Classification of genetic types of (1) gold deposits

According to mineralization, metallogenic model, material source, ore-controlling conditions and deposit characteristics, gold deposits and non-ferrous metal deposits related to gold in Nanling area are divided into 10 main genetic types: ① gold deposits related to magmatic rocks; ② Volcanic gold deposits; ③ Porphyry gold deposit; ④ Altered rock-type gold deposits in the structural fracture zone; ⑤ Fine disseminated gold deposits; ⑥ Midvein gold deposit in metamorphic clastic rock; ⑦ Gold deposits related to supergenesis; (8) Placer gold deposits; Pet-name ruby laterite gold deposit; Participate in the Tiemao Gold Mine.

(2) Classification of genetic types of silver deposits

According to the principle of genetic classification of deposits, mineralization and metallogenic model, material source, ore-controlling conditions and characteristics of deposits, silver deposits and silver-related nonferrous metal deposits in Nanling area can be divided into eight main genetic types: porphyry type, contact metasomatism type, high-middle hydrothermal type, low-middle hydrothermal type, volcanic hydrothermal type, syngenetic sedimentary type, sedimentary transformation type and supergene type.

(1) porphyry deposit

This type of deposit is distributed in Yanbei, Fenghuang Cave, Lianhua Mountain, Xiling and other places on the western slope of Wuyishan in southern Jiangxi. The surrounding rocks are Jurassic volcanic rocks and Upper Paleozoic, and the ore-forming rock mass is early Yanshanian granite porphyry, which is a combination of tin, tungsten, copper, lead, zinc and silver mineralization. The ore body occurs in the contact zone inside and outside the rock mass, which is layered and lenticular, and the surrounding rock is altered by potash feldspar, sericite, chloritization and fluorite. Associated and silver-bearing deposits often occur, and the scale of the deposits is mainly small.

(2) contact metasomatic deposits

Mainly distributed in southern Jiangxi, southern Hunan, northern Guangdong, central Guangdong, western Guangxi, eastern Guangxi and southeastern Yunnan. Such as Li Jiao, Baoshan, Pingtouling, Jinziao, Chuandu, Dongpo, Yaogangxian, Xianghualing, Dayishan, Dachang Mullah and Fozichong. Generally distributed along the tectonic magmatic belt, the ore-bearing strata are mostly Upper Paleozoic D2-P 1, and the surrounding rocks are mainly carbonate rocks or calcareous clastic rocks. Mineralization is related to the small-scale intrusion of biotite granite from the third stage of early Yanshan to the late Yanshan. Most deposits are controlled by NE-trending folds and faults, and the compound parts of regional multi-group fault structures and different types of structures are often very favorable for mineralization. Ore bodies are mostly formed in the contact zone between granite rock mass and surrounding rock, and are lenticular, layered and lentil-shaped, and some are vein-shaped. Main useful element combinations: W, Sn-Pb, Zn-Cu(Au)-Ag (associated), Ag-Pb, Zn-Cu, Sn-W-Bi-Be-Ag (containing Ag), W-Mo-Bi-Cu-Ag (containing Ag), Pb, Zn-Ag (*). Silver in ore can constitute an independent silver mineral or a silver-bearing mineral; The scale of silver reserves is mainly small and medium-sized, and some silver deposits can reach medium scale, such as Mullah, Li Jiao, Baoshan and Fozichong.

(3) Medium-high temperature hydrothermal deposits

It is mainly distributed in the south of Jiangxi, south of Hunan, north of Guangdong, north of Guangxi and southeast of Yunnan, and is dominated by vein-like or vein-like tungsten-tin polymetallic deposits, which were collectively referred to as chronological veins in the past. In recent years, it has been found that the silver content of these deposits or ore segments meets the requirements of * * * generation or even independent silver deposits, and most of them are distributed along the inner and outer belts of the tectonic-magmatic belt. The ore-bearing surrounding rocks are clastic rocks and carbonate rocks of Sinian-Devonian-Carboniferous-Permian. It is mainly related to Caledonian-Yanshanian granitic intrusive rocks, and the metallogenic period is mainly from the first stage of early Yanshan to the first stage of late Yanshan, in which the main metallogenic periods of lead, zinc and silver are from the third stage of early Yanshan to the late Yanshan, and a few are Xuefeng and Indosinian. Such as Xihuashan, Piaotang, Mao Ping, Dajishan, Huangsha, Shawankeng, Shirenzhang, Hongling, Meiziwo, Dongpo, Dayishan, Yaogangxian, Coral, Mangchang Mountain, Wuming Liangjiang and Gejiu Kafang.

