The Qiangnan area is located in the eastern part of the Yangtze block and the northeastern end of the Jiangnan orogenic belt. It is located at the junction of the Jiangnan transition zone and the Jiangnan uplift belt. It is a confluence of the Jiangnan transitional zone and the western Tianmushan metallogenic belt. Metallogenic geological conditions. In recent years, with the deep exploration of prospecting and exploration work, the mineral exploration in southern Anhui has achieved gratifying results. Many polymetallic deposits such as tungsten, molybdenum , silver and gold have been discovered, showing good prospecting prospects. The Yuzishan tungsten-molybdenum mine in Suide County was discovered in the pre-examination of the mineral deposits in the area, and showed a good prospecting prospect in both the deep and the periphery. Based on the mineral pre-examination work, this paper systematically discusses the geological characteristics of the concave mountain tungsten-molybdenum ore body, and initially analyzes the prospecting potential of the area. The discovery of the concave mountain tungsten-molybdenum ore has important guiding significance for the exploration of tungsten-molybdenum minerals in the Jude area and even in southern Anhui.
I. Regional geological background
The Jude Mountain is located in the mountainous area of ​​southern Anhui, and it is the intersection of the Tianmu Mountain and the Huangshan Mountain. It is located on the north side of the ancient land of Jiangnan. The stratum is located in the Jiangnan stratigraphic division of the Yangtze strata. At the end of the Proterozoic, the area was transformed from a structural continental metamorphic to a stable mass. The Nanhua period began a long-term passive continental marginal development stage. The Nanhua-Permian strata are mainly exposed in the area, which is a relatively stable marine caprock deposit. The lithology is mainly limestone, marl , shale , mudstone, siltstone and lithic sandstone. Among them, the Silurian strata are widely distributed in the Jiangnan transitional zone, which is a set of deep-water continental shelf-shore shallow marine clastic sediments; the Devonian-Permian strata are not integrated into the Early Paleozoic strata in the form of residual basins.
The geological structure in the area is more complicated. Since the Pro-Ecaquity, it has experienced multi-phase tectonic activities such as the Chengjiang Movement, the Caledonian Movement, the Indo-Chinese Movement, and the Yanshan Movement. The folds and faults developed, and the regional tectonic line direction was NE-SW (Fig. 1).
Figure 1 Regional geological map
S 3 t Tangjiawu Formation; S 2 k Kangshan Formation; S 1 h Helixi Formation; S 1 x Xiaxiang Formation; O 3 c long docking group;
O 1 -3 n -h Ningguo Formation, Hule Formation, Yanwashan Formation and Huangnigang Formation; O 1 Y Yinzhu Group;
Є 3 O 1 x Xiyangshan Formation; Є 3 h Huayansi Formation; Є 2 h Yangliugang Formation; Є 1 h Hetang Formation; Nh 2 n Nantun Formation;
Nh 1 x xiuning group; Yδ 1 5 Yanshanian granodiorite; Measured/speculated fault; research area
The Yanshanian magmatism in the study area is intense, and the Jude complex rock mass is widely distributed. The rock types are mainly medium-acid rocks, mainly granodiorite, plaque-like granodiorite and plaque-like monzonitic granite . They are calc-alkaline series rocks and granodiorite black mica 40 Ar/39. The age of Ar is 139.1 ± 0.5 Ma. This study found that granodiorite is rich in ore-forming elements such as W, Mo, Ag, Pb, and Zn, and is closely related to mineralization. In particular, in the area of ​​the Confucius Mountain in the northern part of the Jude Rock Mass, a large number of quartz veins are distributed in the surrounding rock, and the tungsten-molybdenum mineralization is obvious. Region, and intrusive rocks associated minerals up to more than 10, such as orchids Ridge neighborhood near the edge of rock and rock wall rock bridge Lang, saw both tungsten and molybdenum mineralization, lead mineralization. Therefore, the contact zone between the rock mass and the surrounding rock and its vicinity is a favorable section for the study area to find tungsten-molybdenum ore.
Second, the mining area geology
The mining area is simple to expose, and it is the upper section of the Silurian Xiaxiang Formation (S 1 x). The main lithology thick dark gray feldspar quartz sandstone, middle folder, the long thin quartz sandstone, fine sandstone. The thickness of the single layer is 50 to 60 cm. The horizontal layer in the sandstone is relatively developed, and the layer is 3 to 5 mm thick. After weathering, black and white stripes are formed.
