Shuangquan Gold Deposit in Qitai County, Xinjiang Uygur Autonomous Region

Shuangquan Gold Mine is located at the junction of Qitai County and Qinghe County in the east of Junggar Basin, Xinjiang, about 180km away from Qitai County, and the center coordinate of the mine is 9017' 31"east longitude. It is 45 02' 50 "north latitude and covers an area of about 0.5km2.

In 2003, Bo and others of the Eighth Gold Detachment of the Armed Police Force conducted an investigation in the Kalamaili-Moqinwula metallogenic belt and Kubusu metallogenic belt in East Junggar, and discovered the Shuangquan gold deposit. By the end of 2006, * * * submitted resources of 13388kg, reaching the scale of medium-sized deposits and becoming the largest gold deposit in East Junggar.

The discovery of Shuangquan gold deposit has set off a round of gold prospecting fever in Kalamaili-Mochinula metallogenic belt. At the end of 2006, the eighth detachment of Armed Police Gold discovered the same type of Sujiquandong gold deposit about 25km east of Shuangquan gold deposit, which is currently under exploration and is expected to form a medium-sized gold deposit.

1 regional metallogenic geological environment

1. 1 geotectonic unit

Shuangquan gold deposit is located in the Devonian-Carboniferous residual sea basin (fourth unit) in the Paleozoic terrigenous active zone (third unit) on the northern margin of Kazakhstan-Junggar plate (second unit), and occurs in the main structure of Qingshui-Sujiquan fault zone on its northern boundary.

1.2 regional stratum

The exposed strata in the area are Silurian, mainly a set of siliceous shale formations in the early geosyncline. Devonian (see the geological part of the deposit), Carboniferous (see the geological part of the deposit) and Permian are mainly composed of a set of continental coarse clastic rocks. Triassic is mainly composed of a set of continental red-orange conglomerate mixed with purple-red and yellow-green argillaceous siltstone and mudstone. Jurassic is a typical inland basin deposit. Among them, the Late Paleozoic strata are the most developed.

1.3 regional structure

This area is located in the first-order structural unit of Tianshan-Mongolia geosyncline fold system. The structures in the area are developed, mainly faults and folds, and the overall strike of the structural line is NW-SE.

The regional fold structures include Hassafin anticlinorium, Pingdingshan-Sareshike fold bundle, Qingshui-Nanmingshui fold bundle and Tiebei Tashan syncline in arman.

The fault structures in this area are well developed, with compression, tension and torsion, but the compression is the most prominent. The formation of these faults mainly occurred and developed with the rise of the Variscan Movement. Although later movements also had activities, they basically maintained the pattern at that time. According to the scale, it can be divided into deep faults, large faults and general faults.

Karamaili deep fault is the representative of deep fault, which is a straight trench with a width of 100 ~ 300 m in geomorphology, with a cross-section of NE dip and an inclination angle of 75 ~ 80, and is a high-angle thrust fault, forming a wide fault zone. Mylonized zone can be seen locally, and fault gouge and fault breccia are also common. Karamaili deep fault plays an important role in controlling strata, intrusive rocks, minerals and structures in this area. North of the fault is a strongly active area with thick strata, strong folds, developed faults, frequent intrusion activities and high degree of rock metamorphism. Its south is relatively stable. In the aspect of mineralization, Karamaili deep fault constitutes the main channel of intrusive rocks, and its related secondary faults and fractures constitute its good occurrence space.

The large fault represented by Qingshui-Sujiquan fault is located in the north of Karamaili deep fault, starting from Qingshui spring in the west, passing through Sujiquan and reaching the high point south of Liushuquan in the east 1045, which is covered by Quaternary. The extension direction is 280 ~ 300, and the length is > > 53km. The fault is a reverse fault inclined to the north, and the dip angle is generally around 60. In geomorphology, obvious negative topography and structural steps are often formed. It forms a fault zone with Karamaili deep fault, which constitutes a favorable factor for the rise and output of ultrabasic magma and a favorable part for mineralization.

