Study on rainfall variations in the middle part of Inner Mongolia,China during the past 43 years

The study area, the middle part of Inner Mongolia including Hohhot city, Baotou city, Wulanchabu city, Ordos city, Bayannaoer city and Wuhai city, is one of typical eco-geographical transition zones in China. Using monthly precipitation data (1961–2003) from 45 meteorological stations in the study area, this paper analyzes characteristics and tendencies of annual and seasonal rainfall variations, and reveals multi-time scales structures of these time series through wavelet analyses; also, the periods of annual and seasonal precipitation series are identified, and the periodical oscillations and points of abrupt change at the principal period scale are discovered. The results show that annual precipitation varies in a large range, and has an ascending tendency at an increasing rate of 1.482 mm/10a; the multi-time scales periodical oscillations are clear; differences in tendencies, ranges and decadal precipitation anomalies exist within each decade during 1961–2000. The seasonal allocation of overall annual precipitation is extremely uneven; in terms of tendencies of seasonal precipitation, winter and spring have upward trends while summer and autumn have downward tendencies; distinctions in tendencies, ranges and decadal precipitation anomalies among each seasons are in existence within each decade during 1961–2000. The periodical oscillations of each seasonal precipitation time series are also evident. The research results not only provide convincing evidence for global climate change research, but also facilitate the understanding of specific natural process and pattern to make steps to rehabilitate and reconstruct vegetation, and contribute to fulfill the sustainability of water management.     

Spatial and temporal variation of precipitation during 1960–2015 in Northwestern China

Natural Hazards - Under the global climate change, research on the response characteristic of precipitation to climate change and its variation trend is of great significance. By employing the...     

Temporal–spatial variability of atmospheric and hydrological natural disasters during recent 500 years in Inner Mongolia,China

Natural Hazards - Inner Mongolia, located in the northern China, is a natural disaster-prone region. This study is dedicated to making a comprehensive and quantitative analysis of the...     

Geological and Geochemical Characteristics of the Zhulazhaga Gold Deposit in Inner Mongolia, China

Located in Alxa Zuoqi (Left Banner) of Inner Mongolia, China, the Zhulazhaga gold deposit is the first largescale gold deposit that was found in the middle-upper Proterozoic strata along the north margin of the North China craton in recent years. It was discovered by the No. l Geophysical and Geochemical Exploration Party of Inner Mongolia as a result of prospecting a geochemical anomaly. By now, over 50 tonnes of gold has been defined, with an average Au grade of 4 g/t. The ore bodies occur in the first lithological unit of the Mesoproterozoic Zhulazhagamaodao Formation (MZF), which is composed mainly of epimetamorphic sandstone and siltstone and partly of volcanic rocks. With high concentration of gold,the first lithological unit of the MZF became the source bed for the late-stage ore formation. Controlled by the interstratal fracture zones, the ore bodies mostly appear along the bedding with occurrence similar to that of the strata. The primitiveore types are predominantly the altered rock type with minor ore belonging to the quartz veins type. There are also some oxidized ore near the surface. The metallic minerals are composed mainly of pyrite, pyrrhotite and arsenopyrite with minor chalcopyrite, galena and limonite. Most gold minerals appear as native gold and electrum. Hydrothermal alterations associated with the ore formation are actinolitization, silicatization, sulfidation and carbonation. A total of 100 two-phase H2O-rich and 7 three-phase daughter crystal-beating inclusions were measured in seven goldbearing quartz samples from the Zhulazhaga gold deposit. The homogenization temperatures of the two-phase H2O-rich inclusions range from 155 to 401℃, with an average temperature of 284℃ and bimodal distributions from 240 to 260℃ and 300 to 320℃ respectively. The salinities of the two-phase H2O-rich inclusions vary from 9.22wt% to 24.30wt% NaCl eqniv, with a mode between 23 wt% and 24wt% NaC1 equiv. Comparatively, the homogenization temperatures of the threephase daughter crystal-beating inclusions vary from 210 to 435℃ and the salinities from 29.13wt% to 32.62wt% NaCl equiv. It indicates that the ore-forming fluid is meso-hypothermal and characterized by high salinity, which is apparently different from the metamorphic origin with low salinity. It suggests a magmatic origin of the gold-bearing fluid. The δ^18O values of quartz from auriferous veins range from 11.9 to 16.3 per mil, and the calculated δ^18OH2O values in equilibrium with quartz vary from 1.06 to 9.60 per mil, which fall between the values of meteoric water and magmatic water. It reflects that the ore-forming fluid may be the product of mixing of meteoric water and magmatic water.Based on geological and geochemical studies of the Zhulazhaga gold deposit, it is supposed that the volcanism in the Mesoproterozoic might make gold pre-concentrate in the strata. The extensive and intensive Hercynian tectono-magmatic activity not only brought along a large number of ore-forming materials, but also made the gold from the strata rework. It can be concluded that the ore bodies were mainly formed in late hydrothermal reworking stage. Compared with typical gold deposits associated with epimetamorphic clastic rocks, the Zhulazhaga deposit has similar features in occurrence of ore bodies, ore-controlling structure, wall-rock alterations and mineral assemblages. Therefore, the Zhulazhaga gold deposit belongs to the epimetamorphic clastic rock type.     

