Characteristics, distribution and genesis of quartz vein type gold deposits

(1997) dividing the Chinese Li Shu and other gold deposits of 10 industrial type, which are quartz vein type, mylonite type, alteration cataclasite type, Adularia - sericite quartz vein type (including sulfate and suicide Rock type), breccia type, skarn type, fine disseminated type, laterite type, iron hat type and gravel layer type.

The statistics show that the quantity and gold reserves of quartz vein type gold deposits account for more than 50% of the total gold deposits and total gold reserves in China. Quartz vein type is an important gold mining industry type in China. Quartz vein type gold deposits refer to gold-bearing geology. The gold-bearing quartz veins, which are mainly quartz veins, contain more minerals such as K-feldspar, which are called K-feldspar quartz vein type gold deposits, but their geological characteristics and geological environment are produced. In terms of industrial significance, these gold deposits are still a typical vein-like deposit of quartz vein type gold deposits. The output of gold-bearing geological bodies is strictly controlled by the fault system; the output surrounding rock is mainly Taiguyu metamorphism. Rock series and Phanerozoic granitic complex, also have Yuanguyu and Xianshengyushallow metamorphic rock series; the composition of gold-containing veins is simple, mainly quartz, pyrite-based sulfide and natural gold, individual deposits There are scheelite , stibnite , etc.; the content of gold sulfide in the vein is not uniform, the grade of gold varies with the amount of minerals such as gold sulfide, and the variability is large. The vein is often divided into many non-mineral sections. Gold-containing veins are usually single veins

The geographical distribution of quartz vein type gold deposits is mainly concentrated in Jiaodong, Xiaoqinling, Yanliao-Wulashan, eastern Liaoji, etc. In addition, in the areas of Xiangxi, Yunnan Sanjiang, and northern Xinjiang, the above areas are mostly located in geological structures. Ancient or ancient plate marginal active belts in the ancient plate, such as the Huaxiong block in the Xiaoqinling area, the Jiaobei and Jiaonan blocks in the Jiaodong area, and the northern marginal active belt in the Yanliao-Wulashan area. There are a large number of gold deposits, such as Shandong Linglong, Jiuqu, Lingshangou, Yushan Xiaoqinling Wenyu, Jinyu, Hebei Jinchangyu, Dongping, Inner Mongolia Hadamenggou, Liaoning Wulong, Jilin Jiapigou, Hunan Woxi, Yunnan Jinchang, Xinjiang Qiyiqiu and so on.

Gold-bearing geological features

The gold-bearing geological body of the quartz vein type gold deposit is a gold-bearing quartz vein. According to its output form, it can be further divided into quartz single vein, quartz complex vein and quartz network vein in different deposits. The main body of gold-bearing quartz veins can be Single vein, complex vein, or mesh vein, but in the same deposit, it is common to see that the single-pulse, complex vein and network vein coexisting gold-bearing quartz veins have a regular change with the elevation (buried depth). In fact, the quartz vein type gold deposit bed (near-surface) is a quartz single vein, which gradually becomes quartz complex vein and quartz network vein downward. This characteristic is particularly obvious in the Jiaodong gold mineralization concentration area.

The gold-bearing quartz veins vary in size, shape and shape in each deposit. The lengths of different veins range from 10 cm to several kilometers (up to 5 km in Jiaodong), and the width ranges from 10 cm to more than 10 m. The output of the vein is strictly controlled by the fracture structure (band), and the distribution of gold-bearing quartz veins generally does not exceed the ore-bearing structure interface. The gold-bearing quartz veins have common branches, complexes, and pinpoints. The branch vein intersecting with the main vein, and the main vein and the branch vein constitute the industrial ore body at the same time. Some of the mining areas are parallel to the main vein and the main vein constitutes a complex vein, and the complex veins are usually perpendicular to the gold-bearing quartz veins. (Net vein), such as the gold ore body (or gold-bearing quartz vein) in the step-like veins of the Woxi mining area, the space is often geese or obliquely distributed to contain gold quartz veins. Changes in the appearance of the changes, whether in the direction or the tendency, most of them are soothing undulations, which are characterized by the expansion and tilting of quartz veins, and their tendency and inclination are like the Xiaoyingpan gold mining area. The overall occurrence of the complex vein zone is: Going to NE46°, tending to SE, dip 4°, Xishan and Dongshan mining sections The tendency of the veins is mainly SE, while the tendency of the veins in the Dadonggou section is dominated by SW.