Silver exists in the form of * * * ore, associated ore or other silver-bearing ore in various ore-forming element combination deposits, and the silver grade of some ore bodies can meet the requirements of independent silver ore. The scale of silver reserves is generally medium.

(4) Low-temperature hydrothermal deposits.

This type of deposit is one of the most important types of silver deposits in Nanling area. They are all distributed in the whole region, such as Gehu, Liumukeng, Chikeng, Daxing Mountain, Changgangling, Houpo 'ao, Yin Shi, Tiandong, Baoshan, Huangshaping, Tongshanling, Xianghualing, Mangchang, Maanshan, Laochang, Fenghuang Mountain, Jinshan, Sino-Soviet, Xia Dong and Xiachang. It is distributed in different tectonic units, mainly in the late Paleozoic-Mesozoic depression area, followed by the uplift area. The ore-bearing surrounding rocks are Sinian to Triassic. Mineralization is mainly related to Yanshanian granite. Some of them are related to Caledonian or Indosinian granitoids, and the ore-controlling structures are mainly east-west, north-northeast and north-west faults. The ore bodies are mainly veined and partly lenticular. The main ore-forming elements are lead, zinc, silver, gold and tungsten. Deposits dominated by lead and zinc coexist with silver, copper, arsenic, tungsten and cadmium; Independent silver deposits are often associated with lead, zinc, copper, tin and individual gold (such as Zhanggongling, Jinshan, Daxing Mountain and Changgangling). Tungsten belongs to a single scheelite (such as Liu Yi mining area). ).

(5) Volcanic hydrothermal deposits

This typical deposit only exists in eastern Guangdong. The bottom of carbonaceous shale in Jinji Formation of Lower Jurassic is andesite, and the surrounding rocks of Ag-Sb deposit are explosive breccia-dacite rhyolite-porphyry breccia lava (Mid-Autumn Ocean) and ignimbrite-tuff breccia-rhyolite tuff lava (Baoshan). The main mineralized elements are silver, antimony, lead, zinc, copper, silver, tin, lead, zinc and silver. In the combination of silver and antimony, silver is rich in grade, and other components are associated with or contain silver. There are large, medium and small silver reserves.

(6) Syngenetic sedimentary deposits

This type of deposits are mainly distributed in the late Paleozoic carbonate platform sedimentary area in the northern Guangdong depression, such as Yangliutang, Tianziling and other lead, zinc and silver deposits. The mining area is controlled by the NE-trending paleostructural fault depression zone, and a large number of contemporaneous sedimentary structural features can be seen. The ore-bearing strata are Devonian-Carboniferous, and the ore bodies are layered, quasi-layered and lenticular. The ore structure often retains layered, disseminated and biological residual structure. The main elements are lead, zinc and silver, accompanied by siderite and stibnite. It is a small and medium-sized * * (associated) silver deposit.

(7) Sedimentary transformation deposit

This type of deposit is one of the most industrially valuable silver deposits. Mainly distributed in the edge of uplift area, that is, the transition zone between depression area and uplift area, mostly carbonate platform deposits. Such as Fankou and Manjiazhai Pb-Zn-Ag deposits or Sb-Ag deposits. Another subtype is sedimentary-magmatic hydrothermal superimposed transformation type, such as Bainiuchang silver, lead, zinc and Dabaoshan polymetallic deposit. The formation of the deposit not only retains the sedimentary characteristics, but also has many magmatic hydrothermal metallogenic characteristics. The ore bodies are layered, layered, lenticular and a few veinlets. The main element combinations of the deposit are Cu, Pb, Zn, Ag, Pb, Zn, Sb and Ag. Silver is rich in grade, which meets the requirements of independent primary silver mine. Silver reserves are mainly large and medium-sized deposits. The genesis of Fankou silver, lead, zinc and Bainiuchang tin, lead, zinc and silver deposits in this kind of deposits is still controversial.

(8) Supergene deposit

Silver deposits are related to the surface weathering and transformation of rich minerals. Primary and supergene deposits are controlled by the same structure. The main elements of the deposit are W-Sn (Heshangtian), Mn-Pb, Zn (banded), Mn-Ag (Fenghuangshan oxidation zone), Sn-Pb, Zn-Ag (Xia Dong, Longshujiao) and so on. Silver grade is rich and poor, and silver reserves are mostly small and medium.

