and negative Eu anomalies. Additionally, both granites display strong Rb, Th, U, and Ce enrichment and Ba, K, Sr, and Ti depletion. Their relatively high εHf (t) values (with averages of 7.13 and 7.87, respectively) and young two-stage Nd and Hf model ages indicate that the two granites may have predominantly derived from the partial melting of a juvenile lower crust, followed by fractional crystallization during magma ascent. The geological, elemental, and isotopic evidence shows that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite formed due to the upwelling of mantle-derived alkaline magma and partial melting of the crust, with a certain degree of mixed dyeing, under a tectonic background of asthenosphere upwelling and lithosphere extension via the subduction of the ancient Pacific plate.

The timings of subduction of the Palaeo-Pacific Plate beneath the North China Craton and of associated mineralisation remain unresolved. We studied a granodiorite porphyry in the Banmiaozi gold mining area, located along the northeastern margin of North China Craton, to shed light on these timings. Using zircon U–Pb geochronology, major- and trace-element geochemistry, Sr–Nd isotopes, and biotite compositions, we show that the granodiorite porphyry formed during the early Middle Jurassic and has a composition similar to those of ‘C-type adakites’ from eastern China. The granodiorite rocks have initial Sr isotopic compositions of 0.713418–0.713694, εNd(t) values of −15.9 to −16.69, and depleted-mantle single-stage model ages of 2.70–2.49 Ga, implying that the parental magma originated via subduction of the Palaeo-Pacific Plate beneath the North China Craton and resulted also in the generation of basaltic magmas and partial melting of thickened lower crust. As the Archaean basement rocks were rich in Au and magnetite, the magma was characterized by high Au contents and oxygen fugacity (fO2 = 10−13 bar). Subsequent mixing with, or contamination by, partially melted Proterozoic marine strata, such as the marble-bearing Laoling Group, played an important role in mineralisation. These country rocks provided large quantities of Cl−, CO32−, and SO42− to the magma, which formed soluble complexes with ore-forming elements such as Au, allowing enrichment and migration of the metals. Our data show that the Banmiaozi gold deposit is an orogenic gold deposit associated with subduction-related adakitic magmatism.

The Early Paleozoic Bianjiadayuan complex of monzodiorite and biotite-bearing monzogranite is located in the southern part of the Huanggangliang–Ganzhuermiao metallogenic belt, southern Greater Khingan, China. The 206Pb/238U ages of zircons from the monzodiorite and biotite-bearing monzogranite are 129.67 ± 0.4 and 143.20 ± 1.2 Ma, respectively. The total REE contents of the rocks are very high, especially LREEs, suggesting obvious LREE and HREE fractionation; the monzodiorite has weak negative Eu anomalies, the biotite-bearing monzogranite highly negative anomalies. These rocks are all rich in large ion lithophile elements (Rb and U) and relatively depleted in high-field-strength elements (Nb and Ta). The monzodiorites and biotite-bearing monzogranites have ε Hf(t) values of 1.39–5.69 and 0.86–2.46 and t DM2 ages of 0.82–1.09 and 1.04–1.24 Ga, respectively. In the ε Hf(t)–t diagram, the data plot between the chondrite and depleted mantle lines of Hf isotopic evolution, showing the rocks were derived mainly from new crustal material that had been derived by the differentiation of the mantle. We conclude that this area underwent an important episode of crustal growth in the Meso–Neoproterozoic. The relationship between the intrusive complex and the orebody was related to faulting; we infer that the Bianjiadayuan Pb–Zn polymetallic deposit is mainly related to Late Jurassic–Early Cretaceous (144–129 Ma) magmatic activity, and it represents large-scale mineralisation in the context of Paleo-Pacific plate subduction and regional extension.