Yunnan Mine Tour (Dongchuan Boka, Topuka Gold Mine-1)

The mountains in Dongchuan are the pride of Dongchuan people. Dongchuan people are the proud sons of the mountains. They come straight to the point. Life, work, and study are all inseparable from mountains. They love mountains passionately, deeply, and persistently. Therefore, they always like to talk to others about the mountains and mountains, and their treasures.

The mountains in Dongchuan are not just for fun. The reason why they are famous all over the country and abroad is because they contain rich copper minerals.

These coppers enable the boudoir lady to see her beautiful face in the water chestnut mirror. The mountains of Dongchuan have made great sacrifices and outstanding contributions to forge the long Chinese civilization, and they still remain today. Dedicate your treasures to the cause of socialist construction in our country.

In 1996, another gold mine was discovered in the Liangka (Boka and Tobka) areas. After several years of deep drilling and exploration, two gold mining sections from Xinshan to Majiagou and Qijiaodi Jiangjiawan have been initially controlled. It is estimated that the cumulative amount of controlled resources and inferred resources in the two mining sections has reached a super large scale. Detailed work has not yet been carried out on numerous abnormal points and zones outside the Liangka area and other gold mineralization points (mainly in the southwest), which fully shows that the Dongchuan area has huge gold prospecting potential.

On April 7, we drove from Kunming to Dongchuan for a one-day trip to Boka and Tobka gold mines. The spring was not bright that day, but we had a bright journey.

Depart from Kunming at 6 a.m. and take the Dongchuan Expressway. The journey takes about 1 hour and arrives in Dongchuan City around 7:10.

Dongchuan is an immigrant city with a diverse population. There are a wide variety of breakfasts, and there are many cheap and good ones. What we had that day was Dongchuan mutton rice noodles. The signboard of this breakfast shop is very small, called "Authentic Dongchuan Haggis Rice Noodles". The location is diagonally opposite the entrance of the local Education Bureau, which is a bit out of the way. There are six or seven breakfast restaurants in the surrounding area. No need to look at the signboard, this one has the most diners.

After breakfast, we set off for the mine and arrived at about nine o'clock. There are roads or simple roads connecting the mining area from Dongchuan, so the transportation is relatively convenient.

The Boka and Tobka gold mines in Dongchuan District, Yunnan Province are located in the northwest direction of Dongchuan District, with a horizontal distance of about 30 kilometers. It is under the jurisdiction of Boka Township and Topuka Township.

When you enter the Boka Mine, there are not many people. Everywhere you go, there are rocks, soil, grass and sparse bushes. Not far away, you can see smoke curling up, and occasionally hear birds chirping. Of course, there is also the fragrance of flowers from time to time, and the mountain road is quiet.

The geotectonic location of the Boka Gold Mine is on the northeast side of the south-central section of the Kang-Dian axis, near the west side of the NS-trending Xiaojiang Deep Fault. The Mesoproterozoic Kunyang Group is exposed in large areas. It is a set of complex marble-like structures with huge thickness, mainly composed of terrigenous fine clastic rocks and secondary carbonate rocks. It is partially interspersed with a small amount of intermediate-basic volcanic rocks and volcanic clastic rocks. clastic rock. After the Jinning movement, comprehensive folding returned, regional low-temperature dynamic shallow metamorphism occurred, and formed part of the Yangtze quasi-platform fold base. The main rock types are slate, phyllite, metamorphic sandstone, recrystallized limestone, dolomite, a small amount of quartzite, marble, greenschist and medium-basic volcanic lava and tuff. The nearly NS-trending Xiaojiang fault and its associated Laoshanmuqing fault zone (including the nearly EN-trending fault group) control the production of intermediate-basic intrusive rocks, and along the Tobka syncline axis located in the Laoshanmu fault zone Partially exposed, it is mainly gabbro, diabase and a small amount of diorite from the Jinning Period. Gold mineralization occurs in the syncline limb (mainly the west limb). The structural belt composed of nearly EW-trending faults, compound synclines in the same direction, and nearly NS-trending faults in the south controls the output of intermediate-basic intrusive rocks and the famous Dongchuan-style copper deposits. The lower part of the Kunyang Group is the main production layer of copper deposits, and the ore bodies occur in dolomite and dolomitic sandy slate intercalated with dolomite lenses. In addition, iron ore deposits such as Baozipu are also produced in the central part of the Kunyang Group, indicating that the Dongchuan area is a copper, iron, and gold polymetallic mineralization prospect.

