2020 Vol. 26, No. 3

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Development process of fault structure and formation and evolution of ore-controlling structure: A case study of the Zoujiashan uranium deposit
CHEN Bailin
2020, 26(3): 285-298. doi: 10.12090/j.issn.1006-6616.2020.26.03.027
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Hydrothermal lode deposit is mainly controlled by fault structure. The ore-bearing or ore-hosting structures controlling the emplacement of ore-body and ore vein are often minor second-order faults or fractures,while the major faults are generally considered as passage-ways for ore fluids; however,they usually contain no ore,even no trace of mineralization alteration or evidence of ore fluids passing by. According to the fracture criterion of rock mechanics,a micro fracture with micropores or defects forms first under compression stress,then the micro fracture gradually extends,forming a minor fault,and finally breaks through to form a main fracture. Relevant simulation experiments also confirmed that in the case of basement faults,the development process of caprock fracture can be divided into four stages:R-fracture stage,P-fracture stage,D-fracture stage and through-going stage,finally forming a major fault with braid structure. The ore-bearing structure of the Zoujiashan uranium deposit,developed on the basis of "X" shear joints and formed by continuous (progressive) deformation,is composed of arcuate fault planes with lenticular rocks in between. The ore-belts (or ore body groups) are arranged obliquely,indicating that the ore-controlling structure is a high-degree hidden left-slip normal fault with NEE-trending (50°~65°) and low-middle angle(30°~45°) dipping to northwest. The ore-bearing structure went through initial formation,forming and metallogenic stages,followed by the through-going of the Zoujiashan-Shidong major fractures and uplift and exhumation,and finally formed the current state.
Ore-forming fluid fracturing treatment of ore-bearing fractures and the characteristics of the related veins in porphyry deposits
ZHAO Maochun, WU Baoqian, YU Haijun, HE Yun, TANG Qiong, YANG Jinsong, LI Jiacheng, ZHANG Sishan, WANG Guanglong
2020, 26(3): 299-315. doi: 10.12090/j.issn.1006-6616.2020.26.03.028
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Veins in porphyry deposits are well developed and their crosscutting relationship is complex. The initial fractures,where the veins fill in,are connected in varying degrees. Mineralization is a process of migration,filling and precipitation of ore-bearing fluid in the existing fractures. During the multi-stage mineralization,if there is no structural stress transformation,it seems that there should not be a large number of multi-stage cutting of veins. However,a large number of veins,which intersect each other,are widely found in porphyry deposits and other hydrothermal deposits. Based on the mechanism of hydraulic fracturing,this paper discusses the fracturing effect of ore-forming fluid on fracture forming. The multi-stage fluid activities result in the well-developed fractures by ore-forming fluid fracturing,which greatly expand the scale and scope of the ore-bearing space. This kind of fractures is an important genetic type of ore-bearing fractures in porphyry deposits. Due to the multistage fluid activities and the rapidity of fracture growth,the cross-cutting between the veins and fractures caused by the fluid fracturing is more common than that caused by the transformation of structural activities on veins. These viewpoints can well explain the frequent and complex cutting and faulting of veins in porphyry deposits.
Physical simulation analysis of the Cenozoic fault activities and structural deformation mechanism of the Youjiang area
NIE Guanjun, YU Hongmei, HE Sheng, LI Bingsu, PAN Lili
2020, 26(3): 316-328. doi: 10.12090/j.issn.1006-6616.2020.26.03.029
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The NW-trending faults in the Youjiang area originated from synsedimentary faults developed in the Youjiang Basin of Late Paleozoic. In Cenozoic these equidistantly spaced faults have undergone multiple left-lateral strike-slip activities,which then led to a simple-shear deformation of the Youjiang area. A 3-D sandbox model is designed to study the deformation mechanism of the Youjiang area. The experimental results show that the NW-trending faults were reactivated and a strikingly left-lateral strike slip occurred under the left-lateral movement and the clockwise rotation of the Indochina block. And then the lateral compression of the Sichuan-Yunnan block resulted in a new round of fast left-lateral strike-slip of the NW-trending faults in the Youjiang area,and it also resulted in crustal compression and thickening in the western part of the Youjiang area. Both the left-lateral strike-slip activities of the NW-trending faults and the simple-shear deformation occurred in the Youjiang area in Cenozoic were driven by the extrusion of the Indochina Block and the Sichuan-Yunnan Block,and they can be viewed as one of the consequences of the India-Eurasia collision.
