Table of Content

10 April 2017, Volume 31 Issue 02

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2017, 31(02):  0. 

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Mineralogy, Petrology and Mineral Deposit

Geochronology, Geochemistry and Geological Significance of Host Rocks in the Jiamante Gold Deposit, West Tianshan, Xinjiang

ZHENG Shaohua, GU Xuexiang, ZHANG Yongmei, WANG Chunshan, MA Haijie, HU Yaohua

2017, 31(02):  209-224. 

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The Jiamante gold deposit is a typical epithermal gold deposit located in the Boluokenu polymetallic belt in the West Tianshan.It occurs in Late Paleozoic Dahalajunshan Formation mainly composed of crystal tuff and granitic porphyry. The LA-ICP-MS zircon U-Pb dating yielded a weighted average age of (365.9±3.0) Ma for crystal tuff and (362.3±4.3) Ma for granitic porphyry.The mineralization age of the Jiamante gold deposit could be constrained between 362 Ma and 331 Ma based on geochronological work in the study and considering the fossils of the Visean period in Lower Carboniferous Aqialehe Formation.Geochemical analysis results indicate that these magmatic rocks show high K calc-alkaline characteristics with enrichment in LREE, Rb, Th, K, and depletion in Sr, Ba, HREE, Nb, Ta, Ti and P. It suggests that crystal tuff and granitic porphyry have the characteristics of arc magmatic rocks. Crystal tuff and granitic porphyry were generated due to the southward subduction of the Junggar Ocean beneath the Yili-Middle Tianshan plate.They were likely derived from partial melting of mafic lower crust, with involvement of mantle-derived magma interacted with subducted sediments.

Geochemical Characteristics of Rhyolite Porphyry and Relationship Between the Rock and Enriched Uranium in Hetaoba, Inner Mongolia

JIANG Xiaojun, YAN Pengbing, XUE Wei, XING Yajie, LIU Xiaogang, YAN Xiaobo

2017, 31(02):  225-233. 

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Rhyolite porphyry in Hetaoba, Inner Mongolia, is closely associated with uranium mineralization of the area. In order to strengthen the theory research and seek the prospecting breakthrough, this article focuses on the relationship between uranium mineralization and rhyolite porphyry, structure by the methods of geochemistry and magma and tectonic evolution. The pluton is located in the southern of Zhenzishan caldera in Duolun volcano basin. The rock has high SiO₂ content (70.15%-78.58%), high K₂O (5.28%-9.30%) and are enriched in alkali contents (Na₂O+K₂O=7.49%-10.82%). It belongs to the alkaline rhyolite as shown in the plot of TAS. Rhyolite porphyry in Hetaoba shows high REE contents and is relatively enriched in LREE, Rb, Th, with evidently negative Eu and Sr anomalies. Especially, U element content is extremely high (6.66×10^-6-966.00×10^-6). The magma came from partial melting of the lower crust materials, and the pluton, belonging to A2 subtype granite, was likely emplaced in the extensional post-collision setting. Eventually, these factors including emplacement of rhyolite porphyry, the ore-forming structure in the late stage, the emplacement and extraction of hydrothermal with rich uranium, have led to the formation of the Hetaoba uranium deposit.

Age,Geochemistry and Petrogenesis of Granites from Badaguan Area in Northern Hailaer, Inner Mongolia

LI Yan, WANG Jian, SUN Deyou, CHEN Debing, HAN Zhibin, CUI Jiarui

2017, 31(02):  234-245. 

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The granite of Badaguan is mainly composed of syenogranite and monzonitic granite. Zircon U-Pb isotopic dating yields age of (212±1.7)-(226.7±1.6) Ma, indicating that they were formed in the Late Triassic. The granites are metaluminous with A/CNK ratios of 1.01-1.10 and differentiation index (DI) of 92.5-95.8. The granites are enriched in K, Rb and LREE, and depleted in Ba, Sr and HFSE, e.g., Nb, Ta, P and Ti, with moderate Eu negative anomalies (δEu=0.51-0.71). The relatively low values of 10,000 Ga/Al (average at 1.91), low zircon saturation temperature (average at 683 ℃) and other geochemical features suggest that the syenogranite and monzonitic granites in the study area are high differentiation I-type granites. The zircons in the granites show high values of ε_Hf(t) (4.50-10.45) with two-stage Hf model ages of 0.59-0.97 Ga, suggesting that they are derived from the newly formed crust which is separated from Neo-Proterozoic depleted mantle. Combined with the U-Pb ages and other geochemical features, we proposed that the granite of Late Triassic formed in an active continental margin setting of the Mongolian-Okhotsk oceanic plate.