Among the general faults, the NW-trending fault is the most developed, which is characterized by being consistent with the direction of regional tectonic lines, extending in the direction of 290 ~ 320, and having strike faults. The fault scale is large, generally, it is 10 ~ 10 km long. Most of them are high-angle reverse faults, dipping NE with dip angle of 50 ~ 70. This group of faults was generally formed in the early Middle Carboniferous, and most of them have long-term activity, especially in Beitashan area. As a result of the activity, the North Tower Mountain keeps rising. This group of faults directly control ultrabasic rocks and gold-bearing quartz veins, and directly provide their occurrence conditions.

1.4 regional magmatism

Magmatic activities in this area are well developed, with frequent intrusions and ejections and obvious cyclicity, ranging from ultrabasic rocks to alkaline rocks. Among them, intrusive rocks are the main ones, followed by extrusive rocks.

Intrusive rocks are mainly distributed in the north of Karamaili deep fault. Seepage rocks appear in the north and south of Kalamaili fault. The intrusive rocks in this area are mainly the products of the middle Variscan period, and the most developed ones are medium-deep diagenesis, which are in the form of bedrock and rock strains of different sizes. Shallow diagenetic rocks are mostly dike rocks, and occasionally small rock bodies like rock plants are seen. Yanshanian intrusive rocks only occur in the Middle Jurassic in southern basta.

Variscan plutonic rocks include seven intrusive stages. Gabbro, the first intrusive body, is mainly distributed in the north side of Karamaili deep fault, which is in the form of veins and small rocks. Due to the intrusion of ultrabasic rocks in the later period, it is generally distributed in the middle or edge of ultrabasic rocks as residues. Mainly gabbro, occasionally gabbro porphyrite; The second intrusion-ultrabasic rock (), mainly intruded along the secondary structural cracks between Kalamaili deep fault and Sujiquan fault, and the rock mass is mostly monoclinic with irregular dikes and rock strains; The third intrusive body-diorite (), only the Kupubei diorite group is seen in this area, which consists of two rock masses; The fourth intrusive body, plagioclase-rich granite-granodiorite (), is mainly distributed in the area from Aotawukaigaishi to Kupu, north of Kalamaili deep fault, and the long axis of the rock mass runs northwest, with irregular bedrock. The fifth intrusive body-albite granite, only Sayashk albite granite body can be seen, which is in intrusive unconformity contact with Pingdingshan Formation (D2p) of Middle Devonian. The sixth intrusive body is alkaline granite (Hehe), which is mainly distributed in the north of Qingshui-Sujiquan fault. The rock mass is bedrock-like, and some of it is rock-like, with irregular plane shape. The seventh intrusive body-granite porphyry () was found near and north of Balebagayi. It appears as irregular veins and small rock plants, and passes through the latest intrusive rocks.

Yanshanian intrusive rocks are not developed in this area, and only the corresponding diabase vein (Nπ5) is found in the Xishanyao Formation (J2x) of Middle Jurassic, which occurs in the Precambrian Mesozoic inland depression of Beitashan.

2 Mining area geology

2. 1 mining stratum

The strata in the mining area are relatively simple, mainly lower Carboniferous and middle Devonian, with Quaternary scattered around (Figure 1).

2. 1. 1 Devonian

It is widely exposed in the area, mainly distributed in the north of the mining area. The outcrop is Middle Devonian Pingdingshan Formation (D2p), which is mainly composed of a set of normal shallow-sea clastic rocks, mainly tuff, sandstone, siltstone and glutenite. The lithology is mainly intermediate-basic volcanic tuff, tuffaceous sandstone and siltstone; Its bottom layer is a purple deep-sea sedimentary siliceous rock and jasper rock. Qingshui-Sujiquan fault is in unconformity contact with Nanmingshui Formation of Middle Carboniferous.

