Geochronological framework of Mesozoic volcanic rocks in the Great Xing’an Range,NE China,and their geodynamic implications

Mesozoic volcanic rocks are widespread throughout the Great Xing’an Range, NE China. However, precise data constraining the exact eruption ages are limited, especially for those from the southern Great Xing’an Range, which severely hampers our understanding of the petrogenesis and geodynamics of these rocks. In this paper, we report precise in situ LA-ICPMS zircon U–Pb age measurements for these volcanic rocks. Volcanic rocks in the southern Great Xing’an Range were divided into four units from bottom to top, namely, the Manketouebo, Manitu, Baiyingaolao and Meiletu formations. The previous studies suggested that these volcanic rocks were mainly formed in the Late Jurassic. Our data demonstrate that the Manketouebo formation erupted during Late Jurassic to Early Cretaceous time, whereas the other formations are all of Cretaceous age. The southern Great Xing’an Range age dataset, along with recently obtained precise ages for volcanic rocks from the northern Great Xing’an Range indicate that Mesozoic volcanism throughout the Great Xing’an Range commenced in Late Jurassic, but peaked during the Cretaceous. They formed under an extensional tectonic setting which resulted from closure of the Mongol–Okhotsk Ocean and subsequent orogenic collapse. The globally elevated mantle temperature in Cretaceous may provided thermal contributions to the generation of the volcanisms.     

Extraterrestrial factors and their role in the Earth’s tectonic evolution in the Early Precambrian

The paper is focused on the fundamental problem of influence of extraterrestrial factors on the Earth’s geologic and tectonic evolution. Extraterrestrial factors played a decisive role in the Earth’s genesis, the formation of the first Hadean continental crust, and the beginning of the Archean era. Their significant influence persisted in the later epochs: Even in the Phanerozoic, extraterrestrial factors might have had a considerable influence on the environment. The sialic cores of protocontinental crust (4.4-3.9 Ga) with first-generation greenstone zones (3.8-3.2 Ga) and the global system of granite-greenstone belts (3.1-2.7 Ga) formed in the rotation-plume regime, mainly in the subequatorial hot belt. The formation of these global structures was, to a large extent, influenced by asteroid impacts, which caused the impact-triggered genesis of mantle plumes. Dramatic changes in the subsequent geologic history began at 2.7-2.0 Ga; at 2.0 Ga they terminated with the Moon’s transition to an orbit similar to the present-day one (50 ± 3 Earth’s radii), accompanied by the abrupt slowdown of the Earth’s axial rotation, the termination of formation of the layer D", and the start of recent plate tectonics, which is accompanied by the plume tectonics.     

Zircon U-Pb geochronology and geochemistry of the intrusions associated with the Jiawula Ag-Pb-Zn deposit in the Great Xing’an Range,NE China and their implications for mineralization

Located in the eastern section of the Central Asian Orogenic Belt, the Jiawula Ag-Pb-Zn deposit is classified as a volcanic to subvolcanic related vein-type ore deposit. New U-Pb zircon geochronology, whole-rock geochemistry, mineral chemistry, and Sr-Nd isotope data are presented for the intrusions in the Jiawula deposit in order to evaluate the timing, petrogenetic type of the granitoid rocks, origin and evolution of magmatism, geodynamics, and to establish its relationship with lead-zinc mineralization. Zircon SHRIMP U-Pb analyses yield weighted mean ages of 150.1 ± 1.8 Ma for quartz porphyry, 148.8 ± 2.2 Ma for syenite porphyry, and 145.3 ± 1.9 Ma for monzonite porphyry, indicating a Late Jurassic (Yanshanian) magmatic event. An earlier magmatic event (Indosinian) occurred during the Late Permian to Early Triassic from ca. 254 Ma to ca. 247 Ma and is represented by granodiorite (254 ± 2 Ma), dacite porphyry (252.9 ± 4.8 Ma), and diorite porphyry (278 ± 4.1 Ma). Both the Indosinian and Yanshanian igneous rocks are classified as I-type granitoids. The late Jurassic intrusions are highly fractionated and characterized by negative anomalies of Eu, Sr, P, and Ti. The hypabyssal intrusions have initial ⁸⁷Sr/⁸⁶Sr values between 0.70458 and 0.70522, and ε_Nd(t) values of −3.4 to −0.2, indicating relatively older crust in Jiawula among more juvenile crust in this area. Magma generation in Jiawula is linked to juvenile lower crustal and slightly enriched mantle sources. The ∼250 Ma magmatic episode in Jiawula might be related to the subduction of the Mongol-Okhotsk oceanic plate towards the south beneath the Erguna massif. The ∼150 Ma magmatic event occurred after the closure of the Mongol-Okhotsk Ocean followed by the change in subduction direction of the Paleo-Pacific plate. Varying temperature, stronger fractionation and higher oxygen fugacity related to the magmatic-hydrothermal transition caused Pb-Zn mineralization.     

