Chapter 2 describes the general geology and mineralization of the deposit.

The formation of this deposit is divided into two stages: one is intense albitization (all kinds of rocks are occupied by this sodium). At this time, it is not a mine, but it is necessary. This alkali metasomatism is the metasomatism product of upwelling supercritical mantle fluid to rocks, and it is a dry metasomatism above 374℃ (the critical temperature of water). At this time, there is no hydrothermal solution (essentially a gas product of high temperature and high pressure). However, mineralization can only be achieved in hydrothermal solution. Therefore, it is necessary to wait for the mantle fluid to be further cooled and decompressed to become hydrothermal, and then the hydrothermal process and mineralization will begin. The second stage is characterized by sericitization, which belongs to K-wave metasomatism after sodium. No matter what the original rock is, all the minerals in it are sericitized. Sericite is a low-silicon mineral (its silica content is only about 46%). After the replacement of feldspar and quartz, a large number of new microcrystal quartz will inevitably remain, so it is collectively called sericitization (note: the appearance of this microcrystal quartz should not be called silicification. Silicification refers to the introduction of foreign hydrothermal silicon, and the above microcrystals are the time of sericitization of feldspar or in-situ precipitation after chloritization, not foreign silicon). After metasomatism, many micro-cavities will inevitably be produced, which is very beneficial to the precipitation and fixation of uranium minerals and is not easy to be carried away by high-pressure hydrothermal turbulence, forming rich or extremely rich minerals, ore bodies and deposits. See table 3- 1 for the chemical composition of sericite beside the ore body of this deposit.

Table 3- Chemical Composition, Uranium Content and Crystal Chemical Formula (wB/%) of Sericite 1

Although Lianshanguan deposit was replaced by sodium, the real mineralization was subsequent sericitization, as shown in photos 3- 1 and 3-2.

Photo 3- 1 shows that * * * contains a lot of muscovite, sericite and syenite, and the latter three minerals are collectively called sericitization. Calcite is an inevitable biological mineral containing calcium sericite in the original rock.

Photo 3- 1 fine-grained crystalline uranium ore aggregate (u) alkali metasomatic quartzite in cemented fissure, × 10

Photo 3-2 shows that uranium minerals produced during sericitization are further enriched in the vein.

Photo 3-2 Uranium vein with U3O8 grade =45. 1% and age 1946 5 1ma consists of crystalline uranium (about 40%), muscovite (20%), quartz (20%) and calcite (/kloc-0) About 10% of PbS in crystalline uranium ore is radioactive lead, which comes from uranium decay.

The quartzite strata in the deposit are replaced by sodium to form mixed granite, and its composition changes are shown in Table 3-2.

Table 3-2 Composition changes of Lianshanguan quartzite and red mixed granite before and after sodium replacement (wB/%)

See Table 3-3 for the chemical composition of ore and sodium metasomatic quartzite in this deposit. It is worth emphasizing that if sericite forms rich ore or extra-rich ore, it needs to be re-broken through structure to produce breccia uranium, which is further enriched in the cement between breccia (photo 3- 1) or uranium ore is filled in the vein (photo 3-2).

Table 3-3 Comparison of Chemical Composition of Alkaline Metasomatic Rocks in Lianshanguan Deposit

As can be seen from Table 3-3, the ore grade is very rich, with U as high as 8% ~ 40%. At the same time, lead, rare earth, niobium, tantalum, vanadium, copper, cobalt, nickel, silver, gold, arsenic and other elements are also associated with enrichment. The enrichment of these trace elements indirectly proves that the ore-bearing rock series is carbonaceous mudstone series. Because these elements are characteristic components of this rock series. This rule has been found in carbonaceous mudstone series all over the world. It is worth emphasizing that the ore in this deposit generally contains carbon (graphite), and C is 0. 1% ~ 0.9% (9 samples) (Fan Jun, 1980).

The ore-bearing surrounding rock stratum of Lianshanguan deposit is the lowest stratum of Langzishan Formation of Liaohe Group, which is not integrated on Archean mixed granite basement. * * * The upper, middle and lower segments are subdivided as follows (Guo Zhitian, Zhong et al. , 1980):

Upper part: thickness

White sugar granular marble 28m

Thin diopside marble12.5m.

