During the Great Wall period, the northern margin of Qaidam-Middle Qilian Plate was an active continental margin. In the western segment of the active continental margin, the intermediate-basic volcanic rocks at the bottom of the Zhu Long Tube Group, namely the Zaojiaogou Formation volcanic rocks, were formed. As mentioned earlier, these volcanic rocks include both ocean island ophiolite and island arc volcanic rocks. Volcanic rocks of Gaolan Group and Xinglong Mountain Group were formed in the east. The normal clastic rock formations in the western back-arc rift basin-Huashugou Formation (Chh) and Nanbaishuihe Formation (Chn) (Figure 3- 1 1) were formed at the same time or later than the above-mentioned volcanic rocks, and the iron-copper deposits occurred in the upper layer of Huashugou Formation, and the associated rock combinations were carbonate rocks, metamorphic sandstone, pyroclastic rocks, barite and volcanoes. In which barite forms industrial deposits.
There are dozens of iron and copper deposits (spots) formed in the back-arc rift basin on the active continental margin, among which Jingtieshan deposit (consisting of Huashugou and Heigou deposits) is large, Liugouxia deposit and Baijianxia deposit are medium, and the rest are small or ore spots. All the above deposits (points) are concentrated, but Huashugou, Heigou and Baijian are concentrated (Figure 7-65438+). The iron ore reserve of Jingtieshan deposit is 639.6 million tons, with medium copper content. Liugouxia iron mine has a reserve of 76178,700 tons and more than 8,000 tons of copper.
Fig. 8-33 Geological Schematic Diagram of Huashugou Iron and Copper Mine Area in Jingtieshan, Gansu Province (revised according to the second episode of Iron and Copper Mine 1974)
1- Quaternary coverage; 2- siliceous dolomite marble; 3— black-gray phyllite; 4- iron ore deposit; 5- grayish green phyllite; 6- calcareous phyllite; 7- carbonaceous phyllite; 8- quartzite; 9- mottled phyllite; 10- iron ore interlayer; 1 1- rock occurrence; 12- late strike reverse fault; 13- early strike reverse fault; 14-oblique fault; 15- Normal fault; 16-Inferring faults and faults with unknown properties; 17-Huashugou West Mining Area; 18-birch structural mining area; 19-heigou mining area; 20- copper producing area
The environment of the above-mentioned back-arc rift basin was maintained until Neoproterozoic, and the Sinian Baiyanggou Group experienced volcanism again (Gansu regional geology,1989; Left 1998) and iron ore deposits. Caledonian granitoids were formed with the further subduction of the plate, and the related diorite porphyrite dikes were the main reasons for the formation of copper deposits. Copper ore bodies are mainly located in the fractured zone at the bottom or lower part of iron ore bodies. After the Variscan period, the deposit was mainly folded and deformed by tectonic compression.
2. Geology of Huashugou iron-copper deposit
1. Ore body characteristics
Ore bodies occur in volcanic-sedimentary rock series and related sedimentary rocks in eruption-sedimentary cycle or rhythm, and are flysch clastic rocks. The ore-bearing surrounding rocks are mostly argillaceous calcareous slate, and a small number of ore bodies occur at the bottom of siliceous rocks and limestone. The ore bodies are mostly layered and lentil-shaped, and the occurrence is consistent with the surrounding rock (Figure 8-34 and Figure 8-35). The ore body and surrounding rock have metamorphic deformation at the same time. The scale of ore bodies varies greatly, and a single ore body is generally 100 m long, tens of meters thick and tens to hundreds of meters deep.
