Geological background of 1
Shuiyindong gold deposit is located in the north of Carlin-type gold deposit concentration area in southwest Guizhou. Together with a large number of gold mines such as Lannigou Gold Mine, Zimudang Gold Mine, Taipingdong Gold Mine, Getang Gold Mine, Banqi Gold Mine and Yata Gold Mine, it has become the main body of the "Golden Triangle" in Yunnan, Guizhou and Guangxi. The "Golden Triangle" in Yunnan, Guizhou and Guangxi is located in the Youjiang Fold Belt and its junction on the southwest edge of the Yangtze Platform, and belongs to the composite part of the Eurasian plate, the Indian plate and the Pacific Ocean (Han Zhijun et al., 1999).
The exposed strata in this area are mainly Devonian, Carboniferous, Permian and Triassic, which are widely distributed. Cambrian only scattered in the southern margin (in Guangxi), and Jurassic was absent. Cretaceous-Tertiary (Paleogene) is only scattered in Guangnan and southwest Luoping, mainly composed of red sandstone, mudstone and conglomerate in intermountain fault basin. Quaternary is a variety of continental deposits.
Igneous rocks exposed in this area include continental overflow tholeiite and dyke diabase, weakly alkaline diabase and weakly alkaline ultrabasic rock (Table 1).
Table 1 igneous rock assemblage in southwest Guizhou
2 Geological characteristics of mining area
The mining area is located in Huijiabao gold mining area in Xingren Anlong gold belt. In space, together with Zimuyou, Taipingdong large gold deposits, Lanmuchang large mercury-platinum deposits, Dabatian-type mercury deposits and several gold-mercury mines, it forms Huijiabao gold-mercury-thallium ore field with a length of about 20km in the east-west direction (Figure 1).
The structure of the ore field is mainly a short-axis anticline near east-west, about 20 kilometers long and 6 kilometers wide. With the Huilong fault (F 18) in the middle of the anticline as the boundary, the strata in the west section are relatively slow, with a dip angle of 5 ~ 20, and the wings are basically symmetrical; The strata in the eastern section are slightly steep, showing an asymmetric shape with steep north wing and slow south wing. The west section is Zimudang gold mine, which contains two large gold mines, Zimudang and Taipingdong, and the east section is Sanchahe gold mine, with Shuiyindong super-large gold mine and Xionghuangyan, Zhaojiaping, Puzilong and Zaofanshan gold mines. The anticline is obviously superimposed by the late ne-trending and near-SN-trending structures, and there is a primary NE-trending anticline with three groups of faults and interlayer faults (interlayer slip) in the east-west, NE and SN directions. East-west faults are developed near the axis of the anticline, basically parallel to the axis of the anticline, mostly low-angle reverse faults, slightly steep in the shallow part and gentle in the deep part. The F 105 fault exposed in the Shuiyindong gold mine area gradually disappeared in the deep Longtan Formation (P3l). The east-west faults are ore-bearing faults, which intersect with later faults and anticlines. Interlayer structures are mainly developed in the axis and side of anticline, mainly in Dachang Formation and Longtan Formation, and are important ore-controlling structures in Shuiyindong, Taiping Cave and zimudang gold deposit.
Figure 1 Regional Geological Schematic Diagram of Shuiyindong Gold Mine
(According to Guo Zhenchun, 2002)
T 1yn—— Yongning Town Formation; T 1y—— Yelang Formation; P3c+D- Changxing Formation+Dalong Formation; P3l-Longtan Formation; 1-anticline; 2- Normal fault; 3- Reverse failure; 4- Fault of unknown nature; 5- Gold deposit (point); 6- Mercury deposition (spots); 7- thallium deposit; The existence of 8-arsenic
3 Geological characteristics of ore deposits (bodies)
Shuiyindong gold deposit is a compound concealed deposit in Longtan Formation of Permian, and the ore body is dominated by stratabound type, supplemented by fracture type. Layered ore bodies mainly include Ⅲ C, Ⅲ B, Ⅲ A, Ⅱ F and Ⅰ A (Table 2), which occur in the range of nearly 30m on both sides of the shaft of Huijiabao anticline. They are layered and quasi-layered, with the same occurrence as rock strata, thin thickness, rich grade, inclined to the east and undulating, and spatially overlapping multiple ore bodies. Broken ore bodies occur in gently inclined reverse faults with small fault distance near the axis of anticline, and are strictly controlled by fault fracture zone.
