The NE silicified fault zone that controls the deposit is a number of NE silicified fault zones with different levels developed in the clamping zone between Huangpi Yingshi fault zone and Dingnan-Ma Shishan silicified fault zone. There are granite faults No.92, 86Sr, 108, 14 and 14. 3 1, equidistant distribution, controlled by ore. Local reconnection is compounded in the short veins of northeast diabase. They are mainly filled with white blocks in time. These faults are compressional torsion, sinistral torsion and dislocation displacement of diabase veins. They are cut and cemented by pitchblende and red microcrystal timely veins.
(1) NE-trending fault structure
The NE-trending fault structures will focus on the characteristics of Wushi-Guanshan, Shui Mu-Shandong-Huangpi and Quannan-Ma Shishan Yingshi (silicified) fault zones and their relationship with uranium mineralization. Other faults-mainly low-grade faults in the east-are described in various sedimentary structures.
1. Wushi-Guanshan Yingshi fault zone
Yingshi fault zone is located in the west (north) margin of Guidong rock mass and on the contact boundary with sedimentary strata. The NE-trending Baijishe rock mass may be connected with Nanxiong Fault (Figure 4- 1) and extend southwest to Yingde area. The fault width is about 30 m, and the fault zone is distributed in 60 direction, inclined to the southeast, with an inclination of about 60.
The fault zone has obvious magnetic anomaly zone distribution. It is located on the linear gravity gradient belt (showing the nature of basement faults) and intersects with the east-west Xiaowu-Yuejincun and Lengdong-Xiba basement faults (Figure 4-2).
The southeast plate of the fault zone is mainly coarse-grained amphibole biotite adamellite. The fault is composed of siliceous breccia, and there are Yanshi mylonite belt and illite broken granite belt on both sides. The rocks are green, and the mineral composition includes quartz, feldspar and illite. It is characterized by deformation residual spots, long axis orientation, wave attenuation and fracture development, and flaky illite is filled between grains and cracks, which is often distributed in a network. The local chronological residual spots and illite are composed of gneiss-like granitic mylonite. Close to the main fault zone is the Yanshi-Yili petrochemical mylonite belt with a width of about 7 m. Granite structure disappears, and many timely veins are interspersed among them. The timely residual spots are wave extinction, and illite is filled along the edge and its cracks. The main fault zone is siliceous breccia zone, and the breccia is mainly composed of white and comb-shaped strongly silicified granite fragments.
In order to understand the influence of tectonic stress on the activation and migration of trace elements, the mylonite and cataclastic rocks in the main belt and side edge of Wushi-Guanshan fault zone are analyzed, and the analysis results are listed in Table 4-2. As can Be seen from Table 4-2, the contents of trace elements such as W, Sn, Bi, Cu, Pb, Rb, Cs, Be, Nb, F, Th and U in rocks gradually increase from the main fault zone, that is, from the metamorphic breccia zone to the upper illite fractured granite zone. However, the content of most elements in siliceous breccia is low, only the contents of Sb, Sr and Li are increased, and the content of Li is 178.2× 10-6, which is 6 ~ 10 times that of footwall tectonic rocks.
Table 4-2 Trace Elements and CO2 Analysis of Deformed Altered Rocks in Wushi-Guanshan Yingshi Fault Zone (10-6)
Therefore, trace elements tend to accumulate in altered cataclastic rocks along the lateral margin of faults. The main fault zone or strong deformation zone of siliceous breccia is the "poor zone" of trace elements.
Baijishe rock mass distributed at the northeast end of the fault controls tungsten mineralization, while Guidong rock mass in the south, especially at the intersection with the east-west belt, controls polymetallic minerals (west section).