The size, shape and occurrence of gold-bearing quartz veins have an effect on mineralization and enrichment. Generally speaking, the thick and stable gold-bearing quartz veins are stable and continuous, sometimes with a small number of rapidly sharpening branches. The high mineral content of the veins often constitutes the main industrial ore body; the stable but small thickness of gold-bearing quartz veins, although the extension is relatively stable, and often parallel veins, but its ore ratio is often not high, industrial value is low, The industrial ore bodies are mostly small-scale lean ore bodies; lenticular gold-bearing quartz veins or vein groups, although they are commonly seen in their strikes, are generally relatively stable in tendencies, often with ore-rich bodies In the case of a combination of gold-bearing quartz veins, a combination of confluence or thin veins, and a thick vein or large lens body, mineralized and enriched areas often appear in gold-bearing quartz veins, which constitutes an important industrial significance. Ore body.

Ore body characteristics

In the quartz vein type gold deposit, the gold ore body is mainly confined to the gold-bearing quartz vein, so the ore body shape, occurrence, scale, etc. vary with the change of the form, occurrence and scale of the gold-bearing quartz vein. There is a clear boundary between the body and the surrounding rock, and some also show that the transitional ore body is generally vein-like, but due to the difference in the location of the ore body in the gold-bearing quartz vein and the mineralization intensity and mineralization. The difference in continuity, etc., often occurs in lenticular, lenticular ore bodies in thick gold-bearing quartz single veins, gold ore bodies tend to be larger in size, mineralization continuity is better, ore bodies are mostly veined. The ore body also appears to be abrupt and reappearing in the trend and tendency. The gold ore body in the gold-bearing quartz complex vein belt has a large number of scales, and the size of the ore body is large. The ore body often presents in space. Regular arrangement, such as the appearance of many geese and oblique rows on the plane, appears in the multi-layer ore body containing gold quartz veins or veins in the section, in the case of a single quartz vein, the mineralization is continuous and stable. High grade, with a large number of gold-containing quartz fines with abrupt boundaries between the surrounding rocks

Such ore bodies tend to be inferior to the ore bodies in the gold-bearing quartz single vein or in the complex veins in terms of their industrial value. The gold ore bodies in such gold deposits often have side-effects, such as the Jinchang gold deposit in Hebei Province. 4 The ore body of the north of the exploration line is facing the NE side, the side angle is 48°, the south side is facing the SW side, the side angle is 25°, the upper side is slow and steep, and the whole is “eight”-shaped distribution; the Xiaoqinling gold ore field 60 vein The ore body of the Yangzhaitun ore section is facing the SW side; the gold ore body of the 108th vein of the Linglong gold ore field is facing the NE side; the gold ore body of the L7 vein of the Qiyiqi gold deposit is located to the NW side, etc. Lateral phenomenon, mastering the law of laterality, is very beneficial for the exploration and development of blind ore bodies.

In short, in the gold-bearing quartz vein type gold deposit, the shape and occurrence of the ore body are simpler than other types of gold deposits, which is conducive to the exploration and exploitation of this type of gold deposit, and is also easy to identify, so it is more A class of gold deposits recognized and exploited 2.3 ore characteristics 2.3.1 Mineral composition The gold ore of the quartz vein type gold deposit is mainly gold-quartz-metal sulfide type, which can be further divided according to the amount of metal sulfide contained in it. It is a metal-depleted sulfide-gold-quartz ore, a small metal sulfide-gold-quartz ore, a sulfide-gold-quartz ore, a polymetallic sulfide-gold-quartz ore, in which a sulfide-gold-quartz ore is the main ore. The ore metal sulfide composition and sulfide content of each type of deposit vary with the geological background of the production and the ore-controlling conditions. The different ore sections of the same deposit are also different (Table 1), but there are also commonalities, namely useful minerals. Silver ore and a small amount of specular iron ore, white lead ore, molybdenum lead ore, scheelite, wolframite , arsenopyrite, etc.; gangue minerals are mainly quartz, feldspar (potassium feldspar, plagioclase, etc.), iron white clouds Stone, sericite, chlorite, calcite , barite, etc. Due to the geochemical background of the ore-forming area, the mineral composition of some quartz vein type gold deposits is very different, such as the gold ore of the Woxi gold deposit in Hunan, metal. The main minerals are stibnite, scheelite and scheelite; the Dongping gold deposit in the alkaline granite on the northern margin of the North China block and the Hadamenggou gold deposit associated with alkaline pegmatite in the Taiguyu metamorphic rocks. A large number of potassium feldspars are found in the stone minerals; the Qiyiqi gold deposit, which is produced in the shallow metamorphic volcanic rocks in the Junggar continental margin, often has toxic sand in the ore.

