Geoscience

Zircon U-Pb Age and Geochemistry of Gabbro from Jiamate Au-Cu Ore District in Northern Junggar, China and Their Geological Significance

LI Yuanyou, LIU Guoren, YU Xiubin, LI Yan, QI Shijun, LI Qiang, JIN Jianbin

2017, 31(04): 651-661.

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Jiamate Cu-Au deposit is located in the northern margin of Junggar. The orebodies are hosted in the contact zone of gabbro and basalt of the Beitashan Formation, as well as within the quartz diorite and contact zone. Orebodies occur as vein and lenticular shape, and mineralization are related to quartz diorite and gabbro. The main wall rock alterations include epidotization, biotitization, chloritization, carbonatization, and magnetite mineralization. LA-ICP-MS zircon U-Pb dating of gabbro yields the age of 380 Ma, which constrains the age of Cu-Au mineralization later than 380 Ma. The gabbro samples show negative anomalies of Th, Nb, Ta, Ti, Nd and Zr, as well as positive anomalies of Rb, K, Pb and P. Combined with the enrichment of LREE and slightly negative to zero Eu anomalies, we propose the gabbro is related to subduction process and was formed in an island arc setting. The primitive magma originated from a mixture of mantle wedge that was modified by the subduction material and the asthenosphere. The magma was evolved and had experienced weak crustal contaminations.

Geochemistry and Geochronology of West Shadegai Granites in Wulashan of Inner Mongolia and Its Geological Significance

DAI Chaocheng, HUANG Cheng, JIAO Zheng, WANG Xinliang

2017, 31(04): 662-671.

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The West Shadegai granites in Wulashan of Inner Mongolia is located in Hadamengou molybdenum orefield,tectonically located in the west part of the northern margin of North China Craton,whose lithology is syenogranite. Geochemical characteristics show that the granite is characterized by high silicon (the mass fraction of SiO₂ is 74.08%-75.95%),rich potassium (K₂O/Na₂O=1.20-3.39),rich alkali (K₂O+Na₂O= 7.03%-8.46%),weakly peraluminous (mass fraction of Al₂O₃ is 11.22%-13.06%,A/CNK= 1.002-1.284).The Litman index belongs to the calc alkaline.The REEs are of enrichment of light rare earth elements,loss of heavy rare earth elements (LREE/HREE=19.84-27.83),and obvious loss of Eu (δEu=0.36-0.53).The enriched trace elements include Rb,Th,U,Pb,Zr,Hf,Sm; the loss elements include Ba,Ta,P,Ti;high field strength elements including Nb and Sr are slightly low,showing the characteristics of continental crust reformation type granite.The LA-ICP-MS ²⁰⁶Pb/²³⁸U weighted average age of 22 zircon samples from Shadegai pluton is (231±0.8) Ma,belonging to Middle Triassic. According to the contrast of the mineralization age and the diagenetic age,the diagenesis and mineralization both occurred in Late Triassic,and the mineralization age is slightly less than the diagenetic age,showing the pluton belongs to the product of extensional tectonic magmatic activity after Indosinian. According to the available age data,we concluded that significant tectono-magmatic molybdenite mineralization events had ever occurred in Indosinian.

Chemical Composition of Biotites Responding to Basicity of Woergei Granite Intrusion in Gansu Province and Implications for Petrogenesis and Mineralization

DU Baisong, SHEN Junfeng, QIN Yuliang, LIU Haiming, LIU Shengqiang, XU Liwei, NIU Gang, OUYANG Erbiao

2017, 31(04): 672-682.

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The formation of ore deposits and the geological genesis of metallogenic rock mass are closely related to the chemical characteristics of rocks. In this paper, we centred on the investigation of relationship between the alkalinity and mineralization. The sampling and measurement of the chemical compositions of biotite, from Woergei granite intrusion in Gansu Province are carried on, and the biotite data from fifty-two kinds of different deposits in China are collected. By analyzing the basicity of host rocks, we regard that the existed metallogenic granite intrusion bearing Cu and Au were located in the high basicity area. The granite intrusion was almost related to the formation of Sn ore deposits belong to the low alkalinity rock. From the early to late period of magmatic melt transformation process, the oxygen fugacity changed from high to low and medium alkalinity increased. The formation of Cu and Au deposits was also followed by the process of diagenetic mineralization. However, the low oxygen fugacity and the high basicity are advantageous to the activation and migration of element Sn in early magmatic crystallization process. The high oxygen fugacity and the lower alkalinity are advantageous to the precipitation of cassiterite in magmatic hydrothermal-fluid stage. The precipitation of cassiterite constantly consumed oxygen, leading to a significant decrease of the higher oxygen fugacity than before. The interaction of the oxygen fugacity and the basicity caused mineralization.