2. Shui Mu-Shandong-Huangpi Yingshi fault zone.
The fault zone is located in the rock mass from Huangpi Village to Baishui Village in Zhuangyan Township, wengyuan county. The rock mass extends to the northeast and reaches the water surface (Figure 4- 1). It is 38 km long, generally 4 ~ 10 m wide, and some sections are more than 30 m, which is greatly affected by stress. The fault strike is 60 ~ 80, and it tends to the southeast with an inclination of 55 ~ 85. The nature of the fault was compressive and torsional in the early stage, and tensile and X-shaped torsional cracks with an angle of 20 ~ 30 were formed on both sides of the fault, accompanied by a large number of white coarse-grained Shi Ying filling, which was subjected to stress after filling, forming a very complex tectonic deformation rock. There are breccia and mylonite, locally filled with fine spar, accompanied by uranium anomaly. The fracture morphology is complex, with expansion and contraction, branching and recombination. The section is gentle and wavy. In order to understand the changes of structural deformation altered rocks, major elements and trace elements in the fault zone, they are introduced as follows:
Characteristics of structural deformation altered rocks in (1) fault zone (footwall to footwall of fault zone)
1) Broken granite belt: this belt is 22 m away from the upper wall of the main belt. The rock is grayish white with broken granite structure. The main mineral components of the rock are syenite, plagioclase, a small amount of biotite, muscovite, magnesium chlorite, illite, kaolinite and fangjieshi, and a small amount of illite-montmorillonite mixed clay minerals. In response to stress, residual spots, developed cracks, wavy extinction and deformation lines are formed, with biaxial positive light. The timely broken mylonite recrystallizes and distributes along the periphery and cracks of the timely residual spots. Under the action of torsional stress, mica sheet is distorted and extinction is wavy, and it is eroded by illite and kaolinite along the edge to form a harbor shape.
2) Silicified fractured rock zone: 7m away from the main rock zone. Due to the complex superimposed stress of the later structure, the rock fractures are in a broken state and contain silicified fracture cuttings.
3) Siliceous breccia zone: 3.5m away from the main zone. The rocks are grayish white, and the rocks and stones are broken and loose due to the compound superposition and crushing of the later structures. Judging from the structure of the remaining rock blocks, silicified cataclastic rocks are the superposition products of multi-stage tectonic thermal activities after crushing and siliceous cementation.
4) shale belt: this belt is a strong schist sandwiched between siliceous breccia and siliceous mylonite belt. Rocks are composed of layered minerals such as chlorite, illite and illite mixed clay, which are oriented to form foliation, like thousands of fabrics. There is obvious octagonal phenomenon in the rock, and the mica fragments are bent, twisted and undulated. Time-dependent wave extinction and biaxial positive light.
5) Siliceous mylonite zone: this zone is the main fault zone. The rock is grayish white with mylonite structure. The rocks are composed of fine quartz (99%) and a small amount of illite. Some vein-like chronological residual crystals with mosaic structure can be seen in a large number of mylonite, and illite and mylonite are roughly oriented.
6) Phyllite zone: near the footwall of the main fault zone. The rocks are grayish green. The rocks are composed of feldspar, quartz, muscovite, chlorite, illite and calcite. The residual lattice twin of microcline becomes rhombic. It is banded, roughly directional and biaxial forward light. Muscovite is oriented. Feldspar, quartz, flaky minerals and mylonite constitute a gneiss-like structure.
7) Altered cataclastic rock zone: this zone is located at the footwall of the main fault 16 m ... The rock is in the fracture structure. The main minerals of rocks are feldspar, quartz, illite, calcite and kaolinite. In response, the feldspar breaks and the response wave is extinguished (Plate 4-28). Illite and kaolinite are locally oriented. Microscopically, the residual spots of micro-plagioclase and biotite can be seen locally in the rocks in this zone, which are roughly oriented and have wave extinction phenomenon. Newborn illite is oriented along cracks or residual spots, forming an eye-like structure locally.
(2) The characteristics of major element oxides of deformed altered rocks in the fault zone (from the upper wall to the lower wall of the fault zone)
The analysis results of main element oxides are listed in Table 4-3. As can be seen from Table 4-3:
Table 4-3 Major Element Oxides of Deformation Altered Rock in Shui Mu-Shandong-Huangpi Yingshi Fault Zone (%)
Note: the serial number 1 ~ 7 in the table corresponds to the description order of the structural deformed rocks in the fault zone.
1) The content of SiO2 _ 2 in the main belt of siliceous mylonite and the breccia belt superimposed by the later structure increased greatly, while other substances such as TiO2 _ 2, Al _ 2O _ 3, K2O, MnO, MgO, Na2O, H2O ++ and LOS decreased obviously except for Al _ 2O _ 3, CaO and FeO. Thermodynamic alteration makes aluminosilicate minerals in rocks unidirectionally change into Si-O bonds, so rocks and rocks are mainly timely.