2. 1.2 Carboniferous

Distributed in the south of the mining area, it is an important ore-bearing stratum, and the exposed stratum is Nanmingshui Formation of Lower Carboniferous. Lower Carboniferous Nanmingshui Formation (C 1n) is NW-SE, with a large exposed area, forming a high-angle syncline. Both sides of syncline are cut by faults, and Karamaili Formation in transition zone is separated from the south by Karamaili fault. Qingshui-Sujiquan fault is separated from Pingdingshan formation in the northern geosyncline, and its lower bound is unknown. This formation is mainly composed of shallow marine clastic rocks and pyroclastic rocks, with a small amount of volcanic lava interlayer or lens. Because it is located in the tectonic compression zone, most strata have been broken and metamorphic. Rock has foliation or phyllite. According to lithology, sequence and sedimentary cycle, it can be divided into two subgroups: Lower subgroup (C 1na), which is mainly composed of gray-green and gray foliated siltstone, phyllite siltstone and calcareous siltstone, with conglomerate, feldspathic sandstone, tuff sandstone, tuff and limestone lens; The upper subgroup (C 1nb) is integrated on the lower subgroup and separated by a layer of flat breccia, glutenite and sandstone intermittently exposed. This group is still dominated by clastic rocks, which is obviously different from the lower sub-group. There is an obvious increase in pyroclastic rocks, a small amount of neutral volcanic lava or lens, and the lithologic trend has little change. From east to west, the granularity of clastic rocks becomes finer from coarse, the calcium content decreases gradually, and the pyroclastic content increases gradually.

Figure 1 Geological Schematic Diagram of Shuangquan Gold Mine Area

1- four yuan; 2- Upper sub-group of Nanmingshui Formation of Lower Carboniferous; 3- Lower Subgroup of Nanmingshui Formation of Lower Carboniferous; 4- Pingdingshan Formation of Middle Devonian; 5- Carboniferous medium-grained potash feldspar granite veins; 6- Carboniferous fine-grained potash feldspar granite veins; 7- alteration zone; 8 veins; 9— Tectonic geochemical profile and number

2. 1.3 Quaternary system

Widely distributed in depressions, valleys, piedmont areas, river valley banks and basin edges in the working area. It is mainly composed of loose sediments such as sandy clay, timely fine sand, rock blocks and gravel sand, and is formed by aeolian, flood, alluvial, accumulated iron, calcium and argillaceous cementation. Quaternary system is mainly Pliocene-Holocene diluvium, angular gravel accumulation, no cementation or micro-cementation, and poor sorting. Generally, from the piedmont to the center of the depression, the gravel diameter changes from coarse to fine, and the composition is complex.

2.2 magmatic rocks in mining area

Magmatic activities are well developed in this area, and intrusive rocks are mainly distributed in the northern part of the study area. Eruptive rocks appear in the north and south of the study area. The intrusive rocks in this area are mainly plagiogranite intrusive rocks in the first stage of middle Variscan and ultrabasic intrusive rocks in the second stage of middle Variscan, with diorite and gabbro scattered around.

The first intrusion-gabbro. Rock mass is scattered in the mining area in the form of small rocks. Due to the invasion and destruction of ultrabasic rocks in the later period, it is generally distributed in the middle or edge of ultrabasic rocks in the form of residues. Single rock mass or residual body length 10 ~ 100 m and width 10 ~ 50 m. It extends along the direction of 270 ~ 300, and is in intrusive unconformity contact with Pingdingshan Formation of Middle Devonian and Nanmingshui Formation of Lower Carboniferous, with uneven contact surface and steep dip angle.

The second intrusion-ultrabasic rocks (). Ultrabasic rocks () mainly intrude along the secondary structural fracture (280 ~ 3 10) between Kalamaili deep fault and Qingshui-Sujiquan fault, and are in intrusive unconformity contact with Nanmingshui Formation of Lower Carboniferous. Rock mass is mostly monoclinic rock mass, with irregular rock walls and strains, generally expanding in the middle and narrowing at both ends. The larger rock mass has bifurcation phenomenon, and the plane shape of individual rock mass is "S". It is distributed in many places in the mining area. A single rock mass is 30 ~ 200m long and 10~50m ~ 50m wide. The main rocks are pyroxenite, dunite and plagioclase peridotite.

Pyrite-bearing dunite and dunite. Dark gray green, dark green, ring structure, block structure. The main minerals are olivine and orthopyroxene. Olivine erodes into serpentine, while pyroxene forms sericite, which constitutes pseudospots of rocks.

Clinopyroxene peridotite is easy to weather and forms gray-green powder on its surface. There are ring structure and block structure. The main minerals are olivine and orthopyroxene.

