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Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodoluminescence (CL) images. The Pb/U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements (e.g., Rb, K), and depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti); they all exhibit marked negative Eu anomalies. Their zircon ɛ( t) values range mainly from +1.86 to +6.21 (for the granites) and +1.39 to +3.89 (for the gabbros), except for one spot with a value of −0.27 (for a gabbro). The T ages for the gabbros and T ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal material, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Ordovician granites and gabbros constitute a typical bimodal igneous rock association, implying an extensional environment that was probably related to the post-collisional development of the Erguna and Xing'an massifs in the early Early Paleozoic. [ABSTRACT FROM AUTHOR]

The Paleozoic to early Mesozoic tectonic framework and evolution of Northeast China, especially the Jiamusi block and its related structural belts, are highly debated. In this paper, geochemical, geochronological and isotopic analyses were carried out on the blueschist in the Heilongjiang Complex to address these issues. The Heilongjiang Complex defines the suture belt between the Jiamusi block and the Songliao block in NE China, and the blueschist is a major composition for this complex, coexisting with mafic-ultramafic rocks, greenschist, quartzite and mica schist. The blueschist has a mineral association of sodic amphibole, epidote, chlorite, phengite, albite and quartz with accessory phases of apatite, titanite, zircon and ilmenite. Together with the lithological association, the major and trace element compositions present that the protoliths of the blueschist can be divided into the alkaline and tholeiitic basalts and have OIB affinities, formed in an ocean island setting, indicated by the (La/Yb) N values of 3.57 – 11.54, and the (La/Sm) N values of 0.69 – 3.64. The high and positive ε Nd (t) values of + 3.7 to + 9.0, and relative enrichment in Nb (vs. Th) and Ta (vs. U) show that both the alkaline and tholeiitic basalts may be derived from the asthenospheric mantle with insignificant crustal contamination. Magmatic zircons from the blueschist in Yilan area yield a 206 Pb/ 238 U age of 281 ± 3 Ma, interpreted as its protolithic age. The youngest ages of ~ 200 Ma of the detrital zircons in the associated mica schist from Mudanjiang area place constraints on the timing of metamorphism for the blueschist. These indicate that a big ocean existed between the Jiamusi and Songliao blocks at least since the early Permian, and the blueschist formed since the late Triassic to late Jurassic by the subduction of this ocean. Such an ocean during the Permian – Jurassic is difficult to be interpreted by the tectonic evolution of the Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]

Located in the east section of the Central Asian orogen in northeastern China, the Xilamulun district comprises several newly discovered molybdenum deposits, primarily of porphyry type and Mesozoic ages. This district is divided by the Xilamulun fault into the southern and the northern parts. In this paper, we present new zircon U–Pb dating, trace elements and Hf isotope, and/or whole rock Sr–Nd–Pb isotopic results for the host granitoids from three Mo deposits (Yangchang, Haisugou and Shabutai) in northern Xilamulun. Our aim is to constrain the age and petrogenesis of these intrusions and their implications for Mo mineralization. Zircon U–Pb LA-ICP-MS dating shows that the monzogranites from the Shabutai and Yangchang deposits formed at 138.4 ± 1.5 and 137.4 ± 2.1 Ma, respectively, which is identical to the molybdenite Re–Os ages and coeval well with the other Mo deposits in this region, thereby indicating an Early Cretaceous magmatism and Mo mineralization event. Zircon Ce/Nd ratios from the mineralized intrusions are significantly higher than the barren granites, implying that the mineralization-related magmas are characterized by higher oxygen fugacity. These mineralized intrusions share similar zircon in-situ Hf and whole rock Sr–Nd isotopic compositions, with slightly negative to positive ε Hf (t) ranging from − 0.8 to + 10.0, restricted ε Nd (t) values from − 3.7 to + 1.6 but a little variable ( 87 Sr/ 86 Sr) i ratios between 0.7021 and 0.7074, indicative of formation from primary magmas generated from a dominantly juvenile lower crust source derived from depleted mantle, despite diverse consequent processes (e.g., magma mixing, fractional crystallization and crustal contamination) during their evolution. The Pb isotopes (whole rock) also show a narrow range of initial compositions, with ( 206 Pb/ 204 Pb) i = 18.03–18.88, ( 207 Pb/ 204 Pb) i = 15.48–15.58 and ( 208 Pb/ 204 Pb) i = 37.72–38.28, in agreement with Sr–Nd–Hf isotopes reflecting the dominance of a mantle component. An integration of geochronological and isotopic data points to three stages of Mo mineralization events (i.e., Triassic, Late Jurassic, and Early Cretaceous) associated with magmas generated from three different source regions in the Xilamulun district, NE China. The variation in the origin of the magmas from which the porphyry Mo systems were generated suggests that the formation of Mo deposit lies not in the composition of magma sources. Other factors, including high magma oxygen fugacity, may have taken a fundamental role in Mo enrichment and subsequent mineralization. [ABSTRACT FROM AUTHOR]