Petrologic and Geochemical Characteristics of Carbonatites in Huayangchuan U-Nb-Pb Deposit, Shaanxi Province

HUI Xiaochao, CAI Yuqi, HE Sheng, FENG Zhangsheng

2017, 31(02):  246-257. 

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The Huayangchuan U-Nb-Pb deposit is a unique metallogenic type in the Xiaoqinling mineralization belt. The broken belt of carbonatite vein is important ore-forming space. The minerals in unmineralized carbonatites are mainly calcite, and there are few other minerals. Uranium mineralized carbonatites include a variety of minerals, major minerals of which are calcite; and minor minerals of which are amphibole, biotite,sphene,allanite,batafite,barite,apatite,quartz,magnetite,alkali feldspar. Carbonatites are characterized by high REE contents, whose δ¹³C_V-PDB and δ¹⁸O_V-SMOW values show the typical characteristics of igneous carbonatite. Based on the diagrams showing ⁸⁷Sr/⁸⁶Sr vs. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb and ¹⁴³Nd/¹⁴⁴Nd vs. ⁸⁷Sr/⁸⁶Sr of carbonatite veins, the authors consider that these carbonatite veins are crystal-fractionational products of alkaline silicate-carbonate melt-solution originated from the EMI.

Geochemical Characteristics and Tectonic Implications of Gabbro in Mayigangri Area, Tibet

CUI Yuliang, WANG Genhou, LIANG Xiao

2017, 31(02):  258-266. 

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The intrusive dikes in Mayigangri area of Tibet are gabbros. Based on the micrograph of the gabbrosamples, the contents of major elements, trace elements and REEs are measured. The results show that the rocks are characterized by an enrichment of LREE, and a depletion of HREE. There is no positive or negative Eu anomaly. The gabbro are enriched in Hf, La, Nd and Ti, and are depleted in P, Yb, Y and other elements. The geochemical features indicate that the gabbros are generated in an intracontinental rift environment; and the magma is derived from enriched mantle with a contamination of salic crust materials. Combined with the fact that gabbro surrounding rocks are Late Paleozoic low metamorphic rock series and undeveloped dike swarms in strata after late Early Permian, and based on the age restrictions that the basic dike swarms in south part of northern Qiangtang is formed from Late Carboniferous to Early Permian by the predecessors, it is deduced that the gabbro is the product that paleo-Tethys ocean in this region opened initially.

Mineralization Characteristics and Indication Significance of Biotite-Rutile from the Gabbro Intrusions in the Yinmin Iron-Copper District, Yunnan Province

SUN Zijian, FANG Weixuan, LU Jia, WANG Tongrong, GUO Yuqian, SONG Lihong

2017, 31(02):  267-277. 

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In order to discuss the metallogenetic and diagenetic environment of iron oxide-copper-gold type deposit, the mineral-geochemical characteristics of biotites, rutiles, chlorites and ankerites of gabbro intrusions in the depth of Yinmin iron-copper district, Yunnan Province were analysed. Rutiles were derived from magmatic crystallization and multiple-stages alteration. The crystallization temperature of rutiles ranged from 820 to 1,082 ℃, and the multi-phases alteration temperature of rutiles ranged from 444 to 730 ℃. Rutiles had a symbiotic relationship with biotites. The biotites were divided into three types: Ti-rich magnesial biotites crystallised from magma, magnesial biotite and ferruginous biotite due to hydrothermal alteration. The crystallization temperature of the primary Ti-rich magnesial biotites ranged from 653 to 750 ℃, the alteration temperature of hydrothermal magnesial biotites ranged from 525 to 619 ℃, and that of hydrothermal ferruginous biotites ranged from 551 to 577 ℃. The oxygen fugacity of all the biotites was near Ni-NiO, indicating that biotites formed in the high oxygen fugacity environment, which was conducive to the formation of rutiles. In conclusion, both of biotites and rutiles formed in the environment with high temperature and oxygen fugacity. Ankerite-siderite alteration was developed in the later stage, forming in the strongly reduced and alkaline environment, playing a corrosive role to rutiles. The alteration temperature of chlorites, which were altered from ferromagnesian, such as biotites, hornblende and pyroxene, ranged from 174 to 243 ℃. The oxygen fugacity was from -44.68 to -51.42, and the sulphur fugacity was from -14.42 to -19.76, showing that chlorites formed in an environment with low-medium temperature, low oxygen fugacity and high sulphur fugacity, which was benefit to the formation of metal sulfide. In sum, the stages of magmatic crystallization, biotitization and rutiles mineralization were characterized by geochemical lithofacies with high temperature and strong oxidization, which was benefit to the Ti-Fe mineralization. Strong reducing geochemical lithofacies followed, which was favorite for the formation of metal sulfide. Above all, the superposition and evolution of geochemical lithofacies were benefit to the iron oxide-copper-gold type deposit mineralization.

