Hechi Danchi ore field

Publish: 2021-04-22 00:38:03

Nandan Hechi tin polymetallic metallogenic area is a famous tin polymetallic metallogenic belt in China. It is mainly located in MANGCHANG Hechi Wuwei area of Nandan. It is located in the junction zone of Youjiang regenerated geosyncline and Guizhong depression in geotectonics. It is NW-SE trending and controlled by Ziyun Nanning Regional large fault zone. The main exposed strata are Devonian, Carboniferous, Permian and Triassic, and the main lithology is carbonate rock and clastic rock. Among them, a set of turbidite is developed in the middle and Lower Devonian, while reef limestone, siliceous rock, quartz and other exhalative rocks occur in the middle and Upper Devonian

There are NW trending basement faults and nearly Sn trending fault block structures in the area; The cover structure is dominated by the NW trending Danchi anticline and Nandan Kunlunguan fault. The fold shape is generally tight, narrow and long, arranged in echelon, with linear fold characteristics. Five short axis anticlines formed by the superposition of NE trending structures control the distribution of Mayang, MANGCHANG, Dachang, BEIXIANG and furongchang ore fields respectively

the magmatic rocks in the area are mainly Yanshanian intermediate acid hypabyssal rocks with Longxianggai rock body, and sporadically distributed in MANGCHANG area in the north as batholith, batholith, dyke and dike. Rock types include granite porphyry, quartz porphyry, diorite porphyry, quartz diorite, quartz andesite porphyry, etc. According to the gravity anomaly, there are concealed rock bodies in Wuwei area in the south. The rocks are distributed in beaded shape on both sides of the Danchi fault, or intrude into the axis of the Danchi anticline, MANGCHANG anticline and Dachang anticline

1:200000 stream sediment survey results show that tin, copper, lead, zinc, silver and other elements have good anomalies, and 6 comprehensive anomalies are delineated, including 3 known ore anomalies and 3 unknown ore anomalies. The anomalies are mainly distributed in Danchi large fault zone and Bama fault zone, and the strike of anomalies is basically consistent with the strike of faults, which is obviously controlled by faults. The anomalies distributed in Danchi large fault zone are closely related to tin polymetallic deposits, with long axis shape, obvious concentration center and outer, middle and inner concentration zoning. The content characteristics of each element abnormal concentration area: the content of tin is more than 70% × 10 - 6 , copper (57-166) × 10 - 6 , Pb > 220 × 10 - 6 , Zn > 469 × 10 - 6 , silver greater than 859 × 10^-9

There are many kinds of mineral resources in this metallogenic area. There are 11 large-scale deposits (Changpo Tongkeng and Bali Longtoushan tin polymetallic deposits reach super large scale), 7 medium-sized deposits and 9 small-sized deposits, which are mainly distributed in MANGCHANG, Dachang and Wuwei ore fields. The preliminary statistics show that the accumulated proven reserves of tin are 125 × 10 4 t, lead zinc 780 × 10 4 t, Sb 130 × 10 4 t, copper 33 × 10 4 t, tungsten 18 × 10 4 t, silver 8000t. The prospecting potential is huge

Dachang tin polymetallic deposit is one of the most important tin polymetallic deposits in the world, which is located in the south of Danchi ore concentration area in Northwest Guangxi. Due to its large scale, complex element combination and diversified occurrence characteristics, Dachang tin polymetallic deposit has been highly valued by the geological circles at home and abroad for a long time, and has been a hot spot in the study of deposit geology. Up to now, there are still different views on the genesis of Dachang tin deposit, which can be divided into three categories: 1. It is considered that the deposit was formed in Yanshanian, belonging to epigenetic metasomatic filling deposit, which is genetically related to granite (Chen Yuchuan, 1964, 1965; 2; Chen Yuchuan et al., 1985, 1993; Li Xilin et al., 1981; Zhang Ping, 1983; Ye Xusun, 1985, 1986; Liang Zhenting et al., 1985). Especially in the 1990s, Chen Yuchuan et al. (1993, 1996) and Wang denghong et al. (1996) systematically studied the genesis of Dachang tin deposit, clearly pointed out that the mineralization was mainly magmatic hydrothermal metasomatism along the strata, and systematically studied the metasomatism along the strata of 91 # orebody and 92 # orebody and lamellar granite in Lamo mining area, The metallogenic model was established and the metallogenic series were determined (Chen Yuchuan et al., 1985, 1993, 1996); ② It is considered that the deposit was formed in Devonian, belonging to syngenetic sedimentary exhalative deposit or marine volcanic origin, and has nothing to do with granite in Genesis (CAI Hongyuan et al., 1983; Han FA et al., 1997; Qin Dexian, 2002); ③ Sedimentary hydrothermal superimposed mineralization suggests that Pb, Zn and pyrite may be derived from strata and Sn from granite (Zeng Yunfu et al., 1982; Tu Guangchi, 1984, 1987; Chen Jun, 1988; Ding tiping, 1988)

one of the focuses of the above arguments is the age of mineralization. Early predecessors used RB Sr and K-Ar dating methods to determine the ages of fine-grained granite exposed in the mining area, potash feldspar altered rock in the early mineralization stage of Tongkeng mining area, and illite formed in the middle and late stage of ore crystal cavity (Xu Wenxin et al., 1986; Xu Wenxin et al; Chen Yuchuan et al., 1993), whose ages range from 91 Ma to 138.6 Ma, indicate that the mineralization occurred in the Yanshanian period and was basically contemporaneous with the Longxianggai granite, which indicates that there is an internal genetic relationship between the mineralization and the Yanshanian granite. In recent years, we have done a lot of work on geochronology and obtained a lot of new data:

1) Wang denghong et al. (2004) studied the diorthosite in 91 # layered ore body of Tongkeng Changpo deposit in the west ore belt of Dachang orefield and 100 # layered ore body of Longtoushan deposit Conventional fast neutron activation and laser in situ 40 AR / 39 Ar dating of quartz show that the 40 AR / 39 ar plateau age of quartz in massive cassiterite sulfide ore of 91 # orebody is 94.52 ± 33 Ma, isochron age 95. 37 ± 45 Ma, with an inverse isochron age of 94. 89 ± The laser 40 AR / 39 ar isochron age of diorite is 91.4 ± 2.9Ma; The plateau age of quartz in 100 # orebody is 94.56 ± 45 Ma, isochron age 93. 5 ± 2 mA, the reverse isochron age was 93. 29 ± 0.16Ma;

Recently, Chen Yuchuan, Li Huaqin and Wang denghong have systematically studied the isotopic geochronology of quartz in cassiterite sulfide ores and granites related to mineralization in three metallogenic belts of Dachang tin polymetallic ore field, Guangxi Province (the methods used include 40 AR / 39 ar fast neutron activation method, 40 AR / 39 ar fast neutron activation method,

2) The 40 AR / 39 ar plateau ages of Cassiterite from dafuluu and Kangma cassiterite sulfide deposits in the eastern ore belt are 119 ± 21 Ma and 114. 7 ma ± 2Ma; The RB SR isochron age of quartz mineral fluid inclusion of ore bearing quartz vein in Lamo Cu Zn deposit of middle ore belt is 100.5 ± The RB SR isochron age of quartz fluid inclusion in chashanao w-sb deposit vein is 44.4 MA (95% confidence) ± The 40 AR / 39 ar plateau age of quartz is 54.7 ± 1.5Ma; The 40 AR / 39 ar plateau age of cassiterite in the middle section of Tongkeng 405 in the west ore belt is 127.8 ± 3Ma; The whole rock RB Sr and zircon U-Pb ages of the cage cover porphyry biotite granite exposed in the middle 530 section of Lamo mining area are 98.6 and 98.6, respectively ± 3mA (95% confidence) and 94 ± 4mA (95% confidence)