Fig. 8-34 Schematic diagram of the distribution of surface ore bodies in Huashugou iron-copper mine area (according to No.5 Team of Jiuquan Metallurgical Geology, 1996)
Fig. 8-35 Profile of Jingtieshan (Huashugou) iron-copper deposit in Gansu Province (according to Yu Shounan of Northwest Metallurgical Geological Exploration Bureau, 1992)
1- iron-bearing dolomite phyllite; 2- Jasper-bearing phyllite; 3- iron ore body; 4- copper ore body; 5- diorite porphyrite; 6- Fault
There are 7 ore (body) zones, iron-bearing ore beds and rock beds in the central and western anticlinorium zone of the fold belt. The ore body is layered, with a length of 450 ~ 1600 m, a thickness of 14 ~ 150 m, and a depth of 30 ~ 400 m. The iron ore is composed of siderite, specularite, jasper, barite and dolomite in a strip shape, with a small amount of pyrite, chalcopyrite, galena and dolomite. The main ore types are: specularite, siderite-specularite, specularite-siderite, massive iron ore and chalcopyrite-specularite. Generally, it belongs to moderately poor iron ore, with TFe of 30% ~ 40% and W (SiO _ 2) > 30%. The main mineral assemblages of chalcopyrite-specularite, siderite-specularite and specularite-siderite are the same, but the copper content changes, ranging from 0. 1% ~ 2%.
In recent years, No.5 Team of Metallurgical Geology in Gansu Province has delineated the industrial copper deposit under the original vanadium-iron deposit in the supplementary exploration of mine iron ore. It is mainly vein disseminated chalcopyrite-pyrite ore. The average grade of the eastern coal seam is 1.6%, and the average inclined thickness is 28 meters. In the drilling of 6-line profile, the average copper content is 2.8% and the inclined thickness is 49 meters. There is still a prospect that copper mines will become rich and expand their reserves in the northwest direction. Now it has reached a medium scale. The iron ore layer generally contains trace pyrite, chalcopyrite and other sulfides, which is very close to the copper layer in the footwall. The copper deposit contains jasper and ankerite, which has strong silicification. The direction of structural line in the mining area is NW-SE, and the direction of ore body is consistent with the structural line. According to the occurrence and distribution of iron ore bodies, the Huashugou mining area is divided into east and west sections with the line 12 ~ 14 as the boundary. Copper ore bodies are distributed in the footwall of the iron ore body in the north of the western section of Huashugou mining area, parallel to the iron ore body (Figure 8-34 and Figure 8-35). Only near Line 6, a copper mineralization belt with a length of140m, a width of1~ 6m and a grade of 0.22% ~ 0.98% is exposed on the surface. The ore body is lenticular, with many deep mineralized horizons. Three main ore belts and eight copper ore bodies are preliminarily delineated, and the maximum thickness is 18.36m, which has the characteristics of pinching out and reappearing expansion and contraction. The average grade of copper ore increased significantly from east to west. The main metal minerals of the ore are pyrite-chalcopyrite and pyrite, followed by chalcocite and a small amount of tetrahedrite, bornite, celestite and malachite. Gangue minerals include Yingshi, ankerite, dolomite, calcite, sericite and barite. During the period of 1998, Yang Hequn and Zhao Donghong of Xi Institute of Geology and Mineral Resources found that copper ore bodies were also produced in the eastern part of Huashugou mining area, which was not limited by the location of iron ore bodies and was closely related to the alteration zone, and were produced on both the upper and lower walls of iron ore bodies.
The structure of iron ore is mainly semi-authigenic granular structure and leaf-like structure, with occasional residual oolitic structure. Layered-banded structure is the most common structure, followed by massive structure, disseminated structure and breccia structure. The structure of copper ore is mainly semi-automorphic granular structure and heteromorphic granular structure, including texture, metasomatic texture, metasomatic residual reticular structure, etc. Automorphic granular structure is occasionally seen. Structures include massive structures, veinlets, disseminated structures, reticulated veinlets, breccia structures and banded structures. Among them, the massive structure is a relatively uniform massive ore composed of chalcopyrite, pyrite and gangue minerals, which are mostly distributed in the middle of the ore body; Vein-like or spot-like disseminated ores are mostly distributed at the edge of ore bodies; The ores of reticulate vein structure composed of pyrite and chalcopyrite or dense vein structure cemented by broken iron jasper are mostly distributed in the middle and lower parts of ore bodies. Breccia structure is mainly found in copper-bearing iron jasper belt. The banded structural ore composed of chalcopyrite, pyrite, jasper or timely is mainly distributed in the upper or middle-upper part of the ore body. Synchrosite (siliceous), carbonate and sericite are closely and widely related to copper mineralization. All beneficial minerals are closely related to carbonate, pyrite and syenite in macroscopic view, and are mainly embedded among various mineral particles composed of carbonate, syenite and pyrite in different proportions in microscopic view, especially among carbonate particles. On the one hand, chalcopyrite fills, metasomatism and cements the cracks (veins) and broken particles of pyrite; On the other hand, the mineral particles on both sides of the aggregate boundary composed of fine carbonate, timely, sericite and chlorite are dispersed.
