• 10 papers in Geology in China won "Frontrunner 5000——Top Articles in Outstanding S&T Journals of China "
  • "Geology in China" indexed in World Journal Clout Index (WJCI) Report of Scientific and Technological Periodicals (2021)
  • "Geology in China" selected as the Source Journal of "Outstanding S&T Journals of China (2020) "

Editor in Chief:HAO Ziguo

Established in:1953

ISSN: 1000-3657

CN: 11-1167/P

Domestic postal code:2-112

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    Volume 49,2022 Issue 6
      In Focus
    • XING Yifei, WANG Huiqun, LI Jie, TENG Yanguo, ZHANG Baojian, LI Yanyan, WANG Guiling

      2022,49(6):1711-1722, DOI: 10.12029/gc20220601

      Abstract:

      This paper is the result of geothermal geological survey engineering. [Objective] The hydrochemical formation and evolution of the geothermal water in the Xiong'an New Area have great significant implications to understand the formation mechanism of geothermal resource. [Methods] Geothermal water and cold groundwater in the Rongcheng uplift, Niutuozhen uplift, Baxian depression, Baoding depression, and Gaoyang low uplift were sampled for hydrochemical analyses. [Results] There are two thermal reservoirs: Sandstone and karst thermal reservoirs. The main hydrochemical types were Cl·HCO3-Na and Cl-Na. The TDS values of geothermal water increased with well depths. Mixing of the geothermal water of the Wumishan Formation and the Guantao Formation was observed in the fault zone. The metamorphic coefficients and desulfurization coefficients of geothermal water in the Wumishan Formation were low, indicating a relatively closed thermal reservoir and reduced state, while the sealing of the reservoirs in the Guantao Formation and Minghuazhen Formation was relatively poor. [Conclusions] The chemical field of geothermal water in the study area is controlled by the extent of water-rock interaction, faults, the sealing of the reservoirs, and so on. Our result is of great significance for understanding the geothermal resources in Xiong'an New Area and promoting clean heating in winter in northern China.

    • Yao Yahui, Jia Xiaofeng, Li Shengtao, Zhang Jianwei, Song Jian, Yang Tao, Yue Dongdong

      2022,49(6):1723-1731, DOI: 10.12029/gc20220602

      Abstract:

      The paper is the result of geothermal geology survey engineering. [Objective]The heat flow values in Xiong'an New Area are mostly measured from the Neogene sedimentary cap and dolomite strata. The previous geothermal exploration and utilization horizons are mainly karst thermal reservoirs shallower than 1800m in the Jixian System and the boreholes exposing the Archean are scarce in Xiong'an New Area. Heat flow determinations and analyses from Archean under the karst thermal reservoir are rarely reported by previous researchers. Since 2018, D01 deep geothermal parameter well with a depth of 3403.67m has been implemented in Niutuozhen geothermal field in Xiong'an New Area. The karst thermal reservoir of the whole Gaoyuzhaung Formation was exposed and the Archean of 1723.67m was drilled by D01 well. The D01 well provides the conditions for the heat flow study from Archean under the karst thermal reservoir in this area. [Methods]Based on borehole temperature measurement and thermal conductivity tests, the study on the heat flow from the Archean of D01 well was carried out. [Results]The results showed that the Archean of D01 well has significant geothermal characteristics of conduction type, and the geothermal gradient is 18.3℃/km, which is lower than the Neogene geothermal gradient of 48.6℃/km. The thermal conductivity values of 25 Archean gneiss core samples of D01 well were measured with an average value of (2.41±0.40) W/(K·m). Based on the temperature measurement curve and thermal conductivity data of 2300-2700m section of D01 well, the Archean heat flow of D01 well was calculated to be (44.1±7.0) mW/m2. The heat flow of the Neogene sedimentary cap of D01 well was estimated to be 84.6 mW/m2. [Conclusions]The higher part 40.5 mW/m2 than Archean of D01 well was considered to be mainly contributed by the lateral convection heat transfer of groundwater in high pore-permeable karst dolomite and the vertical convection heat transfer of groundwater in the Niudong fault. The research results can provide the basic data for the previous heat accumulation mechanism of the groundwater transport and the heat conduction fault. And the results are of great significance to the genetic mechanism of deep geothermal resources and the geothermal field of Archean in Xiong'an New Area.

    • Li Shengtao, Yue Dongdong, Feng Zhaolong, Song Jian, Liu Donglin, Song Zhibin, He Guolei, Long Hui, Hao Wenjie, Zhang Qiuxia

      2022,49(6):1732-1746, DOI: 10.12029/gc20220603

      Abstract:

      This paper is the result of geothermal resource survey engineering. [Objective]Tianjin is abundant in geothermal resources with high utilization level, and section 4-3 in Wumishan Formation of Jixian system is the main development dolomite reservoir at present. With the development intensity of geothermal fluid increasing, the exploitation potential of some areas has reached the limit. Exploring the deep geothermal resources and increasing the allowable productions have become one of the effective ways to ensure the sustainable development of geothermal resources in Tianjin. [Methods] Donglihu area is the key research region in this study. Deep geophysical detection had been carried out and geothermal scientific exploration well CGSD-01 had been drilled. [Results] The main results are listed as follows: (1)CGSD-01 drilling encountered the section 2 of Wumishan Formation at 3715 m, a set of purplish red argillaceous dolomite with light gray fine-grained dolomite is developed at the bottom of the section 3 of Wumishan Formation overlying, the thickness is about 73 m, and the fissures are not developed, which can be considered as aquiclude or aquitard; (2)The completion depth of CGSD-01 is 4051.68 m, and the bottom temperature is 106℃, specific field is 1.53 m3/h·m, permeability is 0.40 m/d, conductivity is 48.69 m2/d; (3)The geothermal fluid type of the section 2 of Wumishan Formation is Cl·SO4·HCO3-Na, salinity is 1.7 g/L. It is preliminarily inferred that the geothermal water is originated from atmospheric precipitation, and mainly occurs mixing, cation alternating adsorption, carbonate dissolution, sulfate reduction, and does not reach equilibrium state; (4)The maximum outflow rate of CGSD-01 can be reach to 130 m3/h, and the temperature is 100℃, which can meet the heating load of 300 thousand square meters building area. [Conclusions] The high-yield new reservoir section 2 in Wumishan Formation of Jixian system was exposed for the first time in the second space of deep thermal reservoir in Tianjin area, and the thermal reservoir structure and main parameters of the reservoir were proved up, showing a good resource prospect.

    • Wang Tinghao, Wang Xinwei, Mao Xiang, Luo Lu, Gao Nan'an, Liu Huiying, Wu Chenbingjie

      2022,49(6):1747-1764, DOI: 10.12029/gc20220604

      Abstract:

      This paper is the result of geothermal geological survey engineering. [Objective] The characteristics and development potential of geothermal resources is an important basis for the development of regional geothermal resources. [Methods]Combined the previous research results with the latest drilling data, the geothermal reservoir model is established based on the analysis of the main factors such as geothermal geological background, thermal reservoir distribution, geothermal field characteristics and hydrochemical resource types in the northern Cangxian uplift. [Results] Under the background of high heat flow value in the extensional sedimentary basin of Bohai Bay, the atmospheric precipitation received by the bedrock in the exposed area of Yanshan Mountain in the north is used as the near source water supply. The cold water enters the bedrock, is heated by the deep heat source in the deep circulation process, and migrates and enriches along the fracture zone and unconformity surface, and forms the geothermal heat transfer mechanism dominated by conduction system. [Conclusions] The geothermal resources in this area are characterized by many types thermal reservoirs, high geothermal gradient of caprock, rapid recharge rate and huge resources. It is mainly shown as follows: Three sets of main hot water reservoir, sandstone thermal reservoir of Guantao Formation, karst thermal reservoir of Ordovician and Jixian Wumishan Formation are distributed in the area; the distribution of geothermal field is mainly controlled by basement structure, and the average geothermal gradient in bedrock uplift area is 45 ℃/km; with the increase of groundwater depth, the groundwater type changes from HCO3-Na, HCO3·SO4-Na to mature Cl-Na; the recoverable geothermal resources in this area is 1.67×1010 GJ, equivalent to 5.72×108t of standard coal. The annual exploitable geothermal resources can meet the heating area of 2×108 m2, considering the balance of exploiting and irrigation, the annual exploitable resource of geothermal fluid in the northern part of Cangxian uplift is 7.06×107 GJ, equivalent to 2.41×106t of standard coal, which can meet the heating area of 8.5×107 m2, which has a good prospect of geothermal market development.

    • Wang Longping, Wei Yongxia, Cheng Hongchao, Kang Jia, Liao Anran

      2022,49(6):1765-1777, DOI: 10.12029/gc20220605

      Abstract:

      This paper is the result of geothermal resource survey engineering. [Objective]The geothermal resources in Anhui of Yangtze River Economic Zone are abundant, which has good prospects for city development and utilization. The evalution of geothermal resources can provide a scientific basis for the optimization of energy structure, sustainable development and utilization of geothermal resources in this area. [Methods]Through analyzing the geological and hydrogeological conditions, e.g., geological structure, formation lithology, and hydrochemical composition of geothermal fluids, this study reveals the distribution characteristics of geothermal resources in Anhui of Yangtze River Econmic Zone, discusses the storage feature of geothermal resources in uplift mountain convective area and conductive-type sedimentary basins, and evaluates its reserves, development, and utilization potential. [Results] The geothermal resources mainly occurred in the uplift mountain including the Chaohu-Hexian bedrock, the Dabie mountain, the bedrock along the Yangtze River, the Jiangnan, and at the sedimentary basin including the Dingyuan, the Feidong, the Huoshan-Jijing, the Luzong, the Anqing, and the Xuancheng, etc. The thermal storage of the former uplift mountain is zonal-type, dominated by granite in the fractured zone of the area. The thermal storage of the latter sedimentary basin is layered and layered-zonal type, dominated by lithologic sandstones and carbonate rocks. The thermal storage is mainly metasilicic acid-fluorine thermal mineral water. The hydrochemical type of the geothermal fluid in uplift-mountain type are mainly SO4 and HCO3 type. The hydrochemical type of geothermal fluid in sedimentary-basin type is mainly HCO3 type. According to the potential evaluation results, the utilization potential of geothermal resources in uplift mountain type is relatively small and is basically in over-exploitation situation while that in sedimentary-basin type is relatively large. There are 4, 6, and 10 basins with big, medium, and small potential in sedimentary-basin type geothermal resources. [Conclusions] The potential distribution of geothermal resources in Anhui of Yangtze River Economic Zone is uneven, and the geothermal resources need to be planned and utilized in different zones. It is necessary to consider the surface water pollution caused by the utilization of high fluoride and high salinity hot mineral water.

