Comprehensive evaluation of ice disaster risk of the Ningxia–Inner Mongolia Reach in the upper Yellow River

The Ningxia–Inner Mongolia Reach, in the upper Yellow River, is one of the most serious reaches suffering from ice flood disaster in China. Firstly, according to its characteristics of ice condition evolution and ice disaster, the concept of ice disaster risk of Ningxia–Inner Mongolia Reach was defined, the risk factors of ice disaster were discussed, and the theory and method of “risk identification–risk estimation–risk assessment–risk management” for the ice disaster risk analysis of Ningxia–Inner Mongolia Reach was proposed. Then, the comprehensive evaluation model of ice disaster risk was established using the projection pursuit, fuzzy clustering and accelerating genetic algorithm method. Finally, the ice disaster risk grade was formulated, and the ice disaster risk of 1991–2010 for the Ningxia–Inner Mongolia Reach was evaluated in this paper. The results show that the application results were consistent with the practical characteristics of water regime, meteorological and ice condition, revealing the rationality of the risk evaluation model. This study aims at enriching and developing the theory and method for the ice disaster risk analysis and providing scientific decision basis for the ice-prevention preparedness of Ningxia–Inner Mongolia Reach, in the upper Yellow River.

     

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.     

Planform channel dynamics along the Ningxia–Inner Mongolia reaches of the Yellow River from 1958 to 2008: analysis using Landsat images and topographic maps

Channel planform dynamics were analyzed for the Ningxia–Inner Mongolia reaches of the Yellow River. Map data were analyzed by means of GIS and used to determine the planform characteristics and changes in width, sinuosity, and shoreline migration rates between 1958 and 2008. The study was based on topographic maps of 1958 and 1967, which had been derived from aerial photos and a field survey and from satellite imagery of 1977, 1990, 2000, and 2008. The channel planform dynamics were determined by comparing sequential changes in the position of the shorelines in these years. Sinuosity adjustments were small during the study (range: 1.34–1.45). The initial sinuosity (1.45 in 1958) gradually decreased to 1.34 in 1990, and then increased to 1.40 in 2008. Channel contraction had been the dominant planform process, but periodic floods resulted in channel expansion (1958–1990). The river’s channel area expanded substantially from 1958 to 1990 (by 42.1 %), then sharply contracted from 1990 to 2000 (by 45.8 %), with no subsequent changes. The bank erosion and accretion rates were severe. The mean erosion rates ranged from 30.7 to 68.3 m/year on the left side and 27.1 to 58.3 m/year on the right side. The mean accretion rates ranged from 44.4 to 68.3 m/year on the left side and 30.5 to 60.4 m/year on the right side. The mean channel midline shifted by 57.8 m toward the right from 1958 to 2008. The mean channel midline moved 4.8 m to right from 1958 to 1967, 54.3 m to the left from 1967 to 1977, 44.2 m to the right from 1977 to 1990, 64.3 m to the right from 1990 to 2000, and 2.8 m to the right from 2000 to 2008.     

Driving forces of aeolian desertification in the source region of the Yellow River: 1975–2005

The source region of the Yellow River, located in the northeastern portion of the Qinghai–Tibet Plateau, plays a critical role in water conservation, biodiversity protection, and wetland conservation. Aeolian desertification of this area is an important concern. Remote sensing and GIS technology were employed to assess the trends in aeolian desertification from 1975 to 2005. The monitoring results showed that, aeolian desert land increased from 15,112 to 17,214 km² during 1975–2005. In addition, it was found that the area of aeolian desertification increased rapidly from 1975 to 1990, was stable from 1990 to 2000, and slightly decreased from 2000 to 2005. Increasing temperature, overgrazing, and drainage of wetlands have been key driving factors of aeolian desertification. Thus, to control the expansion of aeolian desert lands in the source region of the Yellow River and to rehabilitate existing desert areas, the priority should be given to altering human behavior in these areas.     

Tectono-Geochemistry of Superimposed Mineralization in the Bainaimiao Ore Field, Inner Mongolia

Combining geomechanics with geochetnistry, this paper makes a rather systematic study on the stratigraphic division, tectonic evolution and ore genesis of the Bainaimiao ore field and, on such a basis, puts forward some new ideas. It has been emphatically pointed out that, in addition to the prominent E-W structural zone that controls the Cu-Mo deposits, there also exist N-S and NE structures which dominate Pb-Zn and Au mineralizations respectively. The formation of the copper deposit was attributed to the superimposition of three successive stages of mineralization related to volcano-sedimentation and metamorphic and magmatic hydrothermal activities respectively.     