Quantitative and Positioning Study on the Hydrothermal Alteration and Mineralization Relationship of the Yongxin Gold Deposit in the Nenjiang-Heihe Mélange Zone, Heilongjiang Province

YUAN Maowen, ZENG Yongjie, LI Chenglu, LI Shisheng, LI Shengrong

2017, 31(02):  278-289. 

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The Yongxin gold deposit,which was recently discovered in the Nenjiang-Heihe mélange zone, Heilongjiang Province, is a large fracture controlled alteration type gold deposit in Duobaoshan gold-copper metallogenic belt. The ore minerals are composed mainly of petzite, calaverite, native gold, minor sulfides and minor oxide. According to the linear analyses between the thickness of potassium feldspathization zone, sericitization zone, silicification zone and ore-bodies, the thicknesses of the potassium feldspathization zone and silicification zone are positively correlated with ore body thickness. The thickness relation between sericitization zone and ore body are negative. According to the quantitative assessment and the chart of the horizontal projection of the alteration zones, sericitization, potassium feldspathization and silicification zones occurred respectively in the direction from SE to NW, like a “step”. The thicknesses of the potassium feldspathization zone, sericitization zone and silicification zone have a certain corresponding relationship in each “step”. The source of the ore-forming fluid of the deposit is inferred by the authors at the northwest depth, and good prospecting potential in that direction is suggested.

Stratigraphy

High-Resolution Sequence Stratigraphy Research for Xujiahe Formation of the Upper Triassic Series in Sichuan Basin

TAN Cong, YU Bingsong, RUAN Zhuang, HAO Shilong, LI Kun, LUO Zhong, LIU Runda

2017, 31(02):  290-301. 

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In order to further understand the sequence stratigraphic framework and spatial and temporal distribution of Xujiahe Formation in Sichuan Basin, based on the high-resolution sequence stratigraphy and sedimentology theory, and in combination with the data of a large number of outcrops, drilling cores, well logging and seismic, this paper studied the high-resolution sequence stratigraphy and sedimentary facies of Xujiahe Formation in Sichuan Basin.Research found that despite the complexity of structure, the different direction of the material supply,the change of rock facies belts and different naming system in each partition,there are traceable unconformity and maximum flooding surface which enable the study went on.Through the sequence boundary tracking and analysis of sedimentary cycle,Xujiahe Formation can be divided into 3 super long-term cycles,6 long-term cycles and 21 middle-term cycles.According to the sequence stratigraphy contrast in the whole Sichuan Basin,the thickness of north-south strata is stable, however, east-west strata distribution is complex. The whole LSC6 and most of LSC5 are absent in the west, while most of LSC1 is absent in the east. Because the settlement-deposition center is located at the Longmenshan frontal depression, and the sedimentary rate is very high in the west of the basin, the overall distribution of the sedimentary body present like a wedge, which is thick in the west and thin in the east.On the basis of the study of sequence stratigraphy, chronostratigraphic framework was tentatively created.Through the comprehensive comparison of sequence stratigraphy, chrono-stratigraphy and biostratigraphy,the relative age of each cycle and the value of the unconformity sedimentary interval are concluded.This provides theoretical support for the next step of production and practices in Sichuan Basin.