Graphite bicolor schist 29.3m.

Flaky diopside marble, containing mica schist and granulite 21m.

Middle part:

Garnet mica sheet containing mica quartzite 4.0m

Medium-thick quartzite, feldspar quartzite and garnet mica schist 22.8m.

Staurolite garnet mica schist 99m.

Mica quartz schist, staurolite garnet mica schist and quartzite, with amphibole schist at the top.

Garnet biotite schist 20mm

Next paragraph:

Quartzite, metamorphic conglomerate mixed with mica quartzite, with 30m muscovite quartz schist at the bottom.

Metamorphic glutenite (granite antique surface) 1 ~ 2m

In fact, the above strata are typical Proterozoic Carboniferous-siliceous mudstone series containing silicon (metamorphic quartz schist), mud (metamorphic schist, staurolite and garnet) and carbon (carbonate and graphite interbeds).

Looking back now, the detailed anatomical research results of Lianshanguan deposit at the beginning are close to touching the key metallogenic mechanism of hydrothermal deposits. The main points are as follows:

1) There must be dark rock wall penetration of basalt event. It is they that open the rapid upwelling channel after the deep basaltic magma of upper mantle soft fluid and mantle fluid (mantle juice) provide it. This is the first prerequisite for mineralization.

2) The mineralization of upwelling mantle fluid is as follows: ① large alkaline metasomatic bodies are formed, from which minerals (rock U and stratum U) are extracted and released to provide sufficient uranium sources; ② The formation of alkali metasomatic rocks consumes a lot of K and Na in the mantle fluid, transforming it into alkali metasomatic rocks, which greatly reduces the strong alkalinity of the fluid (too strong alkalinity, too high concentration of [K+][Na+] is beneficial to the migration of U and extremely unfavorable to the precipitation of U). Therefore, acidification (sericitization) is needed for mineralization. (3) Although the early alkali metasomatism cannot be used for mineralization, it is a necessary starting stage for hydrothermal mineralization in the later stage of evolution and derivation. Seriphization is the inevitable alteration product of mantle fluid becoming hydrothermal solution.

3) The uranium source of the so-called unconformity vein hydrothermal uranium deposit represented by Lianshanguan deposit in the world is mainly Proterozoic carbonaceous siliceous mudstone. Followed by Archean mixed granite in the basement. In 1980s, we deciphered that the Yuanguyu Carboniferous-siliceous-mudstone series is a huge underground uranium mine. The Upper Sinian, Lower Cambrian, Silurian, Devonian, Carboniferous and Permian Carboniferous-siliceous mudstone systems are widely developed in China, and the regional research institute of our bureau and our hospital have conducted detailed and in-depth anatomy for many years. What is particularly commendable is that the Phanerozoic Carboniferous-siliceous mudstone series in China has a shallow metamorphic deformation, reflecting the original state, which is more helpful to understand the ancient Carboniferous-siliceous mudstone series that have undergone metamorphic deformation and transformation in Canada, Australia, Latin America and Africa.

4) Seriphization should be subdivided into two stages: early sericitization is widely distributed in the region, often thousands of meters wide, far beyond the scope of ore bodies. At this time, U is dispersed and infiltrated by crystalline uranium particles, which belongs to low mineralization preconcentration. In the later stage, the structure must be re-fractured, or further concentrated by torsional compression shearing or stretching breccia U to form ore-rich or ultra-rich ore bodies and deposits.