The fifth intrusive body-sodalite amphibole granite. Intrusive rocks are mainly distributed in the northern part of the mining area. The west and south sides are in intrusive unconformity contact with Pingdingshan Formation (D2p) of Middle Devonian, and the occurrence of contact surface changes greatly. Generally, the south side tends to 190 ~ 240, with an inclination of 40 ~ 70, and some of them tend to the south side with steep inclination. The south side is in intrusive unconformity contact with the sixth intrusive subalkaline granite (), and the rock mass is produced in the form of large bedrock, which is the main rock mass that constitutes the Huangyangshan complex. The main lithology is gray-red-gray medium-fine sodalite granite.

The sixth intrusion-alkaline granite (and). The intrusive rocks are mainly distributed in the northern part of the study area, and they are in intrusive unconformity contact with the Pingdingshan Formation (D2p) of the Middle Devonian, and the occurrence of the contact surface changes greatly. Generally, the dip angle of the south side is 265, 438+00 ~ 240, and the dip angle is 50 ~ 70, and some of them tend to the south with steep dip angle. The situation in the north is unknown. Rock mass appears in the form of bedrock, some in the form of rock plants, and its plane shape is irregular. It is also one of the important rock masses that constitute the Huangyangshan complex, and its main lithology is light red-orange medium-grained potash granite. The intrusive rock is one of the main endogenetic minerals in this area.

Shallow diagenetic rocks in the study area are undeveloped, mainly acidic rocks, forming small rock masses or rock strains. The intrusive age of shallow diagenetic rocks belongs to the middle Variscan period.

2.3 Ore-controlling structure

Shuangquan Gold Mine is controlled by Qingshui-Sujiquan ductile-brittle shear structural system, in which vein No.2 (and 1) is located in the main structural belt, and vein No.3 and vein No.4 are controlled by the secondary fracture system.

Due to the action of Qingshui-Sujiquan fault and the influence of secondary faults, most of the rocks in this structural zone have been altered and broken, showing a strong flaky altered and broken zone. The fault zone creates a favorable space for the infiltration and occurrence of intrusive rocks, so a large number of ultrabasic dikes and rocks are distributed along this zone, and it also creates a favorable space for the infiltration and occurrence of gold-bearing hydrothermal solution, forming ore bodies and mineralized bodies.

Qingshui-Sujiquan fault is a NE-trending inclined reverse fault, and the dip angle is generally > 80. This area is characterized by a structural schist belt composed of many faults, each fault often appears in obvious negative topography and piedmont, and some faults form ore (point) deposits (such as Shuangquan gold mine) due to late tectonic and hydrothermal activities. This fault can be subdivided into the following faults (fault zones).

The F 1 fault zone is located in the southeast of the mining area, with a length of 1600m and a strike of 320. Most of them are covered by Quaternary, and outcrops can be seen locally. This is a solid tuff zone, some of which are filled with timely veins. The timing pulse is discontinuous, which is produced in the form of a beaded lens with an intermittent length of about 3000 meters. The results of electrical measurement show that the curves on both sides of the fracture zone decrease step by step, and the curve of low resistance orthogonal point generally rises on one side, and the separation zone is obvious. The abnormal value of one side is not high, the curve is stable and the separation area is not obvious. The transitional zone between the two oilfields is one of the signs of the existence of structural zones.

The F2 fault zone is located in the middle of the mining area, with a length of 2000m and a strike of 320. It is a purple-red physical and chemical argillaceous rock belt, with gray-green basic tuff in the northeast, and jasper and siliceous rocks sporadically exposed in the south and west. The curve separation zone on both sides of F2 is not obvious, the abnormal value is not high but the curve is stable, and its southern end tends to compound with the main structure F3 at the 40th line.

The F3 fault zone is located in the middle of the mining area, and it is the structure where 1 and No.2 veins appear. Its length exceeds 5440 meters, its width exceeds 100 meters, and its strike is 320, all of which are covered by Quaternary. Because most of the mining area has been stripped, it is a strong foliated altered phyllite belt, and most areas are filled with time veins and metal sulfides to form ore bodies (veins). It is speculated that F3 is the main structure passing through Qingshui-Sujiquan fault.

F4 fault is located in the northeast of the mining area, which is a piedmont fault and is completely covered by Quaternary. From the characteristics of remote sensing images, there are obvious differences between the two sides. The northeast and east sides of the fault are dark gray, and the lithology is dark gray layered tuffaceous sandstone (Devonian Pingdingshan Formation). The south and west sides of the fault are light gray, and the lithology is gray-gray green foliated tuff (Carboniferous Nanmingshui Formation). This fault is the boundary of Qingshui-Sujiquan fault structure belt.