Petrogenesis and Tectonic Implication of Volcanic Rocks from Manitu Formation in the Western Great Xing’an Range

LI Yinglei, XU Guo, LIU Huichuan, BAI Lingqi, SU Yinchun, LIU Xiaonü

2017, 31(04): 683-696.

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Different tectonic settings have been proposed for the Mesozoic volcanic rocks in northeast China, including the mantle plume, subduction of the Pacific Ocean and post-collisional extension associated with the closure of the Mongol-Okhotsk ocean. In this paper, we carried out geochemical studies on the andesite-dacite-rhyolite in Manitu Formation of the western Great Xing’an Range (NE China). Samples show variable major and trace element compositions with SiO₂=56.71%-71.85%, Na₂O+K₂O=5.92%-10.18%, Na₂O/K₂O=0.78-1.33,Mg^#=30.6-56.4. Chondrite and primitive mantle normalized REE patterns and spidergrams show significant Nb, Ta, Ti, Sr and Eu negative anomalies (Nb^*=0.17-0.71, Sr^*=0.24-1.15, Eu^*=0.49-0.77) and high total REEs contents. These results suggest that the source magmas of the Manitu volcanic rocks were derived from a preexistent juvenile crust and a subordinate recycled crustal component. A fractional assemblage of hornblende+plagioclase+K-feldspar+apatite+titanomagnetite was responsible for the systematic elements variations from the andesite to rhyolite. This interpretation is consistent with the tectonic model that the Manitu volcanic rocks were generated in an arc/back-arc tectonic setting in response to the Pacific Ocean subduction.

Formation Time of the Northeastern Jiangxi Ophiolite in the Eastern Jiangnan Orogenic Belt:Evidence from LA-ICP-MS Zircon U-Pb Dating of the Gabbro

JIANG Xingfu, PENG Songbai, KUSKY Timothy, WANG Lu, DENG Hao, WANG Junpeng

2017, 31(04): 697-704.

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Proterozoic Ophiolite of the eastern Jiangnan orogenic belt in Northeastern Jiangxi was mainly composed of serpentinized ultramafic rock, cumulated rock, isotropic gabbro and diabase, low-temperature and high-pressure blueschist and plagiogranite. LA-ICP-MS zircon U-Pb dating for one gabbro sample from the Northeastern Jiangxi Ophiolite yielded a ²⁰⁷Pb/²⁰⁶Pb age of (992±25) Ma (MSWD=1.19), which represented the intrusion time of the gabbro. The geochronological result suggests the existence of Early Proterozoic palaeo-oceanic basin in the southeastern Yangtze block, which is younger than the late Meso-Proterozoic oceanic basin in the northern margin of the Yangtze block. Therefore, it is proposed that the Meso-Neoproterozoic crystallization basement rocks in the Yangtze craton were formed in a gradually aggregated process with characteristics of trending from northwest to southeast direction.

Geochemical Characteristics and Zircon Rare Earth Elements of Houhe Intrusive Complex in Xiaoshan Mountain, Western Henan Province

LIANG Tao, LU Ren

2017, 31(04): 705-715.