3) recently, Liang Ting, Wang denghong, Qu Wenjun and others, with the support of the crisis mine project, have further carried out the Re Os isochron and other new methods of metallic minerals such as pyrite, molybdenite, arsenopyrite, etc., and achieved new results

The samples used for isotopic geochronology were collected from the cassiterite pyrrhotite veins of dafuluu and Kangma deposits in the east ore belt of Dachang orefield; The porphyry biotite granite in Longxianggai biotite granite, quartz in ore bearing quartz vein of Lamo copper zinc deposit and ore bearing quartz vein of chashanao tungsten antimony deposit in Lamo mining area are exposed in the tunnel of 530 middle section of Lamo mining area in middle ore belt; Cassiterite in 91 # orebody occurs in the middle section of Tongkeng 405 in the west ore belt. According to the conventional mineral separation method, pure zircon is separated from granite, cassiterite and quartz are separated from ore, which can also be used for isotopic age determination. In addition, Liang Ting et al. Completed the age determination of arsenopyrite and pyrite in Tongkeng 92 # orebody, and the results show that the Re Os isochron age of arsenopyrite is 89 ± The Re Os isochron age of some pyrite data is 122 ma ± 44Ma

Analysis method

1) zircon U-Pb dating. Zircon samples were collected from the biotite granite in Longxianggai in the field, and zircon samples were separated from the granite in the laboratory. Then zircon samples with good crystal form were selected and pasted on the surface of epoxy resin with standard zircon (TEM) under binocular lens, polished and gilded. Before shrimp isotope analysis, transmission light and reflection light micrographs of zircon samples were taken. In situ U-Pb isotopic analysis of zircon was performed on shrimp-ii ion probe of Beijing ion probe center. The results were corrected for uranium content and age with reference materials

(2) Rb Sr isotopic dating of fluid inclusions in quartz. The RB SR isochron age of quartz minerals was determined by the analytical procere reported by Li Huaqin et al. (1993); RB and Sr isotopic analysis was performed on the MAT-261 adjustable multi receiver mass spectrometer in the Isotope Laboratory of Yichang Institute of Geology and mineral resources, Ministry of land and resources; In the process of analysis, nbs-987 was used to monitor the state, and nbs607 and gbw04411 were used to monitor the process. The above standard values were: nbs987, 87 Sr / 86 sR = 0.71026 ± 0.00006; NBS607，Rb/10^-6=523.22，Sr/10^-6=65.56，⁸⁷Sr/⁸⁶Sr=1.20035 ± 0.00009; GBW04411:Rb/10^-6=249.08，Sr/10^-6=158.39，⁸⁷Sr/⁸⁶Sr=0.76006 ± 0.00009; 87 Rb / 86 Sr and 87 Rb / 86 SR are better than 1.5% ～ 3% (quartz mineral) and 0.008% ～ 0.02%. All operations are carried out in the purification laboratory. The utensils used are made of fluoroplastics, quartz or platinum. After sub boiling distillation, the RB SR blank was 10 - 11 - 10 - 12 G / g. The high purity water was purified by milli-q water purification system, and the blank values of Rb and Sr were 10 - 12 G / g; The blank of the whole process was about 0.3ng. When the content of Rb and SR was less than 10 - 6 , the blank was corrected. RB SR isochron data were processed by isoplot program compiled by Ludwing (2001)

(3) ar fast neutron activation dating of cassiterite. It has been reported that cassiterite can be used to directly determine the age of ore deposits. B. The U-Pb and Pb isotopic dating of Cassiterite from the wuliyan tin deposit in Indonesia and the zaaiplaats deposit in South Africa by L. gulson and M. T. Jones (1992) shows that cassiterite, as an ore mineral, has more advantages than rutile and zircon in direct dating of ore deposits, but the 40 AR / 39 ar fast neutron activation dating of cassiterite has not been reported so far, In this paper, we tried to determine the age of cassiterite 40 AR / 39 AR, and achieved initial success. The cassiterite samples studied were heated by the fast neutron activation method of 40 AR / 39 ar. the analytical method used is reported by Liu Yimao et al. (2002). Ar ar isotopic analysis was performed on mm1200 noble gas mass spectrometer in Isotope Laboratory of Guilin Institute of mineral geology. The vacuum degree of the instrument is about 2 × 10 - 7 PA, 10 - 14 mol for 40 AR, 10 - 16 mol for 36 AR, 37 AR, 38 AR and 39 ar. The sample was cooled by fast neutron irradiation for about 120 days and then put into the all stainless steel ultra-high vacuum extraction purification system. The sample was heated together with the system at 250 ℃ and roasted to remove gas. After cooling, the vacuum degree reaches 10 - 8 - 10 - 9 PA. The samples were heated by electron bombardment furnace, and the gas was purified by sponge titanium, evaporated titanium and Zr al degassing pump. Finally, the Ar isotope peaks were determined by X-ray mass spectrometry. The interference Ar isotope inced by nuclear reaction is corrected by the Ar isotope proced by irradiation of pure potassium and calcium salts. The K-Ar age biotite reference material (132.5ma) was used to calculate the stage age and plateau age of the samples

(2) test results and interpretation

1. Metallogenic age determination results of the east ore belt

the cassiterite of cassiterite pyrrhotite vein in dafuluu and Kangma tin sulfide polymetallic deposits in the east ore belt of Dachang ore field was 40 AR / 39 ar. the results are shown in table 2-1, Figure 2-1, table 2-2 and figure 2-2. The plateau age spectra of cassiterite in dafuluu and Kangma tin deposits show normal flat type spectra, and the 39Ar precipitated at most stages of temperature rise are in line with the plateau forming conditions. The plateau age of 2-4 stages (750-1050 ℃) of the two samples is 119.7 ± 2mA and 114.7% ± The plateau age of the two is similar to that of the corresponding melting age (120 mA) ± 5mA and 115.4 ± 5mA) in the range of measurement error. This shows that the age data obtained from the heating up of 40 AR / 39 AR in the fast neutron activation stage are basically reliable, and it is inferred that the formation age of dafuluo and Kangma cassiterite sulfide polymetallic deposits in the east ore belt of Dachang ore field is early Cretaceous

Table 2-1 cassiterite 40 AR / 39 ar stage heating dating data of dafuluu cassiterite sulfide deposit in Dachang ore field

test: Dai Tongmo and Chen minyang of Guilin Institute of mineral geology, sample weight 0.3992g, j = 0.0040885, Ping age 119.7 ± 2mA, full melting age 120 ± 5Ma

Table 2-2 temperature rising dating data of cassiterite 40 AR / 39 AR in Kangma cassiterite sulfide deposit in Dachang orefield ± 2mA, full melting age = 115.4 ± 5Ma

Fig. 2-1 ar ar age spectrum of cassiterite in dafuluu cassiterite pyrrhotite vein of Dachang ore field

Fig. 2-2 ar age spectrum of cassiterite in Kangma cassiterite sulfide deposit of Dachang ore field

2. yes

Dachang tin polymetallic ore field is located in the middle part of tin copper lead zinc silver antimony mercury metallogenic belt. The whole metallogenic belt is NW-SE along the Danchi fold fault zone

The Danchi fold fault zone is located in Nandan and Hechi in Northwest Guangxi and Dushan in Southern Guizhou, with a length of about 130 km and a width of about 10 km. The overall strike of the structural zone is NW. It is a composite structural belt composed of NW trending compound fold system and a series of NW, NE and nearly S-N trending faults