Trace element

Many studies on the trace element characteristics of ore in quartz vein type gold deposits show that the trace element combinations of most deposits are the same or similar, that is, the elements closely related to Au are mainly Ag, Cu, Pb, Zn, W. , Mo, Sb, Bi, As, etc., while Co, N, Cr, Ba, Se, Te, etc. are not related or related to Au Quercetin. 2), the element combination is: Sb-Hg-As-Ba-Zn-Co-Ni-Cu-Ag, Au-Bi-Pb-Mo-W. That is, the primary halo front elements are Sb, Hg, As'Ba, Zn, the ore body elements are Au, Ag, Cu, Bi, Ni, Co, and the tail elements are Pb, Mo, W. The correlation between the components of the primary halo varies with the elevation, but the general characteristics are: 1Au component (ie refers to the component containing Au) stable components are Au, Bi, Ag, Cu, Sb, As, unstable components The symbiotic relationship of Pb, Co, Hg and Ba; 2Au and Bi decreases from top to bottom. The similarity coefficient of Au and Bi decreases from 0.941 to 0.869, and then deep Pb and Bi closely symbiosis; 3Au, Cu similarity The coefficient increases from 0.609 to 0.871 from top to bottom; the similarity coefficient of 4Au and Cu changes from top to bottom to 0.904-0.710-0.782; the symbiotic relationship of 5Au and Pb is similar to Au and Cu, and As is always reduced.

In short, the trace element combination of ore is affected or restricted by the surrounding rock geochemistry, ore-forming material source and ore-forming hydrothermal properties. The combination of trace elements in each deposit is different, but it can be divided into Au-Ag-(Cu) type and Au. -Ag-Pb-(Zn)-Bi-As-Sb-(W) type, Au-Cu-Cr-Ni-Pb-Zn type and Au-W-Sb type Au-Ag-(Cu) type represent North China Trace element combination of gold deposits in the continental block; Au-Cu-Pb-(Zn)-Bi-As-Sb-(W) type and Au-Cu-Cr-Ni-Pb-Zn type represent continental marginal zone and collision The combination of trace elements in the gold deposits in the orogenic belt; the Au-W-Sb type represents the combination of gold deposits in the Yangtze block.

Ore structure

There are more than 10 kinds of ore structures in the gold-bearing quartz vein type gold deposits, but the most common ones are self-formed granular structures, semi-self-shaped-heavy-grained structures, fragmented structures, filled metasomatic structures, and solid-solution melting structures. The common structures of ore in gold deposits are block-like structure, clump-like structure, strip-like structure, disseminated structure, fine vein-net vein structure.

Surrounding rock alteration characteristics

Wall rock alteration is a common phenomenon in hydrothermal deposits. Quartz vein type gold deposits are also the same as gold-bearing geological bodies. They are also controlled by fault systems and have a linear distribution in space. The type of alteration and its distribution of different deposits and the intensity of each type of alteration are different, but as the same type of gold deposit, the common type of surrounding rock alterations of quartz vein type gold deposits are silicified and shale Because of the spatial differences in the types of surrounding rock alterations and the degree of development, the deformation of the surrounding rock is often obvious, such as chemical, pyrite mineralization, potassium-long petrochemical, sericitization, chlorite, and carbonation. The zonality of the surrounding rock is different in different regions and different deposits.