    • Reviews
    • Wang Hesheng, Gong Jianshi, Tao Xiaohu, Zhao Guizhang, Guo Pengzhe, Zhou Kai'e, Jiao Tuanli, Tan Mengjiao, Zhu Chunfang, Xu Naizheng, Li Liang, Ye Yonghong

      2022,49(6):1778-1791, DOI: 10.12029/gc20220606

      Abstract:

      This paper is the result of groundwater survey engineering. [Objective] The study on the temporal and spatial law of groundwater under changing environment is helpful to the fine management of water resources and the guarantee for regional water resources security. [Methods] Based on the rainfall data of typical weather stations in the Huaibei Plain from 1953 to 2019, the wavelet analysis and M-K test method was used to study the periodic changes and trend of rainfall on a multi-year scale. Combined with 395 national monitoring wells and groundwater monitoring data, the principal components analytical method was used to optimize the evaluation of monitoring wells. [Results]The results show that the rainfall in Huaibei Plain appears multiple temporal and spatial scales variation characteristics: The shallow groundwater level has declined continuously in the northwest, while fluctuated greatly in the other regions; In 1970, 2003 and 2019, the shallow groundwater level in the southern region decreased firstly and then recovered, and on the contrast, the shallow groundwater level in the northern region increased firstly and then decreased; The groundwater level in the study area has generally declined; And since 2000, the water level has somewhat risen; The 277 monitoring wells (221 water wells and 56 natural resource wells) optimized by principal component analysis can represent the overall water level changes of 395 original national monitoring wells. [Conclusions] The long-term monitoring data of the national groundwater monitoring project can well serve the evaluation and management of water resources at the basin scale, but still need to be optimized and densified at the provincial, municipal scales or key areas. The artificial observation in unified time period can also make up for this deficiency which should be densified in the high hydraulic gradient areas such as both sides of important rivers and lakes, the north bank of Huaihe River, and the piedmont plain in the northeast.

    • Du Fangpeng, Ning Shuzheng, Liu Chiyang, Qiao Junwei, Zhao Xiaochen, Li Congcong, Tan Furong, Wei Yunxun, Su Gang, Luo Zheng

      2022,49(6):1792-1807, DOI: 10.12029/gc20220607

      Abstract:

      This paper is the result of mineral exploration engineering. [Objective] Inertinite-rich coal is characterized by the high inertinite content, and several coal properties are personalized accordingly, which affecting its clean utilization. In this paper, we focus on both the determination of the time-space distribution of the inertinite-rich coals in China and the induction of the coal properties, clean potential and utilization mode of the low rank inertinite-rich coals in Northwest China. [Methods] We sort out a large number of exploration data and research results, and coal macerals and coal properties data were analyzed and summarized. The determination of inertinite-rich coal's time-space distribution in China and their coal properties were based on the data. The clean potential and utilization mode of the low rank inertinite-rich coal in Northwest China were carried out along the coal properties combined with the indexes for various purposes. [Results] It shows that the inertinite-rich coals are mainly distributed in the Early-Middle Jurassic in Northwest China. The low rank inertinite-rich coals in Northwest China are characterized by low ash, low sulfur, low harmful elements, low cohesiveness, low hydrogen content, low volatile matter, high carbon dioxide reactivity and high calorific value, among which, the hydrogen content, cohesiveness, volatile matter and carbon dioxide reactivity are obviously related to the high inertinite content. The coal properties show that the Jurassic coals in Northwest China are of high cleanliness and high calorific value, which is a high-quality power coal. The relatively low volatile matter and hydrogen content in the same coal rank make it not conducive to be used as coal for direct liquefaction. The low ash, low sulfur, low cohesiveness, strong reactivity with carbon dioxide are conducive to being used as coal for gasification, which is suitable for a variety of gasification processes. In addition, part of the low rank inertinite-rich coals represented by the northern part of Shaanxi Province are of high tar yield, which is suitable for low temperature retorting. [Conclusions] The low rank inertinite-rich coals in Northwest China are suitable for power coal and gasification coal, and the tar-rich coal should be given priority to low temperature retorting.

    • Liu Weibin, Xu Xingyou, Zhang Junfeng, Chen Shan, Bai Jing, Liu Chang, Li Yaohua

      2022,49(6):1808-1822, DOI: 10.12029/gc20220608

      Abstract:

      This paper is the result of oil and gas exploration engineering. [Objective] Continental shale oil is an important replacement field of energy in China, and precise drilling of long horizontal wells is a key technology to achieve commercial development of shale oil. However, due to the characteristics of continental shale such as high clay mineral content, strong heterogeneity and bedding development, serious instability of horizontal well wall and difficulties in precise steering of thin target layer are caused. [Methods] Taking the shale of the first member of Qinghe Formation in the south of Songliao Basin as the research object, the integrated research of geological engineering is carried out by comprehensively using geochemical, geophysical, rock mechanics, geostress analysis and other means. [Results] The shale in the upper part of Qing-1 Member is bedding shale, which is not suitable for horizontal wells to pass through. The thin oil-bearing sand bars in the lamellar shale in the middle and lower part of Qing-1 Member are both oil-bearing, drillable and compressible, which can be used as the crossing target layer; For shale formation, strong inhibition KCL polyamine drilling fluid system and oil-based drilling fluid system should be selected for horizontal well drilling. The mud density window increases with the increase of horizontal stress difference and well trajectory inclination angle; Logging GR and logging total hydrocarbon can accurately reflect the lithological heterogeneity change of target layer, and combined with high-precision geophysics, it can accurately control the drilling trajectory in real time. [Conclusions] Through application and practice, Jiye 1HF well has safely drilled 1252m along 1.94m ultra-thin target bed, with a penetration rate of 100%, which has achieved a technical breakthrough in accurate drilling of long horizontal section of continental shale oil, laid a foundation for Jiye 1HF well to obtain high-yield industrial oil flow, and has guiding and reference significance for accurate drilling of long horizontal section of continental shale oil of the same type in China.

    • Research Articles
    • Lai Yang, Gong Daxing, Qin Jianhua, Tian Enyuan, Hui Bo, Xu Lu, Gao Zedong

      2022,49(6):1823-1833, DOI: 10.12029/gc20220609

      Abstract:

      This paper is the result of mineral exploration engineering. [Objective]Rare earth is not only important natural non-renewable resources, but also a key strategic resource. Based on the field geological survey and indoor comprehensive study of sedimentary rare earth resources in the eastern Yunnan and western Guizhou area, this paper reveals the advantages and development and utilization potential of the rare earth resources, which not only enriches the industrial types of the global rare earth resources, but also supports the national strategic reserve of key rare earth resources. [Methods]Based on the research on the characteristics of ore-bearing strata, typical ore characteristics, the partition characteristics of rare earth elements and the potential of rare earth resources, this paper discusses the genetic types of the rare earth resources, the occurrence state of rare earth elements and the potential of development and utilization. [Results]The ore-bearing stratum is identified as Xuanwei Formation of Upper Permian (P3x); the lithology of rare-earth rich ore is gray- white aluminite claystone and silty claystone; the origin of rare earth ore belongs to sedimentary type; in Weining County Heishitou—Mazha—Zhejue area, the thickness of ore body varies from 2m to 18m, the ore body extension is relatively continuous, the content of rare earth oxide (TREO) is up to 1.6%, the weighted average grade of ore body block (TREO) is 0.18% to 0.46%, and the inferred resource is over 300,000 tons; the proportion of "Critical rare earth elements (CREE)" in the rare earth resources is up to 22.6% (∑CREO), which is higher than most of the rare earth deposits under development and utilization at domestic and overseas. In addition, the new selective leaching technology is used in the dressing and metallurgy test, and the results indicate that the recovery of rare earth can reach more than 90%. This new type of rare earth mine is expected to realize large-scale industrial utilization. [Conclusions]The sedimentary rare earth resource has the advantages of large ore thickness, high ore grade, large resource potential, low mining cost, high proportion of critical rare earth elements (CREO) in ore, and good development and utilization prospect.

    • Wang Chenghui, Wang Denghong, Liu Shanbao, Xu Jianxiang, Qin Jinhua, Qin Yan, Liu Jinyu, Zhao Zheng, Feng Wenjie, Liu Zhanqing, Zhao Ruyi, Guo Chunli

      2022,49(6):1834-1844, DOI: 10.12029/gc20220610

      Abstract:

      This paper is the result of mineral exploration engineering. In recent years, with the large-scale exploitation of mica-type lithium deposits in the Northwest of Jiangxi Province, hard-rock-type lithium deposits, such as greisen-type and altered granite-type in south China block, have gradually attracted more and more attention. Southern Jiangxi Province is a world-famous quartz vein-type wolframite mining district and producing base. In the past, exploration and research work mainly focused on the tungsten and tin deposits. [Objective]In order to further understand whether lithium mineralization exists in quartz vein type tungsten tin ore and its geological characteristics. [Methods]This study was conducted through systematic microscope identification and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) analysis. [Results]Greisen-type lithium ore was found in the deep part of Shilei tungsten and tin deposit in Chongyuyou Ore cluster located in the Southern Jiangxi Province. The lithium ore body occurred at the top of the deep concealed granite body, and distributed on two sides of W-Sn-bearing quartz-vein and feldspar quartz-vein. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis and microscope identification show that lithium mainly found in muscovite-phengite. The average Li2O content of greisen in hornfelsic sandstone is 0.25%, the average Li2O content of quartz (feldspar) vein greisen in mica granite is 0.21%, and the average Li2O content of mica vein-bearing greisen developed in mica granite is 0.22%, which shows potential comprehensive utilization value. [Conclusions]In this study, lithium mineralization of industrial significance is identified in Shilei quartz vein-type tungsten tin deposit. The discovery enriched the metallogenic theory of tungsten and tin deposits in the Southern Jiangxi Province, broadened the prospecting and exploration ideas of greisen-type lithium deposits in Chongyuyou ore cluster, and provided a basis for further expanding the prospecting space of hard-rock-type lithium deposit in South China Block.