The petrochemical data of gray-green phyllite, the main host rock of copper mine, is projected on the original rock recovery map, which is intermediate acid-tuff, mainly volcanic material. Iron-bearing jasper is produced in fine and stable bands, and the main minerals are timely and iron-bearing minerals, while the latter is often wrapped by the former, and timely is mostly irregular granular with unclear boundaries and fine particle size.
2. Geochemistry of ore deposits
Characteristics of trace elements: the composition of trace elements in surrounding rocks and ore types is obviously different. Copper content in ore-bearing rock series is generally high, while lead and zinc content are low. The Cu content in gray-green sericite phyllite is higher than that in gray-black carbonaceous phyllite, and the Co/Ni values of both are higher than 1, indicating that the Cu element in the mining area is mainly derived from gray-green sericite phyllite (the original rock is chronological porphyritic tuff). According to the characteristics of trace elements, the contents of Co and Ni in copper ore are lower than Clark value, Ni content is higher than Co content, and Co/Ni value is lower than 1, while specularite in the upper part of copper ore body is the opposite. The reason for this may be that the mining area first turned into iron and then into copper.
Sulfur isotope characteristics: δ34S of pyrite varies from+8.1‰ to+31.706 ‰, with a deviation of 23.6‰ and an average of+18.9‰, while δ34S of chalcopyrite varies from+14.0 ‰ ~ Sulfate sulfur isotope δ34S is greater than 127.3 ‰, indicating that the sulfur of barite is also derived from seawater sulfate.
Characteristics of rare earth elements: the variation of ∑LREE/∑HREE of ores is 1.96 ~ 6.57, of which copper ores are 2.75 ~ 3.13; La/Yb = 2.7 1 ~ 13.87, and copper ore la/Yb = 2.32 ~ 3.9 1, all distributed in iron ore and jadeite. Eu is abnormal or not obvious, and the δ eu of iron ore and jadeite is 0.92 ~1.61; Δ EU = 0.93 ~ 0.95, which is weakly negative anomaly. The concentration of rare earth elements in ore changes greatly, and copper ore is obviously higher than iron ore, and the middle part of copper ore rises upward (the middle part is relatively rich in rare earth elements). Generally speaking, iron ore deposits are rich in light rare earth elements, while heavy rare earth elements are relatively scarce. The partition model is obviously different from that of rare earth elements in seawater, which reveals that mineralization is not normal sedimentary mineralization in seawater.
3. Wall rock alteration
The main types of wall rock alteration of the deposit are silicification, sericitization, carbonation, barite, pyrite and chalcopyrite. Vaguely visible in chloritization, mineralization has a certain relationship with alteration. Silicification is closely related to copper mineralization. The closer to the ore body, the higher the silicification degree, while the time content far away from the ore body decreases obviously. The alteration is roughly banded, with pyrite near the ore, and the footwall is replaced by silicification and sericitization. Carbonation and chloritization are far away from ore bodies.
4. Metallogenic model
At present, the origin and age of the deposit are still controversial. Since exploration began in 1950s, the metallogenic type has always been considered as sedimentary metamorphic iron ore. The Geological Survey Team of Jiuquan City, Gansu Province and Changchun Institute of Geology (199 1) have studied the Jingtieshan Iron Mine from the aspects of regional geology, geochemical background, types and characteristics of iron ore, formation mechanism and distribution law of iron ore, and classified the iron mine as a marine terrigenous-volcanic metamorphic syngenetic deposit, and the copper mine is a stratabound deposit coexisting with layered iron ore and transformed by homologous hydrothermal solution. It is also considered that the iron-copper deposit is the product of the same metallogenic process and belongs to volcanic exhalation-sedimentary genetic deposit.