The surrounding rock alteration of the quartz vein type gold deposit in the Xiaoqinling area can be roughly divided into the inner belt, the middle belt, and the outer belt. The alteration effect is strong, the replacement is complete, the development of silicification, pyrite mineralization, sericitization, etc. The two sides of the body are distributed on the two sides of the ore body with correspondingities but the width and width; the middle belt is generally dominated by sericitization and silicification, distributed outside the inner belt, and the rock has the structure of residual and other structures, and is limited to fracture and fracture. In-band development; the outer belt is mainly chlorite, sericitization, and the rock basically maintains the original rock structure, and the outward transition to the gold-bearing quartz vein type gold deposit in the Jiaodong area can be roughly divided into two major eclipses. The zone is changed from the ore body to the outer zone. The inner zone mainly develops silicification, pyrite mineralization, and sericitization. The outer transition gradually changes to the outer alteration zone dominated by sericitization (potassium) to contain gold potassium. The feldspar quartz vein is a quartz vein type gold deposit mainly containing gold geological bodies. The surrounding rock alteration is different from the above. For example, the Hadamenggou gold deposit can clearly distinguish two alteration zones from the ore body: 1 potassium The feldspar-carbonate alteration zone, the internal alteration zone, is produced along the sides of the ore body. Breeding, controlled by the ore-bearing fissure, is characterized by completely interfering with the main fractured rock and forming a 0.5^1m wide block-like alteration, which is formed along the branching fissure to form a few millimeters and a few centimeters wide of the K-feldspar-carbonate The veins or fine veins are formed along the cross-fractures to form a red-recognition network. The breccia in the gold-bearing quartz is completely replaced by the K-feldspar altered rocks or replaced along the edges to form a red alteration ring. The mineral composition of the rock is basically replaced by altered minerals, forming micro-plagioclase, iron dolomite, calcite and a small amount of albite and quartz; 2 chlorite-silica-mite alteration zone, ie external alteration zone, which is represented by the original rock Decoloration occurs, forming altered minerals such as chlorite, sericite, carbonate, etc. The altered rock retains the original rock structure and residual minerals, and its alteration width is much larger than that of the inner belt, regardless of the geological environment. In the quartz vein type gold deposit, most of the surrounding rock alterations show obvious horizontal zoning, which is generally outward from the ore body, showing strong transition from strong silicification, metal sulfide mineralization to sericitization and chlorite. Alteration with distance from mineralization center

In China, quartz vein type gold deposits are mainly produced on the edge of the ancient plate, especially concentrated at the edge of the North China block. These areas are distributed with Archean gold-bearing metamorphic rocks or gold-bearing granitic complexes, the most famous such as the Xiaoqinling gold mineralization concentration area on the southern margin of the North China block, and the eastern Jiaodong gold mineralization concentration area. And the gold mineralization concentration area in the northern margin. In addition, the gold deposits of this type are also present in the margin of the paleo-continent or paleo-uplift zone where the Yuanguyu gold-bearing shallow metamorphic rock series are distributed, in the depression area of ​​the edge of the block or in the Jura Valley. Out.

In the western part of China, this type of gold deposit is mainly produced in the ancient island arc or passive continental margin zone of the ancient plate since the Paleozoic, such as the West Junggar and Ailaoshan gold mineralization concentration areas, which are distributed in this geological tectonic background. There are Paleozoic gold-bearing shallow metamorphic rocks and ophiolitic complexes invading them. The two tend to constitute the mixed-stacked quartz vein type gold deposits. The output is controlled by various fault structures and produced in the Archean gold-bearing metamorphic rocks and granaries. The gold deposits in the complex rocks and the Paleozoic shallow metamorphic rocks are mostly controlled by the brittle-ductile shear zone or the brittle deformation zone superimposed thereon. Under this structural condition, gold-bearing quartz veins or quartz complex veins are formed. The ore body is large in scale and relatively simple in shape. On both sides of the gold-bearing quartz vein, the gold-bearing altered fractured rock sometimes has industrial mineralization, and together with the gold-bearing quartz veins constitutes a gold ore-elemental palaeozoic gold-bearing shallow metamorphic rock series. In the quartz vein type gold deposits, the ore-controlling structures are mostly interlaminar fractures or fractured fracture systems associated with the fold structure. The gold-bearing quartz veins produced in them are relatively small but large in number, and often form gold-bearing quartz networks. Pulse, where The number of ore bodies is large, but the scale is relatively small and the shape is relatively complicated. Table 3 lists the geological environment produced by some quartz vein type gold deposits in China, which basically represents the geological background of the production of the Chinese quartz vein type gold 1 deposit.