Energy Geology

Modification Mechanism of Physical Properties of Deeply-buried Sandstone Reservoir due to the Burial Compaction and Lateral Extrusion in Kuqa Depression

GAO Zhiyong, CUI Jinggang, FENG Jiarui, ZHOU Chuanmin, SHI Yuxin

2017, 31(02):  302-314. 

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Early shallow buried for a long time, the late quickly buried deep and strong lateral compression in western foreland basin are common geological evolution process. Burial compaction (mechanical)-lateral extrusion process plays an important role to deep sandstone reservoir petrophysical properties and reservoir properties. Diagenetic physical modelling experiment is studied, and the process of the transformation mechanism is explored. It is considered that continuous vertical compaction makes reservoir clastic particles from loose to close packing. Under the joint action of the late lateral extrusion and continuous vertical burial compaction, astatic microfracture and conjugated shear fracture are evident in the granules of quartz, feldspar, etc. The emergence of micro-cracks can strengthen particles corrosion resistance, and improve the reservoir permeability. Clearing burial compaction (mechanical)-lateral extrusion process of deep sandstone reservoir physical properties and reservoir properties of transformation mechanism possesses a positive role for the distribution of favorable reservoir evaluation and prediction.

Application of the Characterization Technique of Porous Media Reservoir on Reef-shoal Reservoirs of the Upper Ordovician in Tazhong Area

LI Weiling, QIAO Zhanfeng, DENG Xingliang, NI Xinfeng, ZHANG Zhenghong, CHANG Shaoying, LI Chang, SU Dongpo, SHAO Guanming, YANG Zhao

2017, 31(02):  315-327. 

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The characterization technique of porous media reservoir is an analysis technique for characterizing the reservoir spaces of various sizes and their combination types, using core analysis, logging analysis, seismic analysis, experimental analysis of core samples, production performance analysis and other analysis techniques, and finally evaluating favorable reservoirs. Using this technique, 5 kinds of combination types of the Upper Ordovician of Lianglitage Formation in Tazhong Area, including pore reservoir, vug reservoir, pore-vug reservoir, fracture-cave reservoir and pore-vug-fracture-cave reservoir, are identified. And the pore throat structure, physical property and production performance of various reserviors are characterized. The results show that the pore throat structure of pore-vug reservoir is macroporous and large throat, and is better than pore reservoir and vug reservoir. And fracture makes an improving effect on all 5 reservoirs, which increase the physical property and connectivity. The production performance is affected by different reservoir type. The production performance of pore-vug-fracture-cave type and pore-vug type reservoirs is high and stable, and that of fracture-cave type reservoir is medium and relatively stable, and that of vug type reservoir in the inner platform is relatively low. The pore-vug-fracture-cave type and pore-vug type reservoirs in the platform margin are the favorable reservoir, and the fracture-cave type reservoirs in the inner platform is the main type of exploration target at present, and the pore type and the vug type reservoirs in the inner platform have also a certain exploration value if they develop fractures.

Pore Structure Characteristics of Yanchang Formation Shale Gas Reservoir in Yanchang Exploration Area of Ordos Basin

XU Hongwei, LI Xianqing, QI Shuai, ZHOU Baogang, WANG Zhe, GAO Wenjie, CHEN Jinming

2017, 31(02):  328-337. 

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In order to evaluate the space and the gas storage capacity of terrestrial shale gas reservoirs,many shale samples were taken from the Chang 7 and Chang 9 members of the Upper Triassic Yanchang Formation in Yanchang exploration area of Ordos basin, and the pore type and pore structure of these samples and their influence factors were studied by the use of scanning electron microscope (SEM), high pressure mercury injection and low-temperature gas adsorption experiments with CO₂ and N₂. The results reveal the following aspects: (1)There are many types of microscopic pores in these shale samples, mainly including intergranular pores and intragranular pores,and a small amount of crystal particle pores and dissolution pores exists, and organic matter pores are less development. These pores provide the main storage spaces for the shale gasreservoir. (2)Mesopores (2-50 nm) contribute to the main pore volume and specific surface area of Yanchang Formation, accounting for 74.34% of the total pore volume and 64.40% of the total surface area. The shale samples from the Chang 9 Member have a greater total pore volume and total specific surface area than those from the Chang 7 Member. (3)The pore structure is dominated by slit type pores and plate pores, and the pore size distribution mainly falls in 0.4-0.9 nm,3-25 nm and 5-200 μm. The average pore size of Yanchang Formation shale is 8.53 nm,and the Chang 7 Member shale has a greater average pore size than the Chang 7 Member shale.(4)The organic carbon content, organic matter maturity and mineral composition content affect the pore development of the Yanchang Formation shale.The mineral composition content is the main controlling factor of the pore development of Yanchang Formation shale which is predominated by the mesopore. The increase of the organic carbon content and maturity of shales mainly play a positive role in the development of the micropore in Yanchang Formation shale.