According to the ore and geochemical characteristics of the deposit, it is considered that the ore has gone through the process of sedimentation, metamorphism and hydrothermal superimposed transformation, and the superimposed transformation after mineralization can affect the early mineralization to varying degrees. It is inferred that iron and copper deposits have the same genesis, but the genesis is different. Firstly, the submarine sedimentary jet iron deposit was formed, and after a certain degree of supergene transformation, the hydrothermal copper deposit was superimposed in the later stage.
5. Prospecting prediction
Study in detail the land mass deposition, volcanism, structural characteristics and scope in the western part of North Qilian (possibly including parts of Central Qilian), and carry out geological exploration in Huashugou Formation, Aoyougou Formation and some Beidahe Formation; A detailed study of the existing iron ore occurrences or small iron ore deposits in the above strata is expected to find copper ore bodies and gold ore bodies in these ore bodies (occurrences) and to transform them into copper-gold deposits with industrial significance.
Three. Geology of Liugouxia iron-copper deposit
1. Location of mining area
The mining area is located in Yu 'erhong Township, Subei Mongolian Autonomous County, Gansu Province. It is 0/60km away from Yumen Station/KLOC-on Lanxin Line, which is connected by highway. Geographical coordinates: 96 55 ′ 09 ″ ~ 97 04 ′ 00 ″ E, 39 25 ′ 04 ″ ~ 39 32 ′ 08 ″ N (Figure 7- 1).
2. Mining strata
The stratum of Liugouxia iron and copper mine area is Huashugou Formation in the upper part of Zhu Long Guanqun of Mesoproterozoic Great Wall System, that is, the now abandoned former Jingtieshan Group. The stratum is single, the lithology is simple, mainly phyllite and carbonate rocks, with iron ore layers. The stratigraphic sequence of main ore sections is from top to bottom (Figure 8-36).
Figure 8-36 Geological map of I-IV ore section in Liugouxia iron and copper mine area (based on the comprehensive adaptation of the Second Geological Team of Gansu Geological Bureau (1973) and Jiuquan Geological and Mineral Investigation Team of Gansu Province (1994))
1-silicified limestone; 2- argillaceous phyllite; 3- sericite phyllite; 4- calcareous phyllite; 5- calcareous argillaceous phyllite; 6- carbonaceous phyllite; 7- quartzite; 8— Iron-bearing quartzite; 9- diabase; 10-diorite porphyrite; 1 1- iron-copper ore body; 12- copper ore body; 13- iron ore body; 14- real and assumed normal fault; 15-actual and presumed thrust failure; 16— actual and assumed translational faults; 17- failure of unknown nature; 18- Geological boundary
(9) Gray-green chlorite sericite phyllite and gray-yellow white dolomite with a thickness of > 348.8+0m.
(8) Dark gray-gray black fine-grained limestone with a thickness of 252. 18m.
(7) Gray-green sericite phyllite mixed with green-gray siltstone with thickness > > 31m..
(6) Gray-light gray sericite phyllite mixed with light-colored silicified dolomite, calcareous phyllite, gray-white discolored sandstone and dark gray limestone, with a thickness of 99m.
(5) Black-gray-black carbonaceous sericite phyllite, carbonaceous sericite phyllite, light gray dolomite sericite phyllite and dolomite marble, with a thickness of 35m.
(4) Gray-light gray sericite calcareous phyllite, sericite phyllite, marble, Shi Ying mixed with a small amount of calcareous chlorite, quartzite, brown copper-bearing siderite layer, iron-bearing siliceous rock (or quartzite) and other unstable layers, with a thickness of > > 21.5m.
(3) Light yellow green dolomite sericite phyllite, dolomite phyllite, light gray-light gray green sericite phyllite, sericite timely phyllite, plywood dolomite marble, chlorite sericite phyllite, sericite timely phyllite and unstable limonite, hematite, iron phyllite (lean iron ore), copper-bearing siderite, etc. The thickness is 41m. There are many iron-bearing dolomite particles in phyllite in this layer, which are produced in a long strip and curved shape after later tectonic action, and are arranged directionally to form a linear structure.
The ore body is 50 meters thick. It is mainly composed of brown (hematite) iron ore, limonite and chalcopyrite.