According to the traditional metallogenic theory, the quartz vein type gold deposit is the product of the post-magmatic hydrothermal and metamorphic hydrothermal fluids. The quartz vein type gold deposit is classified as metamorphic hydrothermal type and magmatic hydrothermal type in the genesis, and the ore-forming material is mainly From the surrounding rock, most deposits are formed under medium-deep, medium-shallow conditions. Most of the intermediate-temperature hydrothermal deposits have accumulated a large number of gold deposit isotopes and fluid inclusion test data with the development of testing techniques. These data indicate quartz vein type. The ore-forming medium of gold deposits includes both magmatic hydrothermal fluids and metamorphic hydrothermal fluids. Some of the additions of atmospheric precipitation indicate that the formation of most quartz vein-type gold deposits is a multi-stage re-creation, especially large-scale, industrial value. This is especially true for high deposits.

The gold minerals in the quartz vein type gold deposits are mainly natural gold and silver gold ore. Some mineral deposits also see gold sulfides. The gold minerals such as sulfur gold ore have a large particle size change, and sometimes the particle size is visible in the same light sheet. Gold minerals differ by tens of times, but in general, fine gold and medium gold are common. Some mines also account for a large proportion of coarse gold. The gold in the quartz vein type gold deposit has the following two occurrence states:

1 intergranular gold: also known as crystal gap gold, is the main form of gold minerals, which exists in the gaps of various mineral particles such as quartz and pyrite, or the gold minerals between the sulfide particles are thicker ( >0.001mm), the grain size of the quartz particles is larger, and the shape of gold between the gold particles varies with the shape of the filling space. Common granular, irregular granular, triangular, scoop, diamond shape, blade Shape and so on.

2 Fracture gold: generally fine veins, dendrites, flakes or granules, along the cracks, textures or pores of minerals such as broken quartz, metal sulfides, etc., also known as filling gold, the particle size is generally coarser.

3 inclusion gold: gold minerals are contained in metal sulfides and gangue minerals, mostly in the form of round, lentils, grains, milk droplets, fine veins, etc. The main gold-bearing minerals are quartz, pyrite, yellow. Copper ore, galena, sphalerite, etc., gold minerals are filled along the residual voids of the carrier minerals or the gold minerals and the gold-bearing minerals are in a solid-separated state. In the past, the Shencheng gold deposit was mainly composed of inclusion gold. Gold minerals are metal minerals, while shallow mineral deposits are mainly fissure gold. The gold-bearing minerals are mainly gangue minerals. This has not been the case in recent years. Many gold deposits, such as the Carlin gold mine in the United States and the gold mine in the Aldan region of Russia, Gold deposits in southwestern Guizhou, China, and gold are contained in pyrite. People use electron microscopy, scanning electron microscopy, and electron probe to study the submicroscopic gold in pyrite. Jin Juncheng is a small ball (0.12_ And the chain precipitates on the pyrite crystal face or is filled in the microcracks of pyrite. During the crystallization of pyrite, the fine grain gold attached to the crystal face is easy to be oriented toward the lower crystal edge or broken. Migration and accumulation in cracked pyrite fractures, Eventually, coarse-grained gold and crack gold are formed. Some of the fine-grained gold is entrapped in pyrite due to excessive growth of pyrite or strong adhesion of gold particles during migration. The inclusion gold (the same is true for the formation of inclusions in other sulfides and quartz).

The gold in the quartz vein type gold deposit basically completes this migration and aggregation process. Therefore, the gold minerals are mainly produced in the form of intergranular gold and fissure gold, and the intergranular gold and fissure gold account for more than 80%. The gold ore of the deposit is an easy-to-select metallurgical ore. Generally, the ore selection and smelting adopts the flotation-cyanide process, and the effect is ideal. The recovery rate of gold is over 95% but the content of arsenic sulfide (such as arsenopyrite) is better. High ore containing some gold, the recovery rate of gold by flotation-cyanide process is about 70%. If it is calcined before cyanidation and then cyanidated, the recovery rate of gold can reach over 95%. Therefore, The gold ore with higher arsenic sulfide should be selected from the flotation-baking-cyanide process.