The main materials of this book are taken from the monograph of ищукова et al. (completed in 1996), and the Chinese translation of Uranium Mine in Ste Lesov Minefield (translator: Liu Ping, Zhang Tieling) was printed internally in 2009 (text * * * 299). This is a very valuable uranium mine masterpiece. This mine is the largest volcanic hydrothermal uranium ore field in the world. The information is quite rich, comprehensive and detailed. The exploration workload is huge, and the three-dimensional information of the deposit is invisible to uranium mines in other countries, and the scientific research level is far above that of European and American countries.
In the face of such a book, in addition to understanding and learning a lot of new knowledge, we intend to make some supplements based on our experience in uranium research in China. Here are four new findings for academic discussion.
1. The first stage is potassium metasomatism mineralization, and the second stage is sodium metasomatism mineralization.
Generally speaking, the large uranium ore fields in Streltsov can be summarized as the origin of alkali (K, Na) metasomatism in metallogenic geochemistry. The basement ancient jade in this area has experienced many migmatization and granitization. By Mesozoic, uranium mineralization was basically divided into two main metallogenic periods: early potassium metasomatism and late sodium metasomatism. First of all, a large area of timely microcline potassium metasomatism (age 65438±078ma, formation temperature 330 ~ 400℃) has not been found at 2700 meters below the fault zone. The formation of super-large deposits must depend on the development of super-large alkaline metasomatics, which is the major premise. Whether the ore source is sufficient depends on the scale and intensity of the development of alkali metasomatic rocks (I call them ore root facies) below the deposit. After syenite-microcline, it is the first uranium mineralization with strong sericitization, and the ore-forming mineral is crystalline uranium. Sericite metasomatism plagioclase precipitated Ca2+ to form fluorite. A large amount of Na+(Na2O is only 0. 1% ~ 0.2%) is discharged by potassium replacement, and sodium zeolite is formed. After this area, the second relatively low-temperature albitization and mineralization occurred. The deeper the depth, the stronger the mineralization, with a width of 150m. The ore-forming minerals are mainly pitchblende, and some of them contain more than 5.7% of ZrO2. The author did not realize that as long as the pitchblende contains Zr, it can be proved that it was originally a crystalline uranium mine formed by early sericitization, and it became pitchblende after albitization at low temperature. As mentioned above, according to our country's experience, various combinations of U-Zr, U-Ti, U-P and U-REE often appear in sodium metasomatism; On the other hand, as long as there are combinations of U-Zr, U-Ti and U-P in the ore, it must be alkali metasomatism.
At present, all ore-forming materials are pitchblende. At first, they were all crystalline uranium deposits, and later, due to the superimposed transformation of multi-stage hydrothermal alteration, pitchblende uranium mineralization of crystalline uranium deposits appeared. ивеаьников (translation 136) shows that the oxygen content coefficient of the first generation pitchblende in the main metallogenic period is 2.1; The oxygen content coefficient of the second generation pitchblende is 2. 1 ~ 2. 16, and the unit cell parameter is 5.4 1 ~ 5.44? The reflectivity is 14.5 ~ 15.8. In my opinion, these are the characteristic values of crystalline uranium deposits. The reason why pitchblende is always described is actually pitchblende in the late stage of early crystalline uranium ore (the colloidal shell structure is shown under the microscope). Indeed, in this monograph, it is also mentioned that there are pentagonal dodecahedron and cubic early crystalline uranium residues in the second generation spherical pitchblende. Crystalline uranium ore is a typical ore-forming mineral in the first stage of high-temperature sericitization potassium metasomatism alteration, and the second stage is sodium metasomatism low-temperature pitchblende mineralization superposition.