By the way, there are important differences between the so-called unconformity vein uranium deposits in Australia and the typical unconformity vein uranium deposits in Canada. The former ore body is relatively poor, and its grade generally fluctuates within U=0.n%, while Canada is extremely rich, with U ≈ n% ~ N0%. There are two reasons: ① The minerals in the multilayer faults in northern Australia are easy to disperse, while the multilayer faults in Canada are steep faults (the upwelling of mantle juice is more convenient and rich) and easy to concentrate; (2) The location of Australian ore bodies is far inferior to that of Canadian deposits distributed along the unconformity surface in ancient weathering crust, which is beneficial to the formation of rich deposits. Ancient weathering crust is extremely loose and porous, effectively intercepting minerals. In addition, strong aeration (strong reducibility of H, H2, CO, CH4, etc. ) is an ideal reducing agent to ensure that the metallogenic environment is not destroyed by oxidation. Weathered crust is an extremely special geochemical and geophysical barrier for effective mineralization. In view of the obvious oil infiltration and gas-liquid inclusions of natural gas found in almost all hydrothermal uranium ore bodies and ores in southern China in recent years (Europe and Guangxi, 20 13). Therefore, we suspect that there may be oil, natural gas and asphalt in unconformity vein uranium deposits in Canada.

2. Sericite mineralization in France.

In France, alkali metasomatic rocks are generally called schists, which also affects the uranium geology in Canada and is often used in the documents of some French uranium exploration companies in Canada.

In France, the study of "metamorphic syenite" mainly started from uranium deposits, with a long history and in-depth research. France's scientific research level is obviously at the forefront in western uranium geology. It must be emphasized here that metamorphic syenite itself is not a uranium mine, but a good host rock. Uranium deposits were formed after hydrothermal activities were superimposed again at lower temperature, which showed the combination of polycrystalline muscovite-pitchblende and mixed illite-montmorillonite-uranium. According to my understanding, this kind of mineralization is actually sericitization mineralization.

Leroy( 1976) quoted the following definition of Lacroix( 1920) when he started to use episyenite: "This kind of rock has changed so much in chemistry and mineral composition that it is impossible to restore and determine its initial state with confidence. In this case, the prefix' Table-'('Metamorphic' and' Post') is added before the name of the rock whose chemical composition and mineral composition are most similar to it at present, so as to indicate the supergene characteristics of the studied rock (Metamorphic syenite). Le-roy explained that "this term is only used out of habit, and they have nothing to do with syenite in mineralogy and chemistry". See table 3-4 for his analysis results of metamorphic syenite in Marnek deposit.

Table 3-4 Comparison of Mineral Composition between "Metamorphic Rock" Area of G356 Tunnel and Original Granite (wB/%)

The following changes can be seen from Table 3-4:

It disappeared in time. The amount of disappearance reflects the degree of alkali replacement. The stress time of the original granite at the strongest point is less than 65438 0%. The lost time spread outward, leading to the silicification of the peripheral original granite (the time increased significantly, see samples 2 and 7). This in turn shows that silicification is the inevitable product and exact symbol of alkali metasomatism in petrochemical industry.

2) Metamorphic syenite is NaK mixed metasomatism, mainly Na metasomatism (plagioclase grows more than potash feldspar).

In France, uranium deposits are divided into two types: one is called feldspar type (muscovite and biotite minerals are unstable, disappear or become chlorite). Another type (mica type) is described below, which is characterized by: ① disappearing and discharging in time, and the surrounding time is precipitated again outside the alkaline metasomatic rocks. A large number of secondary stress (autogenous) will be filled in the cavity, and uranium ore can also be filled as ore. ② plagioclase and striped feldspar are completely sericitized; Biotite produces chloritization. The mica type in France is sericitized now; The feldspar type is sodium metasomatic.

The chemical composition of mica metamorphic syenite is shown in Table 3-5.

Table 3-5 Chemical analysis of two silicified metasomatic rocks (wB/%)

The difference between mica metamorphic syenite and feldspar metamorphic syenite is that Na2O of the former is greatly reduced (see Table 3-6), which indicates that plagioclase is unstable and muscovite. According to our current understanding, this is sericitization mineralization, which was produced on the basis of early syenite.

Table 3-6 Comparison of Chemical Composition between Middle-long Rocky Metamorphic Rocks (55) and Mica Metamorphic Rocks (56) in Penny L 651and -225 (wB/%)

Pierre Plantai, a granite body in Marjory, rauzer Province, is also mica syenite.