Table 2 Characteristics of Layered Orebodies
The fractured ore bodies are composed of "Loushang Mine" controlled by F 105 and the orebodies controlled by hidden faults such as F 162, F 163, F 164 and F 165 of Longtan Formation. The "Loushang Mine" occurs in the collapse space of the F 105 fault zone and the core of the hanging wall traction anticline, with a tendency of S. The ore bodies are lenticular and layered, and the ore bodies are scattered sporadically, and only some resources are obtained.
The ore bodies controlled by F 162, F 163, F 164 and F 165 are lenticular in the fault fracture zone, inclined to SE, and the ore bodies swell and contract. The fault shears carbonate rocks, the fracture zone becomes wider, and the ore body is thick, but the shear is viscous.
3. 1 ore-controlling structure
The structure of Shuiyindong gold mining area is developed, which is mainly composed of Huijiabao anticline in the east-west direction and some longitudinal reverse faults along the axis of the anticline, followed by ne-trending faults, near SN-trending faults and unconformity structures.
Huijiabao anticline is a regional structure, with some small anticlines superimposed locally (Zhaojiaping anticline, east-west, about 1.5km in the area), which is a wide, gentle and short-axis anticline near east-west. Due to the later transformation, some areas were transformed into NW or NNW. The anticline in the area is about 5.3km long, the core stratum is nearly horizontal, the dip angle of the two wings strata is 10 ~ 200, and the axial plane is nearly vertical. Shuiyindong gold deposit is located in the middle of the eastern part of Huijiapu anticline, and the ore bodies are mainly distributed within 300m from the axis of the anticline. NE folds are distributed in the southwest of the mining area, and the scale is small. * * * There are 4 anticlines and 3 synclines, and the axis tracks of the surface are nearly parallel, with a length of 0.60~0.90km, which is the famous Lanmuchang anticline.
East-west faults are developed near the axis of the anticline, basically parallel to the axis of the anticline, mostly low-angle reverse faults, slightly steep in the shallow part and gentle in the deep part. The east-west faults are ore-bearing faults, which intersect with later faults and anticlines. There are faults F 10 1 and F 105 in the mining area. F 10 1 control the output of Puzilong and Zaofanshan gold mines; F 105 is the ore-controlling fault of Shuiyindong gold deposit, which controls the output of Xionghuangyan gold deposit eastward.
A series of high-angle tensional and torsional faults with NW dip developed in the southwest of the mining area, and a series of concealed reverse faults with se dip and dip angle of 28 ~ 45 developed near the axis of Huijiabao anticline, which controlled the output of broken ore bodies in Shuiyindong Gold Mine.
There is a parallel unconformity surface between the Middle Permian Maokou Formation and the Upper Permian in Shuiyindong mining area, and an interlayer fault is formed along the unconformity surface and its vicinity, which controls the occurrence of layered and lenticular flat gold bodies in the deep structural alteration variant of the mining area.
3.2 Ore characteristics
The metallic minerals formed in hydrothermal period include pyrite, arsenopyrite, white iron ore, realgar, orpiment, stibnite and cinnabar. Pyrite is dominant, arsenopyrite often coexists with pyrite, and stibnite, cinnabar, realgar and orpiment are distributed in veinlets, which are only found in Ia ore bodies and broken ore bodies. Non-metallic minerals are mainly timely, dolomite and calcite, as well as fluorite, chalcedony and clay minerals. These minerals often form the following * * * combinations: Yingshi-dolomite, Yingshi-fine pyrite-arsenopyrite, Yingshi-calcite-realgar-orpiment-stibnite-cinnabar and coarse pyrite-goethite. The main structures of ores are flaky, biological remains, disseminated, massive and veinlets; The structure is mainly self-granular, strawberry-like, biological illusion and replacement.