The Mongol–Okhotsk suture belt played an important role in the tectonic evolution of northeast Asia during the Mesozoic. However, few studies have examined the influence of this tectonic belt on the geological evolution of northeast China. In this paper, we present zircon U–Pb geochronology, major and trace element geochemistry, and zircon Hf–O isotopic data for Early Jurassic volcanic rocks in the Erguna Massif of northeast China, with the aim of constraining the evolution of the Mongol–Okhotsk suture belt and its influence on the tectonic history of China during the Early Jurassic. Zircon U–Pb dating indicates that the trachybasalt and basaltic andesite in the study area were erupted between 193 ± 5 Ma and 181 ± 9 Ma (i.e., in the Early Jurassic). These Early Jurassic volcanic rocks belong to the high-K calc-alkaline series and are enriched in large ion lithophile elements and light rare earth elements, as well as being depleted in heavy rare earth elements and high field strength elements such as Nb and Ta. The rocks show a small negative Eu anomaly. The zircon εHf (182 Ma) values of the volcanic rocks range from − 1.9 to + 5.1, corresponding to T DM1 values of 640–901 Ma and T DM2 values of 901–1345 Ma. Zircons from two volcanic rocks yield δ 18 O values of 7.2‰ ± 1.5‰ (n = 19) and 6.6‰ ± 0.7‰ (n = 35). Geochemically, these Early Jurassic volcanic rocks are similar to those from active continental margin settings, and their primary magmas could have been derived from the partial melting of a lithospheric mantle wedge modified by fluid from a subducted slab. The discovery of Early Jurassic calc-alkaline volcanic rocks in the Erguna Massif, together with the coeval porphyry Cu–Mo deposits, indicates that an active continental margin existed in the Erguna area during the Early Jurassic. Taken together, we conclude that southward subduction of the Mongol–Okhotsk oceanic plate took place beneath the Erguna Massif during the Early Jurassic. [ABSTRACT FROM AUTHOR]

We undertook zircon U-Pb dating and geochemical analyses of volcanic rocks from the Baiyingaolao Formation in the central Great Xing'an Range, northeastern China, with an aim to determine their age, petrogenesis and sources, which are important for understanding the Late Mesozoic tectonic evolution of the eastern section of the Central Asian Orogenic Belt. Lithologically, the Baiyingaolao Formation is composed mainly of rhyolites and rhyolitic tuffs, with minor trachy dacites. The zircons from three rhyolitic tuffs and two rhyolites are euhedral-subhedral in shape, display fine-scale oscillatory growth zoning and have high Th/U ratios (0.72-2.60), indicating a magmatic origin. The results of LA-ICP-MS zircon U-Pb dating indicate that the volcanic rocks from the Baiyingaolao Formation in the study area formed during the Early Cretaceous time with ages of 134-130 Ma. Petrological and geochemical characteristics of these volcanic rocks suggest that they are all highly fractionated I-type igneous rocks, and their parental magmas were likely derived from the partial melting of lower crustal materials with plagioclase, hornblende and apatite as the residual phases. In addition, the volcanics sampled in this paper, tectonically located in the Xing'an terrain, have high initial 176Hf/177Hf ratios (0.282770-0.283035) and positive εHf(t) values (2.42-11.96), combined with young Hf two-stage model ages of 1134-541 Ma, reflecting that the crustal growth of the Xing'an terrain occurred during Neoproterozoic and Phanerozoic times. These data, combined with previous studies on the contemporaneous magma-tectonic activities in NE China, suggest that the generation of the Early Cretaceous volcanic rocks in the central Great Xing'an Range was related to the lithospheric delamination caused by the subduction of the Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present new zircon U–Pb dating, Hf isotope, major and trace elements, and Sr–Nd isotope data for Early–Middle Triassic intrusive rocks in the Erguna Massif of NE China, in the eastern segment of the Central Asian Orogenic Belt (CAOB). Our aim is to elucidate the tectonic evolution of the Mongol–Okhotsk Ocean and its influence on NE China. Zircons from five representative intrusions in the Erguna Massif are euhedral–subhedral in shape, display oscillatory growth zoning in CL images, and have Th/U ratios of 0.17–1.54, and in combination these features indicate that the zircons are of igneous origin. Zircon U–Pb dating results demonstrate that the Early–Middle Triassic magmatism in the Erguna Massif took place between 241 and 247Ma. The Early–Middle Triassic rocks are composed mainly of a suite of diorites, quartz–diorites, granodiorites, monzogranites, and syenogranites. They have SiO2 =57.71–72.86wt.%, Mg#=19–52, Al2O3 =14.27–17.23wt.%, and Na2O/K2O=0.67–1.59. Chemically, they are metaluminous to peraluminous and belong to the high-K calc-alkaline series. Moreover, they are enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti). The whole-rock εNd(t) and zircon εHf(t) values of these samples range from −4.68 to −3.42, and from −2.0 to +6.6, respectively, indicative of formation from primary magmas generated by partial melting of juvenile crustal material with a contribution from mantle-derived mafic magmas. These magmas subsequently underwent fractional crystallization, contamination, and magma mixing. Geochemically, these Early–Middle Triassic intrusive rocks have affinities with intrusive rocks from active continental margin settings. We conclude, therefore, that the Early–Middle Triassic magmatism in the Erguna Massif was generated within an active continental margin setting related to the southwards subduction of the Mongol–Okhotsk oceanic plate beneath the Erguna Massif. This conclusion is supported by the occurrence of Early Mesozoic porphyry and skarn deposits along the southeastern side of the Mongol–Okhotsk suture belt. [Copyright &y& Elsevier]

