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Recent mineral exploration has identified a new gold metallogenic belt which contains reserves of >120 tonnes Au along the northeastern margin of the Jiaolai Basin, Jiaodong Province. However, the origin of these deposits remains a subject of considerable debate. This paper presents a combination of fluid inclusion and systematic H–O–He–Ar–S-Pb isotopic data of the Tudui–Shawang deposit which is characterized by sulfide-rich ores. Homogenization temperatures of fluid inclusions in the three recognized stages are 245 to 426 °C, 210 to 410 °C, and 160 to 270 °C, respectively, all of which exhibit salinities lower than 15 wt% NaCl equivalent. The δ18OH2O values of quartz in ore stages 1 and 2 range from + 3.4‰ to + 6.3‰ and + 2.3‰ to + 4.5‰, whereas the δDSMOW from − 93‰ to − 86‰ and − 97‰ to − 83‰, respectively. The data suggest that ore fluids are derived from magma gradually mixing with more meteoric water late. The measured 3He/4He (40Ar/36Ar) of hydrothermal fluids in pyrites are 1.53 to 3.21 Ra (732 to 1783) for stage 1, and 0.38 to 2.58 Ra (360 to 1544) for stage 2. The linear correlation between He and Ar isotopes is the result from a mixture between mantle components and crustal fluid. The estimated 3He/heat ratios range from 0.13 to 2.55 × 10−12 cm3 STP J−1, reflecting the hydrothermal fluids are derived by convection rather than conduction. The in-situ δ34S values of three types of pyrite (Py1, Py2-1, and Py 2–2) from two stages have a narrow and similar range from + 7.1 to + 9.7‰, indicating common deep sulfur sources. Lead isotopic compositions of pyrites (206Pb/204Pb = 17.102 to 18.248; 207Pb/204Pb = 15.435 to 15.590; 208Pb/204Pb = 37.659 to 38.691) show a consistent origin as mafic dikes. Thus, we propose deep-seated, most likely mafic dike magmatic and mantle-derived sources for gold ore formation. When compared to other Jiaodong gold deposits, they exhibit similar geochemical signatures and thus consistent geodynamic setting. They are considered to associate with the subduction of the Paleo-Pacific Plate and the destruction of the North China Craton during the Early Cretaceous.

Recycling of noble gases from crustal rocks into the mantle is indicated not only by oceanic basalts and mantle xenoliths, but also by ultrahigh-pressure metamorphic rocks in collisional orogens. It is intriguing whether noble gases in continental crust were recycled into the mantle by deep subduction of the continental crust to mantle depths. Here we firstly report the He, Ne and Ar isotopic compositions of pyroxene from postcollisional mafic igneous rocks in the Dabie orogen, China. The results show that the pyroxene separates from the mafic rocks have low 3 He/ 4 He ratios of 0.002 to 1.8 Ra and air-like Ne isotope compositions. Furthermore, the pyroxene exhibits low 40 Ar/ 36 Ar ratios of 393.6 to 1599.8, close to those of the air. In combination with whole-rock geochemistry it is found that pyroxene 3 He/ 4 He ratios are correlated with whole-rock (La/Yb) N and Sr/Y ratios, e Nd (t) values and MgO contents. These observations demonstrate the mass transfer from the deeply subducted continental crust to the overlying mantle wedge, recording the source mixing between the crust-derived melt and the mantle peridotite in the continental subduction zone. A direct addition of the crustal He via crust-derived melt to the mantle leads to the extremely low 3 He/ 4 He ratios in the orogenic lithospheric mantle, and the dissolved atmospheric Ar and Ne in the subducted supracrustal rocks results in the air-like Ar and Ne isotope ratios. Therefore, the noble gas isotopic signatures of supracrustal rocks were carried into the mantle by the continental deep subduction to subarc depths and then transferred to the postcollisional mafic igneous rocks via the melt–peridotite reaction at the slab–mantle interface in a continental subduction channel. Our finding firstly establishes the slab–mantle interaction model for recycling of supracrustal noble gases in the continental subduction zone.

The intense Cenozoic volcanism of Mt. Changbai provides a natural laboratory for investigating the characteristics of volcanism and the dynamical evolution of the Northeast Asian continental margin. Mt. Changbai volcanoes predominantly consist of Wangtian'e volcano in China, Tianchi volcano spanning China and DPR Korea, and Namphothe volcano in DPR Korea. Geochronology data and historical records of volcanism indicate that the three eruption centers were formed in the following sequence: Wangtian'e volcano to Namphothe and Tianchi volcano, advancing temporally and spatially from southwest to northeast. The three eruption centers of Mt. Changbai volcano are located close together, have similar magma evolution trends, bimodal volcanic rock distribution, and an enriched mantle source, etc. Although the Cenozoic volcanism in Mt. Changbai is thought to be somewhat related to the subduction of the Western Pacific Plate, the regularity of volcanic activity and petrography characteristics have continental rift affinity. We therefore conclude that the occurrence of synchronous and similar volcanic activity on both sides of the Japan Sea (i.e., the Japan Arc and Northeast China) likely respond to the rift expansion and the back-arc spreading of Japan Sea. From many perspectives, Mt. Changbai volcano is a giant active volcano with hidden potentially eruptive risks.

Continental basalts commonly exhibit similar geochemical compositions to oceanic island basalts, but their origin is still enigmatic in chemical geodynamics. This involves a resolution to the nature of crustal components in their mantle sources. For this purpose, we have studied the He and Ar isotopic compositions of mineral phenocrysts from Cenozoic continental basalts in eastern China. The results are combined with existing data for whole-rock geochemistry, yielding two trends between noble gas isotopic and other geochemical indicators. First is high 3He/4He ratios of 6.6 to 7.5 RA and low 4He/40Ar* ratios of 0.07 to 1.39 in association with varying (La/Yb)N values from 10.4 to 31.8. Second is low 3He/4He ratios of 0.6 to 2.4 RA and variable 4He/40Ar* ratios from 0.68 to 15.47 in association with low (La/Yb)N values of 11.3 to 12.0. Phenocryst 40Ar/36Ar ratios vary from 331.0 to 1677.4, in which the low ratios are associated with the low (La/Yb)N values. In combination with whole-rock Ba/Th and Sr/Y ratios as well as initial Sr and Nd isotopic ratios, we suggest three-component mixing between enriched MORB mantle, altered oceanic basalt and seafloor sediment to generate the mantle sources. The two kinds of crustal components would be incorporated into the mantle sources in the form of felsic melts. One is adakitic melt deriving from the altered oceanic basalt and thus low in Ba/Th ratios but high in Sr/Y, (La/Yb)N and eNd(t) values. The other is sialic melt originating from the seafloor sediment and thus high in Ba/Th ratios but low in Sr/Y, (La/Yb)N and eNd(t) values. The atmospheric Ar and crustal He noble gas components would be carried by the both seawater–hydrothermally altered basalt and seafloor sediment on the oceanic crust. These oceanic crust-derived melts would serve as a metasomatic agent to transfer the supracrustal He and Ar isotopic signatures to the mantle sources. The felsic melts would react with the mantle wedge peridotite during slab–mantle interaction in oceanic subduction channel. Therefore, the noble gas isotopic compositions of mantle sources for intraplate basalts are primarily determined by the budget between the mantle and crustal components during the melt–peridotite in oceanic subduction factory.