Mayang, MANGCHANG, Dachang, Wuwei and Lali, which are located in the tectonic belt, are the junction of NE trending anticlines such as Dushan, zhouqin, Laocun, chuan and Huaiqun on the northeast side of the belt, forming five relative uplift areas with roughly equal distance (35-40km). There are secondary NW reversed anticlines and NW, NE and nearly S-N faults in the uplift area. In Dachang and MANGCHANG uplift areas, the late Yanshanian intermediate acid magmatic rocks are exposed (Fig. 4.3)

There are five ore deposits (fields) along the Danchi fold fault belt from north to south, including Mayang, MANGCHANG, Dachang, Wuwei and Yilan in the West. The Dachang tin polymetallic ore field has the largest mineralization scale, with more than 1 million tons of proven tin metal and rich lead, zinc, antimony and silver; The second is Wuwei ore field, where the Pb, Zn, Sb, Ag polymetallic deposits are large scale, accompanied by small and medium-sized Sn, Mo, Hg, Cu polymetallic deposits; MANGCHANG deposit is dominated by tin polymetallic mineralization with relatively small scale; Mercury deposits are distributed in Mayang and Yilan

Fig. 4.3 structural outline of Danchi fold fault zone

1; 2. Permian system; 3. Carboniferous system; 4. Upper Devonian; 5. Middle Devonian; 6. Diorite porphyrite; 7. Granite porphyry; 8. Biotite granite; 9. Normal fault; 10. Reverse fault; 11. Faults of unknown nature; 12. Syncline axis; 13. Anticline axis; 14. Inverted anticline axis

the main exposed strata in Dachang ore field are Devonian, Carboniferous and Permian. Devonian is the main ore bearing horizon, which is a complex lithologic association of carbonaceous shale, mudstone, reef limestone, lenticular, banded limestone and siliceous rock

the magmatic rocks in the ore field belong to the late Yanshanian intermediate acid intrusives, including biotite granite, granite, monzogranite, pegmatite, granite porphyry and diorite porphyry. The main rock body is biotite granite. In the Longxianggai area of the middle part of the ore field, the surface is exposed as branches and batholith, and the lower part is concealed rock stock. Secondly, granite porphyry and diorite porphyry dyke are distributed in the area from Rome village to Longtoushan in the west of the ore field. The largest fold and fault structures in the orefield are NW trending Danchi anticline and Danchi fault. In the west of the anticline, there are NW trending Dachang anticline, cable anticline and corresponding Dachang fault from east to west. NW trending faults are also widely developed in the ore field, and together with NE trending structures control the occurrence of the deposit

The Dachang ore field can be divided into three ore belts according to mineralization types and spatial distribution (Fig. 4.4): ① the west ore belt mainly consists of Changpo and Longtoushan mining areas, and the ore is characterized by cassiterite sulfide sulfide sulfide mineral assemblage; ② The middle ore belt is located in Lamo, Chashan and some surrounding areas in the middle of the ore field, where skarn type zinc copper sulfide deposits and antimony tungsten quartz vein deposits occur; ③ There are dafuluu and Kangma deposits in the east ore belt, and the ore type is cassiterite pyrrhotite assemblage

Fig. 4.4 geological sketch of Dachang ore field

1; 2. Permian system; 3. Carboniferous system; 4. Upper Devonian; 5. Middle Devonian; 6. Syncline axis; 7. Anticline axis; 8. Reverse anticline axis; 9. Normal fault; 10. Reverse fault; 11. Diorite porphyrite; 12. Granite porphyry; 13. Biotite granite; 14. Horizontal projection of ore body; 15. Fractured vein

The Dachang type tin polymetallic deposit in Guangxi is located in the Nandan Hechi fold belt of the South China fold system, Jiangxi Hunan Guangdong Guangxi fold belt. The exposed strata are mainly Devonian, Carboniferous and Permian, followed by Triassic. Devonian system is an important ore bearing stratum, and its lithology is a set of organic rich fine clastic rock siliceous rock limestone assemblage, and the development of reefs. Tin mainly occurs in limestone and siliceous rock, copper and zinc are mostly confined to shale with rich organic matter and marl, mercury is often found in carbonaceous limestone or dolomitized limestone

The second, third and fourth times of biotite granite, granite porphyry and granite are related to mineralization and control the distribution of ore fields and deposits. Large rock bodies are occult semi occult in the deep part of the ore field, and only dyke, sill or dike group can be seen on the surface. Tungsten, tin, molybdenum, lead, zinc and other ore-forming elements in the pluton are several to dozens of times higher than the average value of acid intrusive rocks in China, which belong to crust derived remelting type granite

The structure is mainly composed of NW trending Danchi fault and a series of tight long narrow linear folds arranged in echelon, supplemented by NE trending folds and faults. The composite superimposed position is the favorable position for diagenesis and mineralization. The deposit is closely distributed around the rock mass and occurs in the anticline axis of multiple structural superimposed uplifts. The ore body or ore belt is controlled by NW, NE, EW and Sn faults, collapse position of fold saddle, bedding fracture zone, bedding fracture zone and granite contact zone

There are Mayang, MANGCHANG, Dachang, BEIXIANG and Wuwei ore fields in the metallogenic belt from northwest to Southeast, which show obvious zoning around the late Yanshanian granite body: W-Mo deposit occurs directly in the rock body, Sn polymetallic deposit is adjacent to the rock body, while sb Hg as sulfide deposit is far away from the rock body

The Dachang ore field is located in the middle of the Danchi metallogenic belt. The Danchi fault and the main anticline pass through the middle of the ore field, which divides the ore field into three ore belts: West, middle and East. The West deposit has tin polymetallic deposits such as Tongkeng, Changpo, Bali and Longtoushan; The middlings include Lamo Cu Zn deposit and chashanao W Sb deposit; There are tin polymetallic deposits such as dafuluu and kengma in the east ore deposit. Tin polymetallic deposits in the west ore belt occur in Upper Devonian siliceous rocks, banded limestones and lenticular limestones. From top to bottom, there are large vein type, veinlet belt type, stratoid veinlet type and stratoid stockwork type orebodies, among which the stratoid stockwork type orebodies are large in scale; The Lamo Cu Zn deposit in the middle zone belongs to skarn type. It occurs in the outer contact zone of the Longxianggai biotite granite in a stratoid form and is superimposed with wolframite stibnite quartz fluorite vein deposits; The tin polymetallic deposits in the eastern ore belt occur in the middle and Upper Devonian strata in the form of veins and veinlets

There are three mineralization types in Dachang ore field, namely Cu Zn, Sn polymetallic and W Sb mineralization, corresponding to skarn type Cu Zn ore, cassiterite polymetallic sulfide (sulfide) ore and W Sb ore. Among them, cassiterite polymetallic sulfide ore is the main type in Dachang mining area. Except cassiterite, marmatite, pyrrhotite, pyrite, chalrite, arsenopyrite and galena, metallic minerals are characterized by antimony lead sulfide minerals rich in Ag, Cu and Sn. The ore field association shows a certain zonation, that is, the sulfide of lead and antimony appears as galena and stibnite single metal sulfide in the upper part of the deposit, and occurs as lead and antimony sulfide in the lower part

The wall rock alteration is skarnization and marble developed in the contact zone of the rock mass, and the cassiterite polymetallic sulfide mineralization period is characterized by electrification, potassic feldsparization, muscovitization, silicification, sericitization and siderite mineralization

(3) metallogenic model the formation of Dachang type tin polymetallic deposit in Danchi metallogenic belt is closely related to the crust remelting type biotite granite of late Yanshanian in time, space and genesis. The strong Yanshanian movement caused the intrusion of granite. With the differentiation evolution and crystallization of magma, the post magmatic hydrothermal solution rich in minerals and volatile components was formed. Under the coordination of tectonism, the ore bearing hydrothermal solution migrated along the fissures of surrounding rock. Due to the change of physicochemical conditions, the balance of ore bearing hydrothermal system was destroyed, resulting in the rapid precipitation of minerals, Therefore, a series of ordered tin polymetallic deposit assemblages from high temperature to low temperature are formed around the granite body: greisen type tungsten molybdenum deposit skarn type copper zinc deposit high and medium temperature hydrothermal tin polymetallic deposit medium and low temperature silver polymetallic, tungsten antimony, mercury antimony deposit (Fig. 3-1)