Abstract: In this paper we present U–Pb age data of detrital and magmatic zircons from sedimentary and volcanic rocks in the Zhangguangcailing Group (ZG), NE China, to constrain the tectonic evolution of the region as a whole. The ZG consists of slightly metamorphosed volcanic and sedimentary rocks, and from bottom to top is divided into the Zhenggou, Hongguang, and Xinxing suites. Zircons from three schists in the Zhenggou suite give 12 main groups of age populations (from 226 to 861Ma), whereas zircons from a basaltic andesite give a Late Triassic age (211±2Ma). In the Hongguang suite, zircons from two schists and a greywacke give 6 main groups, 5 main groups, and 3 main groups of age populations (from 262 to 916Ma), respectively, whereas zircons from a gabbro–diorite and two volcanic rocks give ages of 259, 219, and 317Ma, respectively. Zircons from a schist in the Xinxing suite give 12 main groups of age populations (from 284 to 1837Ma). These results, together with the field relationships of the rocks, indicate (1) that the sedimentary and volcanic rocks of the ZG have diverse ages (from Early Paleozoic to Early Mesozoic), (2) that the rocks do not lie in a logical stratigraphic sequence, and (3) that the rocks represent a tectonic mélange. Based on the youngest age (211Ma) for volcanic rocks within the ZG, and the age of deformation (174–184Ma) of the Heilongjiang Complex, we propose that the tectonic mélange formed during the Late Triassic–Early Jurassic. Furthermore, the occurrence of detrital zircons with ages of 0.8–0.9, 1.8, and 2.4–2.5Ga implies the existence of Neoproterozoic magmatism and the remnants of a Precambrian basement in the Songnen–Zhangguangcai Range Massif, NE China. [Copyright &y& Elsevier]

We present zircon U–Pb dating, whole-rock geochemistry, and Sr–Nd isotope results for the Upper Permian–Upper Triassic volcanic rocks to constrain the timing of the final closure of the eastern segment of the Palaeo-Asian Ocean. The volcanic rocks were mainly collected from the Yanbian area in eastern Jilin Province, northeastern China. The zircon U–Pb dating results indicate that the samples can be classified as Upper Permian–Lower Triassic basalts (ca. 262–244 Ma) and Upper Triassic dacites (ca. 216 Ma). The whole-rock geochemical results indicate that the rocks predominately belong to the medium-K and high-K calc-alkaline series. The basalts are enriched in large ion lithophile elements (LILEs, e.g. Ba and K) and depleted in high field strength elements (HFSEs, e.g. Nb and Ta), with weak positive Eu anomalies. The dacites are enriched in LILEs (e.g. Rb, Ba, Th, and K) and light rare earth elements (LREEs) and marked depletion in some HFSEs (e.g. Nb, Ta, and Ti), with significant negative Sr, P, and Eu anomalies. Moreover, the Upper Permian–Lower Triassic basalts have low initial87Sr/86Sr ratios (0.7037–0.7048) and highεNdvalues (4.4–5.4). In contrast, the Upper Triassic dacites possess relatively high initial87Sr/86Sr ratios (0.7052) compared with their lowεNdvalues (1.4). The basaltic magma likely originated from the partial melting of a depleted mantle wedge metasomatized by subduction-related fluids, and the felsic magmas likely originated from the partial melting of a dominantly juvenile source with a minor component of ancient crust. Taken together, the Upper Permian–Lower Triassic basalts (ca. 262–244 Ma) are arc basalts that formed in an active continental margin setting, and the Upper Triassic dacites (ca. 216 Ma) are A-type granitic rocks that formed in an extensional setting. Therefore, the final closure of the Palaeo-Asian Ocean occurred during the Middle–Late Triassic. [ABSTRACT FROM PUBLISHER]

