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Metal migration and precipitation in hydrothermal fluids are important topics in economic geology. The Hongling polymetallic deposit comprises one of the most important parts of the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt, which is in eastern Inner Mongolia. Except for lead–zinc skarn, minor cassiterite in the skarn and disseminated W–Sn mineralization in granitic rocks have also been found. The dominant Sn–W mineralization is in the northern part of the deposit, occurring as disseminated wolframite and cassiterite in aplite hosted in Mesozoic granite porphyry. The aplite together with pegmatite K-feldspar–quartz comprises vein dikes hosted in the granite porphyry, providing evidence for the transition from melt to fluid. The veins, dikes, and Sn–W mineralization in the aplite provide an opportunity to investigate fluid exsolution and the mechanics of metal precipitation. Based on field observations, the micrographic and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) results of the vein dikes, chronology, and the whole-rock geochemistry of the host rock, together with the fluid inclusion results, this paper discusses the characteristics of the causative magma, the mechanics of fluid exsolution and W–Sn precipitation. Our results show that the causative magma is of highly fractionated A-type granite affinity and has an intrusive age of late Mesozoic (133.3 ± 0.86 Ma). The magmatic evolution during shallow emplacement led to immiscibility between highly volatile, high-silica, and W- and Sn-enriched melts from the parent magma, followed by fluid exsolution from the water-rich melt. The alkaline-rich fluid exsolution led to a change in the redox state of the magma and the chilling of the melt. Fluid boiling occurred soon after the fluid exsolution and was accompanied by the degassing of CO2. The boiling and escape of CO2 from the fluid led to changes in fluid redox and W and Sn precipitation; thus, the W and Sn mineralization are mostly hosted in causative intrusions or peripheral wall rocks, which can be used as indicators for Sn–W exploration in the area. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Shamai tungsten deposit is located in the western part of the Xing'an Mongolian orogenic belt of northeastern China and contains quartz‐vein hosted tungsten mineralization. In this paper, we present the results of zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb dating of the fine‐grained biotite monzogranite, medium‐grained biotite monzogranite, and porphyritic biotite monzogranite samples from the deposit as well as in situ zircon Hf isotopic and in situ plagioclase Pb isotopic analyses. Combining new laser Raman spectroscopic data for fluid inclusions with previously HO isotopic data yields insights into the precipitation of ore minerals. The fine‐grained biotite monzogranite, medium‐grained biotite monzogranite, and porphyritic biotite monzogranite were emplaced at 142.5 ± 1.0 Ma, 141.9 ± 1.1 Ma, and 140.2 ± 1.0 Ma, respectively. The fine‐ to medium‐grained biotite monzogranite and porphyritic biotite monzogranite samples contain zircons with εHf(t) values from 3.2 to 7.9 and from 4.2 to 7.6, respectively, yielding tDM2 model ages from 996 to 692 Ma and 923 to 708 Ma, respectively. The geochemical, zircon Hf isotopic, and in situ plagioclase Pb isotopic data indicate that the magmas were generated by the partial melting of juvenile crustal material mixed with mantle‐derived components. The laser Raman and HO isotopic data for fluid inclusions within tungsten‐bearing quartz veins indicate that the tungsten mineralization formed as a result of fluid mixing. Combining the data with the spatial and temporal distribution and tectonic setting of tungsten deposits in NE China suggests that this area records four stages of mineralization at 300–290, 250–230, 200–180, and 150–130 Ma. The Shamai deposit occurred in an intra‐continental extensional regime. [ABSTRACT FROM AUTHOR]

Lithium is one of the important strategic energy metals, which is in short supply in China. There are three major types of lithium deposits: brine and salt lake type, highly differentiated granite or pegmatite type, and carbonate-clay type. In recent years, some new types of lithium deposits have also begun to receive great attention and subject recent research. There are many crypto-explosive breccia pipe type deposits in the world, including copper, gold, lead, zinc, tungsten and tin deposits, but little is known about this type of lithium deposit. This paper introduces the latest research results of the Weilasituo Sn−Li−Rb polymetallic deposit in Inner Mongolia (NE China), which occurs in the middle-southern section of the Great Xing'an Range metallogenic belt. A remarkable feature of this deposit is the coexistence of various mineralization types, including granite type Rb and Sn−Zn, hydrothermal crypto-explosive breccia pipe type Li−Rb, quartz vein type Sn−Zn and sulfide vein type Pb−Zn−Ag mineralization. Among them, hydrothermal crypto-explosive breccia pipe type Li-Rb deposit is currently very rare at home and abroad, which is likely a new type of rare metal deposit that worthy of our attention. This paper systematically summarizes the geology, alteration and mineralization, geochemistry, isotopes and geochronology of the Weilasituo deposit, and establishes a new petrogenic and metallogenic model. [ABSTRACT FROM AUTHOR]

Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite (Si<7.1), chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P- T conditions are estimated as T=350-400 °C and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing'an blocks situated in the eastern portions of the Central Asia orogenic Belt (CAOB). [ABSTRACT FROM AUTHOR]

The Aolunhua Mo deposit is a typical porphyry deposit, which is located in the middle southern section of the Da Hinggan Range metallogenic belt. Here, we report LA-ICP-MS zircon U-Pb age data from the Mo-associated granitoid, together with the element geochemistry of the zircons, discussing the source material of the ore-forming rock of the deposit. The zircon data constrain the crystallization age of the granite porphyry as 135.0 ± 1.0 Ma, correlating it with the widespread Yanshanian intermediate–felsic magmatic activity. The Th/U ratio of the zircon is greater than 0.1, with a significant positive Ce anomaly (Ce* = 1.72–188.71) and a negative Eu anomaly (Eu* = 0.05–0.57). The zircons show depleted LREE and enriched HREE patterns, as well as low La and Pr contents, suggesting crystallization from crust-derived magmas. Based on the geology of the ore deposit and the age data, in combination with the regional geodynamic evolution, we infer that the Aolunhua Mo deposit was formed near the peak stage of Sn poly-metallic metallogenesis in the Da Hinggan Range region at around 140 Ma, associated with a tectonic setting, characterized by the transition from compression to extension. Based on a comparison with the newly found Mo deposits along the banks of the Xilamulun River, we propose that the Tianshan–Linxi is an important Mo-metallogenic belt. It also suggests an increased likelihood for the occurrence of Mo along the north bank of the Xilamulun River. [ABSTRACT FROM AUTHOR]

The evolution history of the Hegenshan Ocean is an important part of studying the evolution of the Xingmeng orogenic belt, but it is still controversial. Here we present an integrated study of petrology, zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd isotopes on a series of intrusive rocks from the Baiyinguole area, Xiwuqi, central Inner Mongolia, NE China. Chronological data indicate that the intrusive rocks can be divided into three stages: 326–317, 297–295, and 259–254 Ma. The 326–317-Ma gabbros and diorites belong to the calc-alkaline series, and are characterized by positive whole-rock εNd(t) values (+1.1–+6.7), relatively low La/Ba ratios (0.04–0.10), and high La/Nb ratios (1.82–3.18), indicating that the magma source is from a subduction-modified lithospheric mantle. These samples have arc features owing to the southward subduction of the Hegenshan oceanic crust. The 297–295-Ma granodiorites and monzogranites show positive εNd(t) values (+1.9–+2.4), low 87Sr/86Sri ratios (0.704185–0.705234), and young Nd two-stage model ages (TDM2), which is consistent with typical I-type granites. On various tectonic setting discrimination diagrams, the granodiorites and monzogranites are plotted in the syn-collisional field. The 259–254-Ma syenogranites have low abundances of mafic minerals, low contents of Zr/Hf (18.31–31.35) and Nb/Ta (6.80–11.80) values, high SiO2 (76.36–78.54 wt.%) content, A/CNK (1.08–1.76), and D.I. of 96.8–97.4 (average 97.1), and notable negative Eu anomalies (δEu* = 0.07–0.17) and weakly tetrad-effects in REE pattern, which is affinity to the characteristics of highly differentiated granites. Moreover, they have positive εNd(t) values (+2.0–+2.1) with scattered TDM2 of 730–1217 Ma and low Nb/U ratios. This study suggests that the syenogranites are formed in a post-collisional tectonic setting, which is related to the closure of the Hegenshan Ocean. In addition, based on a review of the pre-existing literature data, a model of southward ridge subduction is proposed to explain the tectonic evolution of the Hegenshan Ocean. [ABSTRACT FROM AUTHOR]

The Shaolang River metallogenic belt in Inner Mongolia is one of the main lead‐zinc polymetallic belt on the northern margin of the North China Plate. The granodiorites, which are closely coexisting with lead‐zinc veins in deposit, are extensively developed. Previous geochronological research results show that the dikes and veins in the metallogenic belt belong to the products of magmatic hydrothermal activity in the middle Yanshanian, so the genesis of the metallogenic belt deposit is generally considered to be a hydrothermal vein type deposit related to sub‐volcanic dikes. We obtained zircon LA‐ICP‐MS U–Pb ages and Hf isotopic compositions of granodiorites, which are widely distributed in the deposit and were considered to be closely connected with the genesis of the deposits. The zircon U–Pb ages are 419.4 ± 1.4 Ma and 424.5 ± 4.1 Ma for the granodiorites, respectively, and they formed in the late Silurian. The geological and geochemical data indicate that the granodiorites are consistent with the geochemical characteristics of typical adakite. All εHf(t) values of the granodiorites are minus, on the zircon Hf isotope age diagram, εHf(t) are below the evolution curve of chondrite. The two‐stage model ages (tDM2) are 2.45 ~ 2.79 Ga and 1.87 ~ 2.29 Ga, respectively, showing rock‐forming materials mainly derived from the Paleoproterozoic and earlier crustal partial melting, and there may have been mantle‐derived magma underplating of the lower crust. Combining with the previous regional research, it is concluded that the granodiorites were formed during the extinction of the island arc under the background of subduction of the Paleo‐Asian Ocean and North China Craton. Because of the 125 ~ 170 Ma metallogenic age, we concluded that the granodiorites in the ore areas have no obvious relationship with the deposit genesis. However, it provided the advantageous space for the formation of the lead‐zinc veins, it can be regarded as an important prospecting indicator in metallogenic belt. [ABSTRACT FROM AUTHOR]