The gold mineral (chemical) body mainly occurs in the transitional part of the middle and lower parts of the Yinmin Formation. The thrust fault hanging wall where the medium-basic rock mass develops is composed of several nearly parallel, nearly NS-trending interlayers. In the fracture zone composed of small faults and fissures; some are produced in the middle and lower parts of the Yinmin Formation and the upper part of the Meidang Formation. The main ore (chemical) body is a group of ore bodies composed of multiple nearly parallel small ore (chemical) bodies. The grade is relatively stable, like layered and lens-shaped, and some are large vein-shaped and cyst-shaped; the overall trend is close to NS. , tilts to the east, and partially shows an almost EW direction; it is gentle near the surface, gradually steepens toward the depth, and appears to pinch out and reappear, branching and compounding, and is relatively stable along the dip. The ore (chemical) bodies on both sides of the main ore (chemical) body and the individual small ore (chemical) bodies that make up the main ore (chemical) body are mostly produced in the shape of lenses and veins, with large grade changes, along the strike and trend. The continuity is poor. In the densely distributed areas of nearly NS-trending parallel small faults and feather-shaped faults, at the intersection of NNW-trending and NNE-trending faults, and at the variation locations of fracture expansion and contraction and occurrence changes, the mineral (chemical) body becomes thicker and richer, forming a chicken nest-like characteristic in some places. Bonanza sac.

Through deep drilling control exploration, two gold mining sections in Majiagou, Xinshan and Jiangjiawan, Qijiaodi have been initially controlled (Figure 1). The Majiagou gold mine section in Xinshan has a controlled gold mine length of 1,885m and a maximum controlled width of 630m. According to the existing analysis results, the thickness of a single project of the ore (chemical) body is 18.4m ~ 90.85m, and the average thickness of the ore (chemical) body is 58.91m. The average engineering grade of ore (chemical) body is 1.1g/t～10.2g/t, and the average grade of ore (chemical) body is 3.84g/t. The Qijiaodi-Jiangjiawan gold mine section has a controlled ore body length of 1,365m and a maximum controlled width of 214m.

According to the existing analysis results, the single project thickness of the ore (chemical) body is 3m ~ 107.3m, the average thickness of the ore (chemical) body is 62.7m, and the average single project grade of the ore (chemical) body is 2.4g/t ~ 3.2g/t. The average grade of the (chemical) body is 2.68g/t. According to preliminary estimates, the total inferred resources, controlled resources and basic reserves of the two mining sections have reached a super large scale.

Ore types of Boka Gold Mine: The natural types of primary ores are structurally altered rock type and quartz vein type, with a small amount of carbonate vein type and sulfide vein type. Among them, the amount of ore is mainly structurally altered rock type, and the grades are richer in quartz vein type and carbonate vein type. The area extending from the surface to 150~200m is oxidized ore. Due to the strong secondary oxidation, sulfide and iron carbonate near the surface are oxidized into limonite, and the carbonate is leached. There are only two ore types of oxide minerals: structural alteration rock type and quartz vein type.

Structural alteration rock types: including cataclastic rock type and breccia type, with cataclastic rock type being the main type. The rock composition includes phyllite slate, slate, silty slate, siltstone, metamorphic lithic sandstone, relic conglomerate, volcanic breccia, syenite, gabbro, etc., with silty slate , mainly siltstone, followed by slate, metamorphic lithic sandstone, deformed conglomerate, and syenite.

Quartz vein type: including sulfide quartz vein type, carbonate quartz vein type, and sulfide carbonate quartz vein type.

Carbonate vein types: including siderite and dolomite vein types, calcite siderite and dolomite vein types, sulfide siderite and dolomite vein types, and sulfide calcite siderite veins. Ankerite vein type.

Sulfide vein type: including quartz sulfide vein type, carbonate sulfide vein type, and carbonate quartz sulfide vein type.