Central Jilin Province lies along the eastern edge of the Xing–Meng orogenic belt of northeast China. At least 10 Mo deposits have been discovered in this area, making it the second-richest concentration of Mo resources in China. To better understand the formation and distribution of porphyry Mo deposits in the area, we investigated the geological characteristics of the deposits and applied zircon U–Pb and molybdenite Re–Os isotope dating to constrain the age of mineralization. Our new geochronological data show the following: the Jidetun Mo deposit yields molybdenite Re–Os model ages of 164.6–167.1 Ma, an isochron age of 168 ± 2.5 Ma, and a weighted mean model age of 165.9 ± 1.2 Ma; the Houdaomu Mo deposit yields molybdenite Re–Os model ages of 167.4–167.7 Ma, an isochron age of 168 ± 13 Ma, and a weighted mean model age of 167.5 ± 1.2 Ma; and the Chang’anpu Mo deposit yields a zircon U–Pb age for granodiorite porphyry of 166.9 ± 1.5 Ma (N = 16). These new age data, combined with existing molybdenite Re–Os dates, show that intense porphyry Mo mineralization was coeval with magmatism during the Middle Jurassic (167.8 ± 0.4 Ma,r> 0.999). The geotectonic mechanisms responsible for Mo mineralization were probably related to subduction of the Palaeo-Pacific plate beneath the Eurasian continent. Combining published molybdenite Re–Os and zircon U–Pb ages for northeast China, the Mo deposits are shown to have been formed during multiple events coinciding with periods of magmatic activity. We identified three phases of mineralization, two of which had several stages: the Caledonian (485–480 Ma); the Indosinian comprising the Early–Middle Triassic (248–236 Ma) and Late Triassic (226–208 Ma) stages; and the Yanshanian phase comprising the Early–Middle Jurassic (202–165 Ma), Late Jurassic–early Early Cretaceous (154–129 Ma), and Early Cretaceous (114–111 Ma) stages. Although Mo deposits formed during each phase/stage, most of the mineralization occurred during the Early–Middle Jurassic. [ABSTRACT FROM AUTHOR]

The Jiapigou gold belt is located on the northern margin of the North China Craton, and is one of the most important gold-mining and production regions in the circum-Pacific metallogenic zone. Research has been conducted in this area since the 1960s, however, the timing of the gold mineralisation is still unresolved, and an ideal metallogenic model has not been well established. To address these questions, a systematic geological, geochemical and geochronological investigation was conducted. The study revealed that (i) the gold-bearing quartz veins can be divided into two groups, earlier and later gold-bearing quartz veins according to their occurrence and the geochemical characteristics, (ii) the geochemical characteristics of the ore bodies, while similar to granite, are clearly different from the altered rock, and (iii) the geochemical characteristics of the later gold-bearing quartz veins have more similarity to the altered rock than the earlier gold-bearing quartz veins do. Therefore, we conclude that two independent stages of metallogenesis within the Jiapigou gold deposit area are related to magmatic activity in the Palaeoproterozoic and the Yanshanian stage of the Mesozoic, that the ore-forming fluids are mainly of magmatic origin, and that magma contamination by the altered rock was stronger in the Mesozoic. Zircon LA-ICP-MS U-Pb data show that the age of the Palaeoproterozoic granite is ~2426.0 Ma and that of the Mesozoic granite is ~166.2 Ma; these ages can be interpreted as the maximum ages of the two periods of gold mineralisation. In addition to investigating the geotectonic and regional structure of the Jiapigou gold belt, this study also proposes that the WNW-trending zone of gold mineralisation is a result of a magmatic event within the basement in the early Palaeoproterozoic, and that large-scale sinistral strike-slip displacements of the Huifahe and Liangjiang Faults in the late Middle Triassic (Yanshanian epoch) controlled the later tectono-magmatic event and the NNE-ENE-trending zone of gold mineralisation. [ABSTRACT FROM AUTHOR]