I saw many holes of metamorphic syenite, such as sponges, in Marnek open pit. This uranium-rich ore was timely filled with montmorillonite syenite mixed with pitchblende and uranium ore, which was the result of later superimposed filling. At present, Marnek, Penny, Pierre Plantai and other deposits are all feldspar-type, and then sericitization is superimposed to form mineralization. Sericite is easily corroded into montmorillonite. In 1982, researcher Huang carried out ultrasonic beneficiation on altered rock samples collected from uranium deposits in France, and found that it has strong uranium adsorption capacity, in which the U content can be as high as1%~ 4%; The k coefficient of montmorillonite is 0. 1 ~ 0.2 (yellow, 1984). The adsorption capacity of illite for uranium is very low, U≈n0× 10-6.

At first, the French uranium scholars thought that the mineralization was epithermal (Geffroy, Sarcia, 1958), and later the theory of downward leaching of atmospheric precipitation prevailed (Moreau et al.,1966; Barbier, 1974).Poty( 1967) developed the technique of gas-liquid inclusion determination, which helped Leroy and others find that the temperature of feldspar type is as high as 350 ~ 400℃ and the temperature of pitchblende is 345℃, so it is impossible for precipitation to leach downward. Leroy also clearly pointed out that the mica type is later than the feldspar type, and prospectively pointed out that uranium mineralization and the penetration of 285 M a lamprophyre wall occurred simultaneously (Leroy, 1978).

SarciaJ.A.( 1980) pointed out that this kind of hydrothermal uranium deposits mostly occur in the shear zone and breccia zone related to deep faults, and have no obvious connection with magmatism, and alkali metasomatism can account for rocks of any lithology (granite, metamorphic rocks, unreformed sedimentary rocks, etc.). ).

Maison Neuve J., Merg Oil-Daniel J. and Labernardiere h .( 1984) studied the genesis of timely metamorphic syenite and alkali dissolution. Their calculations show that when the pH is below the critical temperature = 9.5 ~10, natural sodium bicarbonate fluid can dissolve syenite and generate syenite (or syenite porous granite), and it is pointed out that CO2 escape under reduced pressure is important to improve the hydrothermal pH, and CO2 escape is a condition for precipitation of uranium enrichment.

Cathelineau( 1983) studied the uranium deposits of Wangdai in western France and Majerie in central France, and thought that the evolution trend of ore-forming hydrothermal alteration was that Na in metasomatic altered rocks decreased continuously, and a series of potassium-rich minerals appeared, such as polycrystalline muscovite-illite, montmorillonite mixed layer-cryolite combination, or polycrystalline muscovite, illite-montmorillonite, or cryolite. The ore-forming hydrothermal solution did not come from the early magmatic stage.

Leroy( 1978) thought that the precipitation was heated by the late basic magma. Finn et al. (1978) and Roger et al. (1980) think that it is the radioactive heat flow of granite U, Th and K, and Kaiserlinnau thinks that it is structural shear that generates heat. At present, hot feet can be provided by high temperature curtain juice.

Dahlkamp( 1993) collated many analysis results of feldspar type, mica type and highly mineralized mica type, as shown in Table 3-7.

As can be seen from Table 3-7, ① feldspar is mainly albite plagioclase of original potassium-rich granite (i.e. sodium metasomatism), followed by chloritization ② mica, with the orthoclase content unchanged, plagioclase decreased and mica increased (but muscovite and biotite are not separated), but in fact, potassium metasomatism ③ rich ore (pitchblende reaches 8.9%) is obviously sericitized (muscovite increases to 265,438+).

The following are the impressions of our on-site inspection:

Bernadang deposit is located 40 kilometers north of Marnek mine and occurs in mica granite body of marche. The ore is also mica type, and the karst caves are filled with uranium ore and uranium black, not pitchblende. In the stope, mica without ore is also seen, which is gray and does not change red; Second, we can't see the timely cavity. It seems that how many minerals are filled in the karst cave is the key to determine whether the ore is rich or not.

Table 3-7 When light-colored granite changes to (a), (b) and (c), the mineral composition (volume percentage) of St. Sylvestre rock mass changes: (a) feldspar changes to syenite, (b) mica changes to syenite, and (c) highly mineralized mica changes to syenite.

