2017年, 第20卷, 第4期　
刊出日期：2017-12-25

  

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  Ore-forming fluid characteristics and genesis of vein-type lead-zinc mineralization of Xiaohongshilazi deposit,Jilin Province, China

  LI Yong, REN Yunsheng, HAO Yujie, YANG Qun

  Global Geology. 2017, 20(4): 191-199. https://doi.org/10.3969/j.issn.1673-9736.2017.04.01

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  The Xiaohongshilazi mineral deposit in Jilin Province, China, is located in the accretion zone in the northern margin of the North China Block. The deposit contains two types of ore bodies:layered Pb-Zn ore bodies in volcanic rock and vein-hosted Pb-Zn ore bodies controlled by fractures. The vein Pb-Zn ore bodies are strictly controlled by tectonic fracture zones trending in S-N direction, which comprise sulfide veins or sulfide-bearing quartz veins distributed along faults or structural fissures. The ores mainly appear mesh-vein and vein structures, and also show solid-solution separation and metasomatic textures. The metal minerals are mainly sphalerite, galena, and pyrite, etc. Wall-rock alteration includes mainly sericitization, chloritization, silicification and carbonatization, etc. Microscope observations and Raman spectroscopy analyses indicate that the ore-forming fluid of the vein Pb-Zn ore bodies was mainly magmatic water with low temperature, low salinity, and a shallow depth of metallogenesis (~1.5 km). Sulfur and lead isotope analyses indicate that the sulfide source is mainly formation sulfur or biogenic sulfur, which is similar to the sulfur source of hydrothermal deposit (negative (δ³⁴S values), while the main Pb source was the upper crust with some mantle input. This article argues that the vein Pb-Zn ore body of the Xiaohongshilazi deposit is a low-to medium-temperature hydrothermal vein type related to the formation of a shallow magma chamber.
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  Dating for Jifanggou metamorphic complex in central Jilin and its tectonic implications

  WANG Zhongcheng, LU Xiaoping, ZHAO Juan, TAO Junyu, CHEN Mingjian

  Global Geology. 2017, 20(4): 200-207. https://doi.org/10.3969/j.issn.1673-9736.2017.04.02

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  Based on the results of four regional geological surveys of 1:50000 including Shulan County map in Jilin, taking Shulan area as the study area,the authors re-delineated the rock type assemblages, e.g. metamorphic rhyolite, metamorphic tuffaceous breccia lava, sericite-quartz schist and tremolite altered rock, etc., and the structural contacts between them. With the help of in-situ LA-ICP-MS U-Pb dating for zircons, it is concluded that the zircon crystallization ages of the metamorphic rhyolite, the metamorphic andesitic tuff breccia lava and the tremolite altered rock are 339.1±1.3 Ma(n=27,MSWD=0.78),351.8±1.7 Ma(n=21,MSWD=0.82),and 362.0±1.8 Ma(n=43, MSWD=2.2) respectively. The metamorphic complex is actually a set of tectonic melange which comprises the rocks in different types, sources, times, or tectonic settings, and was formed by tectonism.
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  Geochronology and geochemistry of Hutouya monzonitic granite of Qimantage, Qinghai

  WANG Yang, SUN Fengyue, GAO Hongchang, HE Shuyue, QIAN Ye, XU Chenghan

  Global Geology. 2017, 20(4): 208-216. https://doi.org/10.3969/j.issn.1673-9736.2017.04.03

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  The geochemical features of the monzonitic granite in Qimantage Hutouya deposit area, Qinghai, in respect to the mineralization, suggest that this granite belongs to weak peraluminous and high-k calc alkaline rock series. The REE of the samples show right slope with obvious LREE/HREE differentiation and negative Eu abnormity. The trace elements show enrichment of LILE (Rb, Th, U, La, Nd), and deleption of Ba, Sr, Nd, P, Ti. The Sr-Nb isotopic data indicate that the magma source is mainly aluminosilicate lower crust with a small amount of new crustal materials. The weighted mean zircon U-Pbage of the Hutouya monzonitic granite is 221±1.7 Ma, belonging to Late Triassic. The Hutouya monzonitic granite was formed in the tectonic setting of transition from compression to extension during Middle-Late Triassic.
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  U-Pb geochronology, geochemistry and tectonic implications ofdiorite from Nangnimsan of Mehe in northern Da Hinggan Mountains

  YIN Yue, WANG Li, SUN Xia, JIANG Hefang, LI Liang

  Global Geology. 2017, 20(4): 217-228. https://doi.org/10.3969/j.issn.1673-9736.2017.04.04

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  LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan, Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma, as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series, with low content of SiO₂ (52.24%-53.64%) and high Mg (MgO=5.67%-6.56%, Mg^#=61.05-65.46). The rocks are characterized by the enrichment of LREE and LILE (e.g. Rb, Ba, Pb), and relative depletion in HREE and HFSE (e.g. Ta, Nb, P, Ti), and with a high content of Sr (442.3-622.3)×10^-6, Yb (2.49-3.42)×10^-6 and Y (25.64-35.49)×10^-6, and slightly negative Eu anormaly (δEu=0.60-0.81). Based on Rb/Sr (0.15-0.25) and Rb/Nb (8.27-15.12), it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution, it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.
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  Application of sedimentary pyrite in paleo-environment:a case study of Meihe Formation

  LIU Hang, ZHU Jianwei, CHEN Jingwu

  Global Geology. 2017, 20(4): 229-236. https://doi.org/10.3969/j.issn.1673-9736.2017.04.05