The recently discovered Weilasituo Sn-polymetal deposit is located in the southern part of the Great Xing'an Range of Inner Mongolia, NE China, which is belonged to the eastern part of the Central Asian Orogenic Belt (CAOB). Sn-polymetal mineralization is closely related to the emplacement of the Early Cretaceous fine- to medium-grained quartz porphyry. Three types of mineralization have been recognized at Weilasituo with the disseminated and stockwork Sn-polymetal mineralization mainly hosted by the quartz porphyry, the vein-type Sn-polymetal mineralization hosted by NE-trending and WE-trending fractures and faults in the upper and outer part of the porphyry, and breccia mineralization occurred within a steep cryptoexplosive breccia pipe. The ore-related alteration typically consists of Na-Ca-Sr alteration and greisen. In order to understand the petrogenetic link between the Sn-polymetal mineralization and the host quartz porphyry, this paper presents new whole-rock geochemistry for the quartz porphyry, EPMA analysis of ore and gangue minerals, and in situ U-Pb dating of cassiterite. The Laser Abrasion Multiple Collector Inductively Coupled Plasma Mass Spectrometer (LA-MCICP-MS) cassiterite U-Pb dating yields two well-defined isochron ages of 138 ± 6 Ma for disseminated ore and 135 ± 6 Ma for the vein-type ore, which could be regarded as the ore-forming age. The cassiterite U-Pb ages (ca. 138–135 Ma) determined in this study, together with previous data, reveals the close temporal and genetic relationship between the mineralization event and the emplacement of the quartz porphyry. The quartz porphyry is characterized by high SiO 2 , Na 2 O, and A/CNK values (1.09–1.21). REE tetrad effect combined with extremely high Rb/Sr, K/Ba ratios and low K/Rb, Zr/Hf, La/Nb, La/Ta and Eu/Eu* ratios indicate that the quartz porphyry is a highly fractionated peraluminous I-type granite that is hydrothermally altered. Low ε Nd( t ) values of 4.27–0.28 and the two-stage depleted mantle Nd model ages (T 2DM = ca. 1279–908 Ma) for the quartz porphyry, are similar to granites in Precambrian microcontinents of the eastern part of the Central Asian Orogen (CAOB). This suggests that the quartz porphyry was derived from the remelting of juvenile crust and Precambrian rocks in an extensional setting. Therefore, the highly fractional crystallization and magmatic-hydrothermal interactions of the quartz porphyry have contributed to the formation of the Weilasituo Sn-polymetal deposit. [ABSTRACT FROM AUTHOR]

The Inner Mongolia Plateau is located in the north of the Late Palaeozoic Hegenshan ophiolitic mélange belt, and its Mesozoic magmatism impacts our understanding of the tectonic evolution affected by the closing of the Mongol‐Okhotsk Ocean and Palaeo‐Pacific Ocean. Here, we present new U–Pb ages, whole‐rock geochemistry and Hf isotopes from the Late Mesozoic magmatic rocks in the Dalai area along the northeastern margin of the Inner Mongolia Plateau. The Late Jurassic rock types include medium‐fine‐grained phenocryst‐bearing and porphyritic monzogranites as well as medium‐fine‐grained monzogranites with the precise age range of 167.7–159.8 Ma. The Early Cretaceous rock types consist of fine‐grained biotite monzogranite and medium‐fine‐grained biotite monzogranite with the precise age range of 140.9–130.7 Ma. The geochemistry data show that the Late Jurassic and Early Cretaceous rocks are peraluminous granites and high‐K calc‐alkaline series and can be classified as A‐type granite. These granites are enriched in large‐ionlithophile elements such as Rb, Th and U, depleted in the high‐field‐strength elements such as Nb, Sr, P, and Ti. Rare earth elements have high total concentrations and present the light rare earth elements enriched with the heavy rare earth elements depleted. Zircon Hf isotopes show that εHf(t) ranges from +8.0 to +15.9 from the Late Jurassic rocks and +6.9 to +13.5 from the Early Cretaceous rocks. Our new results reveal that the Late Jurassic and the Early Cretaceous magmas were derived from partial melting of the younger lower crust, and the Early Cretaceous rocks are more strongly contaminated than the Jurassic intrusions. The Late Jurassic rocks in the Dalai area were formed from a post‐collisional setting related to the closure of the Mongol‐Okhotsk Ocean in the Early‐Middle Jurassic. The Early Cretaceous intrusions were formed from a transition setting from post‐collision to syn‐collision associated with the superposition of the Mongol‐Okhotsk Ocean and the Palaeo‐Pacific Ocean tectonic domain. [ABSTRACT FROM AUTHOR]

In recent years, new methods for seeking concealed ore bodies have become an active area of ore prospecting. Previous studies of water geochemistry have usually been confined to the analysis of the elemental content of surface water, and performing metallogenic predictions based on high element contents. This paper represents the first use of transmission electron microscopy (TEM) to study particles of groundwater in or around the ore district. Comparing the results of the TEM characterization of well waters near the ore district with those of groundwater samples from the deep ore district (hereinafter referred to as the concept of “deep groundwater”), the particles found in both types of water samples were similar. The ore-forming metal particles, such as Fe, Cu, Pb and Zn-bearing particles, are found in both well water and deep groundwater, while the samples in the well waters of the background area (hereinafter referred to as the concept of “background water”) mainly contain only particles, such as CaCO 3 , Ca(OH) 2 , silicate, oxide of Na, K and Fe. In addition, the composition and characteristics of particles from well waters and deep groundwater revealed that they are derived from the concealed ore bodies. Faulting and oxidation are the main mechanisms of particle formation. Because well water samples are similar to the deep groundwater samples, they can be conveniently collected at ground level, and may be used to predict the presence of a deep ore resource. This research establishes a new method for geochemical prospecting using groundwater particles. These particles can reflect more abundant and accurate information regarding the concealed ore bodies than the content of elements. The discovery of metal containing particles in groundwater may improve water-based geochemical prospecting method. [ABSTRACT FROM AUTHOR]

Discovered and mined in recent years, the Jinchangliang gold deposit has not yet been studied in its genetic type. In this paper, the geological features of ore deposit, S isotopic composition, metallogenic age and elements geochemical of the granite closely related to mineralization were discussed. The results of the geological features of ore deposit and S isotopic composition show that ore-bearing hydrothermal solution was closely related with the intrusion of magmatic. The granite is characteristic of high silica SiO2=72.38%-72.98%, high aluminum and Al2O3=14.22%-14.35%, low calcium CaO=0.16% -0.26%, and low value of FeOT/MgO (6.86-7.73), and rich in alkalis Na2O+K2O=9.11%-9.24%, suggesting that it is high-K calc-alkaline, highly fractionated, weak aluminum A-type granite. The REE patterns are inclined to right and show intense fractionation between LREE and HREE, without obvious negative Eu anomaly (δEu=0.80-0.84). The primitive mantle-normalized spidergrams are characterized by depletion of Ba, U, Ta, Nb, Zr, Ti and P, which implies that the granite has the characteristics of the crust-mantle mixing. S isotopes also indicate that the material source of gold deposit is closely related to the granite rocks. The LA-ICP-MS Zircon U-Pb age of the Damiao rock mass medium-fine grained monzogranite (belonging to the early Indo-China) is (245±1) Ma. It shows that Jinchangliang gold deposit was not formed in Yanshanian, but the early Indo-China. Specifically speaking, the deposit was formed in the collision stage of the North China plate and the Siberian plate. [ABSTRACT FROM AUTHOR]

Over the past 30 years, the Cenozoic basalts in eastern China have been the subject of many investigations, but their origin remains highly controversial. The Abaga–Dalinuoer volcanic field in Inner Mongolia consists of an approximately 10,000 km 2 lava plateau and more than 300 volcanic cones and extends northwestward to the adjacent Dariganga lava plateau of Mongolia, forming one of the largest Cenozoic volcanic fields in eastern Asia. In this paper, we concentrate on the Abaga volcanic field that comprises more than 200 monogenetic cones, including scoria cones, lava flows, and maars. Phreatomagmatism has contributed to the generation of several volcanic edifices, and the diameter of the maars craters can reach 3 to 6 km, which are among the largest in eastern China. The volcanic rocks in the Abaga area can be divided into alkaline basalts and tholeiites. According to trace element and Sr–Nd isotopic characteristics, the Abaga magmas were primarily derived from a relatively homogeneous garnet peridotite source within the asthenosphere. Variable degrees and depths of partial melting played a key role in the genesis of magma from alkaline basalts to tholeiites. In contrast to the surrounding Cenozoic volcanic fields, such as Datong, Jining, and Hanuoba, in the western block of the North China Craton, the Abaga volcanic region in the southern part of the Central Asian Orogenic Belt is distinguished by the deepest melting and the thickest lithosphere. Negative Ba-, Rb-, K-, and Ti anomalies and relatively high 87 Sr/ 86 Sr ratios suggest the presence of residual phlogopite/amphibole during mantle melting. The origin of the Abaga magma most likely required involvement of fluids released from the stagnant Pacific slab in the mantle transition zone. [ABSTRACT FROM AUTHOR]