3 Ore body geology

At present, five gold-bearing veins 1, No.2, No.3, No.4 and No.5 have been discovered in Shuangquan Gold Mine, all of which are located in Nanmingshui Formation of Lower Carboniferous. The vein is mainly controlled by the northwest Qingshui-Sujiquan fault and exists in it. The type of the deposit is time-pulse type fractured altered rock.

3. 1 1 pulse

It is a kind of fractured altered rock, which is dominated by fractured altered rock and has a time pulse in the fault zone. The exposed surface is about 1.5km in length and about 1 ~ 15m in width, which shows a slow wave-like distribution in the northwest direction with a strike of 320. The southeast section is inclined to NE with an inclination of 75 ~ 87, the northwest section is inclined to SW with an inclination of 78 ~ 86, and the middle section is nearly upright. The fractured altered rocks are mainly silicified sericite phyllite with schistosity and mylonitization. The color changes greatly, and the boundary with the surrounding rock is not obvious. It is mainly grayish white, grayish green and grayish black. After weathering, it is yellowish brown to light flesh red, with local carbon black and dirty hands. Scale metamorphic structure, thousand-piece, banded and mylonite structure. The timing pulse is in the form of a veinlet or a timing lens, and it is distributed in a strip shape.

The fractured altered rocks have undergone shallow metamorphism due to dynamic compression, schist and cleavage are developed, and small folds are developed locally. Mylonite, phyllite, structural schist and chronological lens are developed in the fault zone, and the rocks along the upper wall (southwest) of the fault zone are strongly altered. The main changes are sericitization, silicification and carbonization, and strong silk luster can be seen along the foliation surface. Followed by chloritization and Kaolinization. Mineralization is pyritization, arsenopyrite and limonite.

3.2 No.2 pulse

The ore type is similar to the 1 vein, which is located on the north side of 1 vein and parallel to it. The exposed surface is about 3km long and 5 ~ 30 m wide. It is distributed in gentle waves along the northwest direction. The main strike of the vein is 320, and the dip angle is nearly vertical. The NE dip angle in the southeast section is 75 ~ 88, the SW dip angle in the northwest section is 74 ~ 86, and the dip angle in the middle section is nearly vertical. The vein is mainly composed of silicified sericite phyllite and a small number of time-dependent (fine) veins and time-dependent lenses.

The fractured altered rocks are mainly silicified sericite phyllite with schistosity and mylonitization. The color changes greatly, and the boundary with the surrounding rock is not obvious. It is mainly grayish white, grayish green and grayish black. After weathering, it is yellowish brown to light flesh red, with local carbon black and dirty hands. Scale metamorphic structure, thousand-piece, banded and mylonite structure. The timing pulse is in the form of a veinlet or a timing lens, and it is distributed in a strip shape. The fractured altered rocks have undergone shallow metamorphism due to dynamic compression, schist and cleavage are developed, and small folds are developed locally. Mylonite, phyllite, structural schist and chronological lens are developed in the fault zone, and the rocks along the upper wall (southwest) of the fault zone are strongly altered. The main changes are sericitization, silicification and carbonization, and strong silk luster can be seen along the foliation surface. Followed by chloritization and Kaolinization. Mineralization includes limonite, pyrite, arsenopyrite, limonite, chalcopyrite and malachite.

3.3 Other veins

Veins No.3, No.4 and No.5 are controlled by the trench engineering system, in which vein No.3 is located about 500m northwest of 1 vein and in the same structural zone as 1 vein. The pulse surface is gentle and wavy in northwest direction, with the occurrence of 38 ~ 62 ∠ 63 ~ 87, with an average occurrence of 53∞. It is mainly composed of altered rocks with timely veins. The vein is mainly composed of silicified sericite phyllite, timely vein and timely lens.

Vein No.4 is located at the northwest 150m of vein No.3, in the same position and structural zone as vein No.3, and the surface of vein is gentle and wavy in NW direction, with the occurrence of 55 ∠ 76. It is mainly composed of altered rocks with timely veins. The vein is mainly composed of silicified sericite phyllite, timely vein and timely lens.