(3) Analysis of metallogenic mechanism

1. structural system transformation and metallogenic enrichment mechanism of gold deposits related to structural fracture zone (shear zone)

In the upsurge of gold prospecting in 1990s, many gold research and related viewpoints related to structural fracture zone (shear zone) appeared. According to the field investigation and summary, it is considered that the structural ore-controlling analysis of gold deposits should be paid attention to in the investigation and evaluation of gold deposits in this area, especially the structural fracture, fluid flow and mineral accumulation mechanism related to gold deposits (Wei Changshan et al., 1996), which involves mineral enrichment mechanism and prospecting direction. In Guangdong Hetai Gold Mine, Hunan Shanziping Gold Mine, Daping Gold Mine, Shenjiaya Gold Mine, Xianrenyan Gold Mine, etc. Thrust or low-gentle structural fracture zone and ductile shear zone, and there are early time-dependent ductile deformation superimposed ore-rich, time-dependent re-fracture ore-bearing, combinable breccia group, vertical and gentle reticulate vein combination, etc. Many ore-bearing fracture zones have lens bodies formed later, which indicate the movement direction of the main structural zone laterally. In Shuikoushan ore field, there are great differences in the gold content of fractures and corresponding veins in different development stages of structural fracture zone (shear zone), and the related prospecting indicators are structural decompression zone and silicified rock zone related to fractures; In Daping-Shanziping gold mine area, the gold ore body is lenticular in the shear zone intersecting with regional foliation, and a large number of alteration zones outside the shear zone are only gold mineralization or non-mineralization; Gold-bearing bodies are mainly silicified rocks produced by strong silicification of early tectonic rocks. Gold-rich gray silicified rocks often have ductile deformation, and pyrite also has crushing and pressure shadow. The residual time in the weak strain domain is similar to sugar grains, and the fracture network veins are superimposed in the later stage, that is, ivory silicified rocks (Cao, 2000; Chen Mingyang, 1996), indicating that the silicified body has undergone brittle → ductile transition and ductile → brittle transition after its formation. Similar tectonic dynamic mineralization can also be seen in Xikuangshan antimony deposit.

2. Genesis of "lateritic" gold deposits and epithermal gold deposits.

Laterite gold deposit is a supergene gold deposit, but it is not entirely formed by weathering of fine disseminated gold deposits. The development of lateritic gold deposits in this area is mainly found in western Guangxi, southern Hunan, northern Guangdong and western Jiangxi. This type of gold deposit has the characteristics of wide distribution, large scale, low grade, easy mining and dressing on the exposed surface, obvious prospecting signs and quick effect. It can become a mineral deposit in itself, and it can also be used as a sign for finding other types of metal deposits, so comprehensive prospecting methods should be paid attention to in mineral resources evaluation.

The epithermal gold deposit in southern Hunan is represented by Xianrenyan in Shuikoushan ore field and Dafang mining area in Pingbao ore field. Its metallogenic conditions can be summarized as "gold-bearing layer, fault structure, magma and hot spring action" (Liu Zhengtao, 2000), in which gold-bearing Ancient Spring deposits such as siliceous dolomite and micro-quartzite in Hutian Formation of Middle-Upper Carboniferous were formed, and hot water deposits in Dangchong Formation of Lower Permian were formed.

The main nappe fault zone in Xianrenyan gold mining area is strongly silicified, forming silicified breccia zone. Fault gouge and breccia belt are weathered and leached to form gold-bearing black soil breccia gold deposit. Thick and rich gold ore bodies are often controlled at the intersection of faults and the intersection of inversion anticline and regional nappe detachment structure. However, the hot spring "silicon cap" belt is generally linearly distributed in the northeast and north-south directions, which are not connected with each other and distributed in groups, forming steep ridges and isolated mountain bags. The shape of a single "silicon cap" is oval, round and long on the plane; On the cross section, most of them are conical, cylindrical and irregular dendritic. The "silicon cap" zone can be roughly divided into two types: silicified breccia body (zone), that is, silicified breccia body (zone) related to nappe structure in the early stage and "silicon cap" such as silica and spring glue formed by hot spring activities in the later stage. Black soil type gold deposits and "silicon cap" belts formed in different periods have different ore-bearing properties.

The lateritic gold deposits in southern Hunan are controlled by basement faults and distributed in a belt shape, with the characteristics of small thickness of weathered section, low maturity, strong dependence on source body type and gold content, single ore-bearing layer and small thickness. The secondary enrichment of gold is closely related to pyrite oxidation and limonite adsorption (Zeng Zhifang et al., 2002).

The lateritic gold deposits in Guangxi can be divided into seven categories, including carbonate rocks, volcanic rocks, altered tectonic rocks, fine clastic rocks, basic-ultrabasic rocks, skarns, hydrothermal sedimentary rocks and ancient glutenite. The first three types are relatively developed, and the gold yield is controlled by the development degree of ore source body, red weathering crust and mineralization physical and chemical conditions.