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The endogenetic mineralization in north Xiaoshan Mountain is weak, and only several Au deposits were found. The petrogenesis of small Yanshanian igneous complexes in north Xiaoshan Mountain is useful to limit the deep geodynamic process, and it is an important evidence to change exploration ideal. In this paper, major and trace elements analytical results of whole rock samples and zircon REEs from Houhe complex were reported. Houhe complex is characterized by higher SiO₂ content and alkali enrichment in K₂O, lower MgO and CaO content. Compositional spots of Houhe complex fell into shoshonitic series in SiO₂-K₂O diagram. A/CNK ratios of Houhe complex are from 1.04 to 1.26. In chondrite-normalized REE pattern diagram, Houhe complex samples have shown the characteristics of LREE enrichment and HREE depletion without obvious Eu anomaly. The (La/Yb)_N ratios of Houhe complex are from 30.95 to 49.38. In spider diagram, the enrichment of Rb, Th, and depletion of Nb, Ta, P and Ti are displayed. Samples of Houhe complex are higher in Sr, and lower in Y and Yb, which indicates that it is adakite. Houhe complex is originated from partial melting of the thickened lower crust, and its residual phases of partial melting source include garnet and rutile. There is no obviously compositional effect of plagioclase fractional crystallization in the process of Houhe granitic magma evolution. Rare earth element content of zircon in Houhe complex has shown the characteristics of LREE depletion, HREE enrichment with Ce positive anomaly and no obvious Eu anomaly. The formation temperature of zircon is from 624 to 701 ℃. In zircon/melts system of Houhe complex, the change of partition coefficients for HREE is a result of magma (fluids) mixing. Houhe complex is product of regional lithosphere delamination in Early Cretaceous; deep fluids and adakitic magma can ascend rapidly in this process. The occurrence of Shenjiayao Au deposits around Houhe complex and the enrichment of Au, Ag, Cu, Mo and W in Houhe complex indicate that it has mineralization potential, and it should be regarded as one of exploration targets in north Xiaoshan Mountain.

The Sedimentary Geochemical Records about the Tectonic Evolution of the East Kunlun Orogenic Belt from Early Paleozoic to Early Mesozoic

WU Ruochen, GU Xuexiang, ZHANG Yongmei, HE Ge, KANG Jizu, YU Fucheng, FENG Liqiang, XU Jingchi

2017, 31(04): 716-733.

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There are six Phanerozoic clastic rock strata distributed in the East Kunlun orogenic belt, including the Lower Cambrian Shasongwula Formation, the Middle-Upper Ordovician Nachitai Group and the Upper Carboniferous-Lower Permian Haoteluowa, the Lower Triassic Hongshuichuan, the Middle Triassic Xilikete and the Upper Triassic Babaoshan formations. Chemical index of alteration (CIA) values of the sandstones indicate the source rocks of the sandstones from the Shasongwula Formation underwent significant chemical weathering, while the other formations were opposite. Major and trace element characteristics suggest that the sandstones in the study area were primarily sourced by felsic rocks with minor intermediate igneous rocks. Moreover, through systematic comparison of the La, Ce, Th, U, ∑REE contents and the La/Sc, Th/Sc, Sc/Cr, La/Y ratios, it is suggested that the sandstones from the Shasongwula Formation and the Nachitai Group were deposited in an active continental margin setting produced by the subduction of the Proto-Tethyan oceanic crust, whereas the sandstones from the Haoteluowa Formation were deposited in a passive continental margin setting related to the rifting between the East Kunlun and Bayanhar terranes. The detritus of sandstones from the Hongshuichuan Formation were mainly derived from continental margin arc volcanic rocks that were produced by the subduction of the Paleo-Tethyan oceanic crust. Due to the both active and passive continental margin-related geochemical affinity, the sandstones from the Xilikete Formation are considered to be deposited during the initiation of the continental collision. The sandstones from the Babaoshan Formation were deposited in an active continental margin setting caused by the complete continental collision and post-collision.

Geochemical Characteristics Comparison and Tectonic Background Analysis of Siliceous Rocks from Qixia Formation and Gufeng Formation of Permian in Chaohu Area, Anhui Province

JIANATIGULI Wusiman, ZHOU Yaoqi, YAO Xu, XU Hanhua, FANG Xue

2017, 31(04): 734-745.