Pierre Prantai deposit: The ore body occurs in the feldspar rock mass cut by the NW-trending fault, showing strong red and brick red. The mineralization period is light green montmorillonite, chlorite and epidote. Because the primary granite is fine, the original rock structure is still fine after alkali metasomatism. The karst cave is too small, with little black ore-forming material and poor ore, and the grade is about 0. 1%(U).

Bedorena deposit: This deposit and the above deposits belong to the mixed metasomatism of potassium and sodium in granite. The difference is that it occurs in the ancient gneiss in the outer contact zone and is a completely open pure sodium metasomatic rock (K is completely discharged from the rock). Pure sodium metasomatic rocks are controlled by faults, and their metallogenic ages are different, ranging from 160Ma to 170 Ma, which is much later. Metallogenic periods are mainly montmorillonite (60% ~ 77%), hydromica (22% ~ 25%), kaolinite (1% ~ 15%) and uranium. The ore is intensely red.

Deposits in France: This deposit is different from the above deposits and occurs at the intersection of NW-trending faults and lamprophyre walls. The ore is especially rich in U = 1% ~ 4%, even as high as 20%! The first uranium mine in France is Henriette deposit, which is the intersection of structure and lamprophyre wall during mineralization, and its grade is as high as U = 10% ~ 30%. There are also examples of sericitization and chloritization in basic rock walls in France.

Comandri deposit: Motagne granite located in Wangdai area, with a reserve of about 4,000-5,000 tons (all deposits in France have several thousand tons of medium and small reserves). Although the average grade is not high and there are many deposits, it is still a very valuable mineralization type. The deposit occurs in mica granite, and the mineralization period is the red fracture (width 1 ~ 2 cm) network vein of montmorillonite+pitchblende.

Xia 'erdong deposit: It is located in the inner contact zone in the north of Motane granite body, with a vertical shaft depth of 320 meters ... The ore body is strongly red (brick red) and strongly mylonitized gneiss granite, and regional faults pass through it. Microcrystalline quartz, carbonate, pyrite and pitchblende are scattered in gneiss. What was the explanation before mining? There is no explanation information.

Benalang deposit: Located in the southern contact zone of Kelander granite body, along the Atlantic coast, only a few hundred meters away from the sea. The deposit is based on Kelander granite body, on which there are mica schist, graphite schist and quartzite, indicating that there is residual carbon-bearing syncline (that is, U-bearing siliceous mudstone series). This deposit is different from the above deposits: ① Uranium ore bodies are not produced behind the rock mass, but before the rock mass. The mineralization age is 340Ma；; ② Rich in ore, 0.7% (U); ③ It is not pitchblende, but crystalline uranium. Crystalline uranium ore is also very special, which is not a single cube or octahedron, but a prism, long plate and radial fiber with a length of 6.0cm perpendicular to the vein wall. This pegmatite crystalline uranium deposit is worthy of in-depth study and quite rare. On both sides of the vein, there are late renal crustal amorphous pitchblende filled in the reopened vein space.