The Baolidao and Halatu plutons are located in the Northern Orogenic Belt (NOB) in Sonidzuoqi area of Inner Mongolia, which has an important significance for the tectonic evolution of Xing-Meng Orogenic Belt (XMOB). The two plutons have been intensively studied but the conclusions are still controversial. Combined with the previous study, this paper gives new geological data about the two correlative plutons for gaining a better understanding of their petrogenesis and the geodynamic setting. The Baolidao granitoids contain two different series, calc-alkaline series mainly formed in the Ordovician and high K calc-alkaline series mainly formed in the Carboniferous. The Halatu granites are formed in the Triassic and belong to high- K calc-alkaline series. This study got the zircon U–Pb ages of 316–322 Ma for the Baolidao granitoids and 233 ± 2 Ma for the Halatu syenogranites, respectively. In the tectonic discrimination diagrams, they mainly fall into the area of post-orogenic granites (POG). Hf isotopic analyses for the Baolidao granitoids (Sample BLD-1 and 3) shows ε Hf ( t ) = 3.0–14.0, with two-stage Hf model age ( T DM2 ) of 436–1138 Ma. The Halatu syenogranite (Sample HLT-1) also shows a depleted ε Hf ( t ) = 3.8–8.2, with T DM2 of 741–1024 Ma, suggesting the major involvement of juvenile crustal components. The various ε Hf values of the Carboniferous Baolidao and Triassic Halatu granitoids indicates a hybrid magma source of juvenile material with old crustal component, and the ε Hf ( t ) values decrease from the Carboniferous to Triassic, suggesting the increasing proportion of old continental material during this period. Combined with the regional geology, the Carboniferous Baolidao granitoids are possibly not arc rocks, but originated from the post-collisional setting. The Triassic Halatu granites were formed in the subsequently extensional environment. [ABSTRACT FROM AUTHOR]

The Langshan area is the northeastern part of the Alxa block and adjacent to the Inner Mongolia-Da Hinggan Orogenic Belt (IMDOB) to the north, and geochronological and geochemical studies of the Langshan plutons would be helpful for unraveling the relationship of the magmatism in the Langshan area with that in the IMDOB. Based on zircon U–Pb ages presented in this study and in published papers, five magmatic stages are recognized in Langshan area: Late Silurian (∼418 Ma), Carboniferous (328–304 Ma), Early Permian (294–272 Ma), Late Permian (260–254 Ma) and Middle-Late Triassic (245–227 Ma). The Late Silurian two-mica granite is peraluminous and has a source from ancient continental crust, indicating a collision event. The late Early Carboniferous mafic plutons are subalkaline, show appinitic affinities, and may originate from the subduction-modified continental lithospheric mantle. The late Early Permian granodiorite is weakly peraluminous and high-K calc-alkaline and may be derived from ancient continental crust, while the late Early Permian alkaline gabbro–diorite displays EM I-like Sr–Nd isotopic signatures, indicating an enriched subcontinental lithospheric mantle source. The Late Permian granodiorite is calc-alkaline and peraluminous and may result from the partial melting of ancient lower continental crust, whereas the Late Permian leuconorite belongs to low-K tholeiitic series and has a cumulate origin from an enriched mantle source with the input of juvenile mantle materials. The Paleozoic–Triassic magmatic stages in the Langshan area are consistent with the main magmatic periods in the northern NCC, which are the Late Silurian to Middle Devonian (∼418–386 Ma) and Early Carboniferous to Late Triassic (∼342–211 Ma, with three magmatic stages of Carboniferous, Permian and Triassic). Especially, the Carboniferous to Late Triassic magmatic period in the northern NCC are closely comparable with that in the IMDOB, indicating the two domains might be involved in similar tectonic processes during Late Paleozoic. [ABSTRACT FROM AUTHOR]

Abstract: The Yimin Ge-coal deposit, located in the Yimin coalfield, Inner Mongolia, is the third largest Ge-rich coal deposit in China just after the Lincang and Wulantuga Ge-coal deposits. Based on the coal and non-coal samples recently collected from the Wumuchang coal mining district in the Yimin Ge-coal deposit, this paper reports some new data on the mineralogical and geochemical characteristics of the Yimin high-Ge coals, and provides some new evidence for the possible mode of Ge enrichment in the Yimin coals. Mineralogical analyses were performed by means of Powder X-ray diffraction (XRD). Major and trace element concentrations were determined by inductively coupled plasma atomic-emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Element affinities were determined by Pearson's correlation analysis. The studied coals fall within the coal rank between sub-bituminous A and high volatile bituminous C, with relatively high moisture content, high volatile matter yield and low to medium ash yield. Quartz and kaolinite are the main mineral matters in the Yimin coals, with small amounts of pyrite and traces of microcline. Common pyrite and As-bearing pyrite occurring in the Yimin coals show an epigenetic origin. The epigenetic precipitation of kaolinite, quartz and As-rich pyrite (with Ge, and other trace elements) in the Yimin coal fractures may be caused by activities of both hydrothermal and low temperature fluids. Compared to common Chinese and worldwide coals, the Yimin coals are markedly enriched in Ge (43mg/kg), As (155mg/kg), and W (9.84mg/kg) and slightly enriched in Pb (22mg/kg) and Hg (0.24mg/kg). Most of the elements (e.g. Al, K, Sc, Ti, V, Cu, Ga, Sn, Th and REEs) in the studied coals present an aluminosilicate affinity as deduced from their obvious positive correlation with Al and ash yields. High correlation coefficients of As and Hg with Fe and S indicate a sulfide affinity of these elements in the Yimin coals. Germanium, B, Mo, and W in the studied coals show an organic affinity and a partial sulfur affinity as deduced from their negative correlation with Al and positive correlation with S, respectively. The preliminary and possible model for Ge enrichment in the Yimin Ge-coal deposit was that Ge was carried by hydrothermal fluids and then these fluids were incorporated in the water existing in the upper porous conglomerates and percolate in the top of the coal seam, where Ge was trapped by organic matter and finally enriched in an early diagenetic stage (humification–gelification). [Copyright &y& Elsevier]

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Abstract: Aluminum-hydroxide (boehmite and diaspore)-, Ga-, REY (rare earth elements and Y)-, and Al-rich Pennsylvanian Taiyuan Formation coals have previously been found in the Jungar and Daqingshan Coalfields, Inner Mongolia, China. Gallium, REY, and Al are potentially extractable and usable elements in combustion residues derived from these coals. This paper reports new results on 50 bench samples of the No. 6 coal from the Guanbanwusu Mine, Jungar Coalfield, Inner Mongolia, and provides new data and evidence for the existence of an Al (Ga, REY) ore deposit in the unique Jungar Coalfield. The No. 6 coal in the Guanbanwusu Mine has a low rank (Ro,ran =0.56%) and a low-sulfur content (St,d =0.58%). The proportion of inertinite in the coal (56.7%; mineral-free basis) is higher than that of vitrinite (31%). The minerals in the coal are mainly represented by kaolinite, boehmite, and chlorite, along with variable proportions in some samples of calcite, ankerite, siderite, and goyazite. Boehmite, goyazite, and part of the kaolinite were derived from bauxite in the weathered surface of the sediment-source region. Ankerite, calcite, and siderite in the coal are of authigenic origin. The chlorite in the Guanbanwusu coals appears to have a chemical composition intermediate between cookeite and chamosite. This mineral mainly occurs as cell-fillings, also indicating an authigenic origin, and was probably derived from hydrothermal fluids. A new mineral phase mainly composed of Ti, Cl, and Fe is probably a Ti-bearing oxychloride or hydroxychloride. Compared to other Chinese coals and to world hard coals, the coal from the Guanbanwusu Mine is enriched in Al2O3 (9.34%), P2O5 (0.126%), Li (175μg/g), F (434μg/g), Cl (1542μg/g), Ga (12.9μg/g), Sr (703μg/g), and Th (12.9μg/g), but has a lower SiO2/Al2O3 ratio (0.74) due to the higher proportions of boehmite and goyazite in the coal. The major carrier of P2O5 and Sr is goyazite. Lithium mainly occurs in the chlorite (cf. cookeite), kaolinite, and possibly, to a lesser extent, illite. Fluorine in the coal has a major boehmite affinity, but a small proportion may also occur in the organic matter and chlorite. Gallium in the coal largely occurs in goyazite. Chlorine is independent of other elements in the coal, associated neither with moisture nor with organic matter, but possibly occurring in molecular form (Cl2) and in the Ti-bearing oxychloride or hydroxychloride. Thorium in the coal occurs in the clay and accessory minerals, and was mainly derived from detrital materials of the source region. Rare earth elements and Y have a mixed (organic and inorganic) affinity, largely occurring in goyazite-group minerals and, to a lesser extent, boehmite and organic matter. Most coal benches and partings have either an L-type or H-type of REY enrichment, owing respectively to the weathered bauxite source region and groundwater effects. The Al2O3, Ga, REY and possibly Li in the Guanbanwusu coals, like those in coals from the Jungar and adjacent Daqingshan Coalfields, are industrially useful metals that could potentially be recovered from the relevant coal combustion residues. It is suggested that, if Ga in ash>50μg/g, REY>800–900μg/g, SiO2/Al2O3 <1 (or Al2O3 >40% in ash), and coal thickness>5m, the coal combustion residues would be expected to be suitably enriched in Al2O3 and can be considered for Al2O3, Ga, and REY recovery. [Copyright &y& Elsevier]