(4) comprehensive information indicators (model)

1) geological indicators: anticline axis of multiple structural superimposed uplift in the depression belt; Sn rich late Yanshanian crust derived remelting granites are developed in the anticline axis; There are fine clastic rock siliceous rock carbonate rock assemblages with organic matter in the middle and Upper Devonian; Many groups of faults and fissures are developed; The wall rocks developed silicification, sericitization, chloritization, pyritization and skarnization alteration; The mineralization of the Wai series rock body has obvious zoning

(2) geophysical indicators: NW local gravity is low at the turning part of the large gravity gradient variation zone of the Bouguer gravity anomaly, and the aeromagnetic △ t local magnetic field is high and the magnetic field is low at the positive magnetic anomaly area of the variation zone

3) geochemical indicators: there are obvious W, Sn, MKO, Bi and Ag, Pb, Zn comprehensive anomalies with large scale and good correspondence with the mining area. The anomalies of single element Sn, W, Pb, Zn and Ag are also obvious

(4) remote sensing signs: remote sensing images show that there are groups of small circular structures distributed in NW trending linear structures, and there are secondary NE trending linear faults intersecting with NW trending structures

The Dabaoshan copper polymetallic deposit in Qujiang, Guangdong Province is located in the South China fold system, the Jiangxi Hunan Guangdong Guangxi fold belt, the basin edge of the late paleo depression in northern Guangdong, and the intersection area of faults and structures

The strata are Cambrian, Sinian basement and Devonian source beds rich in W, Sn, Pb, Zn, Cu, Ag and Au. The deposit occurs in the first transgressive cycle of Hercynian period and the transition from clastic rock to carbonate rock intercalated with clastic rock formation. They are calcareous and dolomitic fine clastic rocks intercalated with quartz fine sandstone at the bottom of the Middle Devonian QIZIQIAO FORMATION AND limestone of the upper Devonian Tianziling formation, which are brittle, porous and active in chemical properties

(2) structure: the deposit is located in the transitional zone between the depression and uplift. Under the action of long-term active EW, NE and NW fault fold belts, the ore body location is controlled by EW faults and interlayer faults along the strata and different lithologic interfaces, and the later folds lead to the thickening and enrichment of ore bodies

(3) magmatic rocks: related to intermediate acid granodiorite and sub dacite porphyry of Yanshanian hypabyssal ultrahypabyssal crust mantle mixed source

Fig. 3-1 metallogenic model of cassiterite sulfide related to Yanshanian biotite granite in Danchi metallogenic belt

The Cu Pb Zn ore bodies are stratoid, lenticular and folded synchronously with the strata, and are enriched in the synclinal trough with multiple layers. The ore mineral assemblage is complex, mainly including siderite and pyrite assemblage, pyrite, galena and sphalerite (silver) assemblage from top to bottom; Pyrrhotite, chalrite (gold) assemblage and peripheral scheelite, wolframite, molybdenite assemblage. Wall rock alteration mainly includes silicification, sericitization, chlorite pyritization, carbonatization and skarnization of peripheral contact metasomatic deposits

(3) metallogenic model: the deposit is located at the dip end of compound anticline and the margin of dome; It is distributed in the transitional layer between the middle and Upper Devonian limestone with fine sandstone and the middle and Lower Devonian clastic rock; High angle faults and medium amplitude folds are developed; The Yanshanian hypabyssal ultrahypabyssal intermediate acid crust mantle mixed source (syntectic) magmatic rocks are exposed (Fig. 3-2)

Fig. 3-2 metallogenic model of stratabound Cu Pb Zn deposits in northern Guangdong Province; The wall rocks are silicified, sericitized, Chloritized or skarn

(2) geophysical indicators: it is located in the northeast or southwest twist position of the isoline of the northwest step belt of the Bouguer gravity anomaly; Aeromagnetic △ t anomaly is a large-scale and irregular concave convex part of positive magnetic anomaly with high and low local magnetic force

Geochemical indicators: there are geochemical anomalies corresponding to the deposit, with complex components, well nested, obvious concentration center and concentration zoning. The main components are Cu, Mo, Pb, Zn and Ag, followed by as, Bi, Hg, Ni, Co, V, CD, Mn and ba. The anomaly trend is NW and consistent with the ore body extension

(4) remote sensing marks: there are diamond structure images in EW direction composed of NWW and NE linear structures and ring images displayed by structures or magmatic rocks

The Yanbei tin deposit in Jiangxi Province is located in the Paleozoic fold belt of Wuyishan uplift area and belongs to the tectonic magmatic activity area of West Fujian southeast Jiangxi Province. Since Mesozoic, it has been characterized by strong faulting, extensional subsidence and magmatic activity, with large-scale volcanic eruption and emplacement of hypabyssal intermediate acid granite along deep faults. The deposit occurs in an acidic intermediate acidic volcanic basin controlled by the NNE trending Shicheng Xunwu deep fault

(2) the Yanbei deposit is located in the southeast of the caldera pass of mikeng mountain, and tin mineralization occurs in EW, NNE and NW fault composite section. The mineralization is related to the activity of subvolcanic granite porphyry with the characteristics of ultra hypabyssal and cryptoexplosion. The ore body occurs in the inner contact zone of rhyolitic tuff lava and granite porphyry in jilongzhang formation (J 3 J), in which the inner contact zone accounts for two thirds. The overall strike of the ore body is NNE, the dip is n, and the dip angle is 18 ° The main ore body is irregular ellipse in plane, 450m long and 250m wide, with the thickest of 89m. In the longitudinal section, the orebody is lenticular and stratoid. The main ore minerals are cassiterite and chalrite, followed by sphalerite, magnetite, pyrite, galena, wolframite and argentite; The main nonmetallic minerals are quartz, topaz, chlorite, sericite, fluorite, etc. The ore structure is mainly disseminated and veinlet disseminated structure, and some breccia structure, with metasomatic structure, crystalline structure and solid solution separation structure. The alteration of the deposit is well developed and distributed in a plane type. Tin mineralization is closely related to the quartzitization of topaz, chlorite Topaz and quartzitization

(3) metallogenic model

the tin bearing granite body closely related to the mineralization of Yanbei deposit is not a subvolcanic rock body, but another tectonic magmatic metallogenic multi-stage intrusive granite series after the eruption of mikengshan volcano. The ore-forming parent rock is a highly emplaced fine-grained porphyry like granite body. The ore-forming bodies are different from the subvolcanic bodies in porphyry tin deposits (Fig. 3-3)

Fig. 3-3 metallogenic model of Yanbei tin deposit. RB, re and Nb TA mineralization occurred in the magmatic stage of tin bearing granite; The W and Sn bearing Topaz quartzite belt formed in the contact zone of the rock mass ring the gasification high temperature hydrothermal period; Cassiterite and sphalerite deposits are formed near the contact zone ring the high-temperature low-temperature hydrothermal period, and silver deposits are fractured far away from the contact zone

the ore-forming fluid mainly comes from magmatic hydrothermal solution with the addition of surface water. The ore-forming materials such as Sn, Fe, Cu and s are mainly derived from deep syntectic intermediate acid volcanic intrusive rocks. After the formation of magmatic stage, the ore bearing hot gas fluid rose along the large fault and paleovolcanic channel