Technology of Fine Characterization of Lower-class Fault Based on Seismic Forward Modeling and Well-seismic Combination

SHU Ningkai, SONG Li, WANG Xinwen

2017, 31(02):  338-347. 

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The development practice of complex fault block reservoir shows that, the lower-class fault controls the distribution of remaining oil obviously, therefore, the fine description of the low-class faults is a key to the research of different types of fault block reservoir development technology. Meanwhile, the development of fault block reservoir is facing more and more complicated geological conditions, that is, the faults, erosion, overlap and syndeposition and other geological phenomena often coexist, which have caused complex stratigraphic contact relationship and fracture system. Aiming at solving this problem, a technology of fine characterization of the lower-class fault and its combination has been formed based on seismic forward modeling and well-seismic combination, such as reconstruction of the stratum contrast pattern by well-seismic combination to guide the accurate fault ridge identification, establishment of lower-class fault seismic identification by the combination of multi-well integrated calibration and seismic forward modeling, well-seismic multi-attribute analysis, and well-control multi-horizon tracking for the fine description of fault edge. Then, a new complex fracture system has been rebuilt in Shahejie Formation of region 2 & 6, Gudong Oilfield, based on this method, which has screened out the confusing relationship between oil and water, and achieved high development performance.

Geological Conditions and Recognition Methods of Oil-gas Leakage out Through Mudstone Caprock Along Fault in Different Periods

WANG Chao, FU Guang, DONG Yingjie

2017, 31(02):  348-356. 

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In order to study the oil-gas distribution law with fracture zone in the oil-gas bearing basin, based on the mechanism of oil-gas leakage out through mudstone caprock by active and static faults, the geological conditions and recognition methods of oil-gas leakage out through mudstone caprock along the active and static faults were studied, and the research indicated that: the geological condition of oil-gas leakage out through mudstone caprock by active fault is the active fault connected up and down in mudstone caprock, which becomes the oil-gas transportation pathway through mudstone caprock, and the condition of oil-gas leakage out through mudstone caprock by static fault is in which the oil-gas residual pressure of underlying reservoir is larger than displacement pressure of still fault rock. Through comparison between oil-gas residual pressure in underlying reservoir and still fault rock displacement pressure, and between fault connected thickness in mudstone caprock and minimum necessary fault connected thickness of oil-gas leakage out through mudstone caprock by active fault, recognition method is set about whether oil-gas leaks out through mudstone caprock by active fault or still fault, which is applied into recognition of whether gas from Es₃ and Es₁ source rocks leak out through Ed₂ mudstone caprock by active fault in Nanpu sag, Bohaiwan basin. The results show that :In faulting period, nature gas can leak out through mudstone caprock of Ed₂ by active NP5-2 fault in lines L₂ and L₈, and in the rest place(L₁、L₃、L₄、L₅、L₆、L₇、L₉) can’t. However, in fracture static period, nature gas can’t leak out through mudstone caprock of Ed₂ along the NP5-2 fault. The recognition result coincides with present gas distribution under mudstone caprock of Ed₂ in the Nanpu Structure 5, which indicates that these two methods are feasible to be applied into recognition of whether oil-gas leak out through mudstone caprock by active and static fault.

Analysis of Burial History and Thermal History in Yubei Area, Tarim Basin

NI Bin, TANG Liangjie, GUO Ying, YU Tengxiao, YUE Yong

2017, 31(02):  357-366. 