Abstract: Aluminum-hydroxide (boehmite)-rich Pennsylvanian coals of high volatile A bituminous rank were found previously in the Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 48 bench samples of the CP2 coal from the adjacent Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, and provides new insights into the origin and modes of occurrence of the minerals and elements present in the CP2 coal. Compared to the same coal in the adjacent mines, the CP2 coal in the Adaohai Mine has a higher rank (Ro, ran =1.58%), which is attributed to igneous intrusions during the Late Jurassic and Early Cretaceous Epochs. The proportion of inertinite (35.3%) in the coal is higher than that in other Late Paleozoic coals in northern China but lower than that in the Jungar coals. Minerals in the CP2 coal include diaspore, boehmite, gorceixite, calcite, dolomite, siderite, clay minerals (kaolinite and ammonian illite), and trace amounts of anatase, fluorapatite, quartz, and pyrite. Based on mineral proportions in the coal bench samples, the CP2 coal may be divided into four Zones (I to IV) from bottom to top. The major mineral in Zones I and IV is kaolinite. Zones II and III are mainly composed of ammonian illite, diaspore, boehmite, gorceixite, calcite, dolomite, and siderite. Diaspore-, boehmite-, and gorceixite-forming materials were derived from oxidized bauxite in the weathered crust of the Benxi Formation in the sediment-source region during peat accumulation. However, gorceixite may have formed earlier than diaspore; the diaspore was derived from gibbsite that was subjected to dehydration by the heat of the igneous intrusions. The ammonian illite may have been formed at a relatively high temperature by interaction of kaolinite with nitrogen released from the organic matter in the coal during metamorphism caused by the igneous intrusion. The calcite and dolomite occur as epigenetic cell- and fracture-fillings and were probably derived from the igneous fluids. Compared to the common Chinese and world coals, the CP2 coal is enriched in CaO (1.69%), MgO (0.32%), P2O5 (0.214%), F (207μg/g), Ga (16.3μg/g), Zr (446μg/g), Ba (276μg/g), Hg (0.33μg/g), and Th (12.4μg/g), but has a lower SiO2/Al2O3 ratio due to the higher proportions of diaspore, boehmite, and gorceixite in the coal. The F occurs mainly in gorceixite and fluorapatite. The major carriers of Ga are diaspore and kaolinite but not gorceixite. Barium mainly occurs in gorceixite and barite. Mercury was probably derived from the igneous intrusion and is distributed in both the organic matter and the minerals. The elements are classified into five associations by cluster analysis, Groups A, B, C, D, and E. Group A represents a REE-Be-Y-Se-Ga-Ge-Sc-In-Pb-Bi-Nb-Ta-TiO2-W-Hg-Sb-Zr-Hf-Th-U association. Most of the elements in Group A are lithophile elements that occur in aluminosilicate minerals. Group B (Sn-Te-Zn-Cd-V-As-Cr-Cu-Mo-Ni-Re) is weakly correlated with ash yield and is associated with unidentified trace sulfide minerals. Elements in Group C (Ad-Na2O-Al2O3-SiO2- Li-K2O-Rb-Cs-Tl association) probably occur in the clay minerals and diaspore. Group D consists of P2O5, Ba, F, Sr, S, and Cl, and with the exception of S, they occur in minerals (gorceixite and fluorapatite). Oxides of Fe2O3-MnO-CaO-MgO make up Group E and mainly occur in the carbonate minerals. The coals are enriched in light REEs and the LREEs–HREEs have been highly fractionated, with an average (La/Yb) N of 8.71. The heavy REEs in the coals have a stronger organic affinity than the LREEs. [Copyright &y& Elsevier]

Abstract: The Early Cretaceous Wulantuga high-Ge coal deposit in Inner Mongolia is one of the major coal-hosted Ge deposits in China. This paper reports new data on the petrological, mineralogical, and geochemical compositions of 13 bench samples of the high-Ge No. 6 coal from the Wulantuga deposit, and provides new insight into the origin and modes of occurrence of the minerals and elements present. The No. 6 Coal has a low rank (Ro,max =0.45%) and is a low-ash coal (8.77%). The total content of inertinite (52.5vol.% on average) in most coal benches is higher than that of huminite (46.8vol.% on average). The dominant huminite maceral is textinite (averages 43.9%), and the dominant inertinite macerals are mainly fusinite (averages 33%) and semifusinite (12.5%), along with trace portions of intertodetrinite, secretinite, funginite, and macrinite. Fungus, seen as the maceral funginite, played a role in the development of degraded maceral forms in the Wulantuga coals. Funginite is present in samples examined in this study, but is not easily extracted during palynological studies; recovered fungal taxa are saprophytes, indicating woody decomposition prior to incorporation in the mire. Palynology revealed a sparse flora that is consistent with the early Cretaceous age. Minerals in the coal include quartz, kaolinite, illite (and/or illite/smectite), gypsum, pyrite, and traces of rutile and anatase. A varying proportion of bassanite was observed in the low-temperature ashes (LTAs). Bassanite in the LTAs was derived both from the dehydration of gypsum in the raw coals and from the interaction between organically-associated Ca and S during the low-temperature ashing. In addition to a proportion of detrital quartz, fine-grained and cell-filling quartz of authigenic origin is also present. Pyrite is of syngenetic origin and derived from sulfate-rich hydrothermal fluids. Compared to common Chinese and world low-rank coals, the No. 6 Coal is enriched in Be (25.7μg/g), F (336μg/g), Ge (274μg/g), As (499μg/g), Sb (240μg/g), Cs (5.29μg/g), W (115μg/g), Hg (3.165μg/g), and Tl (3.15μg/g). Germanium in the coal is organically associated, and its enrichment is attributed to hydrothermal fluids from the adjacent granitoids. Beryllium is probably associated with Ca- and Mn-bearing carbonate minerals and to a lesser extent with clay minerals, rather than with organic matter. Fluorine largely occurs in clay minerals (kaolinite and illite). The elevated concentrations of Tl, Hg, As, and Sb are mainly distributed in pyrite and were derived from the same hydrothermal source. The high W in the coal occurs in both the organic matter and the authigenic quartz. Illite is the major carrier of Cs in the coal. The accumulation of rare earth elements (REE) in the coals had a polygenetic and multistage nature, including two syngenetic stages (early hydrothermal and terrigenous) and one diagenetic (late hydrothermal) stage. The REE distribution patterns of the early hydrothermal and terrigenous stages were characterized by the enrichment of medium REE (M-type REE) and light REE (L-type REE), respectively. A H-type REE distribution pattern (HREE enrichment) occurred in the late diagenetic hydrothermal stage. The high-Ge Wulantuga coals are also abnormally enriched in precious metals. Gold, Pt, and Pd in the coals, calculated from their concentrations in the LTAs, are 3.5–25.8, < 4–25.5, and<2.5–15.5 times higher in comparison with those in the continental crust. The highest concentrations of precious metals occur in the pyrite contained in the coal and are 18 (Pd), 130 (Au), and 725 (Pt) times higher than those of the continental crust. The pyrite is probably the basic carrier of the Pt and some portion of the Au in the coal; additionally, a portion of precious metals may be organically (halogen-organic) bound in the coal. [Copyright &y& Elsevier]

The northern Alxa orogenic belt, a junction between the western and eastern Central Asian Orogenic Belt (CAOB), is not well understood, especially in its Carboniferous to Permian tectonic history. In this paper, an integrated study incorporating the geochronology, geochemistry, and isotopes of magmatic rocks and provenance analysis of clastic rocks is conducted to address the above issue. The zircon U Pb age data, both in this study and in previous studies, indicates that the Permian magmatic activities in the Alxa Block were intensive and peaked at ca. 276 Ma. The magmatic zircons yield negative ε Hf (t) values with a wide range, indicating their dominant derivation from the crustal reworking of the Alxa Block with the addition of juvenile materials. The Permian high-K to shoshonitic, I-type granitoids combined with the A-type granitoids/rhyolites were most likely formed in extensional settings. The late Carboniferous sandstones collected along the Badain Jaran fault yield a high proportion of early Paleozoic zircons peaked at ca. 429 Ma with both positive to negative Hf (t) values and a low proportion of Precambrian zircons with positive to negative Hf (t) values. Thus, their provenance were likely the Precambrian to Paleozoic rocks in the Alxa Block and in the terranes in the CAOB. The zircon age spectra with no indicators of Carboniferous zircons approximating their depositional age supports an extensional setting. The Permian A-type granites and volcanic rocks in the Alxa area have some geochemical affinity with the Permian alkaline granitoids in the eastern Tianshan–Beishan and central-north Inner Mongolia regions. These findings support the extension of the Gobi–Tianshan belt in the Alxa area. • The Permian magmatic rocks were predominantly reworked from the Alxa Block. • The clastic rocks were sourced from the Alxa Block and the terranes in the CAOB. • An extensional setting was proposed for the Alxa area. [ABSTRACT FROM AUTHOR]

This paper deals with the meta-mafic volcanic rocks of the Gongyiming iron deposit at Baotou, Inner Mongolia. The major and trace elements and REE data indicate that the meta-mafic volcanic rocks occurred in the environment similar to a modern continental rift. Sm-Nd and Rb-Sr isotopic studies indicated that the meta-basic rocks were formed during the Early Neoarchean from 2800 Ma to 2900 Ma and reworked during the Late Neoarchean (2500 Ma) by metamorphism. Because of the separation of the North China Craton from the Siberia Craton during the Middle Proterozoic (1600 Ma), the Rb-Sr systematics of the rocks has been changed. The Se' ertengshan greenstone seems to occur during the Middle Archean. A stable continental crust may have existed during the Paleoarchean. [ABSTRACT FROM AUTHOR]

The Early Permian Yuejin Sumu intrusive rocks are located approximately 40 km northwest of Xilinhot City, Inner Mongolia. The magmatic rocks primarily composed of gabbro, diorite, and syenogranite. Through the study of zircon LA-ICP-MS U–Pb geochronology and rock geochemistry, age dates of the three lithologies show that the three formed simultaneously in the late Early Permian (gabbro formation age is 276.7 ± 1.3 Ma; diorite is 276.9 ± 0.8 Ma; syenogranite is 275.0± 1.4 Ma). The geochemical characteristics of the three lithologies are primarily calc-alkaline, and some samples, such as gabbro and diorite, show a transition to the alkaline series. The oxides in the gabbro and diorite are linearly related to SiO2. With magma MgO content, Al2O3 content increases first and then decreases, while CaO content decreases sharply, suggesting that the magma for the gabbro and diorite is a mantle-derived magma that undergoes separation and crystallization. The crystalline minerals include magnesia-rich pyroxene in the early stage and the plagioclase and pyroxene in the late stage. The syenogranite has high aluminum content (12.8–14.6%), and the ratio of FeOT/Mg# is high. Rare earth elements are characterized by a mid-range of the light and heavy rare earth elements. Eu shows significant negative anomalies, and the whole rare earth elements (REEs) are characterized by V-shaped distribution. The syenogranite are enriched in K, Rb, Th, U, Zr, and depleted in Eu, Ba, Sr, Ti, P, Nb, Ta, indicating that the magma may derived from crust in a typical post-orogenic environment. Petrology and geochemical characteristics of the Early Permian intrusive rocks indicate that in the Early Permian (~274–278 Ma) in the Xilinhot area was back-arc extensional environment at the active continental margin. Mantle-derived magma caused partial melting of the crustal material. The mantle-derived magma and the melt of the crustal material formed the Early Permian bimodal-like Yuejin Sumu intrusive rocks. [ABSTRACT FROM AUTHOR]