The results of mineral phase analysis are shown in Table 3.
Table 3 Ore Phase Analysis Results w(Au)/ 10-6
Note: The data in the table were analyzed by the laboratory of Guizhou 105 Geological Brigade and detected by HYX-3A fluorescence analyzer.
Pyrite is the main carrier of gold, which can be divided into sedimentary pyrite and hydrothermal pyrite. The former pyrite is mostly strawberry-shaped or autogenous cube and pentagonal dodecahedron crystal, with large particle size and strip (grain) shape. In hydrothermal stage, pyrite particles are fine and disseminated. Four kinds of pyrite with different morphological and structural characteristics: strawberry-like, bioclastic, coarse-grained and fine-grained.
3.3 surrounding rock alteration and mineral generation sequence
Wall rock alteration mainly includes silicification, dolomitization and pyritization, followed by hydrothermal alteration such as arsenopyrite, male (female) yellowing, clay and fluorite. Among them, silicification, dolomitization and pyritization (associated arsenopyrite) are closely related to gold deposits, and all gold deposits have these three alteration characteristics. Gold deposits (mineralization) often occur in areas with strong alteration and superposition of various alterations, and rocks without alteration or single alteration do not contain gold or have low gold content.
Hydrothermal mineralization of gold deposits can be divided into three stages, and the corresponding mineral assemblage and generation sequence are listed in Table 4.
Table 4 Metallogenic sequence of Shuiyindong gold deposit
4 Geochemical characteristics
4. 1 constant element
The ores in Shuiyindong gold mine can be divided into three categories. Carbonate rock type (impure limestone), siliceous breccia type (breccia claystone, breccia siltstone and breccia limestone) and calcareous sandstone type (calcareous sandstone and calcareous siltstone). Carbonate-type ore is the main ore, followed by breccia-type ore, and calcareous sandstone-type ore only occurs in small ore body P3l 1. The main chemical compositions of carbonate ores are shown in Table 5. See Table 6 for ore composition analysis of different ore bodies.
4.2 Trace elements
The main rock types of the ore-bearing rock series in Shuiyindong Gold Mine are limestone, marl, mudstone, argillaceous siltstone and siliceous rock, which generally have high arsenic, antimony, copper and thallium contents, much higher than normal similar rocks, and the arsenic content is hundreds of times higher than similar rocks. Arsenic, antimony, copper and thallium are characteristic indicator elements of gold mineralization in Shuiyindong gold deposit.
Table 5 Main chemical composition of carbonate ore w(B)/%
Note: The data were analyzed and tested by the Key Laboratory of Deposit Geochemistry of China Academy of Sciences, and the total chemical analysis method was adopted.
The original contents of Au, As, Cu, Sb and Tl in all kinds of rocks (based on unmodified samples) have little difference, and their changes are far lower than those caused by mineralization and alteration. The ratio of Au, As, Cu, Sb and Tl in various mineralized rocks to similar non-mineralized rocks is as high as tens to hundreds. Among them, Au, As and Tl are the highest. Au, As, Cu, Sb, Tl and Pb in the ore-bearing rock series are significantly higher than those in the same kind of unaltered rocks, while Ti, Sc, Nb, Ta, Zr, Hf, V, Cr, Co, Sn, Ga, Ge, Cd, Rb, Cs, Ba, Mn, Zn, th and REE have little change.
Table 6 Composition Analysis Results of Ore Combination Samples
Note: The data were analyzed and tested by the Key Laboratory of Deposit Geochemistry of China Academy of Sciences; Total chemical analysis and plasma mass spectrometry.