    • Ding Weipin, Xie Caifu, Huang Cheng, Zhang Bin, Xin Zhuo, Zhan Huasi, Zheng Lilong, Kong Fanquan, Wang Hongbing, Huang Fulin

      2022,49(6):1845-1861, DOI: 10.12029/gc20220611

      Abstract:

      This paper is the result of the geological survey engineering. [Objective]The genesis of Pb-Zn deposit in Sichuan, Yunnan and Qianhai is diverse, especially the relationship with the Emei Mountain basalt is more controversial. In this paper, we study the source of ore-forming material, starting from Pb-Zn deposit in Permian carbonate rocks, which has received less attention from previous authors. [Methods]Using experimental data of S, Pb, C, H, and O isotopes and fluid inclusion temperature measurements, the source of mineralized materials and the characteristics of mineralized fluids were investigated in the Taipingzi Pb-Zn deposit in Xundian County, Yunnan Province. [Results]The Pb isotopic compositions of the ore are relatively homogeneous and concentrated, with the variations of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ranging from 18.543 to 18.584, 15.646 to 15.694 and 38.799 to 38.958, respectively. These suggest that the Pb in Taipingzi Pb-Zn deposit belongs to normal common Pb with crustal origin. The metal-forming materials are mainly from the basement rocks, and the water-rock reaction may make the mineralized enclosing rocks contribute a small number of mineralized materials. The δ34S in ore sulfide varies from -13.6 ‰ to -7.3 ‰ and δ34S of the galena is higher than that in sphalerite. Sulfur isotope fractionation has not reached equilibrium, sulfur is mainly from crustal source. Biogenic sulfate reduction (BSR) is the main mechanism of sulfur reduction. A large amount of biogenic sulfur reduction has accumulated in the mineralized area before mineralization. The hydrothermal calcite δ13CV-PDB ranges from 3.8 ‰ to 4.7‰ and δ18OV-SMOW ranges from 12.0 ‰ to 16.7 ‰ with obvious low δD and high δ18Ofluid characteristics compared to other important Pb-Zn deposits in northeast Yunnan. The water in the mineralizing fluid mainly originates from a mixture of magmatic and organic water, with medium-high temperature and low salinity characteristics. [Conclusions]Taipingzi Pb-Zn deposit is significantly different from other typical Pb-Zn ores in the region in terms of metallogenic material, fluids and metallogenic temperature, and has typical magmatic-hydrothermal genesis characteristics.

    • Xia Jie, Cheng Shunbo, Xue Xilin, Li Jianfeng, Fu Jianming, Lu Youyue, Yang Qizhi, Li Xiongfei, Ma Liyan

      2022,49(6):1862-1874, DOI: 10.12029/gc20220612

      Abstract:

      This paper is the result of the mineral exploration engineering. [Objective] In order to discuss the genesis of the lead-zinc deposits in Hengyang Basin and its surrounding areas, this paper has carried out work on the highly studied Qingshuitang lead-zinc deposit. [Methods] By means of geological survey, fluid inclusion study of quartz, calcite and sphalerite at different stages and Rb-Sr dating of quartz, we discuss the geochemical characteristics, evolution and mineralization processes of ore-forming fluid. [Results] Based on the mineral assemblages and the intercutting relationships between veins, this paper classifies the metallogenesis of the Qingshuitang lead-zinc deposit into three stages: pyrite-quartz stage (I), quartz-galena-sphalerite stage (II) and barite-calcite stage(III). The research of fluid inclusions show that both L- and VL-type primary and secondary fluid inclusions occur in quartzs and sphalerites at stage II; VL-type primary fluid inclusions predominantly occurs in quartzs at stage I and calcites at stage III. The measured temperature results show that primary inclusions of quartz formed at stage II can be subdivided into four groups according to the homogeneous temperature and salinity, which are 258-296℃ and 8.55%-9.21% NaCl eqv, 260-298℃ and 3.61%-4.18% NaCl eqv, 120-160℃ and 12.73%-18.22% NaCl eqv, 145-168℃ and 3.06%-3.87% NaCl eqv, respectively. By comparison, the homogenization temperature and salinity of sphalerite are mainly concentrated in the range of 102-178℃ and 10.24%-19.45%NaCl eqv. The ore-forming fluid belongs to the NaCl-H2O hydrothermal system of medium-low temperature and medium salinity. Based on occurrence and homogenization temperature of inclusions, the medium and low salinity fluids at stage II may have different sources and evolutionary processes. The former is mostly distributed in groups and might derive from medium temperature (210-312℃) and medium salinity (12.30-19.30%NaCl eqv) fluid at stage I. The latter mostly occurs along mineral fissures, which may be formed by mixing of the late low salinity atmospheric precipitations. In this paper, two quartz Rb-Sr isochron ages are obtained, and they are (88.8±2.4) Ma and (17.86±0.42) Ma, respectively. The former age represents the mineralization age of Qingshuitang lead-zinc deposit, and the latter age records the time of late tectonic superposition. Both of them are significantly later than the diagenetic ages of the Zhoujialing granite ((203.0±1.4) Ma) near the mine site and the adjacent Guandimiao pluton ((223.4±1.9) Ma). [Conclusions]Considering that the metallogenic fluids of lead-zinc in the area are related to magmatic activities, it is inferred that there are the Late Cretaceous concealed intrusions in the deep part of the mining area combined with sulfur and lead isotope characteristics of sulfides from the Qingshuitang and Liushutang mining areas, which provide material and energy sources for lead-zinc mineralization.

    • Wan Xin, Han Runsheng, Li Bo, Xiao Xianguo, He Zhiwei, Wang Jingteng, Wei Qingxi

      2022,49(6):1875-1892, DOI: 10.12029/gc20220613

      Abstract:

      This paper is the result of mineral exploration engineering. [Objective] The Lekai lead-zinc deposit, located in the Pb-Zn deposit concentration of northwestern Guizhou, is one of the small-scale lead-zinc deposits newly discovered in recent years. Different from most lead-zinc deposits in the Pb-Zn deposit concentration of northwestern Guizhou, the Lekai lead-zinc deposit is controlled strictly by NE trending fault-fold structure, which is similar to most lead-zinc deposits in the Pb-Zn deposit concentration of northeastern Yunnan. The current research provided significant implications for the deep exploration in the Lekai lead-zinc deposit and the Sichuan–Yunnan–Guizhou Triangle area (SYGT). [Methods] This study applied a large deal of detailed structural analysis on mechanical properties for faults and folds in the mining area and tectono-geochemistry method. [Results] The results showed that duo-type and λ-type are the main ore-controlling structural styles in this area. Moreover, three tectonic associations have been divided, which are correspond to four tectonic systems, namely Hercynian to Mid Indosinian, Late Indosinian to Early Yanshanian, Mid-Late Yanshanian, and Himalayan epochs. The trace elements concentrations of tectonites represented three element associations of principal factors, including frontal halo elements (Sb-As-Hg) in low temperature ore-forming stage, mineralization-halo elements (Zn-Pb-Cd) in medium-low temperature ore-forming stage, and tail-halo elements (In-Sn-Ni-Cu) in medium temperature ore-forming stage. [Conclusions] In four tectonic systems, ore-forming tectonic system corresponded with Late Indosinian to Early Yanshanian. According to anomaly features and their distribution regularities, the possible migration direction of ore-forming fluid is from southwest to northeast, and six target prospecting areas have been put forward in the depth of mining.

    • Ma Ming, Gao Mingbo, Zhu Decheng, Li Yadong, Gao Jilei, Fan Zhenhua, Feng Qiwei, Li Siyuan, Zhang Yongming

      2022,49(6):1893-1907, DOI: 10.12029/gc20220614

      Abstract:

      This paper is the result of mineral exploration engineering. [Objective] Laiwu Sanchahe iron-gold deposit is the first skarn type iron-gold deposit (without copper) discovered in western Shandong. Previous research on the Sanchahe deposit is weak. The purpose of this paper is to discuss the age of ore-forming pluton,magma sources, petrogenesis and tectonic setting. [Methods] We carried out LA-ICP-MS zircon U-Pb dating, major and trace elements analysis.[Results] Zircon U-Pb age of pyroxene diorite is (138.4 ±1.2) Ma in the Early Cretaceous. Pyroxene diorite is calc-alkalic (Rittmann index σ = 2.20-2.54) and characterized by high Mg# and high contents of Na2O, Sc, Cr, Co and Ni, which demonstrates that it has geochemical affinity with mantle-derived magma. It is enriched in LREE and depleted in HREE, with no obvious Eu anomaly, and shows enrichment in Cs, Ba, Sr and depletition in high field strength elements (Nb, Ta, Zr), indicating involvement of some crustal materials. [Conclusions] Geochemical features of pyroxene diorite combined with geochronological data imply that it may be generated by partial melting of the enriched lithospheric mantle which had been metasomatized by the ancient crust materials of the North China Craton, and formed in the strong extensional tectonic background of lithospheric thinning, which may be caused by the retreat of the subducting Paleo-Pacific plate.

