A gold mine geological overview
The atomic number 79 of gold, the element symbol Au, is derived from the Latin Aurnm, meaning the dawn, the metaphorical sun. Gold has only one natural stable isotope 197, which is an equiaxed crystal at room temperature and a vertical lattice. Naturally good crystal forms are extremely rare, often in the form of irregular granules, agglomerates, flakes, reticular, dendritic, fibrous and spongy aggregates. Gold as gold, containing impurities, the color range change occurs, when silver or platinum color fades, the copper-containing darken. When the streak of gold on the test plate is reddish, the color is high; when it contains 10% silver, the streak is golden yellow; when it contains 20-30% of silver, it is grass yellow; when the content of silver exceeds 30%, it has yellow With a green hue; silver containing more than 50% is silvery white.
Gold is chemically stable and has strong corrosion resistance. It is generally not oxidized from normal temperature to high temperature. Gold insoluble in common acids and bases, but can be dissolved in aqua regia, an alkali metal cyanide, an acidic thiourea solution, bromine solution, boiling solution of ferric chloride, the presence of oxygen, potassium, sodium, calcium, magnesium Thiosulfate solution, etc. Sulfides of alkali metals corrode gold to form soluble gold sulfide. Humic acids in the soil and metabolites of certain bacteria can also dissolve trace amounts of gold. Gold having thiophilic, often intimately associated with the sulfides such as pyrite, arsenopyrite, galena, stibnite, and the like; and easily thiophilic silver, palladium, platinum, copper, nickel, mercury, bismuth, antimony, 铑 and 铱 form an intermetallic compound. Gold has a pro-iron nature, and gold in ferroniobium is three orders of magnitude higher than normal rock. Copper and silver are concentrated in the sulfide phase; while gold and platinum are concentrated in the metal phase. The abundance of gold in the core is 2.6 ppm, the mantle is 5 ppb, and the crust is 1.8 ppb. More than 99% of the gold on the earth enters the core. Therefore, the abundance of gold formed in the early stage of the development of the earth is relatively high. Therefore, the Archean greenstone belt, especially the combination of mafic and ultramafic volcanic rocks, has a higher abundance of gold than the various types of rocks in the earth's crust. Due to the low abundance of gold in the earth's crust, it has the characteristics of sulfophilicity, pro-copper, iron-producing, high melting point, etc., and the formation of industrial deposits requires thousands of times of enrichment. Mines generally have to undergo a fairly long geological period, which may be formed by multiple mineralization superpositions.
Gold can exist in the three valence states of 0, +1 and +3 in nature, and can be produced in the form of independent minerals, isomorphisms and colloidal adsorption. To date, 98 gold minerals and gold-bearing minerals have been discovered in the world, but only 47 species are common, while only 10 minerals are directly used by industry. According to the principle of crystal chemistry, gold minerals and gold-bearing minerals can be divided into:
(1) Natural elements and alloys of silver, palladium, platinum, copper, nickel, mercury, antimony, bismuth, antimony and bismuth are mineral gold (Au) containing Au>80%; silver gold ore (Au; Ag) ), containing Au 80% ~ 50%, Ag 20% ​​~ 50%; gold and silver ore (Au; Ag), containing Au 50% ~ 20%, Ag 50% ~ 80%, containing platinum palladium natural gold, silver copper gold mine, Weishan Mine, Sifang copper and gold mine, black gold mine Au2Bi. (2) Gold-silver bismuth minerals include bismuth gold ore, bismuth gold and silver ore, and acupuncture gold and silver ore. (3) Gold, silver and selenide minerals are selenium gold and silver ore. (4) Gold and silver sulfide minerals are sulfur gold and silver ore.
Natural gold (silver gold ore, etc.) can be divided into clear gold (>0.1mm), microscopic gold (0.1mm-0.25μm), sub-microscopic gold (0.25μm-2nm), and sub-electron diffraction gold according to its particle size. -0.288 nm).
There is a kind of natural gold that is eye-catching, that is the dog's head gold. The dog's head gold is naturally produced, the texture is impure, the grain is large and the irregular shape is gold. It usually consists of natural gold, quartz and other mineral aggregates. Because it looks like a dog's head, it is called a dog's head gold; like a horseshoe, it is called a horseshoe gold. In the middle of the 19th century, a carpenter picked up a dog's head gold on the west coast of the United States, weighing 32kg, which opened the gold rush in California. A caravan in Australia was turned over by the stone when passing through the gold mining area. The check-in was actually a huge dog's head gold weighing 77.6kg.