The ore structure includes euhedral, semi-euhedral and other-shaped granular structures, disseminated and gel-like structures, including structure and metasomatic corrosion structure, and filling structure. Ore structures are divided into clastic structures and brecciated structures according to the degree of fragmentation of ore-bearing rocks. Clastic structures are the most common. Clastic structures can be further divided into massive structures and network veins according to the distribution of metallic minerals in the ore. Breccia-like structures and disseminated structures generally form near faults, and block structures, reticular structures and disseminated structures gradually appear outward.

Ore mineral combination: The metallic minerals are mainly pyrite, followed by limonite, siderite, pentlandite, chalcopyrite, arsenopyrite, goethite, and a small amount of sphalerite. , galena, pyrrhotite, arsenite, nickel-bearing pyrite, azurite, malachite, natural gold, silver-gold ore, argyrite, tellurium gold ore, the gangue minerals are quartz, Mainly ankerite, with a small amount of sericite, muscovite, and mudstone calcite. The chemical composition of the ore is mainly Au, Ag, Fe, Mn, Cu, Ni, As. The harmful elements are C, S, As, and Cu.

Gold occurrence status: The gold minerals are mainly natural gold, followed by silver gold ore and a small amount of needle tellurium gold ore. There are two types of natural gold: fine-grained gold (particle size less than 20 microns) and visible gold (particle size 0.1 to 2 mm). It is mainly lining gold and a small amount of cracked gold. Generally, the gold in the package is thinner and contains almost no silver, while the cracked gold is thicker, rich in silver, and mostly clear gold. The gold particles in the gold particles are 1 to 5 microns in size and are in the shape of other-shaped granules. A small amount of them are in long strips, sub-round shapes and other shapes, with irregular edges. They are mainly contained in pyrite and siderite, and secondarily in quartz. Fissure gold is found in pyrite, siderite, and quartz fissures. Silver-gold ore mainly exists in siderite and quartz fissures, followed by inclusion in pyrite, siderite and quartz. Tellurite occurs in chalcopyrite grains. Natural gold in oxidized ores is mostly fissure gold and occurs in iron oxide and quartz; followed by clad gold, which is surrounded by other-shaped crystal grains and embedded in skeleton-like iron oxide (limonite), and some are euhedral grains and The skeleton-like iron oxide is adjacently embedded or filled in the inner edge zone of the iron oxide mesh.

The fault structure of the Boka gold mine is the primary ore-controlling factor. Regardless of the folds or faults in this area, they all spread in a near-NS direction and are obviously controlled by the regional near-NS-trending deep and large faults in the Xiaojiang lithosphere. The spatial distribution of mineralized zones and mineralized bodies is nearly NS-oriented and consistent with the trend of the fault (Fig. 1). The width of mineralized alteration is positively correlated with the width of the ore-bearing fault; the mineralized zone is tensile and compressive. The nature is mainly controlled by the nearly NS-trending thrust fault zone; the mineralized body is produced in the hanging wall of the thrust fault and is controlled by a number of nearly parallel small faults, feathery small faults, interlayer small fractures, joints, and fissures. The nearly NS-trending complex fracture fracture zone. In the area where small near-NS parallel small faults, feathery small fractures, small interlayer fractures, joints, and fissures are densely distributed, at the intersection of NNW-trending and NE-trending faults derived from near-NS-trending faults, there are variations in fracture expansion and contraction and occurrence changes. , the ore body becomes thicker and richer, forming a chicken nest-like rich ore in some places. The gold mineralization anomalies are distributed in a near-NS direction and are consistent with the fault strike, with linear characteristics. The concentration center is close to the fault zone, and the abnormal concentration is concentrated at the intersection of the near-NS and nearly NNW-trending faults, or at the turning point of the trend. Gold mineralization is directly related to relatively coarse clastic sedimentary metamorphic rocks and mainly neutral-basic intrusive rocks generated along faults. Gold mineralization occurs only after late hydrothermal alteration. These are all Controlled by faults, they collectively form ore-bearing structural alteration zones, and multiple periods of frequent magma activity are important ore-controlling factors. Gold mineralization occurs closely with neutral-basic intrusions in space. Intrusions are mostly produced along the complex fracture fracture zones on the hanging wall of the ore-controlling reverse fault. Gold mineralization is mostly produced in intrusions. In the internal and external contact zone, the area where intrusions develop is where gold mineralization is concentrated. The minerals may come from magma, and the hydrothermal fluids may come from magma water.