    • Liu Jianqing, He Li, Jiang Yongfu, He Jiawei, He Ping

      2022,49(6):1908-1922, DOI: 10.12029/gc20220615

      Abstract:

      This paper is the result of mineral exploration engineering. [Objective]The phosphate deposit accumulation scope of Maidiping Formation of the Lower Cambrian covers a wide area from Leibo County (Sichuan) to Yongshan County (Yunnan). The study of phosphorus-bearing strata is not only helpful to the reconstruction of the paleogeographic environment and its varied characteristics, but also can obtain the formation and distribution of phosphate deposits in combination with the study of tectonic background, and provide a thedeposittical basis for the development of phosphate deposit. [Methods]Based on the cdeposit record and section measurement, this paper studies the thickness, lithology, sedimentary facies, sedimentary model, tectonic background, basin properties, genetic mechanism of phosphate deposit, petrological features of phosphorite, and their changes in Maidiping Formation in Leibo area. [Results]The significant difference of lithology and lithofacies of the Maidiping Formation in Leibo area are within 50 kilometers, and the characteristics of phosphorite are well explained. It is pointed out that the Leibo area was an uplift and depression environment during the sedimentary period of Maidiping Formation, and the shallow shelf facies was absent. Dolomite facies area belongs to tidal flat facies, which is a favorable area for the phosphate deposit accumulation. Siliceous rocks belong to deep-water shelf facies and are of hydrothermal origin formed by volcanic activity. The accumulation of phosphorite is the result of volcanic activity in siliceous lithofacies area, biological development, movement of high temperature ocean current from the bottom to the top, sedimentation of the seawater with high P2O5 carried by ocean current decomposing biological remains in dolomite facies area on both sides of the sag area and post-sedimentation transformation. Based on the tectonic background, basin nature, source of phosphorus, migration, sedimentation and enrichment of phosphorus, the deposit-forming mechanism of phosphate is described, and the formation of phosphate deposit in Leibo area is suggested by the interaction of many factors, and the corresponding deposit-forming model of phosphate deposit is established. The siliceous rocks in the depression are the result of the hot water activity under volcanism. [Conclusions]The study revealed a new phosphorus mineralization style in the late stage of rift basin development from Late Neoproterozoic to Early Cambrian, i.e., the paleogeographic pattern of alternating uplift and depression with the weak volcanic activity. A new idea of predicting and evaluating the phosphate deposit in dolomite facies area on both sides of the depression is put forward. We suggest that the prospecting space of the Maidiping Formation phosphate deposit should be expanded from the depression area to the surrounding areas.

    • Miao Zhongying, Zheng Mianping, Lou Pengcheng, Zhang Xuefei, Sun Haitao, Zhang Zhen, Xu Qihui, Du Xuemiao

      2022,49(6):1923-1935, DOI: 10.12029/gc20220616

      Abstract:

      This paper is the result of the geological survey engineering. [Objective]The Simao Basin hosts the only pre-Quaternary solid potash deposit in China, but the genesis of this deposit has been still controversial. An objective understanding of deposit genesis as well as rational construction of a metallogenic model is not only fundamental scientific issues that need to be addressed urgently in the study of potash mineral deposits, but also have a bearing on the choice of the direction for potash resource exploration in the basin. [Methods]This study focuses on Sr isotope geochemical characteristics of the samples from salt rocks, overlying and underlying clastic rocks and clastic rocks within the salt rocks in Wells L-2 and MZK-3 of the Simao Basin. [Results]The results show that: (1) The bulk-rock 87Sr/86Sr values from the Well L-2 samples are 0.708220-0.727458, with an average of 0.712776; the 87Sr/86Sr values of water-insoluble matter within the salt rock are 0.711342-0.741999, with an average of 0.716574; (2) The 87Sr/86Sr values of the clastic rock overlying and underlying the salt layer in Well MZK-3 range from 0.713318-0.723147 and 0.712470-0.738988, with an average of 0.717255 and 0.719307, respectively; (3) The 87Sr/86Sr values of the clastic rock corrected by 87Rb tore cover their initial sedimentary state are 0.710880-0.727678, with an average of 0.712828; (4) The 87Sr/86Sr values of salt rock are all significantly lower than the average value of the continental weathering system, with some individual samples having 87Sr/86Sr values larger than modern seawater. [Conclusions]Based on the existing research results of the basic geology and potash deposit geology in the Simao Basin, combined with the Sr isotope geochemical characteristics of salt rocks and clastic rocks, it can be concluded that: The potash-bearing salt rocks and clastic rocks are in different Sr isotope equilibrium systems; the matter source of potash-bearing salt rock is mainly seawater, and the recharge of terrestrial freshwater into the evaporation basin during the salinization process would increase 87Sr/86Sr values of the samples. The clastic rocks were deposited in the terrestrial environment and were in the eodiagenesis substage A before contacting with solid salt rock or brine; a more rational potash metallogenic model is that the deep source salt migrated to the surface through faults formed by strike-slip pull-apart process during the deposition period of the Mengyejing Formation, capturing the unconsolidated clastic rocks in the eodiagenesis substage As they migrated from the height to the catchment basin, and forming the present-day clastic-bearing salt rocks. After migrating into the catchment basin, parts of the clastic-bearing salt rocks underwent dissolution and recrystallization, resulting in the formation of salt rock with relatively purer composition. The subsequent deposition of the clastic rocks formed a protective layer against rock salt dissolution. Early-formed potash deposits were influenced by the Cenozoic Himalayan movement, leading to the modification not only in physical structure but also in mineral component.

    • Gao Da, Wang Mingmin, Tao Ye, Huang Lili, Sun Chunyan, Huang Xinmiao, Wu Jianwei

      2022,49(6):1936-1950, DOI: 10.12029/gc20220617

      Abstract:

      This paper is the result of oil and gas exploration engineering. [Objective] Carbonate strata are susceptible to sea-level changes and thus develop high-frequency sequences. However, the accuracy of geochemical indicators reflecting sea-level changes is insufficient, resulting in poor understanding about the high-frequency sea-level fluctuation. The controls of sea-level changes on the high-frequency sequence and sedimentary evolution of the platform-margin reef-shoal deposits remain unclear. [Methods] Continuous core data from a well in the Upper Ordovician Lianglitage Formation in the Tarim Basin were selected for microfacies analysis, carbon and oxygen isotope analyses by densely-collected samples. [Results] Seven microfacies types developed in the middle and upper part of Lianglitage Formation. The analysis of the sedimentary evolution shows that the sedimentary environment evolved from tidal flat to reef and shoal, and to deeper platform during the middle to late period of deposition. The carbon and oxygen isotope values ranges from: δ13C is 0.5993 ‰-1.6228 ‰ (average 1.139 ‰) and δ18O value is-8.3608 ‰- -5.1452 ‰ (average -6.790 ‰). The changes of the δ13C and δ18O correspond well with the evolution of microfacies and sedimentary cycles. The analysis of paleo-ocean conditions shows that the Lianglitage Formation was deposited under warm climate and the reef and shoal samples recorded high paleo-temperature, representing a high rate of carbonate production. The paleo-salinity reflected by the Z-value is high according to the samples at the bottom of the tidal flat, and it is relatively low at the top of high-frequency cycles, probably indicating the influence of meteoric water. The range of δ13C and δ18O values differ from the Tazhong area, the southern margin of Tabei area, and Bachu area, which is mainly related to the difference in environment and water depth. [Conclusions] At least three cycles of sea-level change and two secondary cycles exit in the middle to upper parts of the Lianglitage Formation. Different levels of sea-level changes are mainly driven by paleoclimate changes that control the formation of high-frequency sequences. Sea level rises slowly and then continues to be stable or oscillate on a small scale, which provide a favorable condition for the deposition and development of thick-bedded bioclasts and carbonate sands. Sea level rose sharply during the late sedimentary period of the Lianglitage Formation, and the sedimentary environment turned into inter-shoal lagoons and deeper platforms. The early-stage karstification caused by the small-scale sea-level drop at the top of the high-frequency sequence is an important factor to improve the reservoir quality of reef and shoal faces.

    • Liu Jianping, Xian Benzhong, Zhang Li, Su Ming, Li Yuzhi, Yan Haiqing, Wang Zhen, Chen Peng, Wu Qianran, Li Jin, Tian Rongheng, Yang Xin, Zhou Huanhuan, Luo Xun, Chen Long

      2022,49(6):1951-1969, DOI: 10.12029/gc20220618

      Abstract:

      This paper is the result of oil and gas exploration engineering. [Objective]Debris flow represents an important mechanism of sediment transport and dispersal in deep-water environment, the related sandstone reservoir constitute one of the important targets for petroleum exploration in petroliferous basins, while deep-water systems dominated by debris flows are still poorly understand compared to well-studied turbidity currents and turbidite systems. [Methods]The depositional process and model of gravity flows which developed in the Middle Sub-member of the 3rd Member of the Eocene Shahejie Formation, Dongying Depression, Bohai Bay Basin have been studied through the integration of core data examination, well logging data and 3D seismic data interpretation. [Results]It is suggested that nine base types of lithofacies can be recognized in slump-derived gravity flow deposits, which can be summarized into four main origin types, which indicate mass transport and flow transport processes, respectively. Quantitative lithofacies analysis suggests that the slump-derived gravity flow depositional system is dominated by debris flows, while turbidity currents are less important, and sandy debris flows represent the most important debris flow type. The slump-derived gravity flows undergo five evolution stages including slide, slump, sandy debris flow, muddy debris flow and turbidity currents, which correspondingly develop five types of deep-water depositional elements during transportation and evolution, including slide, slump, debrite channel, debrite lobe and turbidite sheet. Sandy debrite channels, lobes and sandy slides constitute the most important deep-water reservoirs in the study area according to their wide distribution and reservoir property. [Conclusions]It is proposed that adequate sediment supply, high depositional rate on delta-front, frequent tectonic activities and short transport distance are the main controlling factors. Accordingly, a depositional model is proposed to depict slump-derived gravity flow systems based on depositional processes, sedimentary patterns and basin morphology. This study seeks to improve deep-water sedimentary theories and provide guidance for petroleum exploration of deep-water sands in deep-lacustrine basins.