The "laterite-type" gold deposits in western Jiangxi are mainly distributed in Shui Yuan sag, with the characteristics of "three favorable ore-bearing horizons, three favorable ore-bearing lithology and three favorable element combinations" (Chen Dajing, 200 1). Among them, the laterite area formed by Pingle depression belt, which is related to the weathering of the mother rock of fine disseminated gold deposits, is the most favorable area for searching for laterite-type gold deposits.

3. Occurrence characteristics of silver ore related to structural alteration fracture zone.

Silver deposits related to structural alteration fracture zones mainly occur in western Guangdong and northern Guangdong, such as Liannan Bikeng Silver Mine, Yunnan Gaojian Silver Mine and Gaoming Dieping Silver Mine. This kind of silver ore often coexists with pyrite, sphalerite, chalcopyrite and other metal sulfides.

The surrounding rock of Gaojian Silver Mine is altered granite, and the ore body is obviously controlled by the east-west fault structural belt. The occurrence of structural belt is 170 ∠ 7 1, and a breccia belt with a width of 15cm is developed near the roof. Breccia is silicified rock and contains fine powdered pyrite. The breccia is smooth in shape and its long axis is parallel to the structural plane. Silicification, sericitization, pyritization and limonitization are the main characteristics of this zone, and the section is irregular. The ore minerals mainly include pyrite, galena, sphalerite, smithsonite and rhodochrosite, and galena is produced in colloidal lumps. Alteration and mineralization in mining areas can be roughly divided into three stages: ① silicified pyritization stage; ② Carbonization stage, mainly rhodochronization; ③ Silicification and pyritization stage (veinlet occurrence) and lead-zinc mineralization. Early (1) pyrite is authigenic massive; ② In the rhodochrosite stage, disseminated pyrite is distributed; (3) The stage is a timely veinlet (sulfide-bearing stage). The observation of borehole core shows that the deep lead-zinc mineralization in the structural belt is strengthened and the rhodochrosite is obviously reduced. The silver ore body is still mineralized in Cretaceous conglomerate, with grades of Ag270g/t, Pb0.056% and Zn0.052%, respectively, reflecting that the mineralization age is late Yanshan or early Himalayan.

The Bikeng silver deposit in Liannan is a near SN- trending ore-bearing silicified fracture zone in the NE-trending anomaly zone, and the metallogenic belt mostly occurs in the interlayer fracture zone. The metallic minerals in V2 ore body are mainly pyrite, chalcopyrite and bornite, and weak mineralization of chalcopyrite and bornite is found in V5 ore body, indicating that its primary ore is copper-silver mineralized body. The normalized rare earth distribution curve of shale in North America has negative Ce anomaly and negative Eu anomaly. Combined with the trace element content, it is speculated that there may be submarine volcanism in the early stage and magmatic hydrothermal superposition in the later stage.

4. Geological characteristics and alteration types of fine disseminated (Carlin-type) gold deposits in Yunnan, Guizhou and Guangxi.

Fine-grained disseminated type (Carlin type) is a deposit type with unique genesis, huge reserves and economic significance. This type of deposit is abundant in Yunnan, Guizhou and Guangxi, the northwest margin of Xiangzhong depression and the central Guangdong depression.

Fine disseminated gold deposits have a set of low-temperature hydrothermal mineral assemblages, including pyrite, barite, stibnite, realgar, orpiment, arsenopyrite, cinnabar and a small amount of heavy metal sulfides such as sphalerite, galena, tetrahedrite, chalcopyrite and white iron ore.

Combined with a large number of geochemical research results of predecessors, it can be considered that the ore-forming fluid medium of fine-grained disseminated gold deposits mostly comes from atmospheric precipitation, and the medium water leached the ore-forming materials through the mixed circulation of strata and construction water in the basin. The migration of ore-forming fluids is obviously related to the large-scale tectonic-thermal events (magmatic events) in the basin, and the mineralization has experienced fluid mixing, cooling and oxidation.

Fine-grained disseminated gold deposits in Yunnan, Guizhou and Guangxi are concentrated in Youjiang rift basin, sandwiched by Nanpanjiang fault zone in the northeast and Youjiang fault zone in the northwest. They are slightly triangular and structurally located at the intersection of the southwest margin of the Yangtze block and the Youjiang Indosinian fold belt of the South China fold system. Cambrian and Devonian strata are scattered in this area, while Carboniferous, Permian and Triassic strata are widely distributed. The northwest of Nanpanjiang fault is a platform facies area, which is mainly distributed in Permian-Triassic strata. Except Emeishan basalt is exposed between the lower and upper Permian in the northern margin, the lower part of the upper Permian is a coal-bearing stratum with alternating land and sea, and carbonate rocks are distributed in a large area. The southeast of Nanpanjiang fault is a trough clastic facies area, and the Triassic strata are mainly clastic facies with carbonate rocks. Clastic sedimentary rhythm is developed, and turbidite sedimentary structures such as Baoma sequence, groove pattern, contemporaneous slump accumulation and cyclotron bedding can be observed, which are the main gold-bearing rock series in the area. A series of fine disseminated gold deposits have been found in this area. In addition to Zimudang, Getang, Lannigou in Guizhou, Jinya and Gaolong in Guangxi, similar gold deposits have also been found in Dang Ge and Luoping Lubuge in Yunnan, indicating that Yunnan, Guizhou and Guangxi are important micro-disseminated gold mineralization areas and prospecting prospects in China.