2) The contents of SiO2 _ 2, Al _ 2O _ 3, K _ 2O, MnO, MgO and Na _ 2O in phyllite belt on both sides of siliceous mylonite belt are slightly lower than those in fractured granite. However, the contents of CaO, MnO, Fe2O3, FeO, K2O, H2O ++ and LOS in the shale on the upper and lower walls of siliceous mylonite are different. The main reason for the change of the oxide content of the above elements is that the thermodynamic alteration of phyllite in the upper wall of the main belt is stronger than that in the lower wall, that is, there are more argillaceous and chloritization in the phyllite in the upper wall than in the lower wall.
3) The contents of main element oxides and primary minerals are different under different thermodynamic conditions. The general trend is that with the weakening of thermal power, the brought out elemental oxides (except SiO2 _ 2) decrease, and the new layered clay minerals and time increase, and finally they are replaced by time.
(3) Trace elements and CO2 characteristics of deformed and altered rocks in the fault zone (from the upper wall to the lower wall of the fault zone)
The analysis results of trace elements and CO2 are listed in Table 4-4. As can be seen from Table 4-4:
1) The element content of siliceous mylonite zone (No.5 and No.3 in the table) is relatively low, which is the lowest compared with other zones. These trace elements include tungsten, tin, molybdenum, bismuth, copper, lead, zinc, rubidium, cesium, niobium, fluorine, uranium and thorium, accounting for 68% of the total elements in the table.
2) The shale belt (No.4 and No.6 in the table) contains high contents of trace elements, including Mo, Sn, Bi, Sb, Pb, Zn, Li, Rb, Cs, Sr, Nb, F, U and Th, among which the contents of Sb and Bi in the upper shale belt and Pb, Sr, Nb and Th in the lower shale belt are higher than those in other structural rocks. The relative enrichment of these elements is caused by the superposition and recombination of tectonic thermal effects.
3) the cataclastic altered granite belt (No.7 in the table) is the structural belt with the highest content of trace elements, characterized by the highest content of Sn, Mo, Cu, Cs, Be, F and U, and the contents of W, Bi, Sb, Pb, Nb and Th are also high. These elements are concentrated in the cataclastic altered granite zone, which not only shows the migration of elements in the plastic stress zone, but also shows the enrichment characteristics of elements in the brittle stress zone. Therefore, it is an element group feature in the low-grade deformation phase-change tectonic rocks near the big fault, and it is the ore-guiding and ore-controlling information of the big fault.
Table 4-4 Trace Elements and CO2 Analysis of Deformed and Altered Rocks in Shui Mu-Shandong-Huangpi Yingshi Fault Zone (10-6)
Note: the serial number 1 ~ 7 in the table corresponds to the description order of the structural deformed rocks in the fault zone.
4) The contents of tungsten, zinc and rubidium in granite fractured zone and silicified fractured rock zone (No.1, 2 in the table) are higher than those in other deformed rock zones, but the difference between silicified fractured rock zone and other tectonic deformed rock zones is that the contents of sulfur, carbon dioxide and other elements such as cesium, beryllium, strontium and niobium are higher. The composition characteristics of these elements reflect that most of the elements in the rock have not changed and a few have changed.
To sum up, the characteristics of the Shui Mu-Shandong-Huangpi Yingshi fault zone are as follows:
(1) The Shui Mu-Shandong-Huangpi Yingshi fault zone is a tectonic deformation zone with multi-stage strong activity.
(2) With the deformation of rocks and minerals, the activation and migration of elements in rocks are related to the deformation properties and strength.
(3) The main fault zone, especially the siliceous mylonite zone, is relatively poor in elements and trace elements. There are both dynamic alteration minerals and hydrothermal alteration minerals in the phyllite and granite fracture zones. If there are chlorite minerals containing Fe2 ++ and Mg2++, illite and kaolinite containing water, it has the characteristics of plastic-brittle transformation and deformation, and it is the detention place of trace elements.
(4) The fault has both left-handed torsional compression and torsion and NE-E reconnected torsional structure, which has right-handed torsion, and the torsion directions are opposite one after another, making the fault zone relatively wide. Therefore, the fault zone is an important ore-controlling deep fault structure in eastern Guangxi, especially for uranium mineralization in the east.