Characteristics of ore-controlling structures and ore-prospecting of the Xitieshan lead-zinc deposit, northern edge of the Qaidam basin, NW China
FENG Zhixing, CHEN Zhengle, LI Zhengming, ZHAN Weilu, SHI Yonghong, CHEN Bailin, JIANG Wan, LIU Bo, LI Jilin, TAN Renwen
2020, 26(3): 329-344. doi: 10.12090/j.issn.1006-6616.2020.26.03.030
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The Xitieshan deposit,one of the large-size lead-zinc deposits located at the northern edge of the Qaidam basin in western China,is related to marine Volcanic-Sedimentary Hosted Massive Sulfur deposit (VSHMS). Most prior researches are focused on the mineralization age,the nature of ore-forming fluid,and the genesis of the deposit by the method of petrology,geochemistry,and isotopic dating. However,the characteristics of ore-controlling structures,which are essential to prospecting and expanding the mining resources,have been controversial for long time,and it is generally believed that it was the fold that controlled the production of ore bodies in the deposit. This paper mainly presents field evidences to discuss the characteristics of folds and faults and its controlling roles to the distribution of ore bodies,and further to provide the basis for the mining prospecting exploration. Our field investigation and comparative analysis showed that there was no large-scale syncline or anticline in the deposit and only a monocline composed of the Ordovician Tanjianshan Group in general,although some interlayered folds were well developed,including A-and B-type. Both the fold hinge and the strench lineation of A-type fold in a-segment of the Ordovician Tanjianshan Group are dipping to SE-ward,consistent with the dipping tendency of the whole ore-bodies in the deposit,but different with those in d-segment of the Tanjianshan Group as dipping to NW-ward. There are six large-scale NWW-trending faults in the deposit,named as F1 to F6 from the northeast to southwest. The F1 fault in the deposit probably developed on the base of ductile deformation in early stage. And the latterly nappe thrusting of the fault resulted in the reverse of ore-bodies and host rocks near the fault. Large-scale sinistral strike-slipping faulting of the F2 fault played important roles on the convergence together of different segments of the Tanjianshan Group,and also the missing of some ore-bearing geological bodies. Field mapping between the Zhongjiangou and Wuminggou areas revealed that the orientation of the F3 fault gradually changed from 330-trending in northwest to 290-trending in southeast. And several branch sinistral strike-slipping and normal faults were identified in the southeastern end area,composing a pattern of horsetail structure in the shape,which truncated ore-bodies and host rocks. Therefore,ore-prospecting directions were proposed based on the ore-controlling structures together with the metallogenic models of the deposit,suggesting that the deep region in the southeastern side should be one of most favorable ore potential areas,and the dislocation places of ore-bodies by the F3 fault and its branch sinistral-normal faults in the prospecting Line 07 were further forecasted for example.