New Zircon U-Pb Ages of the Granodiorites in the Southern Great Xing’an Range and their Tectonic Implications

The Southern Great Xing'an Range,Northeast China,is located in the eastern part of the Central Asian Orogenic Belt.It is considered to be one of the most important metallogenic belts,commonly hosting a series of skarn.porphyry and magmatic hydrothermal Pb-Zn-Ag-Cu Mo-Sn polymetallic deposits(Fig.1).Complex tectonic events have occurred in this region,including the closure of the Palco-Asian Ocean in the Late Palaeozoic,the opening and closure of the Mongol Okhotsk Ocean and the subduction of the Paleo-Pacific Ocean in the Mesozoic.     

Intraplate earthquakes and their link with mantle dynamics: Insights from P-wave teleseismic tomography along the northern part of the North–South Tectonic Zone in China

The North–South Tectonic Zone (NSTZ) running across the Chinese continent is an important earthquake-prone zone. Around one third of the strong earthquakes (> 7.0) of China in the past occurred in this region. Receiver function study has imaged vertical convection in the mantle beneath the northern part of the NSTZ (NNSTZ), which might be related to stress accumulation and release as well as related earthquakes. Here we perform a P-wave teleseismic tomographic analysis of this region. Our results reveal prominent low-velocity and high-velocity perturbations in the upper mantle beneath this region, which we correlate with mantle upwelling, possibly resulting from lower crustal and (or) lithospheric delamination. Our results also reveal significant contrast in the velocity perturbation of the lithosphere along the two sides of this tectonic zone, suggesting possible material exchange between the eastern and western domains and lithosphere-scale control on the generation of earthquakes.     

Environmental properties of metallic minerals and their applications in environmental protection in China

In terms of environmental mineralogy, the environmental properties of metallic minerals, including chemical activation, adsorption, pore effect and nanometer effect, have been analyzed. On the basis of the analysis of environmental properties of metallic minerals, the applications of iron-bearing sultides, iron and manganese oxides in the purification of wastewaters containing heavy metal ions （Cr^6＋ ,Hg^2＋ , Pb^2＋ , etc. ） have been summarized. Moreover, research on the application of metallic minerals in environmental protection has been anticipated. It should be a piece of dominating work for environmental mineralogie researchers in the future to lucubrate systematically the physical and chemical characteristics of the metallic mineral surfaces, further reveal the reciprocity process between metallic minerals and water surface, perfect the theory and model of the metallic minerals to remove contaminants, intensify study on the facilities and techniques of metallic minerals to remove contaminants, and entail well the extension and propagation of achievements.     

Hydrogeochemical characteristics of groundwater and pore-water and the paleoenvironmental evolution in the past 3.10 Ma in the Xiong’an New Area,North China

The groundwater level has been continuously decreasing due to climate change and long-time overexploitation in the Xiong’an New Area, North China, which caused the enhanced mixing of groundwater in different aquifers and significant changes in regional groundwater chemistry characteristics. In this study, groundwater and sediment pore-water in drilling cores obtained from a 600 m borehole were investigated to evaluate hydrogeochemical processes in shallow and deep aquifers and paleo-environmental evolution in the past ca. 3.10 Ma. Results showed that there was no obvious change overall in chemical composition along the direction of groundwater runoff, but different hydrochemical processes occurred in shallow and deep groundwater in the vertical direction. Shallow groundwater (< 150 m) in the Xiong’an New Area was characterized by high salinity (TDS > 1000 mg/L) and high concentrations of Mn and Fe, while deep groundwater had better water quality with lower salinity. The high TDS values mostly occurred in aquifers with depth < 70 m and >500 m below land surface. Water isotopes showed that aquifer pore-water mostly originated from meteoric water under the influence of evaporation, and aquitard pore-water belonged to Paleo meteoric water. In addition, the evolution of the paleoclimate since 3.10 Ma BP was reconstructed, and four climate periods were determined by the δ¹⁸O profiles of pore-water and sporopollen records from sediments at different depths. It can be inferred that the Quaternary Pleistocene (0.78–2.58 Ma BP) was dominated by the cold and dry climate of the glacial period, with three interglacial intervals of warm and humid climate. What’s more, this study demonstrates the possibilities of the applications of pore-water on the hydrogeochemical study and further supports the finding that pore-water could retain the feature of paleo-sedimentary water.© 2021 China Geology Editorial Office.     