Spatial polarization and dynamic pathways of Foreign Direct Investment in China 1990–2009

The spatial and sectoral distribution of Foreign Direct Investment (FDI) in China has changed dramatically in the past two decades. FDI was largely concentrated in the Pearl River Delta (PRD) and other Southern Coastal provinces in early stages and shifted to the Yangtze River Delta (YRD) and the Bohai Economic Rim (BER) sequentially in later stages. It created unique and dynamic paths of the spatial evolution of FDI in China. Although many provinces have received relatively more FDI since the late 2000s, Guangdong and Jiangsu are still the two major recipients of FDI in China, demonstrating and over-arching polarization process. Furthermore, most FDI in China has been in the manufacturing sector, making China well-known as the “World Factory of Manufacturing”. This paper analyses the most recent trends, characteristics and patterns of FDI in China. It portrays the factors that determined the investment location and the dynamic pathways of different kinds of FDI. This paper also foresees the possible changes in spatial and sectoral distribution of FDI in the near future and provides policy suggestions for both China and other developing countries in seeking new FDI inflows and transforming their industrial structures and economies in this particular phase of globalization.     

Ore Deposit Geology and Genesis of the Haobugao Zn–Fe Deposit, Inner Mongolia, NE China

Please?refer?to?the?attachment(s)?for?more?details.     

High fluoride groundwater with high salinity and fluorite in aquifer sediments in Inner Mongolia, China

Fluoride poisoning is the most widespread and serious endemic disease in the inland river basins of northern China, where igneous rocks containing F-rich minerals of the Yanshan stage (Jurassic-Cretaceous) are extensively exposed in mountainous area. In I…     

Fluid inclusion study of the Wunugetu Cu–Mo deposit,Inner Mongolia,China

Hydrothermal alteration and mineralization at the Wunugetu porphyry Cu–Mo deposit, China, include four stages, i.e., the early stage characterized by quartz, K-feldspar and minor mineralization, followed by a molybdenum mineralization stage associated with potassic alteration, copper mineralization associated with sericitization, and the last Pb–Zn mineralization stage associated with carbonation. Hydrothermal quartz contains three types of fluid inclusions, namely aqueous (W-type), daughter mineral-bearing (S-type) and CO₂-rich (C-type) inclusion, with the latter two types absent in the late stage. Fluid inclusions in the early stage display homogenization temperatures above 510°C, with salinities up to 75.8 wt.% NaCl equivalent. The presence of S-type inclusions containing anhydrite and hematite daughter minerals and C-type inclusions indicates an oxidizing, CO₂-bearing environment. Fluid inclusions in the Mo- and Cu-mineralization stages yield homogenization temperatures of 342–508°C and 241–336°C, and salinities of 8.6–49.4 and 6.3–35.7 wt.% NaCl equivalent, respectively. The presence of chalcopyrite instead of hematite and anhydrite daughter minerals in S-type inclusions indicates a decreasing of oxygen fugacity. In the late stage, fluid inclusions yield homogenization temperatures of 115–234°C and salinities lower than 12.4 wt.% NaCl equivalent. It is concluded that the early stage fluids were CO₂ bearing, magmatic in origin, and characterized by high temperature, high salinity, and high oxygen fugacity. Phase separation occurred during the Mo- and Cu-mineralization stages, resulting in CO₂ release, oxygen fugacity decrease and rapid precipitation of sulfides. The late-stage fluids were meteoric in origin and characterized by low temperature, low salinity, and CO₂ poor.     