As we all know, only petrochemical products will not be mineralized all over the world. Because: ① it was in supercritical state (> 374℃), and there was no liquid water at that time. Feldspar is an anhydrous mineral, which is caused by mantle juice. There was no hydrothermal solution at that time, so it was not a mine. ② However, alkali metasomatism in this period is essential for hydrothermal mineralization in the later period. First of all, it provides the ore source (for hydrothermal uranium deposits, it is the uranium source); (3) Mantle fluid is hydrothermal only after cooling and decompression. In other words, the first stage of alkali metasomatism is the forerunner and forerunner of hydrothermal process. It can be expressed by the following formula: mantle juice → dry fossilization → hydrothermal mineralization.
After potash feldspar, sericitization (this is the beginning of hydrothermal process. Not only for uranium deposits, but also for other metal deposits, sericite and chlorite are already water-bearing minerals. The prominent feature of sericitization is that it is easy to form uranium-rich deposits (U > 0.3%, and then as high as U=n0%). In other words, almost all rich ore bodies and deposits are related to sericitization. Hydrothermal uranium deposits in the world, not only in China, are basically sericitized, which is the third discovery after a large number of international uranium literature studies. The first two are: ① alkali metasomatism mineralization; (2) The penetration of basic rock wall provides a channel for the upwelling of mantle plume (see Chapter 3 of this book for details).
Albitization in Changshi Petrochemical followed closely chloritization and carbonation. Compared with potash feldspar, albitization belongs to low-temperature hydrothermal uranium mineralization, and its outstanding feature is that the ore is not rich, generally U≈0. 1%. The reason for the lack of enrichment is that sodium metasomatism is generally Na+ metasomatism of K+ in minerals, while cations are simply brought in and out, which does not require the destruction of the whole mineral lattice, so the ability to extract uranium sources is far less than that of potassium metasomatism. The latter always destroys the whole mineral lattice and the whole metasomatic protolith, and its uranium extraction ability is much stronger than that of sodium metasomatism, so potassium metasomatism is easy to form uranium-rich deposits. A large number of microscopic observations of potassium metasomatic rocks show dense cracks, fractures and patchy structures, and the original rock structure is completely destroyed; Sodium metasomatism is a simple false metasomatism of potash feldspar, and the original rock structure is basically preserved.
2. Where is the mineralized uranium source?
Although the research on uranium deposits (whether hydrothermal, sedimentary or metamorphic) in the world has been quite in-depth, there is still a major problem (where is the uranium source? So far there is no clear answer, even in Russia. China's experience solved this mystery as early as the 1970s. The question is simple. Uranium source is in alkaline metasomatic body. Alkaline metasomatism can extract and leach uranium from metasomatic uranium-bearing rocks and provide uranium source for upper mineralization. Alkali metasomatic rocks are mineral deficit rocks and source rocks. In academic circles, it is also wrong to simply think that the high background uranium content in rocks and strata is a uranium source. In fact, only the part with low uranium content is the real uranium source.
Happily, we found the related paper (Nicolschi, 2003), which convincingly proved that sodium metasomatism of Antai deposit provided uranium source for upward uranium mineralization, as shown in figure 1- 10.
This photo shows that uranium was depleted after the original basement granite was replaced by albite. It is particularly worth mentioning that a rare deep drilling (2663m underground) is used, and the information obtained by system sampling is extremely valuable. This is the first study on uranium mineralization in the world. The depleted uranium zone in the figure is strongly albitized (see the time-albitized shadow zone in figure 1- 10). The average background value of the original uranium content in the basement granite in this area is 17× 10-6. After sodium replacement, only n× 10-6 is left, and a large amount of uranium provides uranium source for mineralization (see translation page 246). In addition, albitization area also turns red strongly (hematite particles fill pores and penetrate). These strong sodium Na2O can be as high as 8% ~ 10%. The stronger the sodium metasomatism, the redder the color, which widely exists in various sodium metasomatic uranium mines in China. In addition, the Canadian and Belgian uranium mining areas also have reddening development.
In order to compare with figure 1- 10, we found the distribution map of albite metasomatic bodies on the profile of Antai deposit in another paper (figure1-1).