(2) Gray-gray green sericite phyllite, timely sericite phyllite and iron-bearing sericite phyllite, iron-bearing sericite dolomite mixed with brown gray-brown iron-bearing sericite phyllite. Thickness > > 17m.
(1) gray-black calcareous carbonaceous phyllite, with carbonaceous limestone and siliceous carbonaceous shale in the upper part, with a thickness of191m.
The fault has not bottomed out yet.
All the above layers are in integral contact.
3. Mining area structure
The overall structural form of the mining area is fold-thrust structural style. According to the structural characteristics reflected by each layer, it can be divided into early stage and late stage. In the early stage, plastic deformation was dominant, which indicated that the middle-deep tectonic deformation caused strong deformation of strata and coal seams in the mining area, forming folds, schistoses, thousands of cleavage, tensile lineation, soft folds and sticky stone sausages. The strata in the mining area are locally disordered and generally orderly. In the late stage, brittle deformation and shear deformation were dominant, and three groups of faults were formed, which were nearly east-west, northwest and northwest. Among them, the thrust fault is dominated by nearly east-west, generally inclined to the north, locally inclined to the south, with steep dip angle and large fault distance (fault distance F 1 > 200 m), which is also the most destructive to the ore body. Normal faults are also distributed in the east-west direction, inclined to the northwest, and the dip angle is steep. Among them, the F 12 fault staggered the ore bodies and confined the copper ore bodies to the footwall. Strike-slip faults are NW-SE and NE-SW, and some of them are nearly north-south, cutting early structures and ore bodies.
4. Magmatic rocks in mining area
There are few magmatic rocks in the mining area, only a few diabase dikes and diorite porphyrite dikes are seen, but the latter is closely related to copper mineralization. Studies show that it is the product of Caledonian magmatism.
5. Geological characteristics of iron ore deposits
Iron ore bodies mainly occur in phyllite. * * * There are more than 30 large and small iron ore bodies in China, of which II-IV ore section is the main ore section (Figure 8-36). The upper wall of the iron ore body in this ore block is gray-green, light green and light yellow-green sericite phyllite, and the lower wall is dark green, dark gray-green and purple sericite phyllite.
Ore bodies are generally layered or quasi-layered, and a few are plano-convex mirrors and lentils. Their occurrence is consistent with the surrounding rock. They are complete, strike nearly east-west, tend to be NNE, and have steep dip angles ranging from 53 to 8 1. The length of ore body is generally over 300m, and the longest is 13 18m. The thickness is 8 ~ 1 1m, and the maximum thickness is 2 1 .06m. Among them, the iron ore body1is in the shape of a lentil, striking NWW, dipping to the northeast with an inclination of 53. The length is 346m and the average thickness is 8.62m, which varies greatly along the strike and dip, and the east and west ends are cut by translational faults.
The average iron grade of ore body 1 TFe3 1.5%. The main minerals are specularite and hematite, with a small amount of iron-bearing barite. Gangue minerals include barite, quartz and calcite. There are some jasper belts in the ore. Barite is locally enriched, and barium sulfate exceeds 30%.
There are four basic types of iron ore: specularite-hematite, magnetite-hematite, hematite and calcareous phyllite ore. The characteristics of various ores are briefly described as follows:
Specularite-hematite: mainly found in orebodies 1 and 2. The metal minerals are mainly specularite and hematite, with a small amount of magnetite, limonite and pyrite. Specularite is usually arranged in a directional way and has a leaf structure, and some specularite is massive. The gangue minerals in the ore are mainly jasper, and a small amount of barite, calcite, sericite and chlorite can be seen. The ore has a banded structure and is formed by the interbedding of jasper, specularite and hematite. The average grade of this ore is TFe35.55%.
Magnetite-hematite: mainly distributed in No.3, No.4 and No.6 ore bodies and the western section of No.5 ore body. Ore minerals are mainly composed of hematite, followed by magnetite and specularite, and gangue minerals are timely. In addition, the ore also contains a small amount of chalcopyrite, pyrite, malachite, barite and sericite.
Hematite: mainly distributed in ore bodies 1 and 5, mainly purplish red, mainly composed of hematite and yingshi, with a small amount of low-grade barite and limonite.