Newly recognized Late Carboniferous volcanic rocks occur in Ongniud Banner on the northern margin of the Sino‐Korean palaeoplate, including rhyolite, dacite, and related volcaniclastic. The volcanic rocks have for a long time been considered to form in the Early Permian. Our new LA‐ICP‐MS U–Pb zircon dating of two rhyolite samples and one dacite sample yielded ages of 305.6 ± 1.6 Ma, 312.2 ± 2.3 Ma, and 305.3 ± 1.7 Ma, respectively, corresponding to the Late Carboniferous. The volcanic rocks are enriched in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs, e.g., Nb, Ta). The positive zircon εHf(t) values (+6.64 to +9.49) of the volcanic rocks and the high Mg# values (47.05–51.47) of some samples indicate the contribution of mantle materials to the sources. Integrated with geological, geochemical, and Lu–Hf isotopic studies, it is considered the volcanic rocks formed in a subduction‐related continental margin arc setting. Combined with the studies in the southeastern part of the Central Asian Orogenic Belt on the ophiolitic mélanges, magamatic belts and sedimentary environment of the Late Palaeozoic, collision‐related granites, and so on; it is suggested that the southward subduction for the eastern segment of the Palaeo‐Asian Ocean beneath the northern margin of Sino‐Korean palaeoplate was still occurring in the Late Carboniferous. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Hegenshan Ocean is an important but poorly understood issue in the geology of the southeastern Central Asian Orogenic Belt (CAOB). Here we present an integrated study of petrology, geochronology, geochemistry, and Sr–Nd–Hf isotopes on a volcanic suite from the Baoligaomiao Formation near Dongwuqi, central Inner Mongolia, NE China. LA-ICP-MS zircon U–Pb dating indicates that the volcanic rocks formed at the Carboniferous–Permian boundary (ca. 301–297 Ma). Geochemistry data reveal that the rocks belong to alkaline to sub-alkaline series, and are characterized by enrichments in light rare earth elements (LaN/YbN = 13.01–39.30) and large ion lithophile elements and depletions in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti). They have relatively low initial 87Sr/86Sr ratios (0.702570–0.708084) and highly positive whole-rock ԐNd(t) (2.27–2.72) and zircon ԐHf(t) values (0.66–11.92). These geochemical characteristics and Sr–Nd–Hf isotopic compositions reveal that the rocks originated from partial melts of a juvenile, arc-type middle-lower crust, with fractional crystallization as a dominant factor controlling the magma differentiation. The rocks were generated in a post-collisional regime, and occurred as a magmatic response to the final closure of the Hegenshan Ocean at the Late Carboniferous (ca. 305 Ma). In addition, based on a review of the pre-existing literature data, a model of continental arc–back-arc basin system at the southern margin of South Mongolian microcontinent is proposed to explain the tectonic evolution of the Hegenshan Ocean. [ABSTRACT FROM AUTHOR]

The Late Permian on the periphery of the Songliao Basin, eastern Inner Mongolia, is an important hydrocarbon source rock system. Its sedimentary environment plays an important role in the evaluation of hydrocarbon prospects in the area. Unfortunately, until now, the interpretation of the sedimentary environment of this area has been controversial. We investigated the Late Permian sedimentary environment by studying the sedimentary characteristics and geochemistry. Based on these investigations, we conclude that the Linxi Formation is mainly composed of clastic sediments, interbedded with limestone lenses, with bioherm limestone at the top of the formation. Inner-layer marine fossils (calcium algae, bryozoans, and sponges) and freshwater and blackish water microfossils (bivalves) are all present, indicative of a typical shallow water sedimentary environment with an open and concussion background. In terms of geochemistry, the formation is relatively light rare Earth enriched, with significant positive Eu anomaly, slight positive La and Y anomaly, weak positive Gd anomaly, and lack of Ce anomaly. The average B/Ga ratio of the mudstone is greater than 3.3, and the average Sr/Ba ratio of the limestone is greater than 1.0. The range of the 87Sr/86Sr ratio is from 0.707285 to 0.707953. The range of δ13C values is from −4.0‰ to 2.4‰. The sediment assemblages, rare Earth elements, trace elements, and 87Sr/86Sr and C isotopes of the formation indicate that the Linxi Formation formed in a marine sedimentary environment and occasional marine-terrestrial transitional facies. The formation can be further divided into littoral facies, neritic facies, bathyal facies, and delta front. [ABSTRACT FROM AUTHOR]

Bulk-rock elements, isotopes, and zircon U–Pb ages are reported for magmatic rocks in the Dongzi–Changhanboluo Pb–Zn ore district in Chifeng, Inner Mongolia, China. Zircon U–Pb dating identified four stages of magmatism: Late Silurian gabbroic diorite (~ 420 Ma), Middle Permian monzonite (~ 274 Ma), Late Jurassic quartz porphyry and ignimbrite, breccia tuff (153–158 Ma) and Early Cretaceous andesitic porphyrite (~ 127 Ma). Integrating field observations, geochronology, and element and isotope geochemistry indicated a complex petrogenetic history of the magmatic rocks. The gabbroic diorite may have been sourced from EM1-type mantle. The source of the monzonite may have been mantle metasomatized by melt from the subducting plate. The Jurassic volcaniclastic rocks formed in a medium-pressure, high-temperature environment, possibly in the background of crustal thickening in a syncollisional stage and an early postcollisional stage. During this process, shaly sedimentary rocks were brought into the deep crust and heated, followed by the rapid isostatic uplift of the crust, which caused partial melting of the sedimentary rocks. Quartz monzonite porphyry and quartz porphyry formed by partial melting of mantle metasomatized by subducted sediments, but the quartz porphyry experienced high-degree differentiation and evolution. The andesitic porphyrite has characteristics similar to those of Permian monzonite, indicating that its source area was also the zone of mantle metasomatized by subducted sediment. The late Silurian and Permian magmatic rocks in this area most likely formed against a continental arc background related to the subduction of the Paleo-Asian Ocean Plate beneath the North China Plate. The Late Jurassic magmatic rocks suggest that the northern margin of the North China Craton may have been in a post-collisional setting during the Late Jurassic, with no obvious crustal thinning. The Cretaceous andesitic porphyrite may have formed against the background of lithospheric extension and thinning. According to the comprehensive analysis of geological characteristics, diagenetic and metallogenic epochs, and Pb isotope data, the formation of ore bodies in the Dongzi–Changhanboluo ore district was closely related to the Jurassic quartz porphyry. [ABSTRACT FROM AUTHOR]

The petrology, geochronology and geochemistry of the mafic enclaves in the Mid‐Late Triassic Jiefangyingzi pluton from Chifeng area, southern Inner Mongolia, in China are studied to reveal their petrogenetic relationship with the host pluton. Furthermore, the coeval magmatic assemblage and its petrogenesis on the northern margin of the North China craton (NCC) are studied synthetically to elucidate their tectonic setting and the implications for the destruction of the NCC. Zircon U‐Pb dating reveals that the mafic enclaves formed at 230.4 ± 2.2 Ma, which is similar to the age of the host pluton. The most basic mafic enclaves belong to weak alkaline rocks, and they display rare earth element (REE) and trace element normalized patterns and trace element compositions similar to those of ocean island basalt (OIB). In addition, they have positive ∊Nd(t) values (+3.84 to +4.94) similar to those of the Cenozoic basalts on the northern margin of the NCC. All of these geochemical characteristics suggest that the basic mafic rocks originated from the asthenosphere. Petrological and geochemical studies suggest that the Jiefangyingzi pluton and the intermediate mafic enclaves were formed by the mixing of the asthenosphere‐derived and crust‐derived magmas in different degrees. The Mid‐Late Triassic magmatic rocks on the northern margin of the NCC could be classified into three assemblages according to their geochemical compositions: alkaline series, weak alkaline–sub‐alkaline series and sub‐alkaline series rocks. Petrogenetic analyses suggest that the upwelling of the asthenosphere played an important role in the formation of these Mid‐Late Triassic magmatic rocks. Basing on an analysis of regional geological data, we suggest that the northern margin of the NCC underwent destruction due to the upwelling of the asthenosphere during the Mid‐Late Triassic, which was induced by the delamination of the root of the collisional orogeny between Sino‐Korean and Siberian paleoplates in Late Permian. [ABSTRACT FROM AUTHOR]