Pulse No.5 is a rough synchronous pulse, which is located on the northwest extension line of pulse No.2 and pulse 1. The timely pulse of surface exposure is about 250m long, 10~20m ~ 20m wide, and the occurrence is 45 ∠ 86. Carry out a trench exploration project to control the timely pulse width at18.2m.

The metal minerals in the ore include pyrite, chalcopyrite, limonite, pyrite, arsenopyrite and malachite. Gangue minerals include Yingshi, chalcedony, calcite, sericite, chlorite and kaolin.

3.4 Ore Type and Structure

The deposit type is gold-bearing altered rock, which has a corresponding time pulse. According to the field observation and indoor identification, it is preliminarily considered that the natural types of ores can be divided into two types: the first type is time-pulse-type ores with a time pulse width of 0. 1 ~ 2m, which are lenticular and sausage-shaped, and occur along the foliation direction of phyllite, with its long axis basically consistent with the vein direction. Ore structures are mainly cataclastic structures, cryptocrystalline metamorphic structures, massive structures and breccia structures; The second type is altered rock type ore with developed schistosity and relatively broken extrusion. This kind of ore is closely related to silicification and sericitization, and its grade is stable but low. The fabric mainly consists of scale metamorphic structure, thousand-piece structure and strip structure.

The homogeneous temperature range of fluid inclusions in Shuangquan Gold Mine is 190 ~ 3 19℃, with three peaks, namely 160 ~ 180℃, 200 ~ 220℃ and 340 ~ 380℃.

The δ34S values of four samples from Shuangquan Gold Mine are 3.54 ‰ ~ 10.68 ‰.

The hydrogen and oxygen isotopic compositions of ore-bearing fluid inclusions in Shuangquan Gold Mine are shown in Table 1.

Table 1 hydrogen and oxygen isotopic composition of gold deposits in Shuangquan and its periphery

The 3He/4He isotopic composition of pyrite (arsenopyrite) in the gold ore of Shuangquan Gold Mine is shown in Table 2.

Table 2 3He/4He isotopic composition of pyrite (arsenopyrite) in Shuangquan mining area and its surrounding gold mines

The results of 40Ar/39Ar isotopic dating of sericite, an altered mineral related to mineralization, show that the isochron ages of three sericites are 269±9ma, 265±2ma and 260±4ma, respectively, and the isochron age of 16 of the timely sample of 06B22-Q is 269±8ma, indicating the metallogenic age of gold deposits.

4 technical exploration marks

4. 1 direct sign

Limonite mineralization or iron hat formed by chronological veins and metal sulfides are direct prospecting indicators, such as chronological vein-type gold deposits on the surface of Sujiquan mining area.

4.2 Altered Rock Marks

In the structural alteration zone, it is important to find altered rock-type gold bodies with corresponding time veins. Generally speaking, altered rocks with time-dependent veinlets and time-dependent lenses have better gold content. Yellow-brown and reddish-brown altered rocks have good gold content.

4.3 Structural signs

The NW-trending structure controls the gold deposits in this area, which is consistent with the direction of the regional tectonic line. Physical and chemical zones or ductile shear zones caused by NW-trending structures and their secondary faults are often ore-guiding structures and ore-hosting structures formed by gold deposits. Structures, intersecting parts of faults and cutting parts are often favorable ore-storing structures; The cutting position of linear structure is very favorable for mineralization.

4.4 Change the sign

The wall rock alteration of gold ore bodies mainly includes silicification, pyritization, limonite mineralization, galena mineralization, malachite fossilization, arsenopyrite, sericitization, carbonation, chloritization and kaolinization.

4.5 Lithologic signs

Volcanic rocks and pyroclastic rocks are prospecting criteria for gold deposits.

4.6 geochemical anomaly marks

Au anomalies, especially Au, As, Cu anomalies, are generally displayed in favorable metallogenic positions, with extremely stable anomalies, high strength and large contrast, and are often caused by altered rocks.

refer to

Armed police gold geology research institute. 2006. Study on genetic metallogenic model and prospecting prediction of Shuangquan gold deposit in Qitai county, Xinjiang (achievement report) Langfang: Institute of Gold Geology of Armed Police.

(Author Lu Yanming)