It should be pointed out that figures 1- 10 and1-1are papers published by two different authors at different times. Figure 1- 10 only reflects the loss of uranium in rocks, but it cannot be explained that the upward replenishment of uranium source is due to alkali metasomatism. Comparing these two pictures, we prove that the uranium loss is caused by alkali metasomatism, and the ore source is in the granite basement of alkali metasomatism in the deep part of the ore body. The results of this study show that an important discovery can not only depend on a paper and its author, but also be good at finding key information in the ocean of literature. As soon as the two were combined, new laws appeared immediately. This is the key to scientific discovery.
Figure 1- 10 profile of antai uranium deposit
Figure 1- 1 1 albitization metasomatism distribution map of Antai deposit profile.
The center of figure 1- 12 is the intense reddening (sodium metasomatism) of granite on both sides of uranium vein. In the past, Jiang Xingquan, the chief engineer of 26 1 Team, showed me many photos of ore bodies he took when he visited the mine. Turning red is completely similar to the picture above. In this photo, black is rich in U-veins (chloritization is strong, white is carbonized). At 1973, we saw this reddening in the tunnel of sodium metasomatism uranium mine in Liling, Gansu.
Figure 1- 12 Strelitsov mine profile photo.
In our opinion, it is not enough to compare the above two figures, but also to know the chemical analysis results of sodium replacement. Haven't found it for a long time. Fortunately, in 2003, French colleagues published the detailed analysis results of this kind of sediment, as shown in table 1- 10.
From the table 1- 10, we can see the following important issues:
1) samples are deep-hole cores and fresh original rocks (hole depth 1068 ~ 2669 m). The data is very valuable and can explain the problem;
2) Most samples are Na2O>K2O, which proves that it is sodium metasomatism, but it is not strong (Na2O ~ 4%);
3) The uranium content in rocks is generally low, U = (3.4 ~ 7.7) × 10-6, except for one sample, which is 9.5× 10-6. We think this result is very important, which reflects the strong loss and zoning of uranium and uranium during the deep sodium mineralization of the granite body, and provides ore sources upwards. This is consistent with the reduction of u-value loss in the analysis curve in figure 1- 10. It must be pointed out that in the 1970s, when we were studying hydrothermal uranium deposits in China, we found that alkali metasomatic feldspar petrochemical extraction of original uranium provided the ore source. It took decades for Russian uranium deposits to be confirmed. The French paper also lists U = (15 ~ 23 )×10-6 in the molten glass of rhyolite in volcanic basin (the average value of 46 samples is (19 4 )× 10-6), and the U content in Na rhyolite also suffers losses.
Table 1- 10 Chemical Analysis Results of Deep Hole Core (wB/%)
Granodiorite is also found in the deep part of this deposit, which is also sodium (Qiling uranium mine in China is also mineralized in diorite). This diorite is probably a variety of mantle-derived dark dikes. This one was ignored in the past. This diorite may be the precursor of the upwelling of mantle juice (to be determined).
3. Alkaline metasomatism of mantle fluid activities and basalt events.
The study of uranium deposits in volcanic depressions in this area is quite high, and the metallogenic conditions of the anatomical deposits are quite detailed and comprehensive. According to the research results in China, there may be the following two laws to be supplemented:
1) Why are there so many deposits and so many ores in Streltsov giant uranium ore field? I think this is closely related to the special development of basalt in the brazier. There are three basalt quilts and two rough dacite quilts in the volcanic cover of this volcanic basin. There are two favorable factors: ① Multiple infiltration of basaltic magma into mantle fluid leading to mineralization. The multi-layer basalt reflects that the mantle plume activity was quite strong at that time, which may make the whole volcanic basin cover 140km2 of extremely hot liquid alteration and mineralization (* * * generation 19 large, medium and small deposits). ② The so-called rough dacite is actually a kind of potash basalt.