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According to strata division data and the palaeo heat flow analysis, the authors simulated and analyzed the burial and thermal histories of 5 representative drillings in Yubei area, Tarim Basin. In this way, the thermal evolution and maturation processes of source rock are discussed and the mature stages of hydrocarbon source rock and hydrocarbon generation period are pointed out preliminarily in the study area. The research results show that the study area experienced several cycles of sedimentary burial, uplift and erosion during the deposition of Cambrian to Devonian. After the sedimentation of Devonian, Carboniferous-Permian layers show characteristics of sedimentary burial.In the Mesozoic, a few Triassic layers, having been eroded in the eastern of Yubei area, appeared sedimentary discontinuity in the central and western regions. In the Cenozoic, the strata deposited continuously and the deposition rate presented an increasing trend. In the study area, after the Cambrian hydrocarbon source rock had deposited, the maturity evolution appears relatively successive. Cambrian source rock came into the oil-generating window in the Ordovician, and the time of the hydrocarbon generation is early. In the Silurian-Devonian, influenced by the Early Hercynian, the strata underwent the uplift and erosion, and the evolution of the source rock was slow. With the stable sedimentary and the active volcano widely in Carboniferous-Permian, the source rock entered into the high mature stage. Because of the remote effect of the Himalaya Orogeny, with the area subsiding and very thick sediments deposited in the Cenozoic, the source rock reached the over-mature stage, where the gas gets generated.

Geochemistry

Environmental Geochemical Characteristics of Heavy Metals in Surface Sediments from the Western Bohai Sea

LAN Xianhong, GU Zhaofeng, MI Beibei, QIN Yachao, HUNAG Long, XU Yang

2017, 31(02):  367-373. 

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The contents of As,Cu,Cd,Cr,Hg,Ni,Pb and Zn in surface sediments from 44 sampling sites in the western Bohai Sea were measured to investigate environmental geochemical characteristics of heavy metals related to multiple factors. The average concentrations of heavy metals of As,Cu,Cd,Cr,Hg,Ni,Pb and Zn were 11.7 mg/kg,25.5 mg/kg,0.14 mg/kg,68.9 mg/kg,0.037 mg/kg,30.3 mg/kg,22.3 mg/kg and 75.7 mg/kg, respectively. The contents of heavy metals of Cu,Cr,Ni and Zn showed significantly positive correlation with the organic carbon content and the amount of fine-grained sediments (<63 μm), and their distributions in surface sediments were controlled obviously by the content of organic matter and the grain size of sediments while the distributions of As and Hg was not significantly affected by organic matter content. Enrichment factors (EF) were calculated to weigh whether the observed concentrations were higher than background levels. Three groups of elements were sorted: (1) Cr,Ni,Pb and Zn were at background concentrations; (2) Cu and As were slightly enriched; and (3) Cd and Hg were moderately enriched. Compared with variety of background values and the internationally used consensus-based sediment quality guidelines (CBSQGs) for salt water ecosystem,heavy metals in surface sediments from the western Bohai Sea implied a low probability of toxic effect,despite a sharp contamination trend pertaining to Cd and Pb.

Distribution and Influencing Factors of Cadmium Geochemical Fractions of Soils at Carbonate Covering Area in Hengxian and Xiangzhou of Guangxi

LIU Xu, GU Qiubei, YANG Qiong, YU Tao, ZHANG Qizuan

2017, 31(02):  374-385. 

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The carbonate covering area is about 96,372 km², accounting for about 40.7% of district land area in Guangxi Zhuang Autonomous Region. The heavy metals in soil formed from the carbonate weathering were enriched commonly, such as cadmium (Cd), lead (Pb) and mercury (Hg). Preliminary evaluation results showed that there was no corresponding relation between Cd uptake of crops and Cd content in soil. Crops which exceed food safety standards always grew in the soil with low Cd content.Soil with high Cd content generally contained bauxite, Fe-Mn nodules and other particles.In order to discuss factors affecting geochemical fractions of Cadmium, we determined geochemical fractions of cadmium and other soil properties in two study areas in relation to bauxite and Fe-Mn nodules. Soils in the Hengxian area were with bauxite and Fe-Mn nodules. Soils in the Xiangzhou area were without bauxite and Fe-Mn nodules.The results show that: (1) In Xiangzhou area, the Cd content of soil was mainly bounded to mobile fraction and the bioavailability of Cd was high. In Hengxian area, Cd was mainly bounded to residue fraction, the bioavailability was low.(2) Soil pH and organic matter were important factors controlling the Cd mobility.Soil pH value 6.0 is the abrupt change point of the Cd mobility,contents of ion-exchange Cd reached maximum in soil pH value 6.0 in Xiangzhou soils. The percentage of mobile fraction Cd was increasing with soil pH decreasing in Hengxian soils. (3) Cd in mobile fraction was correlated positively with organic matter in Xiangzhou soils, which indicated that Cd is weakly adsorbed by organic matter in soil. Cd fraction has no obvious correlation with organic matter in Hengxian soil. (4) The Cd content of soil with bauxite was high, which occurred in the residual fraction in Hengxian. So, it was not harmful to animals or plants.