We present detailed petrography, geochemistry and zircon U–Pb–Hf isotopes of the Mante Aobao granite porphyry in East Ujimqin Banner, Inner Mongolia, with the aim of determining its age and petrogenesis, important for understanding the early Palaeozoic tectonic evolution of the Xing'an–Mongolian Orogenic Belt. The Mante Aobao granite porphyry consists of plagioclase, quartz and minor biotite, but without amphibole. Zircon U–Pb analyses yield ages of 450 ± 1 Ma and 445 ± 2 Ma for the granite porphyry, indicating that it formed during Late Ordovician time. The granite porphyry is metaluminous to slightly peraluminous (aluminous saturation index A/CNK = 0.98–1.11) with high SiO2, K2O and Na2O concentrations and differentiation index (DI = 85–90). Chondrite-normalized rare earth element (REE) patterns display enrichment of light REEs (LREEs) with high ratios of (La/Yb)N and negative Eu anomalies. In the mantle-normalized multi-element variation diagrams, all samples are characterized by depletions of high-field-strength elements (HFSEs; Nb, Ta and Ti) and enrichments of large-ion lithophiles (LILEs; Rb, Th, U and K). These geochemical features indicate that the granite porphyry is a highly fractionated I-type granite and formed in a subduction-related setting. Zircon grains have positive εHf(t) values of +9.2 to +11.2, and TDM2(Hf) ages of 691–821 Ma, suggesting that the granite porphyry was generated by partial melting of Neoproterozoic juvenile crust with involvement of fractional crystallization during magmatic evolution. It is likely that underplating of mantle-derived magmas during Late Ordovician time provided the necessary heat to partially melt this juvenile crust. Combined with the regional geological data, we infer that the Mante Aobao granite porphyry was emplaced in an active continental margin setting that was probably related to the northwards subduction of the Paleo-Asian Plate beneath the South Mongolian Terrane along the Sonid Zuoqi–Xilinhot axis. [ABSTRACT FROM AUTHOR]

We undertook an integrated approach incorporating whole‐rock geochemistry and detrital zircon U‐Pb geochronology from Permian sedimentary rocks in the Solonker area of central Inner Mongolia, China with the aim of constraining the tectonic evolution of the eastern segment of the Central Asian Orogenic Belt. Geochemical analysis reveals a close relationship between the sedimentary and volcanic rock suites in the study region. Detrital zircons from seven samples collected from the Zhesi Formation yield U‐Pb ages that cluster around 309–275 Ma and 464–435 Ma, with two main age peaks of ~452 and ~288 Ma. However, additional detrital zircons with ages in the range of 2,634–543 Ma are sparse and with no obvious age peaks. The results suggest that the deposition of the Zhesi Formation occurred from the Middle to the Late Permian and from two major age provenances: the Precambrian basement of the North China Plate (~1,880 Ma and ~2,520 Ma) and the Paleozoic Southern orogenic belt along the northern margin of North China (~288 Ma and ~452 Ma). In this contribution, we suggest that the Zhesi Formation in the Solonker area formed in response to the Early to Middle Permian subduction tectonic setting of the Paleo‐Asian Ocean (PAO), probably formed in a forearc basin and that the final closure of the PAO occurred after the Late Permian. [ABSTRACT FROM AUTHOR]

Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andean‐type active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two‐mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U‐Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two‐mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean (PAO) and represents a suture between the North China craton (NCC) and Central Asian Orogenic Belt (CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400‐420 Ma. Magmatism of the second stage in 380‐390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes‐type active continental margin of the CAOB has been proposed, including a development of the subduction‐free PAO before 446 Ma, a subduction of the PAO and arc‐related magmatism during 446‐380 Ma, and formation of a molasse basin during 380‐360 Ma. [ABSTRACT FROM AUTHOR]

Based mainly on field geological observation, we identified the Dong Ujimqin mafic dykes in Inner Mongolia, north of Hegenshan ophiolite accretionary belt. The dykes are mainly dolerite, and their ages and source were determined using geochronological, geochemical, zircon Hf, and whole‐rock Sr–Nd isotopic data. Photomicrographs reveal ophitic texture and amygdale structures of the dolerite dykes. Laser ablation multiple collector inductively coupled plasma mass spectrometry U–Pb analysis of zircons yielded ages of 277.9 ± 1.8 and 275.9 ± 1.2 Ma for two of these mafic dykes, placing them within the Early Permian. The dykes are classified as alkaline and tholeiitic series according to their major elements and characterized by high Na2O (2.62–4.06 wt.%), high TiO2 (1.63–2.71 wt.%), and low K2O (0.74–2.06 wt.%). The mafic dykes have similar geochemical characteristics that exhibit large‐ion lithophile element enrichment relative to high‐field‐strength elements, depletion in Ta and Nb, and an asthenosphere‐like Sr–Nd–Hf isotopic signature. They have high Sm/Nd (0.131–0.141) and LaN/YbN (3.75–9.17), near‐chondritic heavy rare earth elements ([Gd/Yb]N = 1.21–2.39), and low Rb/Sr (0.03–0.08) ratios with negligible Eu anomalies (Eu/Eu* = 0.85–1.00). The dykes contain relatively low amounts of radiogenic Sr, as shown by (87Sr/86Sr)i values (0.7035–0.7042), and have positive values of εNd(t; 4.31–6.96) and εHf (t; 6.0–14.5) and negative values of εSr(t; −0.28 to −10.31), suggesting that the mafic dykes have been derived from partial melts of the depleted lithospheric mantle contaminated by crust in the source region and formed in post‐orogenic settings. All the above indicate an extensional event, which was related to the post‐subduction of the Paleo‐Asian Ocean, at ~277–275 Ma, and significant vertical continental growth of the crustal continuum occurred in the continental interior during post‐collisional extension. [ABSTRACT FROM AUTHOR]

The recently discovered Bulage Pb–Zn deposit is located in the central part of the Erlianhot–Dongwuqi Metallogenic Belt (eastern Central Asian Orogenic Belt) in Inner Mongolia, China. The ore bodies of the deposit are hosted in alkali feldspar granite and in dacitic crystal tuff within Unit 2 of the Carboniferous Baoligaomiao Formation. The Bulage deposit is a low to moderate temperature hydrothermal vein‐type deposit and is controlled by fractures. The hydrothermal mineralization can be divided into three stages: early (quartz + specularite ± magnetite), middle (quartz + sphalerite + galena ± chalcopyrite ± pyrite), and late (calcite ± quartz + sphalerite + galena). The deposit contains liquid‐rich two‐phase (VL‐type) and pure‐liquid (L‐type) fluid inclusions. The initial ore‐forming fluids are attributed to the low to moderate temperature and low salinity of a NaCl–H2O system. Hydrogen and oxygen isotopic compositions of quartz and calcite indicate that the ore‐forming fluids were dominated by meteoric water with minor contributions of magmatic water. The quartz diorite, monzonite porphyry, and alkali feldspar granite in the deposit yield LA–ICP–MS zircon U–Pb ages of 305–300 Ma. These high‐K calc‐alkaline I‐type granitoids are enriched in large‐ion lithophile elements (LILEs; e.g., Rb, Cs, and K) and light rare earth elements (LREEs) and are depleted in high‐field‐strength elements (HFSEs; e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs). The primary magma of these granitoids was derived from the partial melting of lower crust. The parental magma of the quartz diorite may have provided part of the ore‐forming material and acted as a heat source for mineralization. Therefore, we infer that the Bulage Pb–Zn deposit was formed as a result of the southward subduction of the Paleo–Asian Ocean beneath the North China Craton during the Late Carboniferous. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) resulted from accretion during the Paleozoic subduction of the Paleo‐Asian Ocean. The Xilinhot area in Inner Mongolia is located in the northern subduction zone of the central‐eastern CAOB and outcropped a large number of late Paleozoic mafic intrusions. The characteristics of magma source and tectonic setting of the mafic intrusions and their response to the closure process of the Paleo‐Asian Ocean are still controversial. This study presents LA‐ICPMS zircon U‐Pb ages and geochemical features of mafic intrusions in the Xilinhot area to constrain the northward subduction of the Paleo‐Asian Ocean. The mafic intrusions consist of gabbro, hornblende gabbro, and diabase. Their intrusion times can be divided into three stages of 326–321 Ma, 276 Ma and 254 Ma by zircon U‐Pb ages. The first two stages of the 326–276 Ma intrusions mostly originated from subduction‐modified continental lithospheric mantle sources that underwent a variable degree partial melting (5–30%), recording the subduction of oceanic crust. The third stage of the 254 Ma mafic rocks also show arc‐related features. The primary magma compositions calculated by PRIMELT2 modeling on three samples of ∼326 Ma and two samples of ∼254 Ma show that these mafic samples are characterized by a variable range in SiO2 (47.51–51.47 wt%), Al2O3 (11.46–15.55 wt%), ΣFeO (8.27–9.61 wt%), MgO (13.01–15.18 wt%) and CaO (9.13–11.67 wt%), consisting with the features between enriched mantle and lower continental crust. The source mantle melting of mafic intrusions occurred under temperatures of 1302–1351°C and pressures of 0.92–1.30 GPa. The magmatic processes occurred near the crust‐mantle boundary at about 33–45 km underground. Combined with previous studies, it is concluded that Carboniferous to early Permian (∼326–275 Ma) northward subduction of the Paleo‐Asian oceanic crust led to the formation of the mafic magmatism in the Baolidao arc zone. The whole region had entered the collision environment at ∼254 Ma, but with subduction‐related environments locally. The final collision between the North China craton and the South Mongolian microcontinent may have lasted until ca. 230 Ma. [ABSTRACT FROM AUTHOR]