An important factor affecting gold mineralization in this area is Permian Emeishan basalt widely distributed in the north of this area, and Triassic turbidite deposits in deep water and semi-deep water basins are developed in this area.

There are no magmatic rocks in the area, but according to the regional gravity data, it is considered that there are two concealed granite belts in the deep part of the area, one is Xingren-Nandan concealed granite belt, and the other is Longlin-Bama concealed granite belt, but their genetic relationship with fine-grained disseminated gold deposits in the area remains to be studied.

The alteration of fine disseminated gold deposits in this area is not very strong, the zoning is not obvious, and the metasomatic dissolution is not developed, so it is difficult to distinguish the exact boundary between surrounding rock, mineralized surrounding rock and ore body in macro. However, the basic types of wall rock alteration can be determined, including decarbonization, silicification, argillization, vulcanization and carbonization.

Silicification can be divided into at least three stages: silicification in the early stage of mineralization, forming cryptogranular and granular chronology, which is prominent in Banqi and Getang gold mines; During the main metallogenic period, silicification often forms a fine network vein-like time. This period is characterized by clean surface and good transparency, and often coexists with dolomite, arsenopyrite and pyrite. Silicification in the later stage of mineralization forms rough and clean time veins or comb-like time veins, most of which contain coarse authigenic pyrite, chalcopyrite, sphalerite, white iron ore and dolomite-time veins.

Mudification is one of the important alterations of gold mineralization, mainly forming illite and dickite, which are widely developed in all deposits. From the analysis results, the stronger the mud, the higher the clay mineral content and the higher the gold content, indicating that there is a positive correlation between them. Carbonation occurred in the later stage of mineralization, forming calcite and a small amount of dolomite.

The formation of micro-disseminated gold deposits in Yunnan, Guizhou and Guangxi can generally be divided into four metallogenic stages, namely pyrite-isochronous stage, arsenopyrite-pyrite-illite-isochronous stage, polymetallic-dickite or polymetallic sulfide-isochronous stage and late metallogenic stage. Metallogenic period is generally divided into hydrothermal period and supergene period.

5. Formation mechanism of gold and silver deposits related to intermediate-acid granite (porphyry).

Mainly distributed in the middle and lower reaches of the Yangtze River. The ore body occurs in the contact zone between Yanshanian granodiorite porphyry and Triassic carbonate rock. Mineralization is mostly related to Yanshanian intermediate-acid granite (porphyry), and its formation age is consistent with that of intermediate-acid granite (porphyry) (140 5 Ma). Representative deposits are: Jilongshan, Fengsandong, Li Jiawan, Jiguanzui and other large and medium-sized copper-gold polymetallic deposits.

Second, the metallogenic relationship between precious metals and nonferrous metals.

Tungsten-tin deposit is a kind of deposit with strong metallogenic specificity, which is closely related to granite magmatism. Tungsten, tin, niobium and tantalum deposits are closely related to crust-derived granite in the early Yanshanian period, while copper (iron), lead and zinc deposits are closely related to crust-mantle mixed-source granite, belonging to hypabyssal granite controlled by fault zone. Cheng and Chen Yuchuan (1979) proposed lead, zinc and sulfur (silver, copper, mercury and antimony) deposits related to crust-mantle mixed-source granodiorite and rare, rare earth, tungsten, tin, copper, lead, zinc, antimony, mercury and silver (molybdenum and antimony) deposits related to crust-derived biotite granite. Mineralization types are different in different areas of Nanling. Generally speaking, southern Jiangxi is dominated by tungsten mineralization, while the western part of Nandan Hechi in northern Guangxi is dominated by tin, lead, zinc and antimony mineralization, and the eastern part is dominated by lead and zinc. Tungsten, tin, lead and zinc are very important in southern Hunan and northern Guangdong, with tin as the main component in eastern Guangdong and southeastern Yunnan, and lead and zinc as the main component in southeastern Yunnan. The relationship between silver and tungsten, tin, (lead, zinc) minerals also varies with different regions and metallogenic ages. This spatial distribution inhomogeneity depends on the temporal and spatial evolution of structure-magma-mineralization, and is related to the inhomogeneity of element distribution to some extent.