1986, the international atomic energy commission held a meeting in Nancy, France. They had a comprehensive paper on the collection of "vein uranium ore" (B.Poty, J.Leroy, M.Cathelineau and others, 1986). In their conclusion, they focused on the genesis of granite-type uranium deposits in the country. The general contents are as follows: Before 1974, the viewpoint of genesis of supergene precipitation leaching was widely accepted in the world (Roubault and Cop-pens,1958; Bigote,1964; Moro et al.,1966; Barbier,1974; Matos Diaz and Suarez de Andrade,1970; Langford, 1974,1977; Knipping, 1974). But later, the study of inclusions (Leroy and Poty,1969; Poty et al., 1974) combined with the study of biogenic minerals (Cuney,1974; Moro,1977; Le-roy, 1978) found that the deposit was formed by hydrothermal leaching of crystalline uranium in surrounding rocks. Uranium deposits not only appear near the surface, but almost all hydrothermal uranium deposits extend below 350m m. The uranium background content in peraluminous granite is high (10 ~ 20) × 10-6, and crystalline uranium is the source of mineralization (Bebier et al.,1967; Barbier and Ranchin,1969; Lanchin,1971; Renard,1971; Le,1975; Moro, 1977, etc.). Recent research emphasizes the magmatic origin of crystalline uranium deposits in granite, which has two distribution forms: the first is uniform distribution, and its abundance is related to the process of magmatic differentiation; The other is distributed along the shear zone during magmatism. A fine-grained granite is especially rich in incompatible elements such as uranium, lithium, fluorine, tin, etc ................................................................................................................................................... In addition, we should also pay attention to the source of uranium in the old strata before granite (black shale and acidic volcanic rocks). Hematite and pitchblende were not formed at the same time, but later, which shows that the reduction precipitation of uranium has nothing to do with the oxidation of ferrous iron. Mineralization is firstly the replacement of surrounding rock with potassium, and then uranium ore (130 ~ 150℃) and iron sulfide are formed. At this time, cryolite was precipitated in time, combined with montmorillonite, and early muscovite was accounted for. Finally, there can be supergene leaching to form silicate and phosphate of hexavalent uranium, of which uranium ore has never been seen before. The study of age (U-Pb method) shows that there are at least four mineralization periods of Hercynian granite in France: 340Ma or earlier, 260 ~ 280Ma, 190 ~ 170Ma and 0 Ma. The late Permian is the main metallogenic period. At the end of Hercynian orogeny (290 ~ 300 Ma), mantle uplift was accompanied by intense magmatic activity (lamprophyre wall, micro granite and granite). After the deep circulation of atmospheric precipitation in the high heat flow field, granite was syenitized, which may be the beginning of hydrothermal process. Fluids rich in carbon and sulfur (CO2, hydrocarbons, H2S) come from metamorphism and diagenesis and play an important role in the precipitation of pitchblende.

3. Sericite mineralization of McLean deposit in eastern athabasca (Figure 3-2).

In Figure 3-2, the upper figure shows the percentage statistics of metal minerals in the ore belt, and the lower figure shows the percentage statistics of altered minerals.

Figure 3-2 shows the plan of Maclean deposit in East athabasca. It is divided into two parts: A and B. The upper part is A and the lower part is B. There are two ore belts (N ore belt and SW ore belt) in Figure A.. N capsule area, consisting of capsules 1, 2, 3-4 and Candilac capsules; SW capsule zone consists of SE capsule, SW capsule and rabbit ear mineralization. Figures such as 9.6, 7.2 and 9 are mineral content (%). U3O8 content (%) is juxtaposed at the top of the figure; Figure B shows the statistical content (%) of altered minerals in each ore zone in the north and south ore zones of the deposit. This painting is quite fine, but some illustrations are blurred. This paper attempts to reanalyze as follows:

1) First of all, there are a lot of hematite in Figure A ... According to my own experience, this is the relic of the earliest mineralized feldspar alkali metasomatic rock, which was ignored by the author and simply described as "hematitization". The author's shortcoming in making this map is that he only pays attention to the final product of multi-stage alteration and superposition of ore belts, and does not divide the formation stages. In fact, this is the product of at least three stages: the first stage is feldspar alkali metasomatic rock, which has always been red, infiltrated by a large number of highly dispersed hematite, and destroyed by tectonic hydrothermal activities in the later stage. After fossilization and sericitization, the second stage hydrothermal alteration superimposed mineralization in chloritization, in which illite should actually be sericite; After that, all the previous feldspar and mica altered minerals were strongly hydrolyzed into kaolinite by supergene weathering. The author mistakenly attributed the mineralization of the deposit only to kaolinite. In fact, kaolinite is a supergene mineral and should not be regarded as ore-forming alteration of vein. Our experience shows that kaolinite and illite are weathering products of early sericitization.

2) In Figure A, the ore minerals contain a large number of arsenides and sulfides of iron and nickel, and the U grade is very high, which is a prominent feature of sericitization mineralization type.