The folds in the area are not developed, and the exposed Xiaxiang Formation strata are the northern wings of the Jude secondary anticline, with a tendency of 300°-330° and an inclination of 25°±. The NE-trending fault in the mining area is a secondary fault of the north-north-eastern Jude fault, which is often filled by the late positive porphyry vein and quartz vein. The fault fracture zone chlorite, sericite, silicification, pyrite mineralization, lead zinc mineralization, the development of mineralization brass. This group of fractures is both a ore-controlling structure and a structure that destroys the ore body.
The magmatic rocks in the mining area are developed, and the granodiorite is exposed in a large area and the lithology is uniform. The rock is gray, the main mineral components are: plagioclase 45% ~ 55%, potassium feldspar 13% ~ 25%, quartz 20% ~ 25%, biotite 5% ~ 10%, a small amount of hornblende. The surrounding rock of rock mass is generally characterized by silicification and horn rock; the rock is strongly altered in the borehole, and the upper granodiorite is mainly chlorite, sericitization, green curtain petrochemical, silicified, developing fine veins and veins. ore; the lower part of the concealed biotite quartz monzonite, of clay, carbonate rocks of extremely strong, with multi-disseminated mineralization, rich veinlets, disseminated wolframite, scheelite, molybdenite, Chalcopyrite, porphyrite, pyrite, etc.
Third, tungsten molybdenum ore (chemical) body characteristics
The study found that there are more than ten mineralized quartz veins and quartz veins in the mining area, of which ten are in the boundary grade. According to the spatial distribution of the ore body, the type of ore, the ore grade, etc., two mineralized zones and multiple independent ore bodies were delineated. In addition, according to the drilling work, five blind ore bodies were delineated in the deep. The tungsten-molybdenum ore body in the study area mainly exists near the inner contact zone of the granodiorite and is distributed in parallel with the contact zone (Fig. 2).
(1) Characteristics of mineralized belt
1. Characteristics of No. II mineralized zone
The No. II mineralized belt has a surface length of about 800 m and a width of 50 to 200 m, which is closest to the contact zone between the rock mass and the surrounding rock. Due to the degree of denudation, the mineralization in the middle section is not obvious. The mineralized zone has a “C†shape on the plane and is distributed along the contact zone between the granodiorite and the surrounding rock (Fig. 2). The mineralization zone is flat. The northeastern section tends to S~SW, and the southwestern section tends to W~NW. Inclination angle <15°. In-band alteration is mainly silicification, sericitization, and pyrite mineralization. A total of 3 ore bodies were found.
The No. 1 ore body is a quartz large vein type tungsten-molybdenum ore. The length of the ore body is >200m, the thickness of the ore body is 0.93m, the depth is more than 30m, and the shape is 180°<15°. WO 3 grade is 0.48% and Mo grade is 0.1%. The quartz vein is about 60cm thick. In the surrounding rock granodiorite, it is developed with disseminated tungsten-molybdenum mineralization, and the mineralization is about 30cm thick. In the quartz vein, micro-cracks develop, and the fissures are filled with molybdenite, pyrite, scheelite, hematite, and the like.
The No. 2 ore body is located below the No. II ore body and is a quartz fine vein-disseminated tungsten ore. The ore body is about 200m long, with a thickness of 66cm and a depth of >100m. The width of quartz fine veins is generally about 1 to 5 cm, which is sparse and fine veined, with a pulse rate of 1 to 2 strips/m. The appearance is 180° <10°. The WO 3 grade is 0.11% and the MO grade is 0.035%. The scheelite is star-shaped and appears in the cracks of the quartz veins and in the cracks of the surrounding rocks. The particle size is about 0.5 to 1 mm.
The No. 3 ore body is a quartz large vein type silver ore. The length of the ore body is about 200m, the thickness is 0.7m, and the depth is 100m. The shape is 290°<10°. Ag grade 93.2g / t. Fractured quartz veins have also see bismuthinite about the size of 0.5 ~ 1mm. On both sides of the quartz vein, there are a few quartz veins, and no mineralization is observed.
2, mineralized zone characteristics
The No. III mineralization zone is located below the No. II mineralization zone with a relative height difference of about 50 m. It is slightly farther away from the contact zone between the rock mass and the surrounding rock, and is distributed along the contour line in a “one†shape on the plane (Fig. 2). The mineralized belt has a length of more than 600m and a width of 100 to 300m. The main corrosion in the belt becomes silicification, potassium long petrochemical, and sericitization. The mineralized zone is about 320°<20°. Five ore bodies were found in the belt.