Calcareous phyllite ore: mainly distributed in III, V and VI ore sections. It is composed of hematite, sericite, chlorite and pyrite, with some jasper and iron-bearing siliceous rocks.
The influence of late tectonic movement on ore bodies is mainly manifested in metamorphic deformation, multi-stage fold superposition, dislocation and shear crushing of ore bodies.
6. Geological characteristics of copper deposits
It is found that the copper bodies in Liugouxia iron-copper ore field are distributed in various phyllites of Huashugou Formation, and some of them are also distributed in carbonate rocks. The * * * circle 12 ore body is mainly distributed in the north of the main iron ore body (Figure 8-36), and the main copper ore bodies (1 and No.8 ore bodies) are distributed in the middle and lower parts of the iron ore body. Generally speaking, it is closely related to the diorite porphyrite dike.
The copper ore body is layered, branched and convex mirror-shaped, controlled by the interlayer fracture zone of surrounding rock, and its trend is basically the same as that of surrounding rock and fracture zone. The length of ore bodies is generally 69 ~ 260 meters, and the average thickness is 0.26 ~ 3.48 meters. The ore body strikes NWW, inclines to NNE, and the dip angle is 40 ~ 78.
There are seven kinds of complex ore types, namely: hematite-limonite-chalcopyrite type, sychrosite-chalcopyrite type, sychrosite-siderite-chalcopyrite type, sericite-sychrosite phyllite-chalcopyrite type, iron-bearing jasper type copper mine, skarn type copper mine and fractured altered rock type copper mine.
The grade of copper is generally 0.2 1% ~ 2.75%, mostly 0.55% ~ 1.48%.
Ore structures mainly include massive, disseminated, vein-like, thousand-flake, lamellar and so on, and structures mainly include fault structure, semi-authigenic, authigenic granular structure, abnormal granular structure, metasomatism illusion structure and so on.
The mineral composition of the ore is mainly chalcopyrite, bornite, azurite, malachite and sky blue, accompanied by specularite, hematite, limonite and pyrite. Gangue minerals include quartz, calcite, dolomite, chlorite, actinolite, andradite, sericite and feldspar.
Copper ore bodies are not only distributed in the middle and lower parts of iron ore bodies, but also in the diorite porphyrite vein contact alteration zone in the south of iron ore bodies. Iron ore-diorite porphyrite-hematite belt in altered diorite porphyrite-coarse calcite belt-silicified hematite belt isochron and carbonate-isochron (a small amount of carbonate minerals) red (mirror) can also be seen in the surface exploration trench. The hydrothermal alteration of the surrounding rocks of copper ore bodies is intense, mainly including silicification, carbonation, sericitization, chloritization, skarnization and pyritization. The above phenomenon shows that copper deposits are closely related to magmatic hydrothermal activities.
7. Geochemical characteristics of surrounding rocks and ore bodies
Previous studies have found that:
The phyllite around the (1) iron-copper ore body is characterized by high content of SiO2 _ 2, Al _ 2O _ 3, TiO2 _ 2, K _ 2O and H _ 2O+,but low content of MnO, Fe _ 2O _ 3 and Fe _ 2O _ 3. Iron ore is characterized by high Fe2O3, FeO, MnO, MgO, Ba and low al2o 3, SiO2, K2O, TiO2 and H2O+. Copper ore is characterized by high silica, copper, sulfur and low alumina, titanium dioxide, magnesium oxide, calcium oxide, ferric oxide and K2O. The above geochemical characteristics contain abundant genetic information. The geochemical characteristics of surrounding rocks show that they are derived from terrigenous materials, which are generally high in Si, al, Ti and K, while the sources of iron ore are completely different from them. It is generally believed that Ba comes from volcanic materials. The low potassium characteristics of copper ore also indicate that it is not terrigenous.
(2) According to the research of Yang Huazhou (199 1), the original rock was restored by using the petrochemical composition of Huashugou Formation, and the original rock of phyllite surrounding the iron mine was argillaceous rock, with a small amount of volcanic materials added; Quartzite recovered from the metamorphic fabric is timely sandstone, marble belongs to carbonate rock, and the original iron ore rocks are jasper hematite and siderite. Generally speaking, the surrounding rock of the ore body is composed of iron-bearing jasper-clastic rock-carbonate rock, mixed with a small amount of volcanic materials.