Isotope Method for Confined Groundwater Recharge of the Lower Reaches of the Heihe River, Inner Mongolia, China

Environmental isotopes have been applied to analyze confined groundwater recharge in the lower reaches of the Heihe River,Inner Mongolia.CFC is regarded as a tracer that determines the date of groundwater,the date being less than 45 a.The confined groundwater within the Gurinai area and Ejin Basin other than the surface water of Heihe River might have originated from precipitation from Qilian Mountain or/and the Tibetan Plateau.The deep confined groundwater overflows into an upper aquifer and emerges into the ground,forming springs and lakes within the low-lying area.The recharge volume is estimated to be around 400 million-cubic meters.     

A Plate-Tectonic Model for the Evolution of the Daqingshan Granulite belt in Inner Mongolia

One of the most important events in the early geological evolutionary history of the Earthwas the wide occurrence of granulite belts at the end of the Archaean in the world, whichmeans a possible transformation of evolution mechanism of the crust. More and more geo-     

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.     

Analysis of influence of natural disaster on the economy and prediction of recovery time based on grey forecasting–difference comparison model: a case study in the upper Min River

Natural Hazards - After the 2008 Wenchuan earthquake, secondary geological disasters occurred frequently and caused huge economic losses in the upper reaches of Min River. In this paper,...     

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.     

Effect of particles on the photodegradation of PAHs in natural waters-A case study for the Yellow River

Photodegradation of chrysene, benzo （a） pyrene and benzo （g, h, i） perylene in natural water of the Yellow River was studied using simulation sunlight. The effects of particulates on the photodegradation were explored. Several results arose from this study. （1） The photodegradation of PAHs can be fitted with first-order kinetics when no particulate exists in water system, and the first-order constant increases with decreasing of initial concentration of PAHs. The photodegradation rates of the three PAHs are related to their molecule absorption spectrum. （2） The existence of loess exerts two kinds of effects on the photodegradation of PAHs, including the inner filter effects and the photosensitizing effects of humic substance in loess. These two contrary effects lead to the difference of net effects among different contents of loess. When the loess contents are 0.1 and 5.0 g/L, the existence of loess stimulates the photodegradation of chrysene, benzo （a） pyrene. When the loess content is 5.0 g/L, the existence of loess stimulates the photodegradation of benzo （g, h, i） perylene. In addition, the photodegradation of PAHs can be fitted with the second-order kinetics when there is loess in the water system. （3） The soluble humic substances in loess can accelerate the photodegradation of PAHs while the in soluble part cannot. （4） Since the soluble humic substances in the suspended solids of the river have been dissolved in water,     

Genetic Mechanism of Mineral Inclusions in Zircons from the Khondalite Series, Southeastern Inner Mongolia

The early Precambrian khondalite series is widely distributed in the Jining-Zhuozi-Fengzhen-Liangcheng area, southeastern Inner Mongolia. The khondalite series mainly consists of sillimanite garnet potash feldspar (or two-feldspar) gneiss and garnet biotite plagioclase gneiss. These gneissic rocks have commonly experienced granulite-facies metamorphism. In zircons separated from sillimanite garnet potash feldspar gneisses, many mineral inclusions, including Sil, Grt, Ky, Kfs, Qtz and Ap, have been identified by the Laser Raman spectroscopy. Generally, prograde metamorphic mineral inclusion assemblages such as Ky + Kfs + Qtz + Ap and Ky + Grt + Kfs + Qtz are preserved in the core of zircon, while peak granulite-facies metamorphic minerals including Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap are identified in the mantle and rim of the same zircon. However, in some zircons are only preserved the peak metamorphic minerals such as Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap from core to ri     

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.     

LA-ICPMS Zircon U-Pb Dating in the Jurassic Daohugou Beds and Correlative Strata in Ningcheng of Inner Mongolia

LA-ICPMS Zircon U-Pb dating is applied to volcanic rocks overlying and underlying the Salamander-bearing bed in the Daohugou beds of Ningcheng in Inner Mongola and Reshuichang of Lingyuan and Mazhangzi of Jianping in western Liaoning. The results indicate that the youngest age of the rocks in Daohugou of Ningcheng is 158 Ma, and the oldest one is 164 Ma. Synthesized researches indicate that the salamander-bearing beds in Daohugou of Ningcheng, Reshuichang of Lingyuan and Mazhangzi of Jianping were developed in the same period. The Daohugou beds were formed in the geological age of 164-158 Ma of the middle-late Jurassic. Whilst, the Daohugou beds and its corrdative strata should correspond to the Tiaojishan Formation （or Lanqi Formation） of the middle Jurassic in northern Hebei Province and western Liaoning Province, based on the disconformity between the Daohugou beds and its overlaying beds of the Tuchengzi Formation of Late Jurassic and the Jehol Beds of early Cretaceous, and the disconformity between the Daohugou Beds and its underlying Jiulongshan Formation, which is composed of conglomerate, sandstone, shale with coal and thin coal beds.     