Precious metal deposits in Nanling area have obvious genetic relations with tungsten, tin and lead-zinc deposits, mainly in the following aspects:

1. the relationship between gold deposits and tungsten-tin deposits

With the continuous improvement of work and research, a number of primary gold deposits (spots) have been discovered in southern Jiangxi. Up to now, more than 50 rock gold deposits (spots) have been discovered in the study area, which are distributed in Xingguo-Ruijin, Shangyou-Xinfeng, Sannan (Dingnan, Longnan and Quannan)-Xunwu and other areas, mainly concentrated in tungsten-tin ore concentration areas or the periphery of tungsten-tin mines.

This study shows that the gold deposits in Gannan have the following characteristics: ①95% of the gold deposits are distributed in Precambrian strata, and the gold abundance of host rocks is high, which is generally 2 ~ 3 times that of the crust (Wang Dingsheng, 2001); ② Gold deposits are closely related to magmatic rocks, and the gold abundance of magmatic rocks near almost all gold deposits (spots) is relatively high; ③ The structure obviously controls the gold deposits, and the spatial distribution of almost all gold and silver deposits is directly controlled by the fault structure; (4) Gold-silver deposits are mainly distributed in the concentration area or the periphery of tungsten-tin deposits, and the tungsten-tin deposits have obvious mineralization zoning phenomenon. Although some researchers have realized that there may be a certain genetic relationship between gold deposits and tungsten-tin deposits in this area, they have not studied tungsten-tin deposits and gold deposits as a metallogenic system in depth, and the following problems need further study:

1) Metallogenic age of gold deposit. Although gold deposits and tungsten-tin deposits exist in space, they are synchronous in mineralization time, formed by the superposition of mineralization in different eras, or are they the products of metallogenic magma in different evolution stages in the same period?

2) Magmatic rocks related to gold mineralization. That is to say, it is necessary to systematically divide and classify the diagenetic age, lithologic characteristics, geochemical characteristics and structural background of magmatic rocks related to gold mineralization, summarize their laws, and clarify the differences and relations between magmatic rocks related to tungsten-tin mineralization through comparative analysis.

3) Metallogenic mechanism and model of gold deposits in this area.

2. The relationship between silver mineralization and mineralization time of tungsten, tin and lead-zinc deposits.

The metallogenic age of W-Sn (Pb-Zn) in the study area can be divided into five metallogenic periods: pre-Caledonian period, Caledonian period, Variscan period, Indosinian period and Yanshan period, among which Yanshan period can be divided into the second and third periods of early Yanshan period and the early Yanshanian period. Yanshan period is the most important metallogenic period in this area. There are different combinations of deposit types in different metallogenic stages. Silver ore is produced by different stages and types of tungsten, tin and lead-zinc ore, and it also has its own mineralization characteristics.

Tungsten-tin mineralization is dominant in southern Jiangxi, which was formed in 170 ~ 104 Ma, which is closely related to the granite intrusion in the second and third phases of early Yanshan and early late Yanshanian. The whole mineralization can be divided into 5 ~ 7 stages. Silver mineralization began with early tungsten mineralization and ended before the last carbonation stage, but mainly in the third or fifth stage, a series of deposits with different genetic types and mineralization element combinations were formed, including contact metasomatic silver-tungsten deposits, silver-bearing quartz-vein tungsten deposits, (tin) deposits, intermediate-temperature hydrothermal silver-tungsten deposits and silver deposits. This series of tungsten (tin)-silver deposits is a series of products under different temperature and pressure metallogenic conditions in the same magmatic-hydrothermal evolution process. Silver and tungsten are enriched in different mineralization stages of the same deposit, and the peak of silver enrichment is later than tungsten, so the silver content is not high when the tungsten content is high in space, and it decreases when the silver content is enhanced in the middle-high temperature-middle-low temperature stage.

Tungsten, tin, lead and zinc deposits in southern Hunan are concentrated, and the genetic types range from contact metasomatism to medium-low temperature hydrothermal type. Mineralization is closely related to the emplacement of Yanshanian granite. Most of the known deposits are located in the contact zone or surrounding rock of small rock mass with high intrusion. Tungsten mineralization is mostly confined to the high-temperature hydrothermal stage, tin mineralization time is a little later than tungsten, and it is mainly high-temperature hydrothermal. Lead-zinc-silver mineralization time is relatively late, and it is dominated by medium-low temperature hydrothermal stage. In the early stage of tin mineralization, the enrichment of silver was enhanced, but when lead and zinc were enriched in large quantities, tin was at its wit's end and the enrichment intensity of silver was enhanced. Generally speaking, the time sequence of mineralization is tungsten → tin (copper and silver) → lead, zinc and silver.