So far, the world has found that more than 10kg of dog's head gold is about 8,000 to 10,000, especially in Australia, accounting for 80% of the total amount of dog's head gold, the largest of which weighs 235.87kg. The total amount of dog's head gold found in China is about a thousand. In 1909, when the Sichuan Yanyuan gold mining workers were working underground, they were unfortunately dropped from the top. The "stones" wounded their feet and moved the "stones" to the mouth of the pit. It was actually a piece of gold weighing 31 kg. In 1982, Yuejin, the gold rusher of Xinglong Township, Huma, Heilongjiang Province, encountered a piece of gold weighing 3325g. In 1983, Wang Bojun, a farmer from Zhengwu Dangqiao Village in southwestern Shaanxi, picked up a 810g dog gold. Konglonggou, Baiyu County, Sichuan Province, found large gold nuggets weighing 4800.8g and 6136.15g in 1987. At 6:30 pm on June 7, 1997, the 13th gold mining team of the Menyuansigou Gold Mine in Qinghai discovered a large stone gold nugget weighing 6577g on the sand gold chute. Shibaojin is a form of dog's head gold. From the point of view of the dog gold that has been discovered, there are generally three forms, namely, gold, stone, gold and gold. Regardless of the specimen world, in the personal collection world, the valuation of this natural gold is extremely high.
Gold deposits can be produced in almost any type of rock and in any age, but the Precambrian greenstone belt is the most important. The mineralization types of gold are: greenstone belt type (including basic and ultrabasic rocks), volcanic rock type, porphyry type (including alkaline rock, granite ), turbidite type, black rock series, glutenite type , river sediment type; divided by genetic types of quartz vein, sulfide vein type, micro-disseminated, structural alteration type, Fe, Mn hat, clay type.
Second, how to find gold mines?
1. First, attention should be paid to silicified zones, quartz veins, and secondary quartzites . This is because gold mineralization is closely related to silicidation. It can be said that no silicon is not gold. Of course, not all siliceous bodies produce gold, but most of the gold-containing siliceous bodies are smoky and have good water color. This is because the gold-containing siliceous bodies all contain more or less sulfides, and because the sulfides are extremely fine, the quartz is smoky. In particular, sheet-like quartz veins (which may contain a plurality of black strips such as a mixture of carbonaceous and fine-grained sulfides) have good gold content. Even less bright gold sulfide quartz veins, when the package to gold, there is often the presence of antimony sulfides such as brightness, bismuthinite, bournonite, arsenopyrite, roe-like lead zinc ore.
2. Focus again on the fractured structural belt, especially the ductile shear zone. Gold mineralization is all related to faults, and it can be said that there is no structure. In particular, attention should be paid to super-tribes, mylonites, micro-sweet-like quartzites, and talc magnesite schists, which are often rich in gold ore bodies. The gold-bearing properties of the giant to large fault zones are often poor, while the secondary secondary fault zones are often the gold ore bodies.
3. The third is to pay attention to the gold-bearing property of the iron cap, maroon, brownish yellow residual slope and carbonate leaching tank deposits. They can not only become iron cap type, laterite type gold mines, but also indicate the search for primary gold mines.
4. The fourth thing to note is to find gold in the areas of antimony, mercury, and arsenic (especially the realgar or ore). In the case of antimony ore, it can be symbiotic with gold to form a gold deposit; it can also be separated, but Not far from each other, there is a saying that "not in it, not leaving it." The periphery of some lead-zinc mines can also be found in gold, such as the periphery of the Qingchengzi lead-zinc mine; the lower part of the copper deposit. The copper-nickel sulfide deposit alteration zone is also a good place to find gold.
5, related to the alteration in addition to gold silicide, and iron dolomitization, calcite of iron, chromium of white mica, pyrite phyllic, feldspar of ice, fine-grained pyrite, arsenic, antimony, Low temperature alteration combination of mercury, antimony and antimony mineralization.
6. Focus on the fractured fracture zone and its tectonic alteration zone in basic rock, ultrabasic rock, lamprophyre, alkaline rock, alkaline granitic rock, carbon-silica argillaceous rock, impure carbonate rock .
7. Carry out the work of river heavy sand, ditch system secondary halo and various geochemical methods. It is the most important method for gold search.
8. Find gold according to the indicator element of finding gold. For example, the combination of elements such as mercury, antimony, bismuth, arsenic, antimony, selenium, lead, zinc, copper and silver is abnormally gold.
9. Indirectly search for gold deposits by means of geophysical methods to find out the structure of faults and the distribution of sulfides. There are many methods for ore prospecting. There are five commonly used methods: 1 natural heavy sand method, 2 engineering heavy sand method, 3 old mining survey, 4 geological landform analysis, 5 geophysical exploration and aviation new technology method.