According to the discovery and prospecting history of Dachang ore field, the main prospecting breakthroughs can be roughly divided into three main stages. The first stage is the discovery of orebodies 91 and 92 in Changpo deposit from 1960s to 1970s. Before that, people were still very cautious about the prospecting potential of Dachang area, because only a few limited veins were exposed on the surface, Many people are not even optimistic about the prospecting prospect of this area. The second stage is the exploration of No. 100 and No. 105 orebodies in Longtoushan deposit in 1980s. Before the discovery of these two orebodies, many people were not optimistic about the metallogenic conditions and prospecting potential of reef limestone in majiaao formation of Middle Devonian. The third stage is the discovery and exploration of dafuluu and Kangma deposits in the east of Dachang. There are significant differences in shape, occurrence and ore type among the three stages

For a long time, the debate on the genesis of Dachang ore field has been very intense, with the main viewpoints represented by magmatic hydrothermal mineralization and hydrothermal sedimentary superimposed reformation mineralization. Although it is still difficult to distinguish between Bozhong and Bozhong in many aspects, it should be noted that the main ore bearing horizon of Dachang ore field and even the whole Danchi metallogenic belt is Devonian system, and stratabound is one of the landmark features of Danchi metallogenic belt. Therefore, one of the key targets of prospecting work in Dachang ore field is Devonian strata

Of course, the role of Yanshanian magmatic rocks in mineralization can not be ignored. The Longxianggai skarn zinc copper deposit in Dachang ore field is obviously constrained by Yanshanian magmatic rocks in the middle of the ore field in genesis and space. However, it is not enough to emphasize the role of Yanshanian magmatic rocks. In MANGCHANG area in the north-west of Dachang ore field, Yanshanian magmatic rocks are very well developed. Although a lot of exploration work has been invested and the degree of research is very high, no mineralization belt with a certain scale has been found. In contrast, Wuwei orefield in the South East of Dachang orefield has not found Yanshanian magmatic rocks, but its mineralization scale is far larger than MANGCHANG area

The ore-forming conditions of Dachang ore field have the advantages of Wuwei and MANGCHANG, that is, favorable stratigraphic horizon, Yanshanian magmatic activity and favorable position of Danchi fold fault zone, which are also the key to the formation of diversified mineralization types and super large scale of Dachang ore field

From the perspective of dynamic mineralization, cassiterite sulfide deposits, skarn zinc copper sulfide deposits and antimony tungsten quartz vein deposits in Dachang orefield represent the procts of dynamic mineralization in different periods and geological environments, respectively, and their mineralizing element combinations, water rock reaction systems and prospecting indicators are also different. The formation of cassiterite sulfide deposits is related to the Devonian submarine dynamic mineralization, and the main geological prospecting indicators are related to the "layer facies position" system composed of favorable horizon, lithofacies and syngenetic faults, including Devonian siliceous rocks, reef limestones, lenticular banded limestones, and pyrite rich, carbon rich and carbon rich bitumen horizons, Siliceous rocks and lenticular banded limestones constitute a dynamic water rock reaction chain in submarine hydrothermal sedimentary environment, indicating acidic and alkaline brine environment respectively. The Sn Pb Zn sb Ag as element assemblage anomaly can be used as a geochemical indicator for the exploration of cassiterite sulfide deposits. As cassiterite sulfide deposits are also reformed by Yanshanian magmatic hydrothermal activities in varying degrees, the Yanshanian magmatic rocks, mainly the Yanshanian dikes in the west ore belt and the Yanshanian granite convex in the deep, can be used as indirect or auxiliary prospecting indicators for cassiterite sulfide deposits. For the skarn type Zn Cu sulfide deposit, its formation is mainly related to the Yanshanian magmatic hydrothermal activity, and its water rock reaction chain is composed of skarn in the contact zone of rock mass and Cu Zn polymetallic sulfide. The main geological prospecting indicators include Yanshanian granite convex, skarn in the contact zone of rock mass and Devonian lenticular banded limestone, The anomaly of Cu Zn as element combination can be used as a geochemical prospecting indicator for skarn type Zn Cu sulfide deposits

Generally speaking, e to the high degree of exploration and research in Dachang ore field, it is difficult to find new and large-scale deep concealed deposits

According to the comprehensive analysis of the metallogenic geological conditions and prospecting indicators of Dachang ore field, the following areas are regarded as the prospective areas for further prospecting

4.6.2.1 the prospecting prospect area of the west ore belt is below the vein like layered orebody of cassiterite sulfide deposit in the deep part of Changpo mining area, the skarnization is graally enhanced, and obvious mineralization phenomenon is observed. According to the analysis of the shape map of the concealed biotite granite roof predicted by the inversion of gravity anomaly (Fig. 4.17), there are NE trending ridge uplifts in the west ore belt. It is feasible to search for cassiterite sulfide and skarn deposits in the concealed d 2 and d 1 horizons

There is skarn type Zn Cu mineralization in No.95 orebody in the depth of Pali area; In the deep part of Longtoushan area, No. 100 and No. 105 ore bodies are cassiterite sulfide type, and there are signs of transition to skarn type zinc copper mineralization in the deep part and side. The gravity anomaly shows that there is a hidden biotite granite ridge uplift belt in the area of Bali Longtoushan, which is predicted to have further prospecting potential

In the east of Bali Longtoushan, from wayaoshan to cucudong, nearly north-south trending Ag Pb Zn sulfide fracture veins are developed in the shallow part, and there is potential for looking for stratoid Ag Pb Zn deposits in the deep part

In Gengzhuang area, located at the north end of Changpo, in the continuation of Dachang anticline, cassiterite heavy sand anomaly zone is developed, and lead-zinc mineralization is found. There is potential for cassiterite sulfide deposits in the middle and Upper Devonian strata

In the east wing of Dachang anticline on the east side of Nayan, it belongs to the South extension of the west ore belt, with middle and Upper Devonian distribution and exposed quartz vein of lead-zinc sulfide, which is a potential area for looking for cassiterite sulfide deposits

4.6.2.2 prospecting prospect of the east ore belt

in the Xiaocao area in the north of dafuluo, the lead-zinc mineralization is strong, with fracture veins and thin-layer orebodies, which has the potential for lead-zinc ore prospecting

in Kangma mining area, NW trending secondary folds, NW and NE trending faults and fissures are developed, and at the same time, there are fissure veins in the lower part of veinlet type cassiterite sulfide. Compared with the "ribs" type structure of dafuluu deposit, there may be stratiform orebodies in its deep part

4.6.2.3 the prospecting prospect area of the middle ore belt is located in the inner and outer contact zone of Longxianggai biotite granite. According to the development of Sn Mo ore bodies in the contact zone of MANGCHANG deposit, attention should be paid to the possible Zn Cu and Sn Mo mineralization in the contact zone

There are more than 40 stibium tungsten fracture veins on the surface of Dayan and fanbei areas. From shanmuchong to xiangshuiwan, stibium tungsten fracture veins also appear intermittently, which has the potential to search for stibium tungsten fracture vein type deposits

Fig. 4.17 roof shape of concealed granite body in Dachang ore field

1; 2. Anticline axis; 3. Syncline axis; 4. Reverse anticline axis; 5. Reverse fault; 6. Normal fault

4.6.2.4 ore field peripheral prospecting prospect

in the east of the east ore belt on the east wing of the Danchi anticline, from Qingshan to tanghuangcun, NW trending faults are developed, and cassiterite, cinnabar and zircon anomalies are found in the eluvium of d 3 - C

There is a strong pyritization and zinc mineralization at the bottom of banded limestone of Wushan formation in the southwest Kuandong area of the west ore belt, which is the intersection of NW and NE faults

In the Guanshan area on the west side of the west ore belt, it is located at the plunging end of the Suo anticline, with NW trending faults, heavy sand anomalies of zircon and magnesite, and mineralization of zinc, mercury and silver, which has the potential to search for mercury and zinc silver polymetallic deposits