The No. 1 ore body is a quartz fine vein-disseminated tungsten-molybdenum ore, which is the best or largest ore body in the region. The surface of the ore body is exposed to a length of 450 m or more, a thickness of 0.8 to 1.5 m, and a depth of more than 300 m. WO 3 , grade 0.055% to 0.13%, Mo grade 0.084% to 0.11%. The ore body is flat and the inclination is 15°±. The ore type is quartz fine vein impregnation type, and the quartz veins have a width of about 0.5 to 1 cm and a pulse rate of 1 to 2 strips/m. The ore minerals are scheelite and molybdenite, which are present in the fissures of the quartz veins and in the fissures of the surrounding rocks. The thickness of the hole in the ZK2 is 3.5m, only the molybdenum ore is found, and the production is near horizontal.
2 immediately â…¢ â…¢ ore ore body 2, disseminated type quartz veinlets Tungsten. The ore body is generally thin and has a thickness of 0.82 to 0.94 m. The grade is poor, and the WO 3 content is 0.06% to 0.07%. The pattern is gentle, and the vertical distance from the No. 1 ore body is only 3m. It is speculated that the surrounding rock contact zone may merge with the III 1 ore body.
The No. 3 ore body is a quartz vein-disseminated tungsten-molybdenum ore with a small scale. The surface thickness is 0.67m, which is inwardly pointed off. WO 3 grade is 0.042% and Mo grade is 0.04%. The extension is 30m, and it is estimated that the extension is 200m.
The III4 and III5 ore bodies are quartz large vein type, and the WO 3 grades are 0.25% and 0.15%, respectively. The thickness is 0.3 m and 0.5 m, respectively. The ore minerals are scheelite and molybdenum ore, which are distributed in the cracks and crystal cavities of the quartz veins, and the particle size is 1 to 2 mm. The gangue mineral is quartz with a content of more than 99%. The two ore bodies are rapidly tipped along the trend, and the industrial significance is not significant.
(2) Characteristics of ore bodies
In addition to the minerals in the mineralization zone, there are also a number of independent ore deposits in the study area, ranging in thickness from 0.1 to 1.6 m. Among them, the I 1 and I 2 ore bodies are slightly larger (Fig. 2).
The No. 1 ore body is located on the contact zone between the granodiorite rock mass and the surrounding rock feldspar quartz sandstone, which is a quartz large vein type silver deposit. The length of the ore body is about 100m, the thickness is 1.6m, and the depth is about 30m. The ore body is 220°<20°. The large vein width of quartz is about 0.3m, and the sparse quartz veins are visible at the edges, and the width is about 0.5~1CM. Ore minerals are present in the fissures of quartz veins. The silver grade is 45.44g/t.
The No. 2 ore body is located below the I l ore body and is a quartz large vein type molybdenum ore. The length of the ore body is about l00m, the thickness is 1.2m, and the depth is 30m. The appearance is 220 ° < 20 °. The thickness of the large vein of quartz is 0.6m, and sparse quartz veins are visible on both sides. The ore mineral is molybdenite, accompanied by a small amount of scheelite, pyrite, chalcopyrite, which is star-shaped in the cracks and crystal cavities of quartz veins, and the mineralization is uneven. The MO grade is 0.035% and the WO 3 grade is 0.04%.
(3) Concealed ore body characteristics
Using the drilling engineering (ZK l , ZK 2 ), five concealed ore bodies were discovered in the deep part of the study area, which are quartz vein type, quartz vein vein impregnation type and dip dyed (porphyry) type tungsten ore, tungsten molybdenum ore and molybdenum ore. See the blind bore ore ZK 2 N 1, W 2. Drilling ZK 1 sees blind ore bodies IV 2 to IV 5 , of which IV No. 5 ore body is a dip-dyed (porphyry) type tungsten ore with rich grade, which is the newly discovered mineralization type in this study. The transition zone provides a realistic basis for finding porphyry tungsten deposits.
The No. 1 ore body is a quartz vein type tungsten-molybdenum ore with a quartz vein thickness of about 0.3 m. The intra-pulse cracks develop, and the surrounding mudstones of the two sides are strongly green, petrochemical, and sericitizing. The ore body is about 0.92m thick, and the occurrence is gentle, and the inclination angle is <10°. The ore minerals are molybdenite, stibnite, scheelite, chalcopyrite, sphalerite, etc., which are produced in fine veins in quartz vein fissures. The WO 3 grade is 0.124% and the Mo grade is 0.088%. The scheelite exhibits blue fluorescence under fluorescent light.