Environmental Geology

Soil Organic Carbon Pool and Temporal Variation Characteristics in Shandong Province

DAI Jierui, PANG Xugui, DONG Jian, WANG Zenghui, YU Chao

2017, 31(02):  386-393. 

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Soil is an important component of terrestrial ecosystems, research on soil carbon storage in the carbon cycle and global change is of great significance. Based on the double grid, large density and high accuracy data obtained from previous multi-purpose regional geochemical survey in 2003, the carbon density and storage of 0-20 cm, 0-100 cm and 0-160 cm soil in Shandong Province were estimated, meanwhile, a systematic research was conducted on the temporal and spatial variation of soil organic carbon (SOC) density and storage, as well as the potential capacity of carbon sequestration. It was found as follows. (1) The SOC density in 0-20 cm, 0-100 cm, and 0-160 cm soil layers of Shandong Province were 2.22 kg/m², 7.64 kg/m², and 10.09 kg/m², respectively, which were all lower than the national average levels. (2) The distribution of SOC density in Shandong Province generally presented that the coastal area is low, the plain area in northwest part and hilly area in east part is medium, and the mountain area in middle-south part is high. (3) Compared with the data obtained from the second soil survey in 1985, SOC density of top soil increased from 1.43 kg/m² to 2.22 kg/m². SOC storage of whole land territory in Shandong, totally 157,000 square kilometers, increased from 226.41 Mt to 350.65 Mt, with a net increase of 124.24 Mt, which indicates that the SOC density is growing at a rate of 0.044 kg/(m²·a), and representing a “carbon sink” effect. According to preliminary estimate, there is another 505.23 Mt carbon sequestration potential.

River Incision Behavior Response to Climate Change During the Last Glacial Period

DING Yingying, ZHANG Xujiao, HE Zexin, HU Daogong, WANG Chaoqun

2017, 31(02):  394-405. 

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The Last Glacial Period, popularly known as the Ice Age, was the most recent glacial period, which is characterized by high frequency and high amplitude climate fluctuations and unusually cold. How the river system responds to the climate change in this period deserves attention? According to classical geomorphology theory, the behavior of the river incision occured during the interglacial period or glacial-interglacial transition, while the fluvial aggradation occurred during the glacial period. However, this paper believed that the river incision occurred during the Last Glacial Period is an indisputable fact based on summarizing the research results of river geomorphology in recent years. To begin with, the traditional models of river terrace formation were summarized. The simple tectonic driving model is not reasonable because the climate change plays a very important role. The single climate change cannot drive the formation of multistage and higher elevation terrace, so crustal uplift is a necessary factor. The climate change is a key factor for the formation of river terraces by driving the river fill-cut behavior transition. Three models of the river system response to climate change during the Last Glacial Period are summarized: (1) massive flooding events caused by high-frequency climate fluctuations drive rapid the river incision; (2)the high-frequency climate fluctuations combining rapid crustal uplift drive the river incision; (3) the coastal plain sea level which drops significantly triggers the river incision. Those models have very important guiding significance of understanding the river system responses to the short-term climate change and the judgment on the origin of river terraces.

Research on Geomorphologic Evolution of East and West Badain Lake and the Impact on Water Body Features

ZHANG Haoyue, HU Xiaonong, WANG Xusheng

2017, 31(02):  406-414. 