    • Yang Ling, Tian Lei, Bai Guangyu, Pei Shengliang, Zhang Deqiang

      2022,49(6):1970-1983, DOI: 10.12029/gc20220619

      Abstract:

      This paper is the result of the mine environmental geological survey engineering. [Objective] Xin Barag Youqi is located in hulun buir grassland, and mining activities are frequent. Understanding the sources and ecological risks of heavy metals of soil in this area is prerequisite for assessing environmental impact. [Methods] We collected a total of 221 samples of ore, bed rock and soil, and tested contents of 7 elements (Cd, Cr, As, Hg, Ni, Pb and Zn). The pollution degree and distribution characteristics of heavy metals were evaluated by geoaccumulation index method and potential ecological risk index method. The sources of heavy metals in soil were determined by correlation analysis and principal component analysis. [Results] It was found that the heavy metal pollution in the soil of Xin Barag Youqi is mainly mild, and Cd, Ni, As, Cr and Pb are polluted. The contaminated areas are located in Jiawula-Chagan Mining Area, Zhuan Ulanor, northwest shore of Hulun Lake and middle of the Krumlen River. Source analysis results shows that Cr、Ni and Hg are mainly from human activities, Cd, Zn and Pb are affected by both natural factors and human activities, and As is mainly from natural factors. [Conclusions] In general, the ecological risk in Xin Barag Youqi is low, and Cd has the most prominent contribution to the ecological risk of the soil in this area, which should be taken seriously in soil quality monitoring.

    • Zhou Yu, Zhou Xiong, Zhang Yi, Qin Zhipeng, Jia Zhiquan, Liang Bing

      2022,49(6):1984-2001, DOI: 10.12029/gc20220620

      Abstract:

      This paper is the result of geological survey engineering. [Objective]It is of great significance to find out the geochemical and tectonic evolution characteristics of granite in the southeast of the Songpan-Ganze terrane for searching for rare metal minerals in this area. [Methods]we have carried out field geological survey and conducted whole-rock geochemistry and zircons LA-(MC)-ICP-MS U-Pb and Lu-Hf isotope analyses on the monzogranite of the Sudi pluton in the southeast part of the Songpan-Ganze terrane. [Results]The results show that the samples were medium-high potassium, sodium rich and calcium deficiency. The values of AR were 1.44-1.83 and values of A/CNK were 0.98-1.16, which were medium-high potassium calcareous alkaline series. The rocks show relatively enriched large ion lithophile element (LILE), negative high field-strength elements (HFSE), and high REE content (the total amount of REE = 157.16×10-6-187.88×10-6) with the LREE enrichement (LREE/HREE = 6.26-9.46) and weak negative Eu anomaly europium anomaly (δEu = 0.62-0.74). The results of zircon U-Pb dating were (221.1±1.5) Ma (MSWD=0.30, n=22) and (214.5±1.5) Ma (MSWD=0.22, n=22), indicating that the primitive magma of the Sudi pluton crystallized in the middle of the Late Triassic. Its zircon Lu-Hf isotope εHf(t) and TDM2 are -6.56--4.12 and 1.67-1.51 Ga. [Conclusions]According to the comprehensive analysis, we believe that the monzogranite in Sudi pluton is a typical I-type granite and it may be formed by the upwelling and emplacement of the initial magma from the lower crust in the middle of Late Triassic in the process of orogenic collision to post-collisional extensional tectonic setting. The southeastern margin of Songpan-Ganze terrane was under post-collisional orogenic environment in Late Triassic.

    • Zhang Xiaoge, Xie Caifu, Zhang Zhao, Chen Kai, Nan Zhenglu, Yuan Yongsheng, Zhang Honghui, Jin Guodong, Peng Ping, Zhu Yuwen

      2022,49(6):2002-2028, DOI: 10.12029/gc20220621

      Abstract:

      This paper is the result of geological survey engineering. [Objective] A large amount of ~ 100 Ma magmatic rocks are developed in the southeast margin of South China. Shifting to interior of South China, although the period of magmatism has been reported sparingly, they were often related to metal mineralization. Determination of the distribution of magmatism of ~ 100 Ma in the interior of South China would provide a scientific basis for the study of the late Yanshanian tectonic setting, and related ore prospecting and exploration. [Methods] Based on the 1︰50000 regional geological survey and detailed petrographic study, the granites in Qiashui area, which are located near the Chenzhou-Linwu fault in the interior of South China, were divided into five intrusive episodes, including (1) porphyritic coarse-medium-grained amphibole-biotite monzogranite, (2) porphyritic medium-fine-grained amphibole-bearing biotite monzogranite, (3) porphyritic medium-fine-grained biotite monzogranite, (4) medium-fine-grained biotite monzogranite with rare porphyrites and (5) fine-grained biotite syenogranite with rare porphyrites, respectively. Zircon LA-ICP-MS U-Pb dating was carried out systematically for the representative rocks of these intrusions. [Results]U-Pb dating yield ages of the first to fifth intrusive episodes ranges from 102 Ma to 97 Ma, which is at the transition of the Early and Late Cretaceous. [Conclusions] According to comprehensive analysis and comparison of the ~100 Ma magmatic events in the interior and southeast coastal regions of South China, it shows that the geodynamic mechanism of the magmatism of ~100 Ma in the interior of South China might be related to back arc and intracontinental lithospheric extension resulting from Paleo-Pacific plate subduction retreation. It led to reactivation and extension of ancient deep faults such as the Chenzhou Linwu fault, and then the intensive mantle and crust magmatism.

    • Discoveries and Development
    • New and Highlights

    The Online First column displays articles that have been accepted by Geology in China through peer review. These articles are currently in the redaction process and have not yet determined the volume and page number. And the final printed version of the article may be slightly different in individual formatting or text expression, but the overall content of the article is completely consistent. The copyright of its contents is protected by relevant laws and regulations.

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    • Ge Mingna, Bao Shujing, Shi Dishi, Zhang Liqin, Lin Yanhua, Wang Ting

      DOI: 10.12029/gc20210923001

      Abstract:

      【Abstract】: 【Objective】To study the pore structure characteristics of Niutitang Formation shale in Southeast Guizhou and its influence on shale gas enrichment, avoid unfavorable factors, and provide suggestions for shale gas exploration in Southeast Guizhou. 【Methods】Multi-scale characterization of the shale micro-nano pore structure is carried out by means of focused ion beam scanning electron microscopy (FIB-SEM), FE-SEM, and nitrogen adsorption. Combined with the hydrocarbon generation and burial history of the Niutitang Formation shale in the study area, the relationship between tectonic movement and pore structure is studied, and its control effect on shale gas enrichment is analyzed. 【Results】The Niutitang Formation shale mainly develops millimeter-scale micro-cracks, micron-scale pyrite intercrystalline pores and nano-scale organic pores, mainly ink bottle-shaped pores and slit pores with a flat plate structure, and the pore structure is complex. Combined with the results of FIB-SEM three-dimensional reconstruction, organic matter accounts for a relatively high proportion of shale, with a porosity of 0.04-2.48% and a contribution rate of 14%-96% to the total porosity. The pyrite crystals co-existing with organic matter Pores are the main type of pores that communicate fractures , the shale gas in this area is dominated by undersaturated adsorbed gas, and the free gas content is low. 【Conclusions】A large number of structural fractures in the Niutitang Formation shale have connected organic matter pores and pyrite intercrystalline pores, and changed the original pore structure, causing the in-situ accumulated shale gas to escape along the fractures ,which is a key factor in the low gas content of the shale of the Niutitang Formation. Finding areas with moderate thermal evolution and well-preserved structures is a favorable direction for shale gas exploration on the periphery of paleo-uplifts.

    • chenyuanming, gao zhi peng, guohuaming, li wei, chen zongliang, wang xi, ma xuemei

      DOI: 10.12029/gc20180915003

      Abstract:

      The Tailai basin is one of the known hydro-geological units containing strontium mineral water. The study on the genesis and distribution of strontium mineral water in the Tailai Basin can provide direction for the investigation and development of strontium-bearing mineral water in the future. On the basis of the division of different water-bearing rock groups in the Tale basin, water samples such as Karst water, fissure water, porosity water and surface water were collected in the basin. The hydrogeochemical characteristics of four types of water and the evolution of mineral water containing strontium were studied by mathematical statistics, ion ratio coefficient, correlation analysis, isotope analysis and hydrogeochemical simulation. The results showed that the four types of water showed the characteristics of calcium-rich, magnesium-rich, low-sodium, low-potassium and weak alkaline, and the main hydrochemical type of them is HCO3.SO4-Ca.Mg. The four types of water are closely linked and affected by some degree of evaporation and concentration. The Sr2+ concentration of Karst water and pore water in the central basin was high, while the concentration of bedrock fissure water and surface water was relatively low. The enrichment of Sr2+ in groundwater is mainly controlled by weathering dissolution of calcareous minerals such as calcite and dolomite, and affected by evaporation concentration to a certain extent, while the effect of cation exchange is relatively small.