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Aiming to discuss the origin and sedimentary background of Permian chert in Yangtze region, we took the siliceous rocks as samples from Qixia Formation and Gufeng Formation in Chaohu area, which located in the northern margin of the Yangtze block. In this study, we collected previous research data of these two formations and systematically analyzed major, trace and rare elements data of siliceous rocks collected from the two formations.Test results of samples which we got in this study show that rare earth elements (REEs) pattern curves lean slightly to the left, with slight Ce negative anomaly and HREE relative enrichment, reflects the characteristics of the hydrothermal chert.The points pitched on the Al-Fe-Mn diagram of Qixia Formation and Gufeng Formation siliceous rocks indicate that most of the samples are high in Al. In this paper,we proposed that magma suffered the contamination of the Si-Al rich continental crust during the eruption,with high Al ratio. Combined with diagrams of sedimentary environments we came to a conclusion that cherts in Qixia Formation and Gufeng Formation were deposited at continental margin, continental margin-ocean basin, respectively. From Qixia Period to Gufeng Period, transgression scale became large, the depth of seawater became large, the area of ocean basin expanded, which made sedimentary environment different.The siliceous rocks sedimentation in both Qixia Formation and Gufeng Formation was closely related to continental margin chasmic activities.

Geochemical Characteristics and Geological Significance of Retrograde Eclogite in Mengku Area, Shuangjiang County, Western Yunnan Province, China

SUN Zaibo, LI Jing, ZHOU Kun, ZENG Wentao, DUAN Xiangdong, ZHAO Jiangtai, XU Guixiang, FAN Yuehua

2017, 31(04): 746-756.

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The newly found retrograde eclogite in Mengku in Yunnan Province occurs as lenses within muscovite schist. The results of geochemical analysis show that the contents of SiO₂, total alkali (Na₂O+K₂O), Al₂O₃ and TiO₂ range from 47.22% to 50.40%, 2.28% to 4.15%, 13.70% to 15.58% and from 1.39% to 3.95%, respectively, and the TiO₂ can be divided into medium (1.39% to 1.83%) and high (3.30% to 3.95%) groups. Most samples with protolith as tholeiitic basalt are characterized by high contents of TiO₂, inconspicuous Eu anomaly and slight LREE enrichment. The characteristics of REE patterns and trace elements spider diagrams of this type of samples are similar to those of E-MORB but different from N-MORB, and these samples are plotted into the fields of MORB and E-MORB in tectonic discrimination diagrams, suggesting that the protolith was formed under the environment of oceanic basin. Some samples with protolith as alkaline basalt are characterized by medium contents of TiO₂ and higher contents of ΣREE and ΣLREE than those samples metamorphosed from tholeiitic basalt. This type of samples is plotted into the field of OIB, indicating that the protolith was formed under the setting of OIB. The geochemical characteristics of retrograde eclogite are similar to those of their hosting Ordovician Wanhe ophiolite in Mengku area, implying that the retrograde eclogite is the product of the Ordovician oceanic subduction. Additionally, the samples from the study area have both characteristics of E-MORB and OIB, which are similar to those of the central Qiangtang eclogite, implying that a interaction between mantle plume magma and normal mid-oceanic ridge magma existed widely during the evolution of Tethys ocean.

Study on Geochemical Characteristics and Genesis of Calcite Deposit from Ziyun County, Guizhou Province, China

CAO Zhengduan, YANG Ruidong, GAO Junbo, CHEN Jun, ZHANG Wei, SHEN Minglian, ZHANG Xu, LI Ji

2017, 31(04): 757-767.

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The Ziyun calcite deposit is a newly discovered non-metallic deposit in southwest of Guizhou Pro-vince. Orebodies are veined, lenticulared or stratoid in form and are hosted in the carbonate rocks and are found to have been developed in the faults. Calcite is the dominant mineral.The ores revealed a variety of hydrothermal structural characteristics. Ore samples were collected from Huoshanguan, Daze, etc. at Ziyun County and were tested for the isotope geochemistry, trace and rare earth element contents. The carbon and oxygen isotope geochemistry indicate that metallogenetic material came from marine carbonate rocks. Ore-forming fluids are dominated by $\mathrm{HCO}_{3}{ }^{-}$, and thus a great amount of precipitation is added in the following mineralization, which has not a close relationship with magma. In contrast to the surrounding rocks, the Daze ore block has obvious characteristics by analysis of different REE distribution patterns, Eu positive anomalies and high content of Sr, Zn and Ni. This indicates that the ore-forming fluid was probably from deep source evolved in the process of mineralization of the Daze ore block. Both the orebodies and the surrounding rocks have similar REE distribution pattern and regularity variation of ∑REE in the Huoshanguan, Dalao and other ore blocks, which shows that the metallogenetic material may come from carbonate rocks. Compared with the regional mineralization, metallogenetic epoch of the calcite deposit could be Indo-Yanshanian.