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Badain Lake area lies in the southeastern edge of Badain Jaran Desert, and there has a two-lake system with different water properties which are divided by longitudinal dunes, known as East Badain Lake and West Badain Lake. There is relatively little research about the cause of these lakes, especially the systematical research about the impact on hydrochemical and salty features in the process of weathering landform. By analyzing the wind direction and the basin shape of Badain Lake area, the geomorphologic evolution of this area is discussed and the difference of hydrochemical features between the two lakes is identified.The hydrochemical testing result shows that the TDS of water in East Badain Lake is about 1.5 g/L, which is defined as brackish water, while that in West Badain Lake is 100 times as much as that in East Badain Lake, which is defined as salt water.The remote sensing image of Google Earth and DEM indicate that the northwest-direction wind prevails in Badain Jaran Desert and the direction and force of winds in the southeastern edge are more complex and changeable than those of the interior of the desert. In addition, the basin depth of East Badain Lake is deeper than that of West Badain Lake. The geomorphologic evolution of Badain Lake can be divided into three stages: (1) the formation of the crescent lake which is integral; (2) the formation of two-lake system,when the water level of the integral lake decreases and the basin exposes under dry condition, a new barchan dune forms on the basin by northwest-direction wind and divides the lake into two parts(East Lake and West Lake), leading to the east of the basin suffering erosion; (3) the formation of the longitudinal dune,due to the change of local wind direction, the barchan dune extends to northeast by southwest-direction wind and gradually becomes a longitudinal dune. The result of comprehensive analysis comes to the conclusion that the changeable climate is the force of eolian landform’s evolution, and several changes of wind direction cause the difference of two-lake basin pattern, resulting more recharging of phreatic water in the east than that in the west; when the climate turns to be warm and humid, the water level rising of lakes makes the east and the west connect each other, while the water level of the east is 1 m higher than that of the west, so the east exists seasonal salt release and the west exists seasonal salt accumulation. As a result, the two-lake system varies greatly in salt content by the influence of geomorphologic evolution.

High-fluorine Groundwater Formation in Longshoushan Piedmont in Zhangye Basin

WANG Wenxiang, HE Jin, ZHANG Mengnan, AN Yonghui, LI Wenpeng, WU Xi, GONG Lei, WANG Xiaoyan

2017, 31(02):  415-420. 

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Fluorine is one of essential elements of the human body, but excessive F can be harmful to human body. The formation mechanism of high fluorine groundwater has been a hot topic of hydrogeochemical research. The authors analyzed numerous groundwater level and quality data from 1∶50,000 hydrogeological survey in Zhangye Basin. By using hydrogeochemical and oxygen deuterium isotope methods, the authors discussed the formation mechanism of high-fluorine groundwater in Longshoushan piedmont in a high accuracy level. The results show that high-fluorine groundwater mainly origins from Longshoushan mountain fluorine-bearing rock. The high-fluorine surface water in Longshoushan mountain recharge into Quaternary aquifer in Zhangye Basin through seasonal floods and mixes with low-fluorine groundwater from upstream. Different recharge sources divided groundwater into three strips in Longshoushan piedmont.

A Study of Warning and Forecasting of Karst Collapse Geological Disaster in Jinshazhou of Guangzhou

HUANG Jianmin, ZHENG Xiaozhan, HU Rangquan, CHEN Jianxin, LÜ Meina, CHEN Xiaoyue, GUO Yu, DIAO Qun

2017, 31(02):  421-432. 

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Influenced by the pumping of groundwater in Jinshazhou tunnel of Wuhan to Guangzhou High-speed Railway, some large-scale karst collapses and ground subsidences had happened in Jinshazhou of Guangzhou during July 2007 to May 2012, causing serious damages on the economy. For preventing geological disasters, this study used methods such as general geological survey,groundwater monitoring, ground subsidence monitoring, drilling survey, physical detection to build a perfect groundwater and subsidence monitoring system. Based on that, according to the geological environment condition, the situation of karst development and distribution characteristics of geological disasters, the susceptibility of karst collapse of Jinshazhou was zoned.The variable quantity of underground water level and monitoring data of land subsidence which were the most directly sensitive and important parameters were utilized to study on how to select forecast parameters and time scales, to calculate discriminating parameters, to build forecasting method and forecasting model system. Combined with the 3D geological structure model, the comprehensive variable quantity of underground water level and the comprehensive land subsidence on critical day were selected as the discriminating parameter for predicting karst collapse to establish a warning and forecasting model system.This system was success fully employed to forecast two of karst collapses and achieved good results.It is revealed that the system for warning and forecasting karst collapses is useful and efficient and can provide anti-disaster science suggestions for Jinshazhou and technical supports for the local social stability and economic development.