Dachang ore field (deposit) is related to late Yanshanian hypabyssal granite (Rb-Sr age is 99 6 Ma ~115 3 Ma). Chen Yuchuan et al., 1993), the mineralization of cassiterite-sulfide polymetallic, silver, antimony, arsenic and mercury can be divided into five stages. Silver deposits are mainly formed in the second mineralization stage of tin, silver, sulfide-sulfide-carbonate mineralization.

Tungsten, tin, lead, zinc and silver deposits in southeastern Yunnan are all distributed near three small rock bodies protruding on the Yanshanian granite foundation. Due to the development of sulfur-tolerant tin ore in this area, lead, zinc and silver are mainly precipitated and mineralized in sulfide stage, and the metallogenic temperature ranges from 260 ~ 350℃ in Gejiu to 108 ~ 3 1℃ in Bainiuchang (Yu Chongwen, 1987). Generally speaking, the mineralization age of silver is the same as that of tungsten and tin, but the mineralization time is later than that of tungsten, slightly later than that of tin and slightly earlier than that of lead and zinc, ending before the carbonate stage.

The main mineralization is tungsten and tin, and the associated silver mineralization is obvious in the multi-stage development from high temperature to low temperature, and the single-stage silver mineralization is poor or not.

3. Spatial relationship between silver mineralization and tungsten-tin deposits.

Silver mineralization and tungsten-tin deposits in Nanling area are often associated with each other in space, and often show the characteristics of evolution from high temperature to medium-low temperature deposits centered on Yanshanian granite. For example, Gejiu metallogenic area in southeastern Yunnan is centered on Yanshanian granite body, which appears outward in turn: W, Mo, Bi→Cu, Sn→Sn, Zn, Ag→Pb, Zn, Ag gradient deposit series; Dachang ore field in western Guangxi is also centered on the Longgai granite body, and the zoning phenomenon of Co, Zn, Ag (skarn mineralization period) →Sn, Zn, Pb, Ag, Sb (cassiterite-sulfide polymetallic mineralization period) →W, Sb (tungsten-antimony mineralization period) appears in turn. Large independent silver deposits are often associated or tin-bearing in the deep. For example, there are silver, tin, lead and zinc deposits in Houpo 'ao, Chaozhou City. Silver is a large deposit, with tin, lead and zinc all reaching medium scale. Tin associated with silver in the deep part of Bainiuchang silver deposit has also reached industrial grade. This reflects the relationship between thermal effect and temperature gradient of the deposit, which is a common phenomenon in Nanling area.

The regional metallogenic geological environment and the specific deposit location mechanism are mutually restricted and interdependent, which varies from place to place, so there are many deposit combinations, types and scales in the same area (belt). For example, the tungsten and silver deposits in eastern Guangdong are spatially distributed in Yongmeihui sag, especially in Meixian sag in the north, resulting in a huge eastern fold fault-magmatic rock belt, which is controlled by the Yanshanian complex in the third phase. The tin-silver deposit is controlled by Lianhuashan and Chaopuning Haifeng deep faults. Lead, zinc and silver deposits are relatively concentrated in the Lianhuashan fault zone and its vicinity. The spatial distribution of copper, lead, zinc, silver, silver, antimony and gold-silver deposits is mainly controlled by volcanic basins and east-west faults. Another example is the gold and silver deposits on the edge of Yunkai uplift in southeast Guangxi, from Pangxidong-Jinshan-Suzhong-Wangtiandong in Lianjiang, Shike-Xia Ying-Longshui-Zhanggongling, etc. It is obviously controlled by Bobai-Cenxi deep fault and deep source syntectic granite magma activity.