Structural analysis and ore-controlling model of the Xiaohe lead-zinc deposit in ore-concentrated area, northeastern Yunnan, China
ZHAO Dong, HAN Runsheng, WANG Jiasheng, ZHANG Xiaopei, CUI Junhao, LI Ziteng
2020, 26(3): 345-362. doi: 10.12090/j.issn.1006-6616.2020.26.03.031
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The Xiaohe lead-zinc deposit is one of the few typical lead-zinc deposits controlled by NW-trending major faults in the ore-concentrated area in northeastern Yunnan,China. The spatial distribution of mineralization and alteration is strictly controlled by structures. In order to ascertain the characteristics of the controlling effect of the structures on mineralization and alteration in this area,the large-scale tectonic-altered lithofacies mapping method in different level adits is adopted. The faults in different directions were screened and the characteristics of different mineralization and alteration in different level adits were systematically analyzed. The results show that:the composition,type and structure of mineralization and alteration of the Xiaohe lead-zinc deposit are relatively simple. Wall rock alteration is dominated by hydrothermal dolomitization,calcilization,silicification and pyritization. The mineralization mainly occurs to sphalerite and galena. Tectonic assemblages reflect the existence of a 6-phase tectonic system in the mining area:Caledonian-Haixi period,Early-Mid-Indosinian period,Late-Indosinian period to Early-Yanshan period,Middle Yanshan period,Late Yanshan period and Himalayan period. Large scale migration of ore-forming fluid occurred along the NW direction of tensile or torsional faults in the late Late-Indosinian and Early-Yanshan. Meneralization occurs in favorable structural parts such as the upper wall of the faults and its supporting secondary faults,structural fracture zones,joint fractures,etc. The mineralization-alteration zone was formed with the fault as the center and was distributed with zone. The sequence is mineralized marginal zone (Ⅰ),mineralized transition zone (Ⅱ) to mineralized central zone (Ⅲ). Finally,the structure-controlling model of the Xiaohe lead-zinc deposit was established. This understanding has important guiding significance for the prospecting prediction of similar deposits and the border area between Sichuan,Yunnan and Guizhou province.
Analysis of ore-controlling structure in the Changgou gold deposit of the northern Hanyin gold orefield, southern Qinling Mountains
ZHANG Kang, YANG Xingke, YU Hengbin, GUO Runping, WANG Jiawei
2020, 26(3): 363-375. doi: 10.12090/j.issn.1006-6616.2020.26.03.032
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The ore-bearing rock series in the northern Hanyin gold orefield of the southern Qinling mountains mainly consists of the shallow metamorphic rocks in the Silurian Meiziya formation,which underwent complex tectonic deformation in Mesozoic,and the brittle-ductile shear zone is a good place for the enrichment of altered rock type gold deposits in the Meiziya formation. Based on the comprehensive analysis of the metallogenic geological background and ore-controlling tectonic characteristics of the newly discovered Changgou gold deposit and its adjacent areas in the northern Hanyin gold orefield in recent years,the ore-controlling tectonic characteristics and ore-forming rules of this type of gold deposits in the northern Hanyin gold orefield are summarizes,and the hydrothermal genetic type of the Changgou gold deposit is preliminarily discussed. It is found that there are five brittle-ductile shear zones developed in the northern Hanyin gold orefield,and their tectonic patterns and metamorphism are diverse and multistage,among which the second deformation is closely related to gold mineralization. The Changgou gold mining area is controlled by the regional brittlle-ductile shear zone DSZ3 (≈RF5) and S2 bedding in multi-stage tectonic replacement,and the ore-controlling structure is characterized by oblique arrangement. The study of ore-bearing fluid inclusions shows that the formation of ore-bearing fluid inclusions in low-medium-temperature hydrothermal environment is mainly due to the accumulation and mineralization of gold-bearing hydrothermal fluids in favorable tectonic areas such as the weak deformation zone,dense shear joint zone or cleavage zone near the interface of two local lithologic differences and between foliation planes. Therefore,the brittlle-ductile shear zone and its multi-phase plane displacement and dense foliation,shear joint zone and hydrothermal altered rock are the main ore-controlling structural types. Further prospecting and prediction work should focus on the trend extension and dip extension of the brittle-ductile shear zone,and more attention should be paid to the law of lateral oblique accumulation.