The formation of Dachang deposit is obviously controlled by structure. The structure not only controls the distribution of ore deposits, but also controls the shape and change of ore bodies, that is, the structural conditions provide favorable space for the accumulation of ore-forming materials. It is reflected in the following aspects:

1. The structure controls the distribution of magmatic rocks and ore deposits in the mining area

Danchi basin is a secondary rift basin on the edge of Youjiang rift basin, belonging to the ancient Tethys tectonic domain, and the nature, evolution and development of the basin are controlled by the ancient Tethys ocean. During the Tangding stage of Early Devonian, along with the cracking of the Paleo Tethys ocean, NW trending basement faults proced tension activities, forming the NW trending Danchi depression belt and incing NE trending strike slip faults. The two groups of faults jointly controlled the Devonian and Carboniferous deposits in Danchi basin. Under the strong compression of Indosinian movement, NW trending folds and faults (such as Dachang anticline and Dachang fault) were formed, which laid the structural framework of the Danchi metallogenic belt. In the late Yanshanian period, e to the compression of the Pacific plate from the SE-NW direction, the NW and NE groups of faults experienced strike slip extension again. At the intersection of the two groups of faults, the tin bearing granite magma ascended and emplaced to form ore deposits. At the same time, e to the equidistant development of NE trending faults, the ore deposits were roughly equidistant. Therefore, in the Danchi metallogenic belt, there are Mayang, MANGCHANG, Dachang, BEIXIANG, Wuwei and other tin polymetallic deposits (fields) successively from north to south. In the Dachang ore field, the distribution of Longxianggai granite ore bodies is zonal, with dafuluu, maopingchong, kengma and other deposits in the East, Changpo Tongkeng, Paris, Longtoushan deposits in the west, and Lamo zinc (copper) ore bodies in the middle

The structure controls the occurrence, location and scale of ore body. The occurrence of ore bodies is not only affected by the properties of surrounding rocks, but also controlled by the structural properties. It is mainly reflected in the following aspects: 1) Dachang anticline is one of the main structural types in Dachang mining area. The turning end of anticline is the stress concentration position, which is easy to proce transverse joints and collapse space, which is concive to ore fluid filling. Therefore, the dip end of Dachang inverted anticline is a favorable place for the occurrence of large vein like orebodies. With the anticline dipping to se, the large vein like orebodies graally decrease or disappear, The scale of this kind of ore body is small, the continuity of the vein is good and stable, and the grade of the ore body is rich at the top and poor at the bottom; ② Under the action of stress, the shear fold in the strata, the interlayer slippage structure of different lithology and the fracture structure in the strata are the main types of ore hosting structures in the area, which control the layered and stockwork ore bodies in the area, and the scale of such ore bodies is large (such as No. 75, No. 77, No. 79, No. 91, No. 92 ore bodies); ③ In the late stage, the NE, NW and Sn trending faults with both extensional and shear properties are favorable for the formation of vein like orebodies; ④ The turning ends of some secondary folds often form collapse positions, which is concive to the formation of small and rich ore packets; ⑤ The occurrence of layered and veined Zn Cu ore bodies (such as Lamo Zn Cu ore) is favorable to the occurrence of outburst, contact zone and fault structure in the contact area between rock mass and surrounding rock; ⑥ The occurrence of No. 100 orebody is also obviously controlled by the structure. At the top of the reef uplift at the axis of the anticline, e to the strong compression, there are different degrees of interlayer stripping and fragmentation. At the intersection of faults and fissures, some rich ore packets and pillars are proced in a certain range; In the West Wing of the unsymmetrical uplift of the reef, some Sn trending transverse faults and interlaminar dislocations often occur, resulting in some steeply dipping orebodies and layered orebodies; In the axial part of the reef, controlled by two compression torsion thrust faults and the special lithology of the reef, a large "collapse space" is formed in the deep part where the stress is concentrated and the compression is strong, which provides a favorable field for the filling of ore fluid and the formation of No. 100 super large orebody

As a matter of fact, the formation of ore bodies is the combination of various favorable structural features proced by faults, folds and intrusion of rock mass. The distribution of ore bodies is also determined by the direction of the dominant ore controlling structures, and the main ore hosting structures of the deposit are secondary faults derived from the main faults, such as NE trending faults

1、 The tin polymetallic deposits in Dachang orefield, Guangxi, China are closely related to granite body, sedimentary formation and structural style. The ore bodies are large in scale and the types of deposits are complex. Among them, cassiterite sulfide polymetallic deposits are the most important, followed by skarn zinc copper deposits. Dachang ore field includes Changpo cassiterite sulfide polymetallic deposit, Bari Longtoushan cassiterite sulfide polymetallic deposit, yuquandong Tongkeng and Heishuigou skarn zinc copper deposit, Lamo Longxianggai skarn zinc copper deposit, Chashan antimony tungsten deposit, huile and Kangma tin polymetallic deposits. Dachang ore field is rich in mineral resources. The main minerals are Sn, Zn, Pb, Sb, Cu, W, Ag, in, s, as, etc. among them, the metal reserves of Sn, Zn, in, etc. all reach the scale of super large deposits, and are well-known at home and abroad

The Dachang ore field in Guangxi, China is located in the Youjiang fold belt at the southwest end of the South China fold system, in the composite part of the Paleo Tethys tectonic domain and the Pacific Rim tectonic domain (Fig. 1). The deposit occurs in the Devonian System of Nandan Hechi late Paleozoic rift basin. Located in the southwest margin of Jiangnan ancient land, the basin is a sub basin of Youjiang late Paleozoic rift basin, which is closer to the mainland. The strata in the basin are Devonian Triassic argillaceous rocks, carbonate rocks, siliceous rocks and clastic rocks

Fig. 1 geotectonic map of Dachang ore field, Guangxi, China (quoted from Qin Dexian et al., 2004, Revised)

Danchi fold fault zone composed of Danchi large anticline and Danchi large fault, the main structure is NW-SE strike, the anticline axis thrust fault is developed, superimposed with EW, Sn trending faults and secondary fold structures, and granite intrusion occurs at the superimposed structure, forming Dachang, Dachang, Dachang, Dachang, Dachang, Dachang and Dachang MANGCHANG and Wuwei tectonic uplifts controlled the diagenesis and mineralization of the main ore fields in the metallogenic belt

There are Mayang mercury deposit, MANGCHANG tin polymetallic ore field, Yilan mercury deposit, Dachang tin polymetallic ore field, BEIXIANG tin polymetallic ore field and Wuwei lead zinc tin polymetallic ore field from north to south. There are 2 super large deposits, 5 large deposits, 11 medium deposits, and more than 200 ore procing areas of Sn, Zn, Pb, Sb, Ag, Cu, W, Hg, etc. The ore deposits are mainly distributed in Dachang, MANGCHANG and Wuwei ore fields, among which Dachang ore field is the most important

(1) the regional strata are all sedimentary formations of coastal facies to shallow marine facies in Late Paleozoic rift basin, mainly carbonate rocks, followed by clastic rocks. The sequence of strata in Dachang ore field from new to old is: Quaternary alluvium and diluvium, with placer locally; The Middle Permian Heshan formation is composed of limestone and siliceous rock with sand shale; The lower Permian Maokou Formation limestone; Limestone and siliceous rock of Lower Permian Qixia Formation; Limestone of Maping formation of Upper Carboniferous system; Middle Carboniferous Huanglong Formation limestone; Limestone of Shimen formation of Lower Carboniferous system; The upper Devonian tongchejiang formation is interbedded with limestone shale; Lenticular and banded limestones of the upper Devonian Liujiang formation; Siliceous rocks of the upper Devonian Liujiang formation; Limestone of majiaao formation of Middle Devonian system; The crystalline limestone of majiaao formation in the Middle Devonian (reef limestone in the area from Bari mountain to Longtou mountain in the West outer belt); Limestone, shale and sandstone of Lower Devonian CHEHE formation (Fig. 2)