The No. 2 ore body is a quartz vein-disseminated tungsten-molybdenum ore with a thickness of about 1.5 m and an extension of more than 500 m. In ZK 2 , molybdenite and scheelite are distributed in the rock fissures of the altered granodiorite in a star-like shape, with a particle size of about 1 to 3 mm. The WO 3 grade is 0.117% and the MO grade is 0.117%. The granodiorite is strongly altered, chlorite, sericitization, silicification, and pyrite mineralization. When silicidation is strong, silicified rocks (quartz veins) are formed. Rock silicification, pyrite mineralization, and molybdenum mineralization are weakened in ZK 1 . WO 3 grade is 0.076%.
The No. 3 ore body is found in ZK 1 and is a disseminated molybdenum (tungsten) ore with a thickness of about 0.8 m. The original rock is a strongly altered granodiorite, sericitizing, and chlorite. The molybdenum ore is disseminated in the altered rock with a particle size of about 0.1 to 0.5 mm. The scheelite is distributed in a star-like shape with a size of about lmm. The Mo grade is 0.048% and the WO 3 grade is 0.045%.
IV No. 4 ore body is found in ZK 1 and is a quartz fine vein-disseminated tungsten ore with a thickness of about 3 m. The original rock is a biotite granodiorite. The fine vein width of quartz is 1 to 2 cm, and the shape is flat. The scheelite is distributed in the fissures of quartz fine veins or distributed in the surrounding rocks. The molybdenum ore is star-shaped, with a size of about 1 mm and a uniform distribution. Under fluorescent light, the scheelite particles are about 1 to 2 mma and the WO 3 grade is 0.087%.
The No. 5 ore body is a dip-dyed (porphyry) type tungsten deposit, which is a newly discovered mineralization type in the Judeyan body. The original rock is a black cloud quartz monzonite (hidden rock mass). The ore is a disseminated structure. The ore minerals are hematite, molybdenite, chalcopyrite, pyrite, porphyrite, sphalerite, etc., which are disseminated in the rock fissures. Molybdenum ore has wrinkles. The borehole has a thickness of about 2.45 m and a WO 3 grade of 0.23%. The ore body is near horizontal.
(4) Ore characteristics
The type of ore in the mining area is quartz vein type, quartz vein vein type, and disseminated type (porphyry type). Among them, in the quartz vein type ore body, the ore mineral is scheelite, molybdenite, stibnite, sphalerite, pyrite, chalcopyrite, etc., and the gangue mineral is mainly quartz. Ore minerals generally produce fine veins, which are distributed in parallel and have a pulse width ranging from 0.01 to 0.5 mm. The molybdenum ore and chalcopyrite are distributed along the pyrite fissures. The molybdenum ore is a sheet-like aggregate with wrinkling, the particle size is generally 0.04~0.l mm; the stibnite has twin crystals with a particle size of 0.1. ~0.3mm, with a drop-shaped chalcopyrite inclusion body; chalcopyrite particle size 0.O1 ~ 0.lmm, pyrite particle size 0.01 ~ 0.3mm, sphalerite particle size 0.1 ~ 0.3mm. The scheelite is difficult to identify with the naked eye, and star-shaped blue fluorescence is visible under the violet light.
In the disseminated ore body, the ore minerals are hematite, scheelite, molybdenite, chalcopyrite, porphyrite, sphalerite, pyrite, magnetite, etc., which are disseminated in the rock. Among them, the black tungsten ore has a particle size of 0.1 to 1 mm, the molybdenum ore has a particle size of 0.02 to 0.5 mm, the pyrite has a particle size of 0.01 to 0.03 mm, the chalcopyrite has a particle size of 0.02 to 0.1 mm, and the oreite has a particle size of 0.1 to 0.2. Mm, sphalerite particle size of about 0.5mm, magnetite particle size of 0.01 ~ 0.08mm. Gangue minerals are feldspar, plagioclase, biotite, quartz, apatite, epidote like. The molybdenum ore has a wrinkle phenomenon, and the scheelite has a star-like blue fluorescence under the violet light.
The ore structure mainly has a sheet structure, a granular structure, a columnar semi-automorphic crystal structure, and a columnar self-shaped structure. The ore structure is mainly a vein structure, a network vein structure, a block structure, and a disseminated structure.
(5) Wall rock alteration
The ore-bearing rocks are strongly altered. The granodiorite is mainly chlorite, chlorite, and fine veins and veined ore bodies. The black cloud quartz monzonites are muddy and carbonated, rich in fine veins. Immersed wolframite, scheelite, molybdenite, chalcopyrite, porphyrite, pyrite or other ore body; the contact zone between rock mass and surrounding rock is mainly silicification.