Model of tectonite-lithofacies zoning in ore-controlling faults of the Qingshan lead-zinc deposit in northwestern Guizhou
SONG Danhui, HAN Runsheng, WANG Mingzhi, ZHANG Yan, ZHOU Wei
2020, 26(3): 376-390. doi: 10.12090/j.issn.1006-6616.2020.26.03.033
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The Qingshan lead-zinc deposit is one of the typical deposits in the Weining-Shuicheng metallogenic subzone in the northwestern Guizhou ore concentration area, and orebodies are strictly controlled by both tectonic and lithologic factors. The tectonites in the ore-bearing fault zone with remarkable zoning characteristics are not only the hosts of deformation processes but also the responses for the environment of structure deformation. This paper focuses on the weak links in the study of the genetic connection between weakly altered tectonites and hydrothermal metallogenesis in the oblique strike-slip tectonic condition. Based on the tectonite-lithofacies zoning mapping method, we analyzed joints and fracture structures in different lithofacies belts, and systematically collected directional tectonite samples for microstructural and geochemical analysis. The tectonite type, material composition, internal texture and structure, and zoning characteristics were analyzed, and the zoning model of tectonite-lithofacies in this deposit was constructed. That is, outward from the orebody, the zoning sequence is as follows:the tensile initial cataclasite zone→the sludging zone (Level 1, 3 and above)→the torsional initial cataclasite zone→the compressive initial cataclasite zone. Pyritization, lead-zinc mineralization, calcitization and weak dolomitization occur in the torsional initial cataclasite zone, and calcitization occur in the compressive initial cataclasite zone. Mineralization-alteration changes from strong to weak as it moves away from the ore body, and the mineralization environment gradually decreases with the temperature, showing a tendency of oxidation→weak oxidation→weak reduction→reduction. Combined with the stress field analysis of macroscopic and microscopic structure, it is believed that different types of tectonites outside orebodies were caused by the changes in the partial stress field at different locations of the uniform tectonic stress field, and the secondary faults in the footwall of NW trending faults not only controlled the location and morphology of orebodies but also controlled the outward tectonite-lithofacies zone.
Ore-controlling rules of fault structures in the Wangjiaping gold deposit in Shanyang County, Shaanxi Province
XUE Yushan, WANG Ruiting, WANG Chao, MEN Wenhui, LIU Xinwei, HU Xishun, NING Jiangchao, GU Yuming, SONG Shuguang
2020, 26(3): 391-404. doi: 10.12090/j.issn.1006-6616.2020.26.03.034
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The Wangjiaping gold deposit in Shanyang County, Shaanxi province, is a newly discovered carlin-type gold deposit in the southern Qinling orogeny, characterized by obvious ore-controlling structure and developed mineralization and alteration. The mining area is located in the north wing of the Longtougou anticline. The Mantoushan-Daping-Yinghuahe fault F2 and its secondary fault F2-1 run through the whole area, and the ore body occurs in the south of the secondary interbedded fault. Based on the field survey and the classification of metallogenic periods, the tectonic types and their characteristics were sorted out, the tectonic ore-controlling rules were summarized, and the prospecting direction was proposed. Three periods about the ore-forming processes have been identified based on the detail petrography observation. The quartz-sulfides stage is the major ore-forming stage. Four trends of faults have been discovered in the Wangjiaping deposit. It is believed that the EW-trend fault was the main ore-bearing structure formed at Indosinian period, which also acted as the major ore-transmitting structure. The other trends of faults, including NE, NW and near SN-trend ones, were formed at Yanshanian Period, obviously cutting and shifting the ore bodies. The "#"-type structure formed by the NE, NW and EW-trend structures promoted the oxidation enrichment of the ore bodies, leading to the rich orebodies. Based on the study of ore-forming tectonic system of the deposit, the regularity of lateral prostration was discovered firstly, and the plunge angle is about 36° according to the calculation. The fault F2 and its secondary faults (e.g.F2-1) in the south, the deep part of orebody Ⅲ and the lateral direction area of orebody Ⅱ have great prospecting potential, and they are the primary areas for further prospecting.