Isotopic (C–O–S) geochemistry and Re–Os geochronology of the Haobugao Zn–Fe deposit in Inner Mongolia,NE China

The Haobugao Zn–Fe deposit is a typical skarn deposit located in the southern part of the Great Xing’an Range that hosts polymetallic mineralization over a large region. The main ore minerals at the deposit include sphalerite, magnetite, galena, chalcopyrite and pyrite, and the main gangue minerals include andradite, grossular garnet, hedenbergite, diopside, ilvaite, calcite and quartz. There are broadly two mineralizing periods represented by the relatively older skarn and younger quartz–sulfide veins. In detail, there are five metallogenic stages consisting of an early skarn, late skarn, oxide, early quartz–sulfide, and late quartz–sulfide–calcite stages. Electron microprobe analyses show that the garnet at the deposit varies in composition from And_97.95Gro_0.41Pyr_1.64 to And_30.69Gro_66.69Pyr_2.63, and pyroxene is compositionally in the diopside–hedenbergite range (i.e. Di_90.63Hd_8.00Jo_1.37–Hd_88.98Di_4.53Jo_6.49). Petrographic observations and electron microprobe analyses indicate that the sphalerite has three generations ([Zn_0.93Fe_0.08]S–[Zn_0.75Fe_0.24]S). The Zn associated with the first generation sphalerite replaced Cu and Fe of early xenomorphic granular chalcopyrite (i.e. [Cu_1.01Fe_1.03]S₂–[Cu_0.99Fe_0.99]S₂), and part of the first generation sphalerite is coeval with late chalcopyrite (i.e. [Cu_0.96Fe_0.99Zn_0.03]S₂–[Cu_1.00Fe_1.03Zn_0.01]S₂). Magnetite has a noticeable negative Ce anomaly (δCe = ∼0.17 to 0.54), which might be a result of the oxidized ore-fluid. Thirty δ³⁴S_V-PDB analyses of sulfides from the ore range from −2.3 to −0.1‰ in value, which are indicative of a magmatic source. The δ¹³C‰ and δ¹⁸O‰ values for calcite from the ore formed at quartz–sulfide–calcite stage vary from −9.9 to −5.5‰ and from −4.2 to 1.1‰, respectively, contrasting with δ¹³C‰ (2.9–4.8‰) and δ¹⁸O‰ (9.8–13.9‰) values for calcite from marble. It is suggested that the ore-forming fluid associated with late stage of mineralization was predominantly magmatic in origin with some input of local meteoric water.Molybdenite from the Haobugao deposit defines an isochron age of 142 ± 1 Ma, which is interpreted as the mineralization age being synchronous, within error, with the zircon U–Pb ages of 140 ± 1, 141 ± 2, and 141 ± 1 Ma for granite at the deposit. These data and characteristics of lithology and mineralization further show that the Zn–Fe mineralization is temporally and spatially related to the emplacement of granite in an extensional tectonic setting during the Mesozoic.     

The Characteristics and Evolution of Ore-forming Fluids in A’erhada Pb-Zn-Ag Deposit, Inner Mongolia,China

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Extension of the Louzidian Metamorphic Core Complex and Development of Supradetachment Basins in Southern Chifeng, Inner Mongolia, China

The Louzidian metamorphic core complex (LMCC) in southern Chifeng is located on the northern margin of the North China craton. Structural analyses of the LMCC and its extensional detachment system indicate that the LMCC experienced two-stage extension. The ductile regime experienced top-to-northeast shearing extension and the brittle detachment fault underwent top-down-outwards slipping. Between these two stages, a semi-ductile regime recorded the transition from ductile to brittle. The hanging wall of the detachment fault is similar to those classic supradetachment basins in western North America. Analyses of provenance and paleocurrent directions in the basins show that there were two filling stages. In the early stage, materials came from the southwest margin of the basin and the hanging wall of the detachment system and were transported from southwest to northeast; while in the late stage, deposits were derived from the footwall of the detachment fault and transported outwards to the two sides of the     

Analysis of historical drought and flood characteristics of Hengshui during the period 1649–2018: a typical city in North China

Natural Hazards - The objective of this study was to reconstruct the long-term drought and flood time series to analyze their changing characteristics in Hengshui City of North China. Disaster...     