(3) The content of Cr, Ni, Co and V in diabase in Liugouxia mining area is higher than the average value of basalt in the world; Except for Ni, Cr, Co and V in phyllite are higher than the world average value of shale. Cr and Co of diorite porphyrite in Liugouxia mining area are higher than the world average value of diorite porphyrite, while V and Ni are lower than the world average value of diorite porphyrite. The contents of Ni, Co and V in iron ore and copper ore are all lower than the Clark value of the crust, indicating that the ore body and surrounding rock come from different sources. Compared with basalt in the world, diabase in Liugouxia mining area has high copper content, low lead content and similar zinc content. In the world, the contents of copper, lead and zinc in phyllite are lower than those in shale, but the contents of lead and zinc are higher. The contents of copper, lead and zinc in iron ore are higher than those in surrounding rock. The contents of copper, lead, zinc and arsenic in copper ore are higher than those in surrounding rocks. The copper content in quartz diorite porphyrite is extremely high, while the lead and zinc contents are low, indicating that the enrichment of copper in quartz iron ore bodies and copper ore bodies may be related to diorite porphyrite veins.
(4) The total amount of rare earths in the direct surrounding rocks (phyllite and slate) of Liugouxia Iron Mine is 61.87×10-6 ~182.53×10-6, with an average value of134×/kl. Lree/hree = 5.62 ~12.21,(la/Yb) n = 6.19 ~13.90, the distribution curve of rare earth elements is right-leaning (Figure 8-37), and δ EU = 0.70. The ∑REE/∑HREE of Liugouxia Iron Mine is 1. 13 ~ 4. 19, (La/Yb) n = 0.87 ~ 5.66, and δEu is1.24 ~1. He Ruifang and An Sanyuan (1990) set points on the LREE-HREE correlation map. The results show (Figure 8-39) that phyllite and slate both fall near the upper crust, indicating that their provenance comes from the crust. However, banded specularite, jasper and barite are located near chondrite area and lower crust area, indicating that ore-forming materials come from mantle source area.
Figure 8-37 REE Distribution Model of Phyllite in Liugouxia Iron Mine
1-calcareous phyllite; 2- Iron slate; 3- gray phyllite; 4- Black slate; 5- Green Slate
Figure 8-38 Distribution Pattern of Rare Earth Elements in Iron Ore of Liugouxia Iron Deposit
1-specularite; 2- specularite with time-dependent pulse; 3- banded jasper specularite; 4- magnesite
Figure 8-39 HREE-LREE diagram of rocks and ores in Liugouxia iron deposit (according to He Ruifang and An Sanyuan, 1990)
1-phyllite; 2- specularite
(5) The δ 13CPDB of siderite in Liugouxia iron deposit is -3.9 ‰, δ 18OSMOW is 17.6‰, and the estimated δ 13C of mantle source region is -7 ‰ (Faure, 1986 In normal marine carbonate rocks, δ 13C is -2 ‰ ~+4 ‰, and δ 18O20 ‰~ 30 ‰ ~ 30 ‰ (the older you get, the lower and flatter δ18o is, 1980). By comparison, it is not difficult to see that C in iron ore comes from the mantle.
(6) The study of fluid inclusions in Liugouxia deposit shows that the uniform temperature is 280 ~ 340℃, the range of fluid δ 18O is 8.4 ‰ ~1.7 ‰, with an average value of 10.3‰, and that of ordinary magmatic water δ/kloc.
8. Ore genesis and prospecting prediction
According to the above data, Liugouxia deposit and Huashugou deposit have similar geological and metallogenic characteristics. The ore-forming material comes from the deep crust and belongs to the submarine hydrothermal jet sedimentary iron deposit. At the same time as the formation of iron deposits, copper was initially enriched by hydrothermal jets, and further enriched by hydrothermal activities of intermediate-acid magma in Caledonian. These copper deposits are usually related to small intermediate-acid rocks and dikes, and overlap with iron ore bodies in space.
The main points of prospecting and prediction in geological profile of Huashugou iron-copper deposit are expounded.