Alteration nomenclature of "safflower" and "hematitization" often appears in papers on uranium geology at home and abroad, which is very unscientific. It is this naming method that ignores the most important link in the genesis of the deposit-prophase petrochemical. Our past research has proved that this "reddening" is the residue of dragon petrochemical, which is always dyed red by hematite. Later, Putnis et al. (2007) proved this point in detail, as follows:

A. See Figure 3-3 for the process of metasomatism of plagioclase by potash feldspar.

B. Potassium feldspar metasomatism plagioclase is to completely destroy and transform the crystal of plagioclase. If Na+ and Ca2+ are completely drained and replaced by K+, the complex anions will be completely decomposed, and micro-cavities will inevitably be generated and filled with hematite particles, so the whole rock will turn red, as shown in Figure 3-4.

Figure 3-2 Alteration Distribution Map of Maclean Deposit

Fig. 3-3 Scanning electron microscopic backscattering of plagioclase in San Marcos diorite by potassium feldspar.

C. The chromosomes of finely dispersed hematite in potash feldspar are further enlarged (photo 3-5).

To sum up, the so-called "reddening" is actually the residue of potash feldspar replaced by early potassium. It can be considered that such reddening is synonymous with dragon petrochemical.

It must be pointed out here that our intention of choosing this paper in the ocean of literature is not only to say that the red color of feldspar is because hematite is highly dispersed and filled in the micro-cavities produced by K-mineralization of plagioclase. In addition, it is conceivable that uranium minerals can also fill micropores like hematite, which is also an important reason why potassium metasomatism, which is easy to form micropores, is easy to form rich ore. Furthermore, the redder the uranium ore, the richer the uranium, and the same is true.

Photo 3-4a —— Newly-born potash feldspar (gray area) contains metasomatic plagioclase, showing obvious micro-cavities (black spots); B-A enlarged diagram of the upper left corner box, black is micro-void, and white highlights are iron oxide particles; C and d are amplification.

Photo 3-5 Hematite particle filler (hem) in potassium feldspar micropores, with blackness of 200 nm.

4. sericitization mineralization 4. Keyouhu deposit

See Figure 3-3 for zoning of sedimentary alteration profile of key lakes.

Figure 3-3 NW-SE profile of Gaertner ore body in Jihu Lake shows the distribution of alteration, primary and reactivated U-Ni mineralization.

In Figure 3-3, the outermost layer (H) is actually the earliest alkali metasomatic feldspathic sandstone stratum, but due to the transformation and concealment in the later hydrothermal stage, especially in the supergene weathering stage, all of it has become illite except hematite (followed by kaolinite). The width of H is very large, at least 200 m on one side (K, F, P, R subbands are H originally). Ore deposit scholars only pay attention to the study of several meters on both sides of near-mine alteration. In fact, this is only the latest hydrothermal tectonic product and cannot reflect the whole alteration process. It must be considered that K, F, P and R all occurred in turn on the basis of the earliest and largest H alteration zone. Although almost all K, F, P and R have become kaolinite and illite, they are actually weathering products of early sericitization. Sure enough, Polito didn't confirm this until 2004 (see below).

5. The uranium deposit in caswell is also sericitized and mineralized.

What Dominic Peter called gneiss actually has no proper definition. It is a typical potassium metasomatic rock with K2O as high as 5% ~ 8. 1%. Then sericitization occurred, which almost completely eliminated the early potash feldspar and transformed it into sericitization, resulting in uranium-rich veins (Ey, 1985).

6. sericitization and mineralization in northern Australia

The evidence of sericitization of hydrothermal uranium deposits in northern Australia is:

1) There are a lot of sericite and muscovite in altered rocks, which means that K+ is brought in, which is a typical sericitization type (chloritization always occurs, which is determined by strong biotite in the original rock stratum).

2) The prominent feature of unconformity vein uranium deposits in northern Australia is that a large amount of silicon is discharged. This point is easily overlooked. The alkali metasomatism desilication around the ore body in the altered schist of Nabalek deposit takes away 40% of SiO2 _ 2 (Wilde, A.R., 199 1? ) upward silicidation.