Wind erosion occurrence probabilities maps in the watershed of the Ningxia–Inner Mongolia reach of the Yellow River,China

The watershed of the Ningxia–Inner Mongolia reach of the Yellow River suffers serious wind erosion hazards and the areas with high wind erosion probabilities need to be identified to help in the building of the correct wind-sand blown hazard protection systems. In this study, the Integrated Wind-Erosion Modelling System model and Normalized Difference Vegetation Index (NDVI) data set were used to identify the distributions of threshold wind speeds and wind erosion occurrence probabilities. Through field observations, the relationships among NDVI, vegetation cover, frontal area (lateral cover), roughness length, and threshold friction velocity were obtained. Then, using these relationships, the spatial distributions of threshold wind speeds for wind erosion at a height of 10 m for the different months were mapped. The results show that the threshold wind speed ranged from 7.91 to 35.7 m/s. Based on the threshold wind speed distributions, the wind erosion occurrence probabilities of different months were calculated according to the current wind speed. The results show that the distributions of wind erosion occurrence probabilities and threshold wind speeds were related to each other. The resulting maps of threshold wind speeds and wind erosion occurrence probabilities would help environmental and agricultural researchers in determining some strategies for mitigating or adapting from wind erosion hazards.     

Genesis of PGE mineralization in the Wengeqi mafic–ultramafic complex, Guyang County, Inner Mongolia, China

The Wengeqi complex in Guyang County, Inner Mongolia, is one of several Pd–Pt-mineralized Paleozoic mafic–ultramafic complexes along the north-central margin of the North China. The complex comprises pyroxenites, biotite pyroxenites, amphibole pyroxenites, gabbros, and amphibolites. Zircons extracted from a pyroxenite yield a U–Pb SHRIMP age of 399?±?4?Ma. Several 2–6-m wide syngenetic websterite dikes contain 1–3?ppm Pd?+?Pd and are dominated by pyrite–chalcopyrite–pyrrhotite–magnetite–(pentlandite) assemblages with minor sperrylite, sudburyite, and kotuskite. Textural relationships indicate that pyrite has replaced magmatic chalcopyrite and that magnetite has replaced magmatic pyrrhotite. The mineralization is enriched in Pd–Pt–Cu > Au >> Rh–Ir–Os–Ni > Ru, similar to other occurrences of hydrothermally modified magmatic mineralization, but very different from the much less fractionated compositions of magmatic PGE mineralization. Textural, mineralogical, and geochemical relationships are consistent with alteration of an original magmatic Fe–Ni–Cu sulfide assemblage by a S-rich oxidizing high-temperature (deuteric) hydrothermal fluid.     

Petrogenesis and geodynamic setting of Neoproterozoic and Late Paleozoic magmatism in the Manzhouli–Erguna area of Inner Mongolia,China: Geochronological,geochemical and Hf isotopic evidence