The Solonker suture zone has long been considered to mark the location of the final disappearance of the Paleo‐Asian Ocean in the eastern Central Asian Orogenic Belt (CAOB). However, the time of final suturing is still controversial with two main different proposals of late Permian to early Triassic, and late Devonian. This study reports integrated whole‐rock geochemistry and LA‐ICP‐MS zircon U‐Pb ages of sedimentary rocks from the Silurian Xuniwusu Formation, the Devonian Xilingol Complex and the Permian Zhesi Formation in the Hegenshan‐Xilinhot‐Linxi area in central Inner Mongolia, China. The depositional environment, provenance and tectonic setting of the Silurian‐Devonian and the Permian sediments are compared to constrain the tectonic evolution of the Solonker suture zone and its neighboring zones. The protoliths of the silty slates from the Xuniwusu Formation in the Baolidao zone belong to wacke and were derived from felsic igneous rocks with steady‐state weathering, poor sorting and compositional immaturity. The protoliths of metasedimentary rocks from the Xilingol Complex were wackes and litharenites and were sourced from predominantly felsic igneous rocks with variable weathering conditions and moderate sorting. The Xuniwusu Formation and Xilingol Complex samples both have two groups of detrital zircon that peak at ca. 0.9–1.0 Ga and ca. 420–440 Ma, with maximum deposition ages of late Silurian and middle Devonian age, respectively. Considering the ca. 484–383 Ma volcanic arc in the Baolidao zone, the Xuxiniwu Formation represents an oceanic trench sediment and is covered by the sedimentary rocks in the Xilingol Complex that represents a continental slope sediment in front of the arc. The middle Permian Zhesi Formation metasandstones were derived from predominantly felsic igneous rocks and are texturally immature with very low degrees of rounding and sorting, indicating short transport and rapid burial. The Zhesi Formation in the Hegenshan zone has a main zircon age peak of 302 Ma and a subordinate peak of 423 Ma and was deposited in a back‐arc basin with an early marine transgression during extension and a late marine regression during contraction. The formation also crops out locally in the Baolidao zone with a main zircon age peak of 467 Ma and a minor peak of 359 Ma, and suggests it formed as a marine transgression sedimentary sequence in a restricted extensional basin and followed by a marine regressive event. Two obvious zircon age peaks of 444 Ma and 280 Ma in the Solonker zone and 435 Ma and 274 Ma in Ondor Sum are retrieved from the Zhesi Formation. This suggests as a result of the gradual closure of the Paleo‐Asian Ocean a narrow ocean sedimentary environment with marine regressive sedimentary sequences occupied the Solonker and Ondor Sum zones during the middle Permian. A restricted ocean is suggested by the Permian strata in the Bainaimiao zone. Early Paleozoic subduction until ca. 381 Ma and renewed subduction during ca. 310–254 Ma accompanied by the opening and closure of a back‐arc basin during ca. 298–269 Ma occurred in the northern accretionary zone. In contrast, the southern accretionary zone documented early Paleozoic subduction until ca. 400 Ma and a renewed subduction during ca. 298–246 Ma. The final closure of the Paleo‐Asian ocean therefore lasted at least until the early Triassic and ended with the formation of the Solonker suture zone. [ABSTRACT FROM AUTHOR]

We undertake zircon U-Pb dating, Hf isotopes, and geochemical analyses of the Houtoumiao pluton in the Xilinhot microcontinent (XLMC) in the central Inner Mongolia with an aim of determining their ages, petrogenesis, and sources, which are important for understanding the late Palaeozoic tectonic evolution of the Xing’an-Mongolia Orogenic Belt. The Houtoumiao pluton consists of medium-grained granodiorite, coarse- and medium-grained syenogranite. Mafic microgranular enclaves (MMEs) are common in the Houtoumiao pluton. Zircon U-Pb dating has yielded ages of 303 ± 2 and 301 ± 2 Ma for the granodiorite, 295 ± 2 Ma for the syenogranite, and 292 ± 1 Ma for the MMEs. The granodiorite and syenogranite have features of high-K high silica content, rich in Rb, U, and Th, but low content of HFSE, belong to calc-alkaline series. The P2O5 concentration decreases with the increasing SiO2 content, suggesting I-type affinity. The MMEs, which are characterized by low SiO2, relatively high and variable TiO2, Al2O3, FeOT, MgO, CaO, Ni, and Cr contents, also have much higher total rare earth element concentrations that the REE patterns are subparallel to those of the host rocks. Zircons from the host rocks have εHf(t) values from +3.91 to +7.73 and TDM2 values of 820-1067 Ma, suggesting that the granitoids were probably dominated by remelting of juvenile crust materials. The MMEs are of εHf(t) value ranging from +6.23 to +11.04 and TDM1 values from 490 to 693 Ma, suggesting that the primary magma probably was derived from partial melting of a depleted lithospheric mantle, the mafic mineral fractional crystallization and crustal contamination occurred during the magma evolution. Combined with previous studies on the contemporaneous magma-tectonic activities in the Uliastai Continental Margin and XLMC, we suggest that the Houtoumiao pluton formed in a post-orogenic setting. [ABSTRACT FROM AUTHOR]

Dulaerqiao granite is located at the Xinlin-Xiguitu-Toudaoqiao suture zone between the Erguna massif and the Xing'an massif, northeast of Inner Mongolia. The rocks are mainly composed of K-feldspar, quartz, and plagioclase. Zircon LA-ICP-MS U-Pb data show that this granite was deposited in the Late Carboniferous Period (308.7±2.0 Ma). The samples are rich in alkali, Fe, and Al and low in Mg, Ca, and P. Chondrite-normalized REEs exhibit right-inclined patterns with significant negative Eu anomalies. Additionally, the granite shows high quantities of trace elements such as Zr, Hf, Th, K, and Rb and decreased quantities of Sr, P, and Ti. The chemical characteristics identified herein and a series of diagrams that distinguish different types of granite show that Dulaerqiao alkali-feldspar granites belong to the aluminous A-type granite group. Meanwhile, the initial magma crystallizes under high-temperature, low-pressure conditions resulting from a tectonic extension setting. The formation of Dulaerqiao aluminous A-type granite is related to the rejuvenation of the ancient Xinlin-Xiguitu- Toudaoqiao suture zone, which was activated by the interaction between the combined Erguna-Xing'an massif and the Songnen massif in the Late Paleozoic Era. This aluminous A-type granite was deposited about 30 Ma after the collision. [ABSTRACT FROM AUTHOR]

The North China Craton (NCC) witnessed a prolonged subduction–accretion history from the early to late Palaeoproterozoic, culminating with final collision at ca. 1.85 Ga and assembling the continental blocks into the cratonic framework. Subsequently, widespread post-collisional magmatism occurred, particularly along the Trans-North China Orogen (TNCO) that sutures the Eastern and Western blocks of the NCC. Here we present petrological, geochemical, and zircon U–Pb geochronological and Lu–Hf data from a pyroxenite (websterite)–gabbro–diorite suite at Xinghe in Inner Mongolia along the northern segment of the TNCO. The internal structures and high Th/U values of the zircons from the gabbro–diorite suite suggest magmatic crystallization. LA-ICP-MS U–Pb age data on three gabbros and one diorite from the suite yield emplacement ages of 1786.1 ± 4.8, 1783 ± 15 ,1754 ± 16 and 1767 ± 13 Ma, respectively. The εHf(t) shows mostly positive values (up to 5.8), with the lowest value at –4.2, suggesting that the magma was derived from dominantly juvenile sources. The generally low SiO2and high MgO values, and other trace element features of the Xinghe suite are consistent with fractionation from a mantle-derived magma with a broadly E-MORB affinity, with no significant crustal contamination. Recent studies clearly establish that the major magmatic pulse associated with rifting of the NCC within the Columbia supercontinent occurred in the late Mesoproterozoic at ca. 1.3–1.2 Ga associated with mantle plume activity. This, together with the lack of robust geochemical imprints of rift-related magmatism in the Xinghe suite, prompts us to suggest a tectonic model that envisages magma genesis associated with post-collisional extension during slab break-off, following the westward subduction of the Eastern Block and its collision with the Western Block. The resulting asthenospheric upwelling and heat input might have triggered the magma generation from a heterogeneous, subduction-modified sub-lithospheric mantle source for the Xinghe rocks, as well as for similar late Palaeoproterozoic suites in the TNCO. [ABSTRACT FROM PUBLISHER]

This study focused on the entire Hetao Basin, which can fall into four hydrogeological units, the Houtao Plain, Sanhuhe Plain, Hubao Plain, and South Bank Plain of the Yellow River, all of which are under different geological and environmental conditions. To systematically investigate the hydrochemical characteristics and spatial distribution of high-As groundwater (As > 10 μg/L), 974 samples were collected from shallow groundwater. As indicated from the results, high-As groundwater had an extensive distribution, and its spatial distribution in the four hydrogeological units exhibited significant variability. Three concentrated distribution areas were reported with high-As groundwater, which were all in the discharge areas of groundwater, and the arsenic contents in the groundwater were found to exceed 50 μg/L. The hydrochemical types of high-As groundwater in the HT Plain and the SHH Plain consisted of HCO3 SO4·Cl for anions and Na for cations, while those in the other two plains included HCO3 for anions as well as Na·Mg·Ca for cations. According to the pH values, the groundwater was weakly alkaline in the areas with high-As groundwater, and arsenic primarily existed as arsenite. Furthermore, high-As groundwater in the Hetao Basin was characterized by high contents of Fe (mean value of 2.77 mg/L) and HCO3− (mean value of 460 mg/L) and a low relative concentration of SO42− (average value of 310 mg/L). This study did not identify any significant correlation between groundwater arsenic and other ions (e.g., Fe2+, Fe3+, HCO3−, SO42−, NO2− and NO3−) in the entire Hetao Basin over a wide range of hydrogeological units. The results remained unchanged after the four hydrogeological units were analyzed. The special sedimentary environment evolution of the Hetao Basin was found as the prerequisite for the formation of high-arsenic groundwater. Furthermore, groundwater runoff conditions and hydrogeochemical processes in the basin were indicated as the factors controlling the formation of high-arsenic groundwater. [ABSTRACT FROM AUTHOR]

Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO2 flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm) was close to the long-term average (183.9±47.6 mm), while the precipitation in 2008 (136.3 mm) and 2010 (141.3 mm) was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO2 throughout the study period, with a net ecosystem carbon dioxide exchange (NEE) of −7.2, −22.9, and 26.0 g C m−2 yr−1 in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEEsat) and the temperature sensitivity coefficient of ecosystem respiration (Reco) exhibited significant variations. The values of NEEsat were −2.6, −2.9, and −1.4 µmol CO2 m−2 s−1 in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP) and Reco, and the drought sensitivity of GPP was greater than that of Reco. The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution. [ABSTRACT FROM AUTHOR]