Fig. 7 response map of geological, geophysical and geochemical anomalies of different denudation surfaces in Dachang ore field, Guangxi, China

1、 Deep structure and metallogenic enrichment mechanism "Changpo Tongkeng deposit deep area" and "Heishuigou dashujiao area" are the two deep prospecting areas of the Dachang Mine replacement resource exploration project. Among them, the deep area of Changpo Tongkeng deposit refers to the footwall area of Dachang fault (F1). Tin polymetallic mineralization in the area is mainly controlled by a group of NW trending imbricate thrust faults and secondary folds; Heishuigou dashujiao area is located in the eastern part of LAOCHANGPO deposit, with a distance of 300-500m. The zinc polymetallic mineralization in the area is mainly controlled by NE, NW trending faults and NE trending flexure structures

The characteristics of imbricate structure in the deep part of Changpo deposit and its control on mineralization (1) imbricate structure the NW trending fault structure is developed in Changpo mining area, and the surface is represented by Dachang fault (F1), which occurs near the axis of the West Wing of Dachang inverted anticline. Deep drilling revealed that there are a series of parallel thrust faults (f1-1, F3, F5, etc.) in the footwall of F1. The hanging wall of these faults thrusts upward in turn and overlaps upward and downward on the profile, forming imbricate structure (Fig. 5-15)

The NW trending faults have the same characteristics and strike nw330 °～ three hundred and forty °， Inclination ne, dip 25 °～ eighty °， The fault plane is steep in the upper part and gentle in the lower part, and occurs in the shape of plough. The faults developed on the basis of Devonian synsedimentary faults. Geophysical data show that NW trending faults are still clearly reflected on the Mohs depth map, indicating that their influence depth reaches the middle and lower crust or upper mantle. Since Mesozoic, the faults have experienced thrust movement in Indosinian and extensional and torsional reactivation in Yanshanian (CAI Minghai et al., 2004)

Fig. 5-15 profile of 125 exploration line in deep area of Changpo deposit

Taking F 1 , f 3 and f 5 as the natural boundary, the deep part of Changpo deposit is divided into three imbricate structural zones from top to bottom (Fig. 5-15)

No.1 imbricate structural belt: composed of F 1 fault and a series of secondary folds and faults on its hanging wall, it is the occurrence position of 91 and 92 layered orebodies and vein orebodies in Changpo Tongkeng mining area

The second imbricate structural belt is distributed between the f 1 and f 3 faults in the West Wing of Dachang inverted anticline, which is composed of the first secondary fold and several secondary faults in the West Wing of Dachang inverted anticline. The f 1-1 fault further complicates the east wing of the secondary syncline. No. 115, 77, 77-1 and 77-2 ore bodies are all hosted in the fold fault zone

No.3 imbricate structural belt: it is distributed between F 3 and f 5 faults on the West Wing of Dachang inverted anticline, and is composed of the second secondary anticline and several secondary faults on the West Wing of Dachang inverted anticline. No.116 and No.117 orebodies are found in the southern part of the structural belt

(2) mineralization characteristics in imbricate structure belt

in NW imbricate structure, there are many cassiterite sulfide orebodies, which occur as stratoid and fissure veins. The relationship between main orebodies and imbricate structure is as follows:

Changpo Tongkeng Tin polymetallic deposit includes large vein type, veinlet type and 91 and 92 orebodies, It occurs in the No. 1 imbricate structural belt in the east wing of Dachang anticline, which is strictly controlled by the axial fracture zone of Dachang anticline and the secondary fold, bedding sliding fault and NE trending fracture structure in the northeast wing. The occurrence form of ore bodies has obvious zonal characteristics, The order from top to bottom is: fractured vein and veinlet zone orebody → interlayer stripping stratoid orebody → stratoid veinlet zone type 91 orebody → stratoid veinlet zone type 92 orebody

LAOCHANGPO silver zinc deposit is located in the West Wing of Dachang anticline in the No.2 imbricate structural belt, in the south of the deep area of Changpo Tongkeng deposit. There are No.111, 112, 113, 114, 115 and 16 orebodies, among which no.111-114 orebodies are steep inclined fissure vein orebodies, and NO.115 and No.16 orebodies are gently inclined stratoid orebodies

The tin polymetallic deposit in the deep part of Changpo Tongkeng deposit is a newly discovered deposit in recent years. It occurs in the No.2 imbricate structural belt in the West Wing of Dachang inverted anticline. It is between F 1 and f 3 and there are many layered and fractured vein like orebodies. There are 115, 77, 77-1, 77-2, 75-1 and 79-1 stratoid orebodies, and 200 NW and NE trending mineralized fracture veins in fracture vein orebodies

In addition, there is no instrial ore body in the area between F 3 and f 5 , that is, in the No. 3 imbricate structural belt, e to the low degree of engineering control

(3) structural ore controlling regularities the ore controlling regularities in the deep area of Changpo Tongkeng deposit are as follows: ① the occurrence of strata on the profile changes from gentle to steep, and the thickness and strength of ore veins increase, which shows that the late Yanshanian extensional and torsional tectonic activities controlled the mineralization; ② It is easy to proce interlayer fracture zone and interlayer sliding near rigid and plastic rock interface, which is a good metallogenic space; ③ The ore bodies (veins) tend to be enriched in mineralization in the middle, coexisted with Sn and Zn, and become poor at both ends. The ore-forming elements become mainly Sn or Zn instead of Sn and Zn; ④ The dip extension of fissured veins is often greater than strike extension

In recent years, Heishuigou dashujiao area is an effective exploration area for deep geological prospecting in the periphery of the old mining area. Through deep drilling in 2005-2006, rich and thick orebody 96 was found in the lower part of orebody 95, and four orebodies in the six boreholes were more than 10m thick, The maximum thickness is more than 30 meters, which breaks through the previous view that No. 96 ore body is smaller and poorer to the north, opens up a new idea for the prospecting of this area, expands the scale of the deposit, increases the amount of zinc and copper resources by (333) 980000 tons, and the deposit boundary is not controlled, showing a good prospecting prospect

The Heishuigou dashujiao deposit is located at the junction of the west ore belt and the middle ore belt of the Dachang ore field, adjacent to the Changpo Tongkeng superlarge tin polymetallic deposit in the west, the Bali Longtoushan superlarge tin polymetallic deposit in the south, and the Longxianggai large skarn zinc copper deposit in the North (Fig. 5-16)

(1) structural characteristics of Heishuigou dashujiao area

Heishuigou dashujiao area is located in the northeast wing (flat wing) of Dachang inverted anticline. In the deep part, there is a NE trending flexure structure with a length of 2500m, a width of 500-700m and an axial direction of 30 m °， The orebodies are mainly distributed along the northwest wing of the bend. The fault structures in the area are relatively developed, mainly including Dachang fault in NW direction and Heishuigou fault in NE direction (Fig. 5-16)

Dachang fault. Dachang fault runs through the axis of Dachang anticline, and its length is more than 8km. The dip angle of the north section (north of Pali) is 15 °～ thirty °， The fault distance is 150-250m and the extension depth is more than 800m; The shallow part of the middle section (Bali Longtoushan) is mainly in the form of fracture zone, with fracture bandwidth of tens of meters, and the deep part is a group of fracture zones; The dip angle of the southern section (south of Longtoushan) is 40 °～ forty-five ° The fault is exposed on the surface of the west side of the mining area, and the lower part cuts into the deep part of the mining area, which is the ore guiding structure in this area