Characteristics and Formation Mechanism for the Saline Lacustrine Oil from the North Dongpu Sag

ZHANG Hongan, LI Sumei, XU Tianwu, PANG Xiongqi, ZHANG Yunxian, WAN Zhonghua, JI Hong

2017, 31(04): 768-778.

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Conventional geochemical methods including GC/MS, Rock-eval combined with ESI FT-ICR MS and compound specific carbon isotopic analysis are used to reveal hydrocarbons generation and migration style for the saline lacustrine oils from the Wenmingzhai and Weicheng Oilfield in the North Dongpu Sag, Bohai Bay Basin, which is still unclear enough up to date. It was observed that the crude oils bearing typical characteristics of saline lacustrine oils such as predominance of phytane to pristine and C₃₅-hopane to C₃₄-hopane, enrichment of gammacerane, and low extent of isomerization of steranes. The oils are also featured by two-stage carbon isotope distribution of n-alkanes:the δ¹³C for the n-alkanes with carbon number less than 21 is ranged in -29‰ to -28‰, while those larger than 21 is ranged in -31‰ to -29‰, which is different from “parallel lines pattern” for the saline lacustrine oils from the Western Qaidam Basin, suggesting different paleoenvironment and precursors for the n-alkanes in the North Dongpu Sag. Abundant NSO’s compounds including S₁,S₂,O₁S₁,N₁,O₁,O₂ and O₃ with low extent of aromatization are detected from the oils analyzed, which were predicted having a close genetic relationship with the immature oils in the area. A detailed oil-oil and oil-source rock correlations showed that the crude oils analyzed are primarily derived from Es₃ and Es₄ source rocks with burial depth larger than 3 000 m. It was suggested that the crude oils are mixed by different source rocks with varied thermal maturity, which would be instructive for the further petroleum exploration in the area.

Origin of Salt Minerals and Oil-gas Geological Significance of $\mathbf{E}_{3}{ }^{2}$ Reservoirs in Saline Lacustrine Basin of the Yingxi Area, Qaidam Basin

HUANG Chenggang, LI Zhiyong, NI Xianglong, MA Xinming, ZHANG Shiming, GAO Yanfang, YANG Sen, CUI Jun, WU Kunyu

2017, 31(04): 779-790.

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In recent years, an important discovery in exploration has been made in $\mathbf{E}_{3}{ }^{2}$ of Oligocene in Yingxi area of Western Qaidam Basin. Based on core observation, systemic microscopic characteristics analysis, mineralogy analysis and geochemical analysis, the salt minerals characteristics, origin and role in the process of hydrocarbon accumulation in Oligocene in saline lacustrine basin are systematically studied in the Yingxi area of Qaidam Basin。 (1)In this area, there are 4 important salt minerals, halite, gypsum, glauberite and celestite, which are gathered to form saline layers with certain thickness, or developed in matrix carbonate rock in the form of mineral particles. In upper reservoir group in middle of saline layers, the saline layers are thicker, and mainly rock salt, where thin oil layers are developed. In lower reservoir groups, the saline layers are thinner, and mainly gypsum. (2)Salt minerals has geochemical characteristics of ‘low content of Mn’, the matrix carbonate rock associated with salt minerals has ‘low temperature’ C-O isotope geochemical characteristics, petrological characteristics without the hydrothermal minerals and distribution characteristics of a very wide range. All of the above characteristics show the salt minerals in this area are typical deposition type in saline lacustrine basin, not hydrothermal brine precipitation type. (3)‘salt’ plays an important role in the process of hydrocarbon accumulation. Salt minerals play roles of filling crack and roles in sealing of preventing dissipation of oil and gas. Salt layers play a role in sealing and covering due to high capillary breakthrough pressure and plastic characteristics. Salt minerals promote the secondary pore development in dolomite and negative effect is occupying certain reservoir space. So the results of this research can provide an important guidance for oil and gas exploration in subsalt layer of saline lacustrine carbonate rocks.

Diagenesis and Porosity Evolution of Carboniferous KT-Ⅱ Carbonates in Zanazor, Kazakhstan

YI Shuo, HUANG Wenhui, JIN Zhenkui, GAO Baishui, ZHU Xiaoer

2017, 31(04): 791-801.