Fourth, prospecting potential analysis
The study area is located at the northern edge of the Jiangnan uplift belt and has good metallogenic geological conditions. The western Huaiyushan molybdenum deposit and the eastern Lanling tungsten-molybdenum deposit are both quartz veins, and the type of mineralization is consistent with the type seen in the Judezizishan area. Mineralization is related to granodiorite, which is a high-temperature tungsten-molybdenum mineralization closely related to magmatic activity. The surrounding rock is Silurian sandstone. Molybdenum mineralization is particularly noticeable on the surface or near the surface. So far north, in the Yunlechengtan area, the mineralization type transitions to medium-low temperature lead-zinc mineralization.
The main body of the Jude complex rock mass exposed in the Confucius Mountain area is the biotite granodiorite, and the black cloud quartz monzonitic concealed rock body is found in the borehole, accompanied by dip-type tungsten mineralization, indicating the concave mountain. The area has similar magma-source conditions to known mining areas (such as Baizhangyan Tungsten Mine, Lanling Tungsten Molybdenum Mine). The 1:5 million water system sediment study shows that the average value of tungsten element in the Jude granitic diorite is 5.14ppm, and the average value of molybdenum element is . 0.83ppm; the average value of tungsten element in the plaque-like granodiorite of Shixiashan is 8.2ppm, and the average value of molybdenum element is 2.4ppm, which is obviously higher than that of surrounding rock (W: 2.8lppm, Mo: 0.6ppm), which is rich in minerals. .
Soil geochemistry studies show that the ore-forming elements have obvious zoning and clear layers in time and space. High-temperature elements such as W, Mo, and Bi have high abnormal strength, are closely symbiotic, and have an abnormal inner band, which is distributed in a long strip. The active elements such as Au and Ag have moderate anomalous intensity and are distributed in the center and outside of the high-temperature element. The range is wide and extends far in the direction of the abnormal long axis. The medium temperature elements such as Cu, Pb and Zn are widely distributed, and there is no obvious concentration center.
The characteristics of surrounding rock alteration indicate that quartz veins are developed in the surrounding rock far from the contact zone, with a pulse width of 0.5 to 1 cm, and the alteration type is chlorite, silicification and horn lithification. The outer contact zone sees a small amount of quartz veins with a pulse width of 0.3 to 0.6 m. The elongation is greater than l0m and the alteration type is silicidation. The inner contact strip is common with quartz veins and quartz veins. Quartz large veins generally develop different degrees of scheelite mineralization, molybdenum mineralization, and pyrite mineralization, and the accompanying surrounding rock erosion becomes chlorite, green curtain petrochemical, sericitization, pyrite mineralization and silicidation. The fine veins of quartz have good ore-bearing properties, and when the pulse rate reaches about 3/m, the mineralized cut-off grade can generally be achieved. The veins are mainly composed of vertical rock mass and surrounding rock. In the borehole, the upper 0~100m alteration is often silicified, sericitized, muddy, and the quartzite mica can be formed in the strongly altered section. The associated metal mineralization is pyrite mineralization, scheelite mineralization, and molybdenum Mineralization mainly occurs in a strong area of ​​silicification. At the bottom of ZK l , the rock is strongly muddy and carbonated, but there is a better mineralized potassium alteration zone in the deep, which needs further work.
In addition, in the quarry near the north of the Xiangyang Village and the Fuzishan Reservoir, which is a little farther from the study area, the diagenetic surface of the granodiorite is found to have better scheelite mineralization, and the scheelite is film-like. Compared with the dilute-type scheelite in the Ouzishan Erchang granite, it may be the result of the ascending migration of the quartz monzonite during the diagenesis and mineralization process, which is to find the hidden type (porphyry type) in this area. ) Tungsten ore indicates an important direction.
The ore bodies found on the surface have a flat overall shape and tend to be surrounded by contact zones. The quartz vein type ore body at the shallow surface is subject to different degrees of denudation, but the quartz monzonite buried in the ground and the disseminated tungsten ore produced therewith have not been affected by weathering and denudation. The black cloud quartz monzonite is seen at 145m in the ZK 1 hole, and the thickness of the diffracted tungsten ore controlled in the 5m range can reach 2.45m. Therefore, the exploration of tungsten-molybdenum ore in the Ouzishan area of ​​Suide County is worthy of further exploration.
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