The mineralization of tungsten, tin and silver in this area has the overlapping transition relationship of "synbiotics" and "synbiotics" in space. For example, the Yaogangxian tungsten-silver deposit is a multi-stage and multi-stage metallogenic superposition, and the magmatic activities in each stage have experienced gas-generated high-temperature hydrothermal solution to medium-low temperature hydrothermal solution, forming various types of silver deposits of tungsten, tin, copper, molybdenum, lead, zinc and other minerals and "contemporaneous" silver deposits of tungsten and tin. But generally speaking, from rock mass outward or from deep to shallow, from silver, tungsten and tin deposits to silver, lead and zinc deposits. For example, Yaogangxian 50 1 vein is 950m→820m→ 1 10m, and the average grade of silver is 57.6g/t → 1 18.5g/t, reflecting silver. There are two types of ore-forming elements in the tungsten-silver deposits in southern Jiangxi and southern Hunan: ① Tungsten and silver in the tungsten (tin) and silver * * * * deposits are zoned, in which the silver-bearing chronological tungsten deposits and the mesothermal tungsten-silver deposits are generally vertically zoned in reverse, with tungsten enriched in the middle and upper parts and silver enriched in the lower parts; Skarn-type silver-tungsten deposits are generally divided along the direction, with tungsten ore bodies below and silver ore bodies above. This zoning is also manifested in the horizontal direction, where tungsten ore bodies and silver ore bodies are parallel or banded. (2) There is no zoning or zoning phenomenon in lead and silver deposits, which is not obvious. The vertical zoning between silver-tungsten-tin deposits in eastern Guangdong also has obvious regularity: general tungsten-tin mineralization has the characteristics of multi-stage and multi-stage reverse zoning, tungsten-tin mineralization is mostly concentrated in the middle and upper parts of ore bodies, and polymetallic sulfides increase downward, that is, the middle and upper parts of ore bodies are tungsten-tin deposits, and the lower parts are gradually transformed into lead-zinc-copper-silver ore bodies. For example, in Houpo 'ao mining area of Chaozhou, tin appears in the upper part and lead, zinc and silver appear in the lower part; Zoning phenomenon of tungsten, (tin), copper and silver in the upper part of Guankeng mining area

4. The correlation between silver mineralization and tungsten-tin mineralization and the relationship between silver mineralization and metallogenic granite types.

1) For silver deposits related to molten granitoids, silver is mostly associated with gold and polymetallic ores or occurs in * * *, but has no obvious correlation with tungsten and tin ores. The geochemical characteristics of the deposit are that the contents of Ni, Co, Cu, Mo, Ag and other elements are high, which are basically the same as or similar to the trace elements of syntectic granite. Such as Pangxidong, Jinshan, Zhanggongling and other deposits, the primary halo is vertically zoned: the pre-element is Sr-Mn-Ni-Co, the ore element is Cu-Ag-Pb-As-Zn-Au, and the ore tail element is Sb-Mo. This kind of deep syntectic granite intrudes along Bobai-Cenxi fault zone and Lianhuashan fault zone, and the rock mass generally contains high Ag, which can form independent (or * * *) silver deposits. Mineralization related to syntectic granitoids in southern Hunan and eastern Guangdong mainly exists in the depression and its edge. The second stage of Yanshanian is dominated by mineralization of intermediate-acid granite, mainly forming lead, zinc and silver deposits, often accompanied by copper, tin and tungsten mineralization.

2) Mineralization related to remelting granitoids in continental crust is manifested in uplift area, with the mineralization of granite in the first stage of early Yanshanian as the main stage, forming a mineralization concentration area dominated by tungsten deposits. For example, early Yanshanian biotite granite or biotite feldspar granite in southern Jiangxi uplift area formed silver-bearing time-pulse type tungsten (tin) deposits, contact metasomatic silver, tungsten deposits, intermediate hydrothermal silver, tungsten deposits and silver deposits (including gold and silver deposits containing tungsten and tin). At the edge of the uplift and depression, a metallogenic belt dominated by tungsten and tin accompanied by copper, lead, zinc and silver deposits was formed. Chenzhou area is on the edge of uplift and depression, and granite magma activity lasts from early Yanshan to late Yanshan. Mineralization has gone through the stages of mainly tungsten → mainly tungsten and tin → mainly lead, zinc and silver, and the metallogenic peaks overlap many times, forming many large deposits such as Shizhuyuan, Hongqi Ling, Yaogangxian, Darjeeling and Dongpo Mine.

3) Multiple intrusions and mineralization of granite magma are another feature of Nanling mineralization. For example, the Yaogangxian complex granite body has four intrusions and four mineralization, and the size of the rock body decreases from large to small from morning till night. The first three times of mineralization were dominant, and each intrusion was accompanied by metal mineralization. From the first time to the third time, the metal sulfide gradually strengthened and invaded from southeast to northwest, forming the zoning of tungsten-silver mineralization → lead-zinc-silver mineralization. Another example is an old mining field. In the west of Indosinian-Yanshanian granite, there are Jiashahui monzonite, Longchahe porphyritic biotite granite, Baiyunshan alkaline syenite and Changlinggang nepheline syenite. There are many occurrences of silver-lead and tin-lead in the outer edge of Longchahe complex. The eastern part is a buried composite biotite granite foundation with a buried depth of 200 ~ 1000 m, and only a small area is exposed in Baishachong, Beipaotai and Baishapo. The protruding parts of the buried rock mass (Ma Song and Laoka) are all mineralized with industrial tin, lead, zinc and silver.