In the research papers on uranium deposits in northern Australia, it is only mentioned that mineralization is related to chloritization, which is simply called magnesium metasomatism. Chloritization time is1650 ~1600 ma (Rb-Sr method), which is controlled by the structure of breccia zone and cataclastic rock zone. Uranium mineralization and chlorite * * *, chlorite is a breccia cement, the content can reach more than 10%, and some of it can be all chlorite. Chloritization has a wide halo (Jabiluka deposit) of 200 ~ 500 m. The surrounding rock of the deposit is slate, but a large area of biotite and muscovite is developed, and the matrix is composed of fine-grained Shi Ying, anorthite and orthoclase (винокуров, омл). Chloritization related to mineralization is not isolated, but the inevitable product of the reverse evolution of potassium metasomatism. In the alkali metasomatism of biotite granite or iron-rich magnesium rock, there will always be a large number of chlorite. Furthermore, the original rocks in chloritization are extremely strong, probably basic rock walls, and were mistaken for "amphibolite".

The protolith (slate) is biotite, muscovite and orthoclase, which was brought in by early potassium and replaced by potassium. Then the chloritization and Ordovician petrochemical of mica, which is the explanation of sodium; The muscovization and sericitization of albite and chlorite is another potassium metasomatism. It can be seen that there is a law of K+→Na+→K+ K -Na waves alternating here. Mg2+ metasomatism is only a neutral metasomatism from alkali metasomatism, not an independent alteration. The mineral deposits in this area are huge. However, scientific research only puts forward the concept of chloritization, a shallow mineral, and the genesis of the deposit has been in a chaotic state.

In Nabalek deposit, the surrounding rock is amphibole, which is actually a basic rock wall penetration without proper name. The alteration is characterized by chloritization of amphibole, biotite and plagioclase (muscovite is also developed in the inner zone). Crystalline uranium ore and late uranium ore closely associated with chlorite form ore bodies.

It should be emphasize that that so-called polycrystalline muscovite k0.9al1.8fe0.1mg0.3al0.8si3.2o10 (oh) 2 formed before mineralization is actually a typical sericite with a k coefficient as high as 0.9.

Paul ·A·Polito and T Kurt Kaiser (2004) clearly distinguished sericite from illite when studying the alteration of Nabalik deposit in northern Australia, as shown in Table 3-8.

Table 3-8 Granite and Subsequent Alteration Stage of Nabalek Deposit

Sericite and sericite are obviously separated in Table 3-8, and they are not altered minerals in the same period. The night before and the next morning. Although these are the results of studying uranium alteration in northern Australia, they can be used for reference to distinguish late illite from early sericite in Canadian uranium mines. We in China have also gone through this process. Table 3-9 shows the chemical composition of these minerals.

Table 3-9 Composition of Sericite, Illite, Chlorite and Kaolinite Probe

Table 3-9 shows the detailed chemical composition of illite and sericite. Polito classified the two minerals into primary sericite (sample number 1, 2); Further altered illite (sample 8). Please note that sericite and illite are obviously different in K2O and H2O contents, which is completely consistent with our research on hydrothermal uranium deposits in China. K2O of sericite is higher than illite, the former is 1 1%, and the latter is less than 8%. The former is less than 6% H2O, and the latter is more than 6.8%, which obviously shows that illite is the product of hydrogen replacement in which sericite is further hydrolyzed and [K+] is replaced by [H+]. The content of 4- coordinated Al Ⅳ in illite decreased obviously, while the content of 6- coordinated Al Ⅳ increased correspondingly, and transformed into kaolinization, and H+ pushed all K+ away.

Figure 3-6 Sericite at Different Stages (S 1→S2→S3)

The microscopic identification results of altered rocks in this area also fully prove the difference and alteration sequence of S 1→S3. Microscopic identification is shown in Figure 3-6.

7. Olympic dam deposit (typical sericitized metallogenic type)

Its prominent feature is that the main gangue minerals are sericite+syenite (collectively referred to as sericitization), plagioclase and potash feldspar metasomatism. According to the literature, the closer sericite is to the main ore body of breccia, the stronger its development is. If the original rock is basic rock, chlorite and epidote also develop, releasing iron, copper and gold to form sulfide, which is later oxidized into a large number of hematite, bornite and chalcocite. It seems that the genesis of the giant deposit of the Olympic Dam is not as puzzling as the western academic circles have been for so many years.