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The carbonates of KT-Ⅱ layer in Carboniferous are the main layer of exploration and development of Zanazor Oilfield. The research of diagenesis is of great significance to influence the pore evolution of reservoir. Based on the observation of thin sections, and geochemical analysis on carbon oxygen isotope, cathodoluminescence, and fluid inclusion, we expound the main diagenesis types, the diagenetic sequence and its influence on pore evolution of KT-Ⅱ layer in the study area, and draw the following conclusions: (1) The diageneses which have obvious effects on reservoir quality include compaction, pressolution, cementation, dissolution and cataclasis, etc.; (2) There are two kinds of diagenetic evolution pattern and pore evolution model: the sparry grain limestone in shoal and mud limestone in tidal flat. Furthermore, the former can be subdivided into sparry foraminifera-fusulinida limestone and sparry arene-oolitic limestone; (3) The diagenesis is one of the main controlling factors of reservoir quality. The difference of rock types (controlled by sedimentary micro environment) determines the differentia in early diagenetic response, which affects the late diagenetic reconstruction, and controls the formation of differential reservoir. Therefore, in terms of the control on the differential distribution of reservoir performance, the diagenetic alteration which is on the basis of sedimentary and depositional conditions are of equal importance.

Characteristics of Controlling Hydrocarbon and Prediction of Favorable Exploration Zones of the Palaeouplift in ZhuⅠ Depression, Pearl River Mouth Basin

LI Hongbo, PANG Xiongqi, PENG Huijie, WANG Zhuochao, WANG Tianbao, JIANG Dapeng, WANG Wenyong

2017, 31(04): 802-813.

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The palaeouplift in Zhu Ⅰdepression is the most important factor for controlling hydrocarbon. This paper analyzes the conditions and distribution characteristics of palaeouplifts from the qualitative and quantitative views. According to the analysis of regional tectonic and formation evolution, the paper clarified regional distribution characteristics of three level paleouplift tectonics. A three-stages of tectonic evolution was identified for the palaeouplift, including Eocene, Early-Mid Miocene and the Late Miocene. In general, the evolution of palaeouplifts have characteristics of inherited long-term development. Moreover, the paper summarized the palaeo-uplifts geological characteristics of controlling hydrocarbon from three aspects. Firstly, the range of palaeouplifts controlled the distribution of oil and gas reservoirs. Secondly, the tectonic evolution of palaeouplift controlled the types of traps and oil gas reservoir. Thirdly, the position of palaeouplift controlled the direction of oil and gas migration. A geological model and a mathematical model for Zhu Ⅰdepression were established, which based on the application of Multi-factor Matching Model. From this research, the palaeouplifts which controlled the critical reservoiring condition and reservoir controlling rule were clear. Not only the top and upper of palaeo-uplifts controlled 93% of the reserves distribution, but also the oil fields’ number and reserves were decreases with the increase of distance to the top of palaeouplifts. Base on the pattern of palaeouplifts reservoir controlling, the research predicted favorable exploration zones of palaeouplifts in five target layers, which include Dongsha uplift, northern uplift zone, the southwest of Huizhou sag, and the periphery of Lufeng sag, PY4 sag and Enping sag.

Technology of Polymer-Surfactant Flooding on High-Temperature, High-Salinity and High-Viscosity Reservoir

ZHUANG Yongtao, LIU Pengcheng, HAO Mingqiang

2017, 31(04): 814-821.

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According to the technical bottleneck problems of high-temperature, high-salt,middle-low permeability and heavy oil,which has become the constraints to enhance oil recovery, the lab and field experiment researches of polymer-surfactant flooding technology were carried out based on the oil formation of V in G109-1 reservoir after the polymer and surfactant systems were optimized. Through to the laboratory optimization,the association polymer AP-P7 and the surfactant BHS-01 system had better temperature-resistance and salt-resistance than the regular system, and this result extended the temperature and salinity scope of application; The association polymer could build the resistance coefficient and residual resistance factor effectively after the core shearing. According to the core displacement experiments,this system could enhance the heavy oil recovery factor,which extended the oil viscosity scope of application. After the well injection test in the field, the starting and the injecting pressure increased and the longitudinal profile-log monitoring was improved,which could demonstrate that this system could reduce the mobility ratio of oil to water obviously.