Understanding the mechanism of arsenic mobilization from sediments to groundwater is important for water quality management in areas of endemic arsenic poisoning, such as the Hetao Basin in Inner Mongolia, northern China. Aquifer geochemistry was characterized at three field sites (SH, HF, TYS) in Hangjinhouqi County of northwestern Hetao Basin. The results of bulk geochemistry analysis of sediment samples indicated that total As concentrations have a range of 6.8-58.5 mg/kg, with a median of 14.4 mg/kg. The highest As concentrations were found at 15-25 m depth. In the meanwhile, the range of As concentration in the sediments from background borehole is 3-21.8 mg/kg, with a median value of 9 mg/kg. The As sediments concentrations with depth from the SH borehole were correlated with the contents of Fe, Sb, B, V, total C and total S. Generally, the abundance of elements varied with grain size, with higher concentrations in finer fractions of the sediments. Distinct lithology profile and different geochemical characteristics of aquifer sediments indicate the sediments are associated with different sources and diverse sedimentary environments. Up to one third of arsenic in the sediments could be extracted by ammonium oxalate, suggesting that Fe oxyhydroxides may be the major sink of As in the aquifer. Sequential extraction results indicate that arsenic occurs as strongly adsorbed on and/or co-precipitated with amorphous Fe oxyhydroxides in sediments accounting for 35 and 20%, respectively, of the total contents of arsenic. The release of As into groundwater may occur by desorption from the mineral surface driven by reductive dissolution of the Fe oxide minerals. Furthermore, small proportions of As associated with iron sulfides occur in the reductive sediments. [ABSTRACT FROM AUTHOR]

The Yellow River flows through an extensive area of aeolian desert and extends from Xiaheyan, Ningxia Province, to Hekouzhen, Inner Mongolia Province, for a total of 1,000 km. In the desert channel of the Yellow River, the major chemical components are SiO, FeO, AlO, Ti, CaO, MgO, Ba, P, Mn, Ce, Co in which SiO, AlO, FeO and Ti have significant value as indicators of the sources of the coarse sediment. The spatial distribution of the elements' weight percentages and the ratios of Si/Ti, Si/Al between sediment sources and riverbed sediment of the Gansu reach and the desert channel of the Yellow River, indicating that the coarse sediments deposited in the desert reach of the Yellow River are mostly controlled by the local sediment sources; and due to the higher mobility of the fine sediments, they are primarily contributed by the local sediment sources and the tributaries that originate from the loess area of the upper reach of Yellow River. The results of R-factor analysis illustrate that the first component score mainly shows negative values in the desert channel, suggesting that the coarse sediments in this reach contain a higher content of Si and a lower content of Mg + Ca + Al + Fe, which further proves that the Ningxia Hedong, Inner Mongolian Wulanbuhe, and Kubuqi deserts are the primary sources of the coarse sediment in the desert channel of the Yellow River. [ABSTRACT FROM AUTHOR]

The Solonker Suture Zone is thought to record the terminal evolution of the Central Asian Orogenic Belt (CAOB) in Inner Mongolia. However, two contrasting interpretations of the timing of suturing of the Solonker Suture Zone exist: (i) Permian to Early Triassic; and (ii) Middle Devonian or Late Devonian to Carboniferous. The Shuangjing Schist is exposed in the Linxi area along the Xar Moron Fault Zone, which marks the southern boundary of the Solonker Suture Zone in the eastern section of the CAOB, and thus provides insight into the timing of suturing of the Solonker Suture Zone. Detailed and systematic analysis of the petrology and geochemistry of the Shuangjing Schist shows that the Shuangjing Schist developed by greenschist facies prograde metamorphism of a volcanisedimentary rock series protolith. The volcanic parts of the Shuangjing Schist are a calc-alkaline series with large volumes of intermediate members and subordinate acidic members. Volcanism occurred in a magmatic arc on the continental margin and was induced by subduction-related magmatism resulting from mantle metasomatism. The sedimentary parts of the Shuangjing Schist reflect a transition from continental shelf to abyssal plain sedimentation. The formation of the Shuangjing Schist is suggested to be related to closure of an arc/forearc-related ocean basin. The timing is constrained by a laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb magmatic zircon age of 298 ± 2 Ma from a carbonaceous biotite-plagioclase schist that was intruded by granite at 272 ± 2 Ma. In the Linxi area, southward subduction of the arc/forearc basin led to uplift, thickening, collapse, and erosion of the overriding continental crust. Collapse induced extension and widespread magmatism along the volcanic arc at the northern margin of the North China Craton. The closure of the arc/forearc-related oceanic basin led to the formation of Late Permian to Middle Triassic collisional granites and the subsequent end of the collision of the Solonker Suture Zone. [ABSTRACT FROM AUTHOR]

Mineralogy and geochemistry of No.6 Coal from the Heidaigou Mine of the Jungar Coalfield of North China were studied using instrumental neutron activation analysis, inductively coupled-plasma mass spectroscopy, X-ray fluorescence spectrometry, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The results show that gallium concentration is as high as 44.8 µg⋅g-1 in the whole coal-channel sample, and varies from 30.1 µg⋅g-1 to 76.0 µg⋅g (mean 51.9 µg⋅g ) in the main minable benches of No.6 Coal. Such high concentration of Ga in the coal is far higher than the industrial grade (30 µg⋅g ). The thickness of the main minable benches accounts for 81.9% of the whole coal bed. The laboratory high-temperature ashes (550°C) of the main minable coal benches also contain a high concentration of Ga, varying from 62.2 µg⋅g-1 to 178 µg⋅g- 1, with an average of 89.2 µg⋅g-1. The boehmite significantly enriched in No.6 Coal is the main carrier of the high Ga in the coal. Average concentration of Ga in boehmite is 0.09%. The average content of boehmite is 6.1% in the whole coal and 7.5% in the main minable benches. Boehmite is derived from the bauxite in the weathered crust of the underlying Benxi Formation in the north of the basin during the peat accumulation. The colloidal idrargillite had been shortly transported from the weathered crust to the peat mire, and owing to the compaction of the overlying strata during the peat accumulation and early diagenesis, the idrargillite colloid had begun to be dehydrated, leading to boehmite formation. A preliminary estimation showed that the ensured and prospected reserves of Ga in No.6 Coal are up to 6.3 x 104 and 8.57 x 105t, indicating a superlarge gallium ore deposit. The particular paleogeography of the Jungar Coalfield and the peculiar carrier of Ga in coal suggest that this Ga ore deposit is unique in the world. Rare earth elements are also enriched in coal and laboratory ashes. The weighted average concentration of the total rare earth elements is 255 µg⋅g-1 and 830.36 µg⋅g-1 in the main minable benches and their laboratory ashes, respectively. Because Al is the main composition of boehmite, aluminum and rare earth elements in No.6 Coal are also the available and valuable resources. [ABSTRACT FROM AUTHOR]

Coal geochemistry compositional data on whole-coal basis can be converted back to ash basis based on samples' loss on ignition. However, the correlation between the concentrations of elements reported on whole-coal versus ash bases in many cases is inconsistent. Traditional statistical methods (e.g., correlation analysis) for compositional data on both bases may sometimes result in misleading results. To address this issue, we hereby propose an improved additive log-ratio data transformation method for analyzing the correlation between element concentrations reported on whole-coal versus ash bases. To verify the validity of the method proposed in this study, a data set which contains comprehensive analyses of 106 Late Paleozoic coal samples from the Datanhao mine and Adaohai Mine, Inner Mongolia, China, is used for the validity testing. A prediction model was built for performance evaluation of two methods based on the hierarchical clustering algorithm. The results show that the improved additive log-ratio is more effective in prediction for occurrence modes of elements in coal than the previously reported stability method, and therefore can be adopted for consistent interpretations of coal geochemistry compositional data on whole-coal vs. ash bases. [ABSTRACT FROM AUTHOR]

The Great Hinggan Range (GHR) hosts many large Mo deposits and vein-type Pb-Zn deposits and is one of the most important polymetallic metallogenic belts in China. Although Mo and Pb-Zn deposits are locally closely related in space in the GHR, it is disputed whether the Mo and Pb-Zn deposits have a genetic relationship. The Diyanqinamu Mo deposit located at the middle part of the northern GHR is a Late Jurassic large porphyry Mo deposit and closely adjacent by vein-type Pb-Zn deposit. In this work, we discussed the relationship between Mo and Pb-Zn deposits in Diyanqinamu mine based on the data of S and Pb isotopic geochemistry and geological information. In this mine, the Mo deposit is concentrated in the southern area with a distance of 500 m to the vein Pb-Zn deposit. The δ34SCDT values of the galena and sphalerite from the Mo deposit range from +1.73‰ to +7.29‰ with average of +5.04‰. By contrast, δ34SCDT values of the galena and sphalerite from the Pb-Zn deposit, ranging from +2.38‰ to +5.46‰ with average of +4.04‰, is similar to that of the Mo deposit. The formation temperatures of the Pb-Zn deposit calculated based on the sulfur isotope balance fractionation between sphalerite and co-existed galena range from 220 °C to 315 °C (average 247 °C), which is lower than that of the Mo mineralization (292–510°C). Pb isotopic results show that the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the Pb-Zn deposit range from 18.326–18.364, 15.541–15.589, and 38.054–38.214, respectively, which are slightly higher than those of the Mo deposit ranging from 18.287–18.331, 15.532–15.569, and 38.034–38.139, respectively. In the 206Pb/204Pb˗207Pb/204Pb diagram, sulfides sampled from the Mo and Pb-Zn deposits overlapped with each other and formed a linear distribution, indicating that they are derived from a mixed metal source with more external contribution to the Pb-Zn mineralization. This mixed signal is further confirmed by the geologic facts that the host rocks of the vein-type Pb-Zn deposit have abnormally high contents of Pb, Zn, and Ag, and experienced strong hydrothermal alteration. Combined with the ore geology, mineral assemblage, and isotopic geochemistry of the two types of mineralization, we propose that the Mo and Pb-Zn deposits in the Diyanqinamu mine represent different faces of the same porphyry system. This Mo-Pb-Zn metallogenic system would provide important clues on further prospecting of Mo and Pb-Zn resources in the GHR. [ABSTRACT FROM AUTHOR]