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    Volume 49,2022 Issue 6
    • Chenyang LI, Xinchun WANG, Chunzhen HE, Xuan WU, Zhaoyu KONG, Xiaolei LI

      2019,46(S1):1-10, DOI: 10.12029/gc2019Z101

      Abstract:

      As the only one of its kind, China National Digital Geological Map (Public Version at 1:200000 scale) Spatial Database (CNDGM-PVSD) is based on China's former nationwide measured results of regional geological survey at 1:200 000 scale, and is also one of the nationwide basic geosciences spatial databases jointly accomplished by multiple organizations of China. Spatially, it embraces 1163 geological map-sheets (at scale 1:200 000) in both formats of MapGIS and ArcGIS, covering 72% of China's whole territory with a total data volume of 90 GB. Its main sources is from 1:200 000 regional geological survey reports, geological maps, and mineral resources maps with an original time span from mid-1950s to early 1990s. Approved by the State's related agencies, it meets all the related technical qualification requirements and standards issued by China Geological Survey in data integrity, logic consistency, location accuracy, attribution fineness, and collation precision, and is hence of excellent and reliable quality. The CNDGM-PVSD is an important component of China's national spatial database categories, serving as a spatial digital platform for the information construction of the State's national economy, and providing information backbones to the national and provincial economic planning, geohazard monitoring, geological survey, mineral resources exploration as well as macro decision-making.

    • MAO Jing-wen, ZHOU Zhen-hua, FENG Cheng-you, WANG Yi-tian, ZHANG Chang-qing, PENG Hui-juan, YU Miao

      2012,39(6):1437-1471, DOI:

      Abstract:

      Abstract:Triassic tectonic evolution in China is characterized by high intensity and wide influence. However, the metallogenic study related to the major Triassic tectonic events has obviously been lagging behind. This paper preliminarily and systematically discusses the space-time distribution and basic characteristics of the large scale Triassic mineralization in China based on the latest research achievements. Triassic deposits in China are distributed mainly in the two main Triassic orogenic belts of the Kunlun-Qinling orogenic belt and the Red River - Ailaoshan orogen belt and their adjacent regions; Besides, there are a series of polymetallic deposits developed in the three intraplates of southern China, northeastern China and Xinjiang area. Major types of Triassic deposits mainly include: ① Cu-Ni sulfide deposits related to basic-ultrabasic rock; ② porphyry Cu-Au, Cu-Mo, Mo deposits, skarn Cu-Pb-Zn, Cu-Fe, Sn, W deposits and vein-type Au deposits related to intermediate-acid rocks and acidic plutons; ③ pegmatite-type rare metal deposits related to high temperature gas-fluids; ④ orogenic Au deposits related to tectonic-hydrothermal activities in the orogenic process; ⑤ MVT Pb-Zn deposits related to basinal fluids in the orogenic process; ⑥ carbonated vein-type Mo deposits related to mantle fluids. Most of the Triassic deposits in the Kunlun-Qinling orogen belt were mainly formed in collisional stage, or in the post-collision setting. In East Qinling area, the Triassic deposits are dominated by Mo, Au, with the formation ages mainly concentrated in 233-221Ma. In contrast, Au deposits and Pb-Zn deposits of Triassic are widely distributed in West Qinling area, Au deposits are distributed along the NW-trending brittle-ductile shear zones, and Pb-Zn deposits are largely concentrated in the two targe basins of Xicheng and Fengtai, whose metallogenic epochs are mainly in the Late Triassic (232-214Ma). In East Kunlun area, newly discovered Cu-Mo-Fe polymetallic deposits were formed in 240-210 Ma. Influenced by Neo-Tethys evolution, Triassic metal mineral resources are scattered in the Red River - Ailaoshan orogen belt, mainly distributed in Zhongdian ancient island arc, Yunnan-Guizhou-Sichuan border area in the east of the orogenic belt and Dulong area of southeast Yunnan. In Zhongdian area, the metallogenic ages are concentrated in 228-201Ma and their distribution shows the characteristics of porphyry-skarn Cu deposits in the middle part and porphyry-epithermal Cu-Pb-Zn deposits and Au deposits on both north and south sides. The dating results obtained in recent years indicate that Pb-Zn deposits in Yunnan-Guizhou-Sichuan border area were mainly formed in Triassic. Moreover, a series of Triassic W-Sn deposits have been discovered recently in Dulong area of southeast Yunnan, whose peak age is 214-209Ma. In addition to the two main collision belts, rare metal and W-Sn deposits in South China, rare metal and Mo deposits in Xinjiang, porphyry Mo deposits, Cu-Ni sulfide deposits and vein type Au deposits in Northeast China and its adjacent areas were also formed in Triassic, and all of these deposits were closely related to the collision regime, most Triassic deposits in South China were related to EW-extending tectonic-magmatic systems and derived from the emplacement of aluminum granite resulting from the remelting of thickened crust. The mineralization of Triassic deposits in Northeast China and its adjacent areas, Xinjiang, and some neighboring areas of Mongolia and Russian Altay as well as Siberia were probably related to mantle plume activities.

    • LI Xu-bing , ZHAO Can, LIU An, WEI Kai, LI Jitao

      2013,40(5):1493-1504, DOI:

      Abstract:

      Abstract:This paper divided and depicted in detail two second-order sequences and seven third-order sequences which are regionally well correlatable according to the Ediacaran system, by employing the research method of sequence stratigraphy “from lithofacies to meter-scale cycle,from depositional facies to sequence classification”. With the reservoir as the center, the authors mainly studied the temporal and spatial distribution of source rocks and reservoirs based on sequence framework, and comprehensively considered the matching relationship of source rocks and cover rock affecting reservoir formation. The source-reservoir-cap rock combinations in carbonate rock of the Ediacaran system were divided into 3 types, i.e., boundary type, transgression type and high water type. The findings indicate that the source-reservoir-cap rock combinations associated with sequence boundary in the study area have the most superior initial geological condition, the high water type is usually combined with the karst or boundary type, thus serving as another source-reservoir-cap rock combination with obvious effectiveness.

    • QU Cui-xia1, YANG Xing-ke1, HE Hu-jun1, GAO Ping2, SONG Hong-ye3

      2013,40(5):1409-1420, DOI:

      Abstract:

      Abstract:This paper deals with petrologic and geochemical features and zircon U-Pb isotope ages of the intrusive rocks from Yantan belt in Beishan area,which are mainly composed of quartz diorite, granodiorite, monzonitic granite, K-feldspar granite, granite and granite-porphyry, belonging to high-K calc-alkaline and calc-alkaline series; All the rocks are characterized by enrichment of LREE,depletion of HREE and strong Eu negative anomalies. The trace elements are enriched in LILE(Rb, Th), and depleted in Sr, Nb, Ta evidently. The zircon SHRIMP U-Pb ages of the quartz diorite and granite are (296±4.1) Ma and (294±3.7) Ma respectively,both of the data are consistent within test errors, suggesting that the rocks were formed at the beginning of the early Permian period. An analysis suggests that these intrusive rocks are I-type granite which are indicative of the underplating of the mantle material into the lower crust and the formation of these rocks in the post-collision tectonic environment after the closure of Beishan rift. The result shows that the Beishan rift was closed in the early Permian in the study area.

    • GAO Lin-zhi1, LU Ji-pu2, DING Xiao-zhong1, WANG Han-rong2, LIU Yan-xue1, LI Jiang2

      2013,40(5):1443-1452, DOI:

      Abstract:

      Abstract:In the zircon study of bentonite from the Danzhou Group and overlying strata of the Nanhua System, the authors accurately determined the age of (801±3) Ma for zircon from the Hedong Formation and (778±6) Ma for zircon from the Gongdong Formation. (778±5) Ma is the age of zircon from the Chang’an Formation, which is the bottom of the Nanhuan System, and (661±7) Ma is the age of zircon from Datangpo Formation of the intraglacial period. Some zircon ages of tuff bedding were reported for the first time from the Sibao and Xiajia Groups in Guangxi and Guizhou. In combination of the SHRIMP U-Pb age of the granite (834±4 Ma) which intruded into the Sibao Group (842±13 Ma) and the SHRIMP U-Pb age of (837±7) Ma of Bendong granite, the authors hold that the Sibao Group is Late Neoproterozoic strata below the strata of 820 Ma. These isotopic data are very important for us to redefine the age of the Sibao Group and to conduct regional correlation of strata of the corresponding period as well as to study tectonic evolution. There is an angle unconformity between the Sibao Group and overlying Danzhou Group and a nonconformity between the Danzhou Group and the Nanhuan System, suggesting the existence of three levels of tectonic factor. The revised age column will influence the whole metamorphosed basement in the Jiangnan Orogen and the constraints on the relationship of the cover strata in South China.

    • DU Xiao-dong1, 2, ZOU He-ping1, 2, SU Zhang-xin1, LAO Miao-ji1, CHEN Shi-ai1, DING Ru-xing1, 2

      2013,40(4):1112-1128, DOI:

      Abstract:

      Abstract:The Daoyaoshan-Damingshan area is located in the southwestern section of the Qinzhou-Hangzhou juncture between the Yangtze Block and the Cathayian Block.The study of the early Paleaozoic sedimentary environment and tectonic setting of this area is a key to understanding the geotectonic problems in South China. Major and trace elements of 27 pieces of samples from Cambrian sandstones and mudstones in this area were analyzed and discussed. The samples generally have high ratios of Al2O3/TiO2 ( in the range of 11.95~36.26,20.81 on average) and lower ratios of Rb/Cs(in the range of 13.02~68.27, 32.21 on average) and Cr/Zr(ranging 0.14~1.15,averagely 0.59). Geochemical characteristics, such as the plots of Ni-TiO2,Th/Sc-La/Sc and La/Th-Hf , indicate that the Cambrian sediments in the Daoyaoshan-Damingshan area were mainly sourced from the upper crustal felsic quartz rocks,with the addition of a small amount of igneous sources and ancient recirculation sediments.The distribution of trace and rare-earth elements and the data of La-Th-Sc,K2O/Na2O-SiO2, δCe,δEu,Tb/Yb,La/Sc,La/Th,Th/U as well as the comparison with different tectonic settings show that the study area belonged to a passive continent-marginal setting. In addition, such evidence as the marks of shallow-sea deposits,the data of sedimentary palaeogeography,regional geology and geochemistry suggests that during the Early Paleozoic there existed no geochemical evidence for the so called “ancient ocean in South China”.