Permian–Triassic amalgamation of Asia: Insights from Northeast China sutures and their place in the final collision of North China and Siberia

The Central Asia Orogenic Belt (CAOB) corresponds to the domain where Siberia and Mongolia were welded to North China. The eastern extension of the CAOB in Northeast China is disputed, since both suture location and timing are poorly documented. This paper reports for the first time the recognition of two suture zones in the southern part of Northeast China (Manchuria), between the Fushun Mishan and Yilan-Yitong faults. In the Jilin Province, west-directed thrust sheets involving successively, from west to east, passive continental margin rocks, metamorphic rocks and ophiolites, block-in-matrix formations and arc plutons indicate a Permian–Early Triassic collision. In the Liaoning Province, arc plutonism and top-to-the-north ductile shearing, coeval with the emplacement of an ophiolitic nappe, suggest a Palaeozoic collision. These two sutures are correlated with the Ondor Sum and Solonker sutures, described in Inner Mongolia. A new geodynamic model involving rifting and collision of the southern part of the Xilinhot Block with North China is proposed.     

Crustal Poisson’s ratio anomalies in the eastern part of North China and their origins

Seismic tomography can provide both fine P-wave and S-wave velocity structures of the crust and upper mantle.In addition,with proper computation,Poisson’s ratio images from the seismic velocities can be determined.However,it is unknown whether Poisson’s ratio images have any advantages when compared with the P-wave and S-wave velocity images.For the purposes of this study,high-resolution seismic tomography under the eastern part of North China region was used to determine detailed 3-D crustal P- and S-wave seismic velocities structure,as well as Poisson’s ratio images.Results of Poisson’s ratio imaging show high Poisson’s ratio(high-PR) anomalies located in the Hengshan-North Taihang-Zhangjiakou(H-NT-Z) region,demonstrating that Poisson’s ratio imaging can provide new geophysical constraints for regional tectonic evolution.The H-NT-Z region shows a prominent and continuous high-PR anomaly in the upper crust.Based on Poisson’s ratio images at different depths, we find that this high-PR anomaly is extending down to the middle crust with thickness up to about 26 km.According to rock physical property measurements and other geological data,this crustal Poisson’s ratio anomaly can be explained by Mesozoic partial melting of the upper mantle and basaltic magma underplating related to the lithospheric thinning of the North China craton.     

The ~1.85 Ga carbonatite in north China and its implications on the evolution of the Columbia supercontinent

Mantle-derived carbonatites provide a unique window in the understanding of mantle characteristics and dynamics, as well as insight into the assembly and breakup of supercontinents. As a petrological indicator of extensional tectonic regimes, Archean/Proterozoic carbonatites provide important constraints on the timing of the breakup of ancient supercontinents. The majority of the carbonatites reported worldwide are Phanerozoic, in part because of the difficulty in recognizing Archean/Proterozoic carbonatites, which are characterized by strong foliation and recrystallization, and share broad petrologic similarities with metamorphosed sedimentary lithologies. Here, we report the recognition of a ~1.85 Ga carbonatite in Chaihulanzi area of Chifeng in north China based on systematic geological, petrological, geochemical, and baddeleyite U-Pb geochronological results. The carbonatite occurs as dikes or sills emplaced in Archean metasedimentary rocks and underwent intense deformation. Petrological and SEM/EDS results show that calcite and dolomite are the dominant carbonate minerals along with minor and varied amounts of Mg-rich mafic minerals, including forsterite (with Fo > 98), phlogopite, diopside, and an accessory amount of apatite, baddeleyite, spinel, monazite, and ilmenite. The relatively high silica content together with the non-arc and OIB-like trace element signatures of the carbonatite indicates a hot mantle plume as the likely magma source. The depleted Nd isotopic signatures suggest that plume upwelling might be triggered by the accumulation of recycled crust in the deep mantle. As a part of the global-scale Columbia supercontinent, the Proterozoic tectonic evolution of the North China Craton (NCC) provides important insights into the geodynamics governing amalgamation and fragmentation of the supercontinent. The Paleo-Mesoproterozoic boundary is the key point of tectonic transition from compressional to extensional settings in the NCC. The newly identified ~1.85 Ga carbonatite provides a direct link between the long-lasting supercontinental breakup and plume activity, which might be sourced from the “slab graveyard,” continental crustal slabs subducted into asthenosphere, beneath the supercontinent. The carbonatite provides a precise constraint of the initiation of the continental breakup at ~1.85 Ga.     