The first three methods are to investigate whether there is gold deposit and determine whether it is ore, which is a direct prospecting method. The latter two methods mainly analyze and evaluate the ore-forming conditions, study the environment and sediments. Some characteristics, to infer whether it is possible to form ore, is an indirect ore prospecting method, in which geological and geomorphological investigation is the basis of sand gold prospecting analysis. Generally, it is mainly based on geological and geomorphological analysis to determine where to go to find gold deposits and where to place sampling projects. The following are the specific methods for gold prospecting.
First, the natural heavy sand method
The natural heavy sand method is based on the fact that the density (specific gravity) of the gold particles is very large, and can be directly selected by using the panning disc. The surface of the loose debris is deposited or not pitted for sampling, and it is directly determined in the field to determine whether there is A method of gold deposits. Sampling includes heavy sand sampling of river sediments, sampling of outcrop sediments on terraces, and heavy sand sampling of slopes on hillsides.
The first two samples can be used to understand the gold content of water sediments, the approximate distribution of gold, and the grade and thickness of the gold layer in the terrace. The sampling in the residual slope of the hillside is used to trace the source of gold in the small ditch mountain area where sand gold is known. By sampling the shallow pit at a certain interval on the slope and slope foot, the sample is washed and washed according to the gold result. The distribution range narrows the rock gold prospecting target area. Among the three types of sampling, the most widely used method is the river natural heavy sand method.
Sampling of natural heavy sands in rivers is generally carried out from the bottom up along the upstream of the water system or along the small and medium-sized valleys containing gold. The advantages are: the tool is simple (as long as a hoe, a pan wash tray), the sampling workload is small (digging shallow pit 0.3-0.5m deep, sample weight 20-40k g), simple and easy, one can also do, very You can get the gold information at the near surface directly. The disadvantage is: because the sample is taken at a shallow surface, it does not reflect the gold content of the gravel layer in the deep, and the gold is usually concentrated in the lower part of the gravel layer near the bedrock. Therefore, the measurement results of the heavy sand in the near surface are looking for Mines generally have only qualitative significance.
The natural heavy sand sampling effect depends on the choice of sampling points and horizons. In the plane, the sampling points should be placed in places where sand gold is enriched, such as the sudden widening of rivers, the convex bank of rivers, the gravel sedimentary area of ​​riverbed shoals, the intersection of main and tributary, and the rock in the riverbed. Above the beach, above the rock, at the beach or at the heart of the beach, in front of the large obstacles in the water flow, the slope of the river bed is steeped and steeped, “close the mountain, above the river valley or in front of the “Yingmen Mountain†accumulation area. In the vertical section direction, the bottom of the gravel layer near the bedrock is the best. In the glutenite area, it should be taken in the riverbed sediment below the branch valley of the cut glutenite layer. In the mountainous area with multi-level trench net development, Samples should be sampled in the branch valleys. When taking the outcrop samples, they should be taken as far as possible at the bottom of the gravel layer or near the bedrock. Each sample should be 0.2-0.5m long. The sample weight should be at least 20kg or by volume. 0.01m3 (approx. 1 standard ship shape panning plate full disk sand sample). When sampling along the river, the spacing is determined by the size of the valley, without mechanical fixing.
The determination of sampling points should be based on the principle of favorable geological and geomorphological conditions. Small trenches of three to five kilometers long can be sampled at approximately 800m intervals, and trenches of about ten kilometers long can be sampled at a distance of 1600m. When taking the slope product sample, the sampling points are arranged according to the parallel hill slope contour line, and the point distance is 80-40m. All sampling layers are taken as far as possible in the gravel layer or in the clay- bearing gravel layer, avoiding the pure clay layer. The old tailings pile should be directly sampled from the near upper surface layer, and the pit depth is 0.3-0.5m. All kinds of heavy sand sampling must calculate the weight or volume of the product to calculate the grade. Samples are sent to the laboratory after being washed in the wild.
Second engineering heavy sand method
It is an effective method to use sand drill or exploratory engineering to penetrate loose sedimentary layer and systematically sample to understand the gold content of loose deposit and directly determine the grade of gold-bearing layer. Since the gold and industrial gold deposits mainly exist at the bottom of the loose sedimentary layer, the engineering heavy sand method can find out the deep sand gold enrichment and provide direct prospecting information. The basic point of adopting this method is to have a sufficient basis for the construction of the sampling point and the feasibility of the construction. Secondly, no matter what kind of sampling main course is to penetrate the gold-bearing layer and control the bedrock surface below at least 0.2 deep. The use of sampling engineering for sand gold prospecting must be based on the analysis of geological and geomorphic conditions. According to the prospecting signs and clues, the favorable parts are selected in the favorable ore-forming section, and the project is arranged according to the certain engineering network. The favorable part should be determined according to the gold enrichment and metallogenic regularity.