Sequence Stratigraphy and Tectonic Environment of the Chartai Group,Inner Mongolia

The Middle Proterozoic Chartai Group separated by two unconformities consists of three depositional se-quences: the Shujigou Formation-Zenglongchang Formation (DS Ⅰ), the Agulugou Formation (DS Ⅱ), andthe Liuhongwan Formation (DS Ⅲ). The carbonate platform and back-platform basin are the basic environ-ment model of the Chartai Group. The syndepositional faults on the oceanward side of the carbonate platformand large-scale slumping in the soft sediments are important marks of facies tracts. The newly establishedZenglongchan uplifting, an epeirogenetic uplifting, plays an important role in the formation of thepalaeogeographic framework of the Chartai Group. The stratigraphic correlation between the Chartai Groupand the Bayan Obo Group is made for the first time by using sequence stratigraphic principle and model estab-lished by P.R. Vail. The Chartai Group, which was deposited on the northern passive continental margin of theNorth China platfom, represents the platform cover.     

The final collision of the CAOB: Constraint from the zircon U–Pb dating of the Linxi Formation, Inner Mongolia

The Linxi Formation occupies an extensive area in the eastern Inner Mongolia in the Central Asian Orogenic Belt(CAOB).The Linxi Formation is composed of slate,siltstone,sandstone and plant,lamellibranch microfossils in the associated strata.Major and trace element data(including REE) for sandstones from the formation indicate that these rocks have a greywacke protolith and have been deposited during a strong tectonic activity.LA-ICPMS U—Pb dating of detrital zircons yield ages of 1801 to 238 Ma for four samples from the Linxi Formation.425—585 Ma,together with the ~500 Ma age for the metamorphism event previously determined for Northeast China,indicates that their provenance is the metamorphic rocks of Pan-African age that have a tectonic affinity to NE China.A few older zircons with U-Pb ages at 1689-1801 Ma,1307-1414 Ma,593-978 Ma are also present,revealing the Neoproterozoic history of NE China.The youngest population shows a peak at ca.252 Ma,suggesting that the main deposition of the Linxi Formation was at late Permain.Moreover,the ca.250 Ma zircon grains of all four samples yield weighted mean ~(206)Pb/~(238)U ages of 250 ± 3 Ma,248 ± 3 Ma,249 ± 3 Ma,and 250 ± 2 Ma,respectively.These ages,together with the youngest zircon age in the sample ZJB-28(ca.238 Ma),suggest that the deposition of the Linxi Formation extended to the early Triassic.Combining with previous results,we suggest that the final collision of the Central Asian Orogenic Belt(CAOB) in the southern of Linxi Formation,which located in the Solonker-Xra Moron-Changchun suture,and the timing for final collision should be at early Triassic.     

Discovery and Significance of Quaternary Glacial Vestiges in the Hexigten Area of the Southern Da Hinggan Mountains, Inner Mongolia

1 Introduction Hexigten is situated at the eastern part of the Inner Mongolian Plateau, south of the Da Hinggan Mountains and northwest of Chifeng City, Inner Mongolia, China. It is also at the junction of the Da Hinggan Mountians, Inner Mongolian Plateau and Yanshan Mountains. It is about 650 km north of Beijing. The geographic coordinates are 116?30'?118?20'E and 42?20'?44?10'N (Fig. 1). The elevation range is from 1100 m to 1700 m, and the highest peak (2029 m) of the Da Hinggan…     

Molybdenite Re–Os and U–Pb zircon dating and genesis of the Dayana W-Mo deposit in eastern Ujumchin,Inner Mongolia

The Dayana W-Mo deposit in eastern Ujumchin of Inner Mongolia is a quartz-vein type deposit in the mid-western part of the Central Asian Orogenic Belt (CAOB). Biotite monzogranite, quartz porphyry and hornfels host W-Mo in quartz veins. Based on spatial relationships, molybdenite was deposited first followed by wolframite. This contribution presents precise laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) U–Pb zircon dating and geochemical analysis of the biotite monzogranite. The U–Pb dating shows that the monzogranite is 134 ± 1 Ma. Major and trace element geochemistry shows that the monzogranite is characterized by high SiO₂ and K₂O contents, a “Right-inclined” shape of the chondrite normalized REE patterns, enrichment of large ion lithophile elements (LILEs), and depletion of high field strength elements (HFSEs) such as Nb, P, Ba. The monzogranite is high-K calc-alkaline, has a strong negative Eu anomaly (Eu/Eu* = 0.04–0.45), low P₂O₅ content, high A/CNK of > 1.2, enriched in large-ion lithophile elements (LILEs; such as Rb, Th, U, Nd, and Hf), and notably depleted in Ba, Sr, P, Ti, and Nb. These characteristics define the Dayana monzogranite as a highly fractionated peraluminous granite. Re–Os isotopic analysis of seven molybdenite samples from the deposit yield an isochron age of 133 ± 3 Ma (MSWD = 2.2), which indicates that the monzogranite and ore have the same age within error, are probably genetically related, and related to a major Early Cretaceous mineralizing event in China known as the Yanshanian.