Composition and evolution of accessory mineralization of Li–F granites in the Far East as indicators of their ore potential

The ore potential of Pacific Li–F granites is considered on the basis of original and published data on composition of these granites and related metasomatic rocks in the Badzhal (Amur region) and Kuiviveem–Pyrkakai (Chukchi Peninsula) ore districts. The accessory mineralization in rare-metal granites is compared with that in W–Sn deposits. The main features in evolution of magmatic and hydrothermal mineralization are pointed out. A conclusion on the similarity between mineralization of the zwitter–tourmalinite type and accessory minerals in Li–F granites is drawn. It is established that magmatic and hydrothermal types of mineralization belong to the same evolutionary sequence. Genetic links between Li–F granites and the large ore deposits in the East Asian tungsten–tin zone are suggested.     

Late Jurassic–Early Cretaceous tectonic evolution of the Great Xing’an Range: geochronological and geochemical evidence from granitoids and volcanic rocks in the Erguna Block,NE China

ABSTRACT

The late Mesozoic magmatic record within the Erguna Block is critical to evaluate the tectonic history and geodynamic evolution of the Great Xing’an Range, NE China. Here, we provide geochronological and geochemical data on Late Jurassic–Early Cretaceous plutonic-volcanic rocks in the northern Erguna Block and discuss their origin within a regional tectonic framework. Late Mesozoic magmatism in the Erguna Block can be divided into two major periods: Late Jurassic (162–150 Ma) and Early Cretaceous (140–125 Ma). Late Jurassic quartz monzonite and dacite show adakite characteristics such as high Al₂O₃, high Sr, and steeply fractionated REE patterns. Contemporary granitoids and rhyolites are also characterized by strong enrichment of light rare earth elements (LREE) and significant depletion in heavy rare earth elements (HREE), but with more pronounced negative Eu anomalies. Early Cretaceous trachytes and monzoporphyries exhibit moderate LREE enrichment and relatively flat HREE distributions. Coeval granites and rhyolites have transitional signatures between A-type and fractionated I-type felsic rocks. Both Late Jurassic and Early Cretaceous rocks have distinctive negative Nb, Ta, and Ti anomalies, and positive zircon ε_Hf(t) values, suggesting that these magmas were derived from partial melting of Meso-Neoproterozoic accreted lower crust, although melting occurred at a variety of crustal levels. The transition from adakite to non-adakite magmatism reflects continued crustal thinning from Late Jurassic to Early Cretaceous. Our data, together with recently reported isotopic data for plutonic and volcanic rocks, as well as geochemical data, in NE China, suggest that Late Jurassic–Early Cretaceous magmatism in the Erguna Block was possibly induced by post-collisional extension after closure of the Mongol-Okhotsk Ocean.     

First Occurrence of M andarinoite in China

This report describes the first occurrence of the rare mineral mandarinoite (Fe3+2 Se3Og · 6H2O) in China. It occurs in the Lower Permian Maokou Formation carbonaceous shale in Yutangba Village east of Enshi City in southwestern Hubei Province. The shale is selenium-rich and contains native selenium, V-Mo-Cr-bearing iron oxide, clay and quartz. Weathering of the selenium in the bedrock under moderate to high redox conditions in the presence of ferric iron has formed mandarinoite.     

Hydrocarbons in the Basement of the South China Sea (Vietnam) Shelf and Structural–Tectonic Model of their Formation

Geotectonics - The paper considers the origin of hydrocarbon accumulations within the Pre-Cenozoic basement of the Vietnam shelf. It is shown that the formation of hydrocarbon deposits is...