2) Heishuigou fault. It is a normal fault, about 4km long, strike 37 °， The dip angle is 60 °～ seventy ° The fault cuts across the mining area and intersects with Dachang fault in the West. The ore bodies in the area are mainly distributed along the fault and its two sides, which indicates that the fault plays an important role in controlling mineralization and is the ore matching structure in the area

In addition, in the Luofu formation, e to the compression tectonic stress in the early stage, the different lithologic combinations of marl, calcareous mudstone and shale are easy to proce interlayer sliding, forming interlayer detachment and interlayer fracture zone structure, and in the late stage, the interlayer folding structure, interlayer detachment zone and small folds near EW direction are formed e to the tectonic extension and shear deformation, No. 95 and No. 96 orebodies occur in this kind of structure

(2) mineralization characteristics

the orebodies in the area are mainly distributed in the northeast wing of Dachang anticline, and occur in the marl and calcareous mudstone in the middle and lower part of Luofu formation of Middle Devonian in a stratoid manner. The occurrence is basically the same as that of the stratum. Due to the influence of the NE trending flexure structure in the deep part of the area, the orebodies are inclined from northwest to northeast, and mainly distributed along the northwest wing of the flexure, tending to NW, At the tip of the tree (the foot of the big tree), it turns to NNE. The plane shape of the ore body is simple and tongue shaped, spreading from SW to ne (Fig. 5-16). The tin polymetallic sulfide ore body is located in the south-west end, and the zinc copper ore body is located in the north-east end. A number of instrial ore bodies have been found in the area, of which No. 95 and No. 96 are the two main ore bodies. They are nearly parallel, with a vertical distance of 70-130m. No. 95 overlies No. 96 ore body (Fig. 5-17)

No. 95 orebody. It occurs in the middle part of Luofu formation with strike of 25 °， Dip NW, dip 21 ° Left and right, northeastward and laterally. The ore body is controlled to be 2600m long and 60-800m wide with good continuity. Taking line 39 as the boundary, the South ore section (Bali wayaoshan) is mainly tin polymetallic sulfide ore body, and the North ore section (Heishuigou dashujiao) is mainly zinc copper ore body

No. 96 orebody. It occurs in the lower part of Luofu formation, strike 58 °， Dip NW, dip 28 °， The extension length is 2550m and the control area is 1.15km 2 . Line 9 of ore body inclines to n with dip angle of 15 ° The ore bodies are stratoid, discontinuous, and the thickness varies greatly. The ore body is characterized by expansion, contraction and branching. There are tin polymetallic ore bodies in the south of line 39 and zinc copper ore bodies in the north. The tin polymetallic sulfide ore block is controlled to be 340m in length, 160-240m in width and 10.30m in average thickness; The control length of zinc copper ore section is 1850m, the width is 100-500m, and the average thickness is 9.50M. The thickness is unstable, and the thickness variation coefficient is 129%

Fig. 5-16 geological sketch of Tongkeng Heishuigou dashujiao zinc copper deposit C 2 H 2 - dolomitic limestone of Middle Carboniferous Huanglong Formation; C 2 H 1 - chert banded limestone of Middle Carboniferous Huanglong Formation; C 1 C - quartz sandstone of Lower Carboniferous Simen formation; D 3 T 3 - limestone and shale of Upper Devonian tongchejiang formation; D 3 W 2 - lenticular and banded limestone of Upper Devonian Wushan formation; D 3 L 1 - siliceous rocks of the upper Devonian Liujiang formation; D 2 L 2 - marl and mudstone of Middle Devonian Luofu formation; D 2 L 1 - reef limestone of Middle Devonian Luofu formation; δμ 3B 5 - diorite porphyrite; γ 3C 5 - granite porphyry; 1 - stratigraphic boundary; 2 - unconformity stratigraphic boundary; 3 - anticline axis; 4-reversed anticline axis; 5 - syncline axis; 6-normal fault; 7 - reverse fault; 8 - ore body and number; 9-placer tin deposit

(3) the characteristics and laws of structural ore control

the control of structure on mineralization is shown as follows: NW trending structure (Dachang anticline, Dachang fault) and NE trending structure (Heishuigou fault, concealed deflection) superimposed section and concealed rock uplift jointly control the deposit location in this area. In the southern part of the deposit, e to the mainstay action of reef limestone in the core of Dachang anticline, the local stress field changes, which makes the overlying Luofu formation form interlayer stripping and interlayer crushing structure, controlling cassiterite sulfide orebody. The northern part of the deposit is affected by late tectonic extension and shear deformation, resulting in intrastratal folding structure and interlayer detachment zone, controlling skarn type zinc copper orebody. The NE trending flexure structure is developed in the deep part of the area, and it is inclined from southwest to northeast. The dip end is shown in Fig. 5-47 Tongkeng Longxianggai section of Dachang mining area (revised according to the data of No. 215 geological team of Guangxi Huaxi Group). II. The deep prospecting results are shown in Dachang Mine of Guangxi

The study of metallogenic regularity is a systematic work for human beings to give full play to their subjective initiative and comprehensively and objectively understand the natural laws of the formation and distribution of mineral resources. Its research contents cover material (what), time (when), space (where) and Genesis (why), The temporal distribution of mineral resources can only be inferred from diagenetic age or macroscopic analysis 30 years ago. With the development of isotopic dating technology, especially the rapid development of Re Os dating technology for molybdenite, it provides a technical guarantee for the objective and accurate direct determination of the formation age of metal minerals, creates conditions for the further development of metallogenic law research, and provides new inspiration for metallogenic prediction and geological prospecting. For example, the isochron age of 95.40 Ma for Damingshan tungsten deposit and the model age of 95.00 ma-95.79 Ma for Maling tungsten deposit are obtained by Re Os isotopic dating of Molybdenite in ore bearing quartz vein of Damingshan tungsten deposit and molybdenite in borehole core of Maling tungsten deposit, which indicates that their metallogenic ages are consistent. The results show that the mineralization of the Danchi metallogenic belt from the Damingshan ore field in the south to the Dachang ore field in the Northwest (ore bodies 91 and 100 are concentrated around 94.5 MA) occurred in the late Yanshanian period, and almost simultaneously. Considering the widespread existence of mantle derived magmatic rocks in the same period and the regional tectonic setting in the Danchi ore belt, it is considered that the mineralization may be related to the upwelling of mantle derived materials and the access of deep faults to the mantle. In this dynamic background, the Danchi metallogenic belt has a good prospecting prospect. We should learn from the "four in one" model of Damingshan tungsten deposit, pay attention to tin polymetallic ore in Damingshan ore field, and independent tungsten ore in Dachang ore field. There are four in one model of vertical vein type, gently inclined quartz vein type, net vein type and rock type tungsten deposits in Damingshan, which is also worthy of reference in southern Hunan and southern Jiangxi

Hot content

Inn digger Publish: 2021-05-29 20:04:36 Views: 341

Purchase of virtual currency in trust contract dispute Publish: 2021-05-29 20:04:33 Views: 942

Blockchain trust machine Publish: 2021-05-29 20:04:26 Views: 720

Brief introduction of ant mine Publish: 2021-05-29 20:04:25 Views: 848

Will digital currency open in November Publish: 2021-05-29 19:56:16 Views: 861

Global digital currency asset exchange Publish: 2021-05-29 19:54:29 Views: 603

Mining chip machine S11 Publish: 2021-05-29 19:54:26 Views: 945

Ethereum algorithm Sha3 Publish: 2021-05-29 19:52:40 Views: 643

Talking about blockchain is not reliable Publish: 2021-05-29 19:52:26 Views: 754

Mining machine node query Publish: 2021-05-29 19:36:37 Views: 750

Hechi Danchi ore field

Related to Hechi Danchi ore field