4.3 Rare Earth Elements
The content of rare earth elements in ore bodies ranges from10.8×10-6 to 37.0×10-6, with an average value of 2 1.8× 10-6. The value of δEu is between 0.88- 1.20, and the average value is 1.03. Except for a few samples with weak negative anomalies, there is no Eu anomaly or positive anomaly. The average σσREE of surrounding rock is 24 1.9× 10-6, and the average δEu value is 1.00, which is normal. The average σσREE ratio is 48. 1× 10-6, and the average δEu value is 0.8 1, showing a weak negative anomaly. The average σσREE of limestone is 9.59× 10-6, and the average δEu is 0.65, with negative anomalies (Table 7).
Table 7 Rare Earth Element Analysis Results and Characteristic Parameters w(B)/ 10-6 of Shuiyindong Gold Mine
Note: Ⅲ C-4 and Ⅲ C-5 are siliceous rocks, and the rest are tuffaceous bioclastic limestone type; There are 6 surrounding rocks on average, and the lithology is mainly clay rock and siltstone with a small amount of limestone. The two ore-free sections are generally limestone with more tuff. According to Shen, et al, 2005.
4.4 isotope
The sulfur isotope analysis results of Shuiyindong Gold Mine are shown in Table 8. The lead isotopic composition and related parameters of hydrothermal pyrite in ore are shown in Table 9.
Table 8 Sulfur Isotope Analysis Results of Shuiyindong Gold Mine
(According to Liu Jianzhong, 2006b)
Table 9 Lead Isotopic Composition and Related Parameters of Hydrothermal Pyrite in Shuiyindong Gold Mine
Note: δ β = (β-β m)/β m×1000; δγ=(γ-γm)/γm× 1000； β = 207 Pb/204 Pb； of the sample; γ = 208 Pb/204 Pb of the sample; β m of mantle = 207 Pb/204 Pb =15.33; The γ m of the mantle is 208 Pb/204 Pb = 37.47; The testing unit is Isotope Laboratory of Yichang Institute of Geology and Mineral Resources. According to Liu Jianzhong, 2006b.
4.5 Characteristics of Inclusions
The shape of inclusions is isolated and irregularly distributed, characterized by negative crystal shape, and the diameter is generally 5 ~ 60μ m, and most of them are10 ~ 50μ m. According to the phase characteristics of inclusions at room temperature (25℃) and the phase changes during freezing, the types and components of inclusions can be divided into four categories: liquid, gas and gas-liquid phase VCH4+N2+CO2.
The results of temperature and pressure measurement of nearly 200 fluid inclusions show that the homogenization temperature of fluid inclusions in the main metallogenic period is 200 ~ 220℃ and the salinity is 5% ~ 6%. The pressure of ore-forming fluid is1000×105 ~ 2000×105, which shows the properties of overpressure fluid. It has the characteristics of hydrothermal mineralization at medium-low temperature and ultra-high pressure.
refer to
Guo Zhenchun. 2002. "Two-layer" model of Huijiabao gold ore field in southwest Guizhou and its prospecting significance. Gold Geology, 8 (4): 18 ~ 23.
Han, Wang, Feng Jizhou, et al. Geology and exploration of gold deposits in southwest Guizhou. Guiyang: Guizhou Science and Technology Press.
Liu Jianzhong, Liu Chuanqin. 2005. Geochemical characteristics of rare earth elements in Shuiyindong gold deposit, Zhenfeng County, Guizhou Province. Bulletin of Mineral Rock Geochemistry, 21(2):135 ~139.
Liu et al. 2006a. Metallogenic conditions and metallogenic model of Shuiyindong stratabound super-large gold deposit in Zhenfeng County, Guizhou Province. Geology of China, 33 (1):169 ~177.
Nhat Minh Dang, Liu, et al. 2006b. Study on inclusion and isotope geochemistry of Shuiyindong gold deposit. Geology of Guizhou, 23 (1): 5 1 ~ 56.
Shen, Zhang Zhuru, Zhou, et al. 2005. Geochemical characteristics of ore-bearing rock series in Shuiyindong gold deposit, Zhenfeng, Guizhou. Geochemistry, 34 (1): 88 ~ 95.
(Li,, writing)