Third, the old mining and mining survey of gold
Many sand gold hand-made old tracks are common in the upper reaches of the river in the gold-plated area or in the fine valleys of the branch ditch. They are effective signs for gold prospecting. According to the old mining tracks, further exploration of the periphery can often achieve good results. The large-scale artificial tailings in the old mining area are also often industrially valuable ore bodies. In addition, through the civil mining survey, many valuable information about the geological characteristics, regularity and prospecting clues of the sand gold deposits can be obtained. Therefore, the sand gold mining survey has important prospecting significance.
Fourth, geological and geomorphological survey
It is the basic method for gold prospecting, mainly used for the analysis of gold mineralization conditions and the prediction of favorable ore-forming areas.
In the prospecting stage, the main survey is the river valley route. Among them, the geological survey can adopt the natural outcrop method, the river debris observation method, and use the known gold-growing ditch in the area as a control analogy, and at the same time take some natural heavy sand samples to understand the gold content. Indirectly or directly determine whether there is no gold replenishment and the level of wealth. In the investigation, attention should be paid to understanding the tectonic setting of the valley and the geological phenomena associated with gold mineralization.
The geomorphological observation mainly divides various landform units of the valley type and determines its distribution, and understands its scale, genesis, sediment characteristics and gold content, and maps the Quaternary on the 1:50000 or 1:25000 scale topographic map. Geological sketches, drawing the boundary line of the main geomorphic unit, providing reference for the layout of the sampling project and the subsequent delineation of the ore body.
V. Some experiences of the folks looking for gold and gold mines
Heilongjiang Province is a major producing area of ​​sand gold in China. It has a long history of mining and has accumulated rich experience in finding sand gold mines.
(1) Determining the prospects section according to the geomorphology and the law of sand gold enrichment
1. Look at "Three Mountains" and "Four Nothing", one is "mountain mountain", "closed mountain", "Yingmen Mountain", "not exposed before the ditch", "not blocked after the ditch", "not exposed in the ditch" Wind and "the whole ditch is not exposed."
The “mountain mountain†is the golden mountain in the upper reaches of the river valley. It is characterized by high (not blocked) and "Ma Ding" veins (quartz). Experience suggests that there is a greater likelihood that a mountain will form a gold deposit in the valley.
"Guanshanmen" is the valley-shaped mountain, also known as "close the door." “Yingmen Mountain†is the mountain facing the river in the corner of the river valley. It is also called “no mouth†and “no mouthâ€. This landform is a favorable sign of gold deposits. In the valley above the "Guanmen Mountain" or in the valley in front of the "Yingmen Mountain", it is a place where sand gold is enriched.
“No wind†is also called “no waistâ€. The mountains on both sides of the river producing sand are higher, and the “wind†seems to be unable to get out. “Unbone†means that the rock on the bottom of the river bed is not exposed, indicating that the valley is in the accumulation stage.
2. "Small ditch out of the mouth", "the big ditch has legs", "not too big or too small in the belly." The small ditch refers to a small valley with a length of less than 3 km. “Small ditch out†is to pay attention to looking for gold deposits at the exit of Xiaogou.
When the length is above l0km, it is a large ditch. “The big ditch has legs†means that gold deposits are found in the larger valleys, so it is also possible to find gold deposits in some of the valleys upstream. Conversely, if there is a gold deposit in the valley, there may be a gold deposit in the main valley. It is not too big or small (Zhonggou) with a length of 3-10km, and the main mineralization is in the valley.
3. “Gold out of the shadeâ€. According to folk experience in the cold region, alluvial gold deposits, especially terraces, are mostly distributed on the side of the valley. That is, the east-west river valley, there are many gold deposits on the terraces on the south side of the valley, and there are few gold deposits on the north side of the valley. On the north side, there are few rivers and valleys in the north-south direction. The gold deposits are mostly from the west terraces, and the ore deposits on the east side are rare. .
(2) River heavy sand sampling to find gold
Taking heavy sand samples along the river for gold prospecting is one of the most common methods used by the people.
Its main experience is:
1. The sampling points should be reasonable and representative. Usually, the sampling line spacing should be 200-300m.
2. The sampling position should select the inner part of the river to change the flow direction (turning); the river water flow rate is significantly slower; the front of the large obstacle object in the river bed; the side of the main tributary convergence.
3. Pay attention to the sampling horizon. When mud (clay), sand and gravel are available, it can be taken.
4. When sampling on the old exploration pit or the old tailing sand pile, the topsoil part should be stripped first, but do not dig too large. It is best to find the gravel sample with the bedrock fragments. It is not possible to take the purely washed gravel part. .
5. Can not be used for water in the sample.
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