2) Basalt is a particularly favorable host rock in the formation of hydrothermal uranium deposits. After careful investigation, it can be found that most of the deposits and ore bodies in this area are located in basalt layer and its variation coarse andesite (figure 1- 13). It is worth mentioning that, according to my analysis, the original rock of this rough andesite is still basalt, and then it has undergone strong metasomatism by silicon and potassium, and its K2O%, Na2O and SiO2 contents are: 5.28% ~ 5.44% respectively; 2.38%~4.3 1%; 65. 14%~69.96%。 Potassium plagioclase comes first, and then sericitization (sometimes called greisenization in the original text) According to our country's experience, sericitization (called fine-grained diagenesis of pyrite, see page 95 of the translation) is a typical hydrothermal activity for uranium deposits to form rich ore. Page 95 also clearly points out that the so-called "hydromica" below Antai deposit 1500m is actually sericite and muscovite. Basalt events led to the upwelling of deep mantle fluid during the formation of hydrothermal uranium deposits in this area, which became the premise of strong hydrothermal mineralization. Through the strong metasomatism of silicon and potassium, basalt is transformed into coarse andesite, which is the most favorable surrounding rock for ore enrichment (and most of them are high-grade ores, U > 0.7%). See page 1 17 of the translation.
In the west of this ore field, there are three very close deposits (Ergon-Nozzle-Five Years), which can be regarded as large deposits (Figure 1- 14). The deposit is controlled by the NW-trending deep fault and occurs in the breccia fine rock at the top of syenite porphyry. As far as I know, this "syenite porphyry" is actually an acid vein porphyry, which has infiltrated into the mantle-derived bimodal rock series of basalt. This syenite porphyry is the magma product of potassium-rich mantle fluid after deep metasomatism of basalt. Single magma has no blasting ability at all, and only mantle juice has extremely powerful blasting function. The ore bodies of more than a dozen deposits in the volcanic cover of this ore field are complex, which mainly reflect the blasting structure, rather than a single structural stress fracture.
Figure 1- 13 Geological Profile of Streltsov and Antai Deposits1/Exploration Line.
Figure 1- 14 Geological Profile of Exploration Line 52 of Ergon, Nozzle and Wunian Deposit.
4. Study on mantle xenoliths around the mining area
In the research literature of many mantle peridotite xenoliths of Mesozoic and Cenozoic basalts in Sinuik (становик) in the north of the mining area, we found the possible deep source of mantle fluid that formed the strong alkaline metasomatism in Streltsov large ore field. In this mantle rock, potassium metasomatic phlogopite and sodium metasomatic amphibole are developed. In the molten glass with slurry pool, Na2O is 7.5%, K2O is 3.3% (8 analyses); The glass chemical composition of another xenolith is shown in table1-1(семеова et al., 1984). The contents of Na and K in the glasses of seven samples in this area are quite high: Na2O = 4.7% ~ 9.8%; K2O= 1.2%~8.2%。 Twenty-seven samples of 9 mantle xenoliths from Daliganga basalt in southeast Mongolia west of Streltsov mining area were analyzed, and Na2O = 7% ~ 10.6%. K2O = 0.5% ~ 4.7% (Ionov et al., 1994).
Table 1- 1 1 glass composition in plasma unit of siweike mantle xenolith (spinel lherzolite) (wB/%
Incidentally, basalt overflowed from the volcanic uranium deposit in Dachayuan, Zhejiang Province was discovered in China as early as the 1990s, in which the molten glass in the cytoplasm of mantle xenoliths (the fossil record of mantle juice) is particularly rich in potassium, with K2O as high as 9. 18% ~ 15.88% (three samples, 16 analysis). The microscopic state of plasma cells is shown in figure 1- 1. Our work proves that plasma cells are formed by the replacement of mantle juice, and the molten glass is the solidified body of alkaline mantle juice rich in K and Na.
So far, we first learn from the high-level research results of Russian counterparts on large-scale ore fields in Streltsov. However, we are not satisfied with this, so we should revise and supplement it as much as possible. In view of the blind imitation and plagiarism of international documents in the field of mineral deposits and lithofacies in China, it has not improved China's academic status, but has become more and more disappointing. I hope to blindly follow the scientific research route and completely transform it. Otherwise, it will waste youth and state funds and do great harm to scientific development.