    • CHEN Gang1, LI Shu-heng2, ZHANG Hui-ruo2, DING Chao1, YANG Fu1, LEI Pan-pan1

      2013,40(5):1453-1465, DOI:

      Abstract:

      Abstract:Geochronology of oil-gas accumulation (OGA) is a key research frontier for petroleum reservoir-forming dynamics in the multi-cycle superimposed basin. The OGA timing and stages of the Permian reservoirs in northeastern Ordos Basin (OB) are constrained in this paper by K-Ar dating of authigenic illite (AI) and indirect dating of fluid inclusions (FI) from oil-gas-bearing sandstone core samples of the Lower-Upper Permian period. AI dating results of the Permian samples show a wide time span of 178~108 Ma and a spatial decreasing trend from 178~122 Ma in the south to 160-108 Ma in the north. The distribution of the AI ages generally reveals 2-stage primary OGA of the Permian reservoirs, which were mainly developed in the time spans of 175~155 Ma and 145~115 Ma respectively with 2-peak ages of 165 Ma and 130 Ma. Additionally, the FI temperature peaks of the samples and their projected ages on AFT thermal path of the FI-host rocks not only statistically present two groups with a low and a high peak temperatures in ranges of 90~78 °C and 125~118 °C, respectively corresponding to 2-stage primary OGA processes of 162~153 Ma and 140~128 Ma in the Permian reservoirs; nevertheless, there is also a medium temperature group with the peak of 98 °C in agreement with a secondary OGA process of ca. 30 Ma in the Upper Permian reservoirs. An integrated analysis of the AI and FI ages with the regional tectonic thermal evolution reveals that the Permian reservoirs in the northeast OB mainly experienced 2-stage primary OGA processes of 165~153 Ma and 140~128 Ma during the Mid-Early Mesozoic multi-cycle burial heating processes, and then the Upper Permian reservoirs further experienced 1-stage secondary OGA of ca. 30 Ma in accordance with a critical tectonic conversion from the slow to rapid uplift-cooling process during the Late Cretaceous-Neocene period.

    • ZHANG Wan-Yi1, 2, NIE Feng-Jun3, LIU Shu-wen2, ZUO Li-Yan2, SHAN Liang2, YAO Xiao-Feng2

      2013,40(5):1583-1599, DOI:

      Abstract:

      Abstract:Located in Chagan Obo-Aououte-Chaobuleng area along the southern edge of the Siberian plate, the study area on the western slope of the southern section of the Da Hinggan Mountains metallogenic belt (northern Dong Ujimqin Banner of Inner Mongolia ) is controlled by multiple subduction, collision and connection of North China platform, and characterized by widely exposed Paleozoic volcanic-sedimentary rocks, complex structures, all kinds of intense magmatic activities, and widespread ore deposits and ore spots. The study area has special favorable geological structure and setting for mineralization. On the basis of geological survey, the authors studied geological features of ore deposits and genesis of typical deposits, and summarized metallogenic regularities of this area. The results show that there are many kinds of ore deposits such as iron, silver, copper, lead, zinc, gold, and molybdenum. The δ34S values of typical deposits vary from +1‰ to +8.6‰. The sulfur isotope compositions show different sources. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of different samples vary in ranges of 17.949~18.529, 15.370~15.691 and 37.653~38.460, respectively. The lead isotope compositions indicate that the sources of lead were wall rocks and granites. The main types of ore deposits were skarn deposits and medium-low temperature hydrothermal deposits, which were significantly affected by formation, structure and magma. In general, the wall rocks of metal deposits were Ordovician, Devonian and Carboniferous volcanic- sedimentary rocks. Skarn deposits were formed near the contact zone between the carbonate and granite, while medium-low temperature hydrothermal deposits were formed in argillite and sandstone without carbonate. NE- and NW-trending faults were important ore channels or places for ore storage. The regional ore deposits in the study area were formed in three periods, i.e. Hercynian, Indosinian and Yanshanian. They were closely related to granite intrusions in temporal and spatial distribution.

    • SUN Zhong-shi1, LIU Si-chuan1, 2, ZHENG Chang-qing1, TAN Lian2, SUN Li1, LI Juan1, SHI Lu1, CUI Fang-hua1, FAN Si-qi3

      2013,40(2):529-537, DOI:

      Abstract:

      Abstract:Ore-controlling structure is always one of the difficulties in the study of hydrothermal deposits. With Chaihezhen-Moguqi region of the Da Hinggan Mountains as the study object, this paper puts forward some conclusions on the basis of the 1:250000 geological investigation of. Chaihezhen-Moguqi region. 1. The main ore-controlling structures are Daheishan-Taipingling-Jiguanshan fracture zone and Zalantun City-Haduo River fracture zone, and the formation ages are mainly Hercynian and Yanshanian. 2. Ore-controlling structures mainly show compression, tensile and shear properties, and between the three properties, there existed the conversion between shear and tensile and between shear and torsion, with the principal compressive stress field changing in the directions of E-W, SE-NW to SSE-NNW in succession. 3. The regularities of the main ore-controlling structures, the branching ore-control structures, and the parallel and inclined ore-controlling structures are summarized in this paper. These regularities, the structures as passageways for ore fluids and the ore source were closely related to deep subduction which produced molten magma. These new ideas are of great significance for the detailed study of geological foundation, metallogenic theory and prospecting work in this region.

    • WANG Lei, LONG Wen-guo, ZHOU Dai

      2013,40(4):1016-1029, DOI:

      Abstract:

      Abstract:LA-ICP-MS U-Pb dating was conducted for zircons from four gneissic granites in Yunkai area, which were assigned to Precambrian basement rocks or Neoproterozoic intrusion in 1∶250000 geological survey. The dating yielded 206Pb/238U weighted mean of 443.3±2.6 Ma (sample 1009, Lutou Reservoir in Luchuan City), 445.7 ±2.3Ma (sample 1010, Yuedong in Luchuan city), 441.1±2.0Ma (sample 1012, Xieji in Gaozhou city) and 443.7±1.7Ma (sample 1018, Zhusha in Xinyi city), suggesting that these rocks are Caledonian products rather than Precambrian basement or Neoproterozoic intrusive rocks. In combination with previous studies, the authors hold that these granites probably resulted from partial melting of the Proterozoic materials due to the Caledonian orogeny in South China. These results and recently published data (Caledonian) for the so-called Precambrian basement rocks, such as the crystallization age or metamorphic age of gneissic granite and gneiss, indicate that Yunkai area has undergone extensive reformation by the Caledonian orogeny. Actually, the Precambrian basement of Yunkai area mainly consists of gneissic rocks and meta-sedimentary rocks, which serve as the representative of the Gaozhou complex and the Yunkai Group, respectively. The Gaozhou complex was formed during the Meso- to Neo-proterozoic and the Yunkai Group might have been formed in the Neoproterozoic. The Paleo- to Meso-Proterozoic crystallized basement does exist in Cathaysia Block, however,which is not so widely distributed as previously thought.

    • WANG Kai-ming

      2013,40(2):430-438, DOI:

      Abstract:

      Abstract:Using samples from typical sections, drilling data and geochemical information from the Devonian black shale in Guizhong depression of central Guangxi, the authors analyzed the accumulation condition of shale gas reservoirs. The results demonstrate that there exist two suites of excellent marine source rocks in the middle and lower Devonian strata of Guizhong depression, which are characterized by large thickness and extensive distribution, high abundance of organic matter and moderate buried depth, thus possessing basic conditions for the formation of shale gas reservoirs. However, the preservative condition of shale gas is very poor because of the subsequent multistage severe tectonic movements as well as the development of faults and magmatic activities in some areas. Therefore, the central and western areas of Guizhong depression with integrated strata, underdeveloped faults and magmatic activities seem to be the favorable places for shale gas exploration. It is suggested that the preservation condition is very important in exploring shale gas resources under the conditions of high organic thermal evolution extent and subsequent multistage severe tectonic movements. The preservation condition is one of the key factors for shale gas exploration in China.

    • ZHOU Jie1, 2, JIANG Yao-hui1, ZENG Yong2, GE Wei-ya2

      2013,40(5):1379-1391, DOI:

      Abstract:

      Abstract:Jingde pluton is one of the Mesozoic plutons in eastern Jiangnan orogen of northeast Yangzte Block. New LA-ICPMS zircon U-Pb dating for one granodiorite yielded an emplacement age of (141.0±1.0) Ma. The pluton is composed of monzogranite and granodiorite. New petrographical and petrochemical data show that the pluton is intermediate-somewhat acid (SiO2=66.01%~70.87%), and has high content of Al2O3 (Al2O3=14.91%~16.24%) and rich alkali (K2O+Na2O = 6.64%~8.01% ), with K2O/Na2O value ranging from 0.78 to 1.04. The pluton has relatively low content of MgO, TFe2O3 and P2O5 (MgO = 0.68%~1.06%, TFe2O3=2.0%~3.34%, P2O5 = 0.10%~0.14% ). As for trace elements, the pluton is enriched in Sr (189×10-6~452×10-6) with high Sr/Y ratios (23~66) and also enriched in light rare earth elements (LREE) ((La/Yb)N = 13 ~ 58) , but somewhat depleted in Nb, Ta, P, Ti, Y, Yb, with slightly negligible to positive Eu anomalies (δEu=0.81~1.18), similar to the geochemical characteristics of Mesozoic adakitoid in eastern China. Jingde pluton has relatively high Nd isotopes (εNd(t)=-6.28~-7.32), high εHf (t) values (-6.5~-1.1) and younger tDM2 model ages (1.4~1.5Ga), with mafic microgranular enclaves (MMEs), suggesting the importance of mantle material in the magma source. The mafic magmas ascended and heated the lower crust, triggering the partial melting of the lower crust to form the Jingde pluton, with the input of mantle-derived materials.