Hydrochemistry and Formation of the Yangchimi Hot Spring in the Lanping Basin of Yunnan

WANG Jieqing, ZHOU Xun, LI Xiaolu, WANG Mengmeng, SHEN Ye, FANG Bin

2017, 31(04): 822-831.

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The Yangchimi hot spring is located in the Yunlong County of Yunnan Province, China, and flows out from the karstic fractures in limestone. Quaternary sands and pebbles occur along the river valley around the spring, and Permian and Triassic carbonates outcrop and underlie the unconsolidated sediments. There are three spring orifices with water temperature of 35.6-35.9 ℃, and the total flow rate is 0.25 m³/s.The chemical characteristic of the hot spring water is as follows: pH=6.3-6.5, TDS=0.982-1.116 g/L, F^-=0.86-1.92 mg/L and H₂SiO₃=24-24.2 mg/L. The hot water belongs to HCO₃·SO₄-Ca type. The ²H and ¹⁸O isotopes of the hot spring water indicate that the hot water is of meteoric origin. The recharge altitude is estimated as 2 500 m or so, the temperature of the geothermal reservoir as 60-70 ℃, and the depth of the groundwater circulation as approximately 1 255 m. The Yangchimi hot spring lies in the carbonate in the uplift area surrounded by the redbed in the Lanping Basin in Yunnan. Groundwater receives recharge from infiltration of precipitation in the recharge area, undergoes deep circulation in the carbonate aquifer, obtains heat from heat flow and flows up to the surface in the river valley. It is an erosion karst hot spring with low temperature.

An Analysis of Geothermal Geological Conditions of the Southern Dongba Sag in the Tianzhu Geothermal Field of Beijing

LIU Zongming, ZHANG Jinping, WANG Xinjuan, LIU Kai, LIU Yingchao

2017, 31(04): 832-842.

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This paper takes the Dongba Sag in the Tianzhu geothermal field in Beijing as an example, in which the thermal groundwater is of the highest temperature and the highest total dissolved solids. Data of the geothermal wells and related geological survey in the recent years were used to better examine the mechanism of the rela-tive high temperature and total dissolved solids by analyzing the geological conditions of the geothermal filed, such as faults, geothermal reservoirs, cap rocks, hydrochemistry and occurrence of the thermal groundwater. The results show that the northern section of the Taiyanggong fault, Liangxiang-Qianmen fault and Louzizhuang fault are big faults, and they deeply cut the Jixian geothermal reservoir. The Jixian geothermal reservoir in the Dongba Sag is approximately 1,000 m lower than two sides of the sag. Thus, the Dongba sag is a relatively closed area like a “black box”. This kind of geological structure leads to a very weak lateral recharge, and the south of Dongba Sag is in a closed reduction environment. The results also show that the deep heat source can flow up into the northern section of Taiyanggong fault along the fault. The high temperature geothermal fluid in the deep part of the sag is ruptured in the geothermal reservoir in the southern Dongba Sag. As a result, the geothermal fluid is of high temperature, high dissolved solids and week yield to wells. This work is of positive significance for the development of geothermal resources in our country.

Application of GF-1 Satellite in Remote Sensing Monitoring on Mine Exploitation in Beijing and Tianjin

YU Bowen, TIAN Shufang, ZHAO Yongchao, LU Fei, FANG Yanqi

2017, 31(04): 843-850.

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GF-1 satellite was launched successfully in 2013. It will be widely used in remote sensing monitoring on mine exploitation owning to its 2 m panchromatic image and 8 m multispectral image. Data processing flow and method of GF-1data in remote sensing monitoring on mine exploitation were studied and summarized. According to the characteristics of GF-1 data, interpretation symbols of mine images were established and some patches were verified during the wild work. Finally survey and monitoring on mines of Beijing and Tianjin were implemented. It draws the conclusion that GF-1 data are with high resolution and good quality due to its clear object texture, convenient data processing and high precision of interpretation. Management of mineral resources planning, renovation of the order in mineral resources development and treatment of mine geological environment will obtain good technical support after using GF-1 satellite data to monitor mines.

Extraction of Linear Structure and Alteration Information Based on Remote Sensing Images and Ore-prospecting Prognosis for Sangmugang in Tibet

ZHAO Xiaoxing

2017, 31(04): 851-859.