Model of rock and ore controlling structures in the Baoshan Cu-Pb-Zn polymetallic deposit, southern Hunan province, China
CHEN Pengyuan, WU Peng, HAN Runsheng, ZHOU Mengxiang, LI Maoping, ZHAO Dong, JIANG Longyan
2020, 26(3): 405-418. doi: 10.12090/j.issn.1006-6616.2020.26.03.035
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The Baoshan Cu-Pb-Zn polymetallic deposit, located in the overlapped part of the Nanling EW-trending tectonic belt and the Leiyang-Linwu SN-trending tectonic belt, is a typical large and super-large mineral deposit in this area. The deposit and ore-bodies are spatially closely related to the early Yanshanian granodiorite porphyry and obviously controlled by the structure. Based on precise measurement of the large-scale structural sections, this paper analyzes the structural types and their main characteristics, and summarizes the rules of structural control on rock and ore. The results show that the SK-type Cu-Mo ore-bodies are mainly controlled by NE-NEE-trending folds. The hydrothermal vein-type Pb-Zn-Ag ore-bodies are mainly controlled by the interlayer faults of fold flanks and the NE-trending compression-torsion faults. The direction of the max principal stress of the tectonic stress field experienced the transformation from near SN-trending before mineralization to near EW-trending during mineralization to NE-SW-trending after mineralization. The NE-NEE-trending compression-torsion faults are the main ore guiding structures, and the NWW-trending compression-tension faults are the main rock control structures. The structures not only control the distribution of ore-forming bodies, but also control the change of ore-forming types. On this basis the model of rock and ore controlling structures is established, indicating the deep NW-trending of the known ore-bodies is the favorable prospecting area. This study provides favorable evidence for ore-prospecting work at depth, and has reference significance for the suggesting of prospecting plan and deep exploration of the Pingbao ore field.
Element association anomaly of tectonites and prediction of concealed deposit in the Xiaozhuqing exploration area on the periphery of Huize lead-zinc mine area, northeastern Yunnan Province
GONG Hongsheng, HAN Runsheng, LI Ziteng, REN Tao, LI Wenyao, WANG Jiasheng, CHEN Gang
2020, 26(3): 419-431. doi: 10.12090/j.issn.1006-6616.2020.26.03.036
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The Huize super-large Ge-rich Pb-Zn deposit in Yunnan is located on the southwestern margin of the Yangtze block and east of the Xiaojiang deep fault in Sichuan-Yunnan-Guizhou lead-zinc metallogenic areas, and it is controlled by the NE-trending thrust-fold structures. Although the Huize Pb-Zn deposit has a high research level, the geological research level of the Xiaozhuqing exploration area, which is a key prospecting area on the periphery of the mining area, is relatively low. According to the prospecting method of Metal-element association halos within mineralization-related fault zones(MEAHFZ), through geological survey and structural analysis, it is considered that the Xiaozhuqing exploration area has good metallogenic geological conditions, and its tectonic style is the fault-fold structures composed of the Yinchangpo sinistral oblique strike-slip fault and its hanging wall inverted and tilted anticline, which is basically consistent with the ore-controlling structural style of the Kuangshanchang deposit and Qilinchang deposit. Combined with previous research results, it is determined that the structural system in the exploration area has developed from the NE structural zone to the late SN structural zone to the EW structural zone since the Indosinian period. On this basis, based on the 1:10000 tectono-geochemistry, altered lithofacies mapping and gravity profile survey, a comprehensive map of Pb-Zn-Cd element combination anomaly and Pb, Zn single element anomaly is drawn. Combined with the gravity anomaly in this area, it is found that the comprehensive anomalies distribute along the NE-directed compressive and torsional interlayer fault zone in the Upper Sinian Dengying Formation and Lower Carboniferous Baizuo Formation of the hanging wall of Yinchangpo fault, and the key prospecting target areas I, Ⅱ and Ⅲ are delineated. This achievement not only indicates the direction for the exploration and verification of the exploration area, but also has important guiding significance for the prospecting prediction of similar deep and peripheral deposits.