    • LIN Jin1, 2, LI Yun1, 2, HE Jian1

      2013,40(5):1542-1551, DOI:

      Abstract:

      Abstract:By investigating data extracted from well cores, field outcrop samples, thin sections, cathodoluminescence images and the laboratory tests, the authors conducted a comprehensive study of the Carboniferous Benxi Formation in Yanchang area of Ordos Basin and then deduced its source directions from the angles of the mineral composition, genetic type, paleocurrent features, and enrichment regularities of rare earth elements. On such a basis, the authors analyzed the sedimentary facies distribution and evolution. It is revealed that from north to south in the study area, the sandstone grains decrease in size and increase in psephicity; the quartz cluster cathodoluminescence images are mainly fuscous, light-dark brown in color, indicating metamorphic genesis. The debris component is chiefly metamorphic debris, which is up to 85.1%. The paleocurrent of field outcrop moved northward, from northwest southward and southeastward. the distribution of the rare earth elements is quite similar to the Daqingshan old land at the northeast edge of the basin. It is thus concluded that the Benxi Formation primarily originated from Yinshan-Alxa in the north. The second stage of Benxi Formation in late Carboniferous epoch constituted a major turning point in the Upper Palaeozoic evolutionary history of Ordos. Due to the invasion of the slowly-subsiding sea water from the east, the study area formed a system composed of shallow argillaceous shelf, barrier island-lagoon and lagoon. The first stage was similar to the second stage in general features, but had larger argillaceous shelf and lagoon because of the intense water invasion, which had a good performance in the sand body continuity in parallel with the coastline.

    • SHAN Liang1, 2, XU Rong-ke3, ZHENG You-ye1, 3, ZHANG Yu-lian4, CAO Liang5, PANG Ying-chun5

      2013,40(5):1600-1611, DOI:

      Abstract:

      Abstract:Beishan area is an important metallogenic belt, and the Baishantang Cu polymetallic deposit is one of the representative porphyry copper deposits. Two kinds of magmatic rocks along ore belt I in the Baishantang ore district were dated by the zircon LA-ICP-MS U-Pb method, which yielded a porphyry granite diagenetic age of (275.0±3.0)Ma (MSWD =1.17) , indicating early Permian. Two groups of ages were obtained for rhyolite porphyry: a magma zircon group of the rhyolite porphyry has an age of (371.1±2.8)Ma (MSWD=1.7) , suggesting late Devonian. The other inheritance zircon group of inheritance zircon with remarkable rounded shape or enveloped in the former group has ages of (2627±35)Ma, (2598±35)Ma, (705±44)Ma, (1722±48)Ma, (1642±51)Ma, (1213±54)Ma, which can be assigned roughly to 2.6 billion years, 1.7 billion years and 1.2 billion years, indicating that the rhyolite porphyry was related to the remelting of the upper-middle crust in late Devonian, as also shown by the geochemical characteristics.

    • WANG Yong-lei1, CHEN Yu-chuan2, WANG Deng-hong1, XU Jue1, CHEN Zheng-hui1, LIANG Ting3

      2013,40(5):1366-1378, DOI:

      Abstract:

      Abstract:Antimony is one of the dominant minerals in China, which was listed as the first global shortage minerals by British Geological Survey in 2011. In this paper, based on the mineral resource potential assessment project, in combination with data available and grade III metallogenic belt research, the authors summarized the characteristics of antimony resources in China and preliminarily assigned antimony deposits in China to 13 large ore concentration areas, with a brief description of their geological characteristics. Meanwhile, based on the existing data and new advances in the exploration of antimony deposits in recent years, this paper makes a comment on the metallogenic characteristics of the six most important antimony ore concentration areas with an analysis of their resource potentials. The authors hold that there are still some blank areas for working as well as some potential prospecting areas around the known mines. The new prospecting direction is also pointed out.

    • LI Bing1, 2, CHAO Dai-chao3, WEI Ming-jun2, 4, LI Yong-feng2, 5, LUO Zheng-zhuan2, 5, SHANG Jian-ge1

      2013,40(5):1644-1654, DOI:

      Abstract:

      The application of electromagnetic sounding method to deep iron ore exploration:A case study of the Wuyang iron mining area of Henan

    • YAN Jian-she1, NIU Shu-yin2, FENG Jian-zhi3, SUN Wei-zhi3, SUN Ai-qun2, WANG Xing-cun3, CUI Xie-xiang3, CHEN Chao2

      2013,40(2):538-548, DOI:

      Abstract:

      Abstract:The Xiaoqinling gold ore concentration area is known for its great uplift amplitude, high denudation extent, intense tectonic movement, clear structural features and concentrated distribution of ore deposits. The study area experienced four periods of folding, comprising from early to late plastic flow folding→regional EW-trending main folding →NS-trending crossing superimposed folds→transverse folding of vertical uplift, and was subjected to four periods of shearing, in order of plastic flowing →brittle ductile transpression→ductile brittle tenso-shearing →brittle forward detachment caused by uplift. The main stage brittle-ductile shearing was developed in the main limb of the weak tectonic belt. The third phase ductile-brittle shearing process of Yanshanian period provided favorable ore-hosting conditions for the large-scale injection of ore-forming fluids and mineralization. Researches show that the ore-forming fluids were mainly derived from the depth and, through the multistage evolution of mantle plume, injected into the ductile shear zone to form ore deposits via accumulation. In the ore district, there often exist one or two main ore veins which control more than 50% of metallic reserves.

    • NIU Xiao-lu1, YANG Jing-sui1, CHEN Song-yong1, LIU Fei1, XIONG Fa-hui1, LIU Zhao1, GUO Guo-lin2

      2013,40(3):756-766, DOI:

      Abstract:

      Abstract:Located in the western part of the Yarlung Zangbo suture zone, the Dongbo ultramafic rock massif is comparable with the Luobusa ultramafic rock massif which holds the largest chromite deposit in China in terms of their petrology and mineralogy. In this paper, the authors attempted to characterize its origin by examining the geochemistry of platinum group elements (PGE), major elements and rare earth elements (REE) of the harzburgites which are the main rocks of the rock mass. The harzburgites are characterized by high abundances of Os (3.52×10-9~4.36×10-9), depleted major element compositions and low REE content (0.89×10-6~1.37×10-6) which is lower than that of the primary mantle, indicating that the Dongbo ultramafic rocks belonged to depleted residual mantle rocks after a significant degree of partial melting and melt extraction. They also have high PGE content (23.97×10-9~31.98×10-9) which is higher than that of primary mantle, and display IPGE-depleted, PPGE-enriched chondrite- and primary mantle- normalized PGE patterns with Pd/Ir being 1.49~2.65. Their chondrite- and primary mantle-normalized REE patterns are all U- or V-shaped with (La/Sm)m being 1.05~3.37 and (Gd/Yb)m 0.28~0.64 (primary mantle-normalized values). These features are consistent with the opinion that the Dongbo ultramafic rocks were formed by the interaction of depleted residual mantle rocks with melts/fluids which were enriched with incompatible elements and PGE, especially IPGE relative to PPGE. In addition, the low Cu/Pd ratios (1226~3448) argue that the melts/fluids should also have high content of sulfides. The authors infer that the melts/fluids that reacted with the residual mantle rocks probably originated from the magmas produced in a subduction-related tectonic setting.

    • XU Tong1, PEI Xian-zhi1, 2, LI Rui-bao1, 2, LI Zuo-chen1, 2, PEI Lei3, LIU Cheng-jun1, CHEN You-xin1, WANG Xiao-wei1, YANG Jie1, HU Nan1

      2013,40(6):1777-1792, DOI:

      Abstract:

      Abstract: Zhangyangou bimodal volcanic rocks are located in Hengxianhe area,Sanchazi-Lueyang segment of Mian-Lue tectonic zone. The bimodal volcanic rocks consist of metamorphosed basic volcanic rocks and metamorphosed acid-intermediate rocks in close association, and the protoliths are sub-alkaline basalt and sub-alkaline rhyolitic-dacite. On account of the higher REE concentrations in basalt than in rhyolitic-dacite, the authors hold that the origin of rhyolitic-dacite was partial melting of the crustal material rather than the fractional crystallization of the basaltic magma. Basic volcanic rocks show the intraplate geochemical characteristics such as high Zr concentrations and Zr/Y ratios, and their marks of arc result from the hybridism of the crustal material. The result of U-Pb isotope dating by means of Laser Ablation Inductively Coupled Plasma Mass Spectrometry makes it clear that the formation age of the rhyolite is (728±10) Ma(n=4, MSWD=0.14). Combined with the regional geological background, the authors consider that Zhangyangou bimodal volcanic rocks were formed in a continental rift environment under the crust extensional mechanism. The formation of Zhangyangou bimodal volcanic rocks heralded the opening of Neoproterozoic Ocean. This new achievement is of important significance both for the further study of the evolution of Mian-Lue tectonic zone and the breakup of Rodinia supercontinent and other continents on the north margin of the Yangtze block.

    • DONG Lian-hui1, WANG Ke-zhuo2, ZHU Zhi-xin2, ZHAO Tong-yang2, XU Shi-qi2, ZHENG Jia-xing2

      2013,40(5):1552-1568, DOI:

      Abstract:

      Abstract:Located in the convergence zone of India plate, Tarim-Sino-Korean paleoplate and Siberia ancient plate, Xinjiang has complicated geological structure. With an analysis of the characteristics of large deformation as a starting point, this paper comprehensively summed up such characteristics of the large-scale deformation structure as its type, size, pattern, material composition, structural order and deformation stage, discussed the control role of the large-scale deformation structure over stratigraphic framework, magmatic activities, metamorphism and deformation, regional tectonic evolution and metallogenesis, and divided the tectonics into 34 large deformation structures. The relationship between the evolution of large-scale deformation structure and the mineralization was tentatively investigated.

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