U–Pb dating and Hf isotopic analyses of zircons from various granitoids, combined with major and trace element analyses, were undertaken to determine the petrogenesis and geodynamic setting of Neoproterozoic and Late Paleozoic magmatism in the Manzhouli–Erguna area of Inner Mongolia, China. The Neoproterozoic granitoids are mainly biotite monzogranites with zircon U–Pb ages of 894 ± 13 Ma and 880 ± 10 Ma, and they are characterised by enrichment in large ion lithophile elements (LILEs; e.g., Rb, Ba, K) and light rare earth elements (LREEs), depletion in high field strength elements (HFSEs; e.g., Nb, Ta, Ti) and heavy rare earth elements (HREEs). The Late Devonian granitoids are dominantly syenogranites and mylonitised syenogranites with zircon U–Pb ages of 360 ± 4 Ma, and they form a bimodal magmatic association with subordinate gabbroic rocks of the same age. The Late Devonian syenogranites have A-type characteristics including high total alkalis, Zr, Nb, Ce and Y contents, and high FeOt/MgO, Ga/Al and Rb/Sr ratios. The Carboniferous granitoids are mainly tonalites, granodiorites and monzogranites with U–Pb ages varying from 319 to 306 Ma, and they show very strong adakitic characteristics such as high La/Yb and Sr/Y ratios but low Y and Yb contents. The Late Permian granitoids are dominated by monzogranites and syenogranites with zircon U–Pb ages ranging between 257 and 251 Ma. Isotopically, the ε_Hf(t) values of the Neoproterozoic granitoids range from +4.3 to +8.3, and the two-stage model ages (T_DM2) from 1.2 to 1.5 Ga. The Late Devonian granitoids are less radiogenic [ε_Hf(t) from +12.0 to +12.8 and T_DM2 from 545 to 598 Ma] than the Carboniferous [ε_Hf(t) from +6.8 to +9.5 and T_DM2 from 722 to 894 Ma] and Late Permian granitoids [ε_Hf(t) from +6.1 to +9.4 and T_DM2 in the range of 680–895 Ma]. These data indicate (1) the Neoproterozoic granitoids may have been generated by melting of a juvenile crust extracted from the mantle during the Mesoproterozoic, probably during or following the final stages of assembly of Rodinia as a result of the collision and amalgamation of Australia and the Tarim Craton; (2) the Late Devonian granitoids may have formed by partial melting of a new mantle-derived juvenile crust in a post-orogenic extensional setting; (3) the Carboniferous granitoids appear to have been produced by melting of garnet-bearing amphibolites within a thickened continental crust during and following the collision of the Songnen and Erguna–Xing’an terranes; and (4) the Late Permian granitoids may have been generated by melting of garnet-free amphibolites within the Neoproterozoic juvenile continental crust, probably in the post-collisional tectonic setting that followed the collision of the North China and Siberian cratons.     

Rb–Sr dating of sulfides and S–Pb isotopic study of the Bayanbaolege Ag polymetallic deposit,Inner Mongolia,NE China

The large-scale Bayanbaolege Ag polymetallic deposit is situated in the Tuquan–Linxi Fe-Sn-Cu-Pb-Zn-Ag metallogenic sub-belt in eastern slopes of the southern Great Xing’an Range, NE China. The sulfide-quartz vein-type orebodies in the deposit are hosted primarily in the Early Cretaceous granodiorite porphyry and Late Permian strata. Three primary paragenetic stages of veining have been identified: (I) arsenopyrite- pyrite-quartz stage, (II) pyrite-sphalerite-quartz stage, and (III) galena-silver minerals (pyrargyrite, argentite, and pearceite)-calcite stage. The Rb–Sr dating of sulfides yielded an isochron age of 129.9 ± 2.9 Ma (MSWD = 2.1) for the sphalerite, which constrains the mineralization age to the Early Cretaceous. Rb and Sr concentrations in the sulfides ranged from 0.0940 to 1.0294 ppm and 0.0950–3.3818 ppm, respectively. The initial ⁸⁷Sr/⁸⁶Sr value of the sphalerite was 0.70852 ± 0.00018, indicating that the mineralized materials were derived from the mixed crust-mantle source area. S isotope analysis showed that the δ³⁴S values of the sulfide samples varied in a narrow range, from −1.5‰ to +1.3‰ (mean −0.65‰), indicating a magmatic S source. Pb isotopic ratios of the sulfides (²⁰⁶Pb/²⁰⁴Pb = 18.306–18.416, ²⁰⁷Pb/²⁰⁴Pb = 15.524–15.605, ²⁰⁸Pb/²⁰⁴Pb = 38.095–38.479) and the granodiorite porphyry (²⁰⁶Pb/²⁰⁴Pb = 18.341–18.933, ²⁰⁷Pb/²⁰⁴Pb = 15.539–15.600, ²⁰⁸Pb/²⁰⁴Pb = 38.134–38.944) reflect that the ore-forming materials originated from contemporaneous magma with Early Cretaceous granodiorite porphyry. This study of the Bayanbaolege deposit and other hydrothermal deposits in the area provides compelling evidence that the widespread Mesozoic magmatism and mineralization in the southern Great Xing’an Range occurred in an intracontinental extensional tectonic setting, which was associated with the westward subduction of the paleo-Pacific plate.