Methods of ASTER remote sensing data used in extracting mineralization and alteration information in the Hutouya mining area of the Qimantag metallogenic belt, Qinghai Province
CHENG Sanyou, YANG Xingke, YU Hengbin, LIU Wei
2020, 26(3): 432-442. doi: 10.12090/j.issn.1006-6616.2020.26.03.037
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Using ASTER remote sensing images as the data source, the extraction of mineralization and alteration anomaly in the Hutouya mining area of the Qimantag metallogenic belt in Qinghai Province is studied through two methods. One method is using the minimum noise component (MNF) transform, pixel purity index (PPI), n-Dimensional Visualization to do the end element recognition and mixture tuned matched filtering (MTMF), in order to obtain the mineral distribution map of the mining area. The other is principal component analysis, through which ferric contamination anomaly is extracted in ASTER1, 2, 3, 4 band, skarnization alteration anomaly in 1, 3, 4, 5 band, montmorillonite, illite and sericite in 3, 4, (5+6)/2 band and calcite, biomica, chlorite and other minerals in 1, 3, 4, 8 band. The results of remote sensing extraction of alteration anomaly verified by ArcGIS10.1 software are in good consistency with the mineral deposits and mineralization points determined by the field survey, indicating that the extraction results and the data processing method are reliable, which is of great guiding significance for the expansion of the prospecting scale and the discovery of mineralization enrichment areas.
Geochemical characteristics of gold-bearing minerals and its geological significance in the Ashawayi gold deposit in the southwestern Tianshan Orogen
ZHANG Tao, CHEN Zhengle, HUANG Hongye, ZHANG Wengao, ZHANG Qing, PAN Jiayong, ZHOU Zhenju, ZOU Mingliang, FENG Hongye, WANG Xiaohu, HAN Fengbin, SUN Yue, HUO Hailong, MA Ji, YANG Bin
2020, 26(3): 443-458. doi: 10.12090/j.issn.1006-6616.2020.26.03.038
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Ashawayi gold deposit, the second largest gold deposit in the southwestern Tianshan Orogen, NW China, is located at the southern margin of the Central Asian Orogenic Belt of the "Asian Golden Belt". Detailed field observations showed that the regional area experienced two tectonic processes from early compression to lately strike-slip extension during the Paleozoic, and the mineralization was related to the transition from compression to extension. By the methods of mineragraphy, EMPA, SEM and S isotope analysis, the gold-bearing minerals in the ore deposit, the occurrence state of gold, the source of ore-forming materials, were determined in this paper, suggesting that gold-bearing minerals should be mainly composed of arsenian pyrite and some arsenopyrite. The formation of arsenic pyrite can be divided into three stages, i.e. sedimentary diagenesis stage (Py1), early ore-forming stage (Py2), and main ore-forming stage (Py3). The Py2 and Py3 are rich of As-Te, and deficit of S-Fe, while the content of S and As is significantly negatively correlated. The ratio value of Co/Ni indicates that the pyrite should be the origin of deposit-hydrothermal. The gold is mostly hosted in arsenic pyrite as the form of nano-scale "visible" natural gold (Au0). The δ34S value of pyrite and stibnite changes from 9.5‰ to 16.3‰, suggesting that the sulfur in ore-forming fluid should be a thermochemical reduction product of marine sulfate and ore-forming material probably resourced from the stratum. Therefore, the Ashawayi gold deposit should be a typical medium-shallow orogenic-type gold deposit, and the buried depth of ore-bodies is relatively shallow, suggesting a favorable prospecting potential in the deep.