3. Dingnan-Ma Shishan fault zone
The fault zone is located from Aocun, Ma Zhong, Guidong Town, Lianping County to Dakeng, extending northeast to dingnan county and southwest to the study area. The fault is large in scale, belongs to a regional deep fault with long strike, crosses the Guangdong-Jiangxi border, is about 200 km long, strikes 60-70, and has a northwest (southeast) dip angle of 65-85 (Figure 4- 1). Most faults occur in the form of cataclastic rocks, containing a small amount of siliceous fillings, and sometimes there are alterations such as Yingshi, Yili Petrochemical and chloritization. In metamorphic rock areas, schistosity and steep strata often develop. According to the regional data, the fault is a basement fault, and the remote sensing image also shows it.
The fault zone is located in the contact zone outside the rock in eastern Guangxi, which controlled the distribution of K2-E basin in the early stage. And cut out the medium-grained porphyritic biotite granite (Figure 4-5). Cambrian strata are mainly distributed in the northwest plate of the fault, and Devonian-Carboniferous strata are mainly distributed in the southeast plate, which indicates that the northwest plate of the fault has a great thrust uplift during the compression period (Caledonian-early Yanshan period) and the southeast plate has a relative decline. A similar phenomenon also appears in the Anji Mountain fault zone, but it is not as obvious as the Ma Shishan fault zone.
Fig. 4-5 Geological map of xia zhuang area (according to Gaode series, 1995)
The fault controlled the formation and distribution of the red basin. The composition of red bed gravel is complex, mainly composed of metamorphic rocks, followed by granite gravel. Judging from the characteristics of large gravel size difference, disorder, poor sorting and unclear bedding, these red beds are the products of rapid accumulation when the northwest plate of Mashi Mountain slipped.
The Dingnan-Ma Shishan fault is complex in structural form, and the pinch-out phenomenon reappears, showing right alignment. The section is gentle and wavy. According to the characteristics of cataclastic rocks, schists, low-order, low-order tensile faults and "X"-shaped torsional faults, the fault is compressive and torsional in the early stage and extensional before the late stage, and the northwest plate slides down to form graben-type fault blocks.
(2) NE-trending controlled rock fracture
The strong activity of NE-trending faults has created favorable conditions for extensive magmatic intrusion, and it has become a rock-controlling fault of small NE-trending intrusions all over eastern Guangxi. Such as fine-grained biotite granite, fine-grained biotite granite and Pingtian fine-grained biotite granite distributed along the Wushi-Guanshan fault zone in the west; Fine-grained mica granite controlled by Taoshuba fault zone and east-west structure; Fine biotite granite veins (branches) are widely exposed in the eastern part of rock mass, such as Guidong, Tian Xin, Si Qian, Liling, Xiazhuang-Xinqiao Highway, Bayi Highway and Shituling, especially in mining areas. The overall strike of rock mass is NE (attached figure).
(3) NE-trending silicified fracture zone
The NE-trending silicified fault zone is located in NE-trending silicified fault zone (granite fault zone, F2, 92, 86Sr, 108, 14, 365438), which has the same properties as the areas sandwiched by Shui Mu-Shandong-Huangpi Yingshi fault zone and Dingnan-Ma Shishan silicified fault zone (the southwest end of the whole south graben). Their strike is 50 ~ 70, and they tend to the northwest (partly to the southeast) with an inclination angle of 60 ~ 85. In the early activities, fracture zone, mylonite zone, eyeball structure, cataclastic rock, etc. With the filling of white coarse-grained Shi Ying, etc. In the later stage, the structure was strongly reconnected and compounded, forming superimposed tectonic rocks and fractured rock belts. Many minerals such as microcrystalline syenite, fluorite, pyrite, pitchblende, chalcopyrite and calcite were filled and replaced, accompanied by strong syenite, goethite and illite.
The structural form is complex, including "multi" shape, "S" shape, lenticular shape, multiple branches, pointed out and so on. The section is gentle and wavy (upward, upward). There are often scratches on the cross section, and "in" structure and schistosity are developed on the upper and lower walls of the fault. Due to fault displacement, the boundary between diabase vein and granite body is staggered to the left. The fracture properties are compression-torsion and left-lateral torsion. The detailed characteristics of each silicified fracture zone are discussed again in the structure of the deposit.