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Based on remote sensing images and ore-prospecting prognosis, this article describes a way to extract linear structures and the alteration information through a case study from Sangmugang in Tibet.Using principal component analysis in ENVI4.8 software,convolution filter and morphological analysis and false color composite method, this article enhanced the linear structure and carried out a visual interpretation.The principal component analysis was used to effectively enhance the spectrum and space information in this area and to extract the iron-stained and hydroxyl-alteration information,according to the unique characteristics of alteration minerals.After compared the linear structure with iron-stained and hydroxy alteration information, it is found that the densely linear-structure areas are roughly coincident with the alteration anomaly information in a distribution trend of NW direction and are also consistent with the regional and metallogenic structural patterns; as a matter of fact,eight percent of known deposits are located in alteration anomaly areas.By the comprehensive analysis of linear structures,alteration information,regional geology,geochemical and geophysical information,stratigraphy,igneous rocks, etc.,ten exploration targets with three levels of probabilities are figured out, and the No.1 prospecting area is considered to be one of the most promising area.This study confirms that the linear structure in remote sensing images and the alteration information can be used as markers for ore-prospecting prognosis.

Fault Activity and Characteristics of Earthquake Distribution in the Engineering Area of Bohai Strait Cross-sea Channel

LIU Zhongya, PENG Xuanming, ZHAO Tiehu, SUN Jun

2017, 31(04): 860-868.

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Newly collected data of high-resolution seismic sections have been used in the analysis of distribution characteristics and the vertical activity rate of active faults in the engineering area of Bohai Strait Cross-sea Channel. This analysis shows that the average vertical activity rate of NE-NNE trending faults is 0.103 mm/a, and that of NW trending faults is 0.080 mm/a since the Late Pleistocene. The analysis results also show that the vertical activity rate is gradually increasing from south to north in both NE-NNE trending faults and NW trending faults, and the NW trending faults show a significantly trending of gradually increasing from west to east. By comparing with the modern small earthquakes and the historical seismic data, it is found that the earthquake distribution in the study area is inhomogeneous, and the seismicity is weakened with the increase of the distance from the fault, and the activity is strong at the intersection point and the end point of the fault. The elastic rebound theory can be used to explain the distribution characteristics of earthquakes. Additionally, the relationship between the seismic activity and the horizontal displacement velocity of the fault is likely to be closer, and the relationship between the seismic activity and the vertical velocity of the fault needs further studies.

Slip Tendency Analysis of the Mid-segment of Tan-Lu Fault Belt Based on Stress Measurements

LIU Zhuoyan, WANG Chenghu, XU Xin, SHEN Naiqi, JIA Jin

2017, 31(04): 869-876.

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The slip tendency of Tan-Lu fault belt is of great importance for regional crustal stability evaluation. The ranges of the ratios of the maximum and minimum horizontal stresses to vertical stresses are obtained by analyzing in-situ stress data from 12 boreholes in the vicinity of the mid-segment of Tan-Lu fault belt(from Xinyi to Bohai). The results show that the stress state of the mid-segment of Tan-Lu fault belt is predominantly reverse faulting and partly strike-slip faulting. The stress ratio K increases gradually from west to east and reaches the maximum value in the northeast of the study area. The calculated ratio of shear stress to effective normal stress on fault planes is smaller than the frictional coefficient defined by the Byerlee’s law, which indicates that the mid-segment of Tan-Lu fault belt is in a relatively stable state nowadays. Meanwhile, the ratios of shear stress to effective normal stress of the northwestern striking fault are bigger than those of the northeastern striking fault. The results of stress accumulation index μ_m in this area and the distribution characteristics of earthquakes reveal that earthquakes are more likely to occur along the northwest-striking faults of the mid-segment of Tan-Lu fault belt, and the degree of stress accumulation near the northwest-striking faults is low. On the contrary, the degree of stress accumulation along the northeast-striking faults is high, especially along the northeast-striking faults in the northeastern part of the mid-segment of Tan-Lu fault belt, and the seismic gap occurs in this stress-accumulating area which is speculated as a deadlocking zone. As a result, it is concluded that the mid-segment of Tan-Lu fault belt is more likely to slip along the north-west direction.

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