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  The indices related to sedimentary pyrite are widely used in paleo-environmental studies; however its application principles and flaws have not been presented in detail so far, therefore it is necessary to review the controlling factors of them. In this study the authors described the application principles in detail, including pyrite morphology, C/S ratio, DOP, size distribution, sulfur isotope, and further discussed the C-S-Fe system in oil shale in Meihe Formation which indicates oxic or suboxic conditions during oil shale deposition. The concentration of TOC and S in the oil shale in Meihe Formation is more than that in background mudstone, and the pyrite formation is limited by sulfate. Therefore studying the indices related to pyrite proves to be of great importance.
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  Volcanic edifices of Yingcheng Formation in Changling fault depression of Songliao Basin and their seismic identification

  WU You, SHAN Xuanlong, YI Jian

  Global Geology. 2017, 20(4): 237-245. https://doi.org/10.3969/j.issn.1673-9736.2017.04.06

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  Volcanic edifices play an important role in controlling the spatial distribution of volcanic reservoirs. Taking the volcanic rocks of the Yingcheng Formation as an example, the types of volcanic formations, seismic attributes and reservoir characteristics are studied in detail using drill cores and logging and seismic data. A volcanic edifice model is established. On the basis of lithology and internal flow unit, the volcanic edifices can be divided into 4 types, including acidic lava volcanic edifices (single flow units and composite flow units), rhyolitic lava debris volcanic edifices, and basaltic lava volcanic edifices. Among these types, the acidic lava volcanic edifices (single flow unit) consist of a single lava flow unit, and the seismic profile is characterized by a hill-like blank reflection. Additionally, this type of edifice shows a contiguous petal-like pattern in the waveform classification chart. The acidic lava volcanic edifices (composite unit) consist of several acidic lava domes and plate-like lava flows, and the seismic section is a combination of parallel and hill-like reflections. This type shows noise and short-line clutter in the waveform classification diagram. The rhyolitic lava debris volcanic edifices have multiple layers of stacked volcanic debris. The seismic section features a draping continuous parallel reflection over a large area, and this type of edifice is characterized by a ripple pattern in the waveform classification diagram. The basaltic lava volcanic structural seismic section shows a large area of parallel reflectors. The waveform classification phase diagram shows a single and continuous distribution. The volcanic edifices with better physical properties have the following characteristics:the primary porosity belt is well developed, the units in the volcanic edifices are superimposed, and the volcanic structure is not integrated. Acidic composite flow unit volcanic reservoirs have the best physical properties, and the acidic single flow unit volcanic reservoirs are the worst. This study provided some reference for volcanic exploration and reservoir study in areas with few or no wells.
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  Application of high-frequency magnetotelluric method in porphyry copper deposit exploration:a case study of Duobaoshan deposit area

  LIU Caihua, QU Xin, FENG Xuan, TIAN You, LIU Yang, QIAO Hanqing, WANG Shiyu

  Global Geology. 2017, 20(4): 246-252. https://doi.org/10.3969/j.issn.1673-9736.2017.04.07

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  The Duobaoshan mine area in Heilongjiang is located in the northeast section of Xingmeng orogenic belt and is in the west side of Hegang Mountain-Heihe fault zone. There exist many deposits in this area, and its metallogenic conditions are superior, which has been one of the hotspots in geological prospecting and metallogenic research in Northeast China. On the basis of previous studies, the authors used the EH-4 electromagnetic imaging system to carry out the data acquisition of three survey lines in Woduhe Village, Duobaoshan Town, Nenjiang County. Through the analysis of apparent resistivity section under TE and TM polarization modes, integrating regional geological data, it is concluded that:① the electrical characteristics of the metal ore in this area show a relatively low resistance, and according to its resistivity difference with surrounding rocks, the geometrical structures and apparent resistivity parameters of the low resistivity bodies in the lower section of the survey line are defined, and the electrical anomalies can be identified; ②faults F1 and F2 may have a good metallogenic environment, so they are recommended for further exploration; ③ low resistance metal ore bodies have good correlation with local small structures or faults, which may play an iconic role for the delineation of key target areas; ④ in the process of using apparent resistivity to define the geometric structures of ore bodies underground, comprehensive analysis integrating the advantages of TE and TM models should be carry out to achieve more reliable inversion results.
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  Seismic inversion modeling method for faulted basins:a case study of Liaohe Beach in Bijialing region

  JING Siliang, LU Qi, WANG Dian

  Global Geology. 2017, 20(4): 253-258. https://doi.org/10.3969/j.issn.1673-9736.2017.04.08

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  There is not much correlation between sand content and P-wave impedance in faulted basins, and the prediction results cannot be guaranteed. Due to sedimentary facies control, there is inconsistency between sand content and low frequency trend of P-wave impedance, causing problems for seismic inversion modeling, which directly affects final seismic inversion results. The acoustic impedance increases with burial depth. When the same layers of sand and shale formation endure different compaction, the acoustic impedance values will be different. Therefore, The seismic inversion modeling of faulted basin is different from that of conventional basins. The authors built an inversion model using uncompact sandstone percentage, directly compensating for the low frequency trend of the inversion model. In addition, the model's intermediate frequency is similar to P-wave impedance, ensuring that the inversion results are converged correctly. The final results of the inversion can be used directly as sandstone percentage. The aforementioned method was applied to Liaohe Beach in the Bijialing region and obtained optimistic lithology inversion effects:the results were correlated well with the depositional facies map and with lithology in the well borehole. The inversion results can be used to define the sand body horizontally and can separate sand bodies vertically, which is very difficult on conventional seismic section. Therefore the inversion results played an important role in reservoir prediction.