my country has a vast territory, with various magmatic (eruptive) rocks from ultrabasic-basic-neutral-acidic-alkaline ages; deposits from Archean to Quaternary ages, including various sedimentary rocks Series, volcanic sedimentary rocks, and sedimentary metamorphic rocks created conditions for the formation of different types of iron ore. Iron deposits of industrial significance in my country can be divided into six main types according to their genesis: sedimentary metamorphic type, magmatic type, contact metasomatic-hydrothermal type, volcanic type, sedimentary type and weathering type, among which sedimentary metamorphic type is the most important. important. The introduction is as follows: (1) Sedimentary metamorphic iron deposits
This type of iron deposit is also called metamorphic sedimentary iron deposits. It is mainly produced in the ancient regional metamorphic rock series of the Precambrian (Archean and Proterozoic). It is a very important type of iron ore in my country, and its reserves account for 57.8% of the country’s total reserves. And it has the characteristics of “large, poor, shallow, easy (selection)”, that is, the ore deposit is large in scale, low in iron content, and the ore body is exposed on the surface or shallow part, and it is easy to sort. Mainly distributed in southeastern Jilin, Anshan-Benxi, East Hebei, Miyun, Beijing, northern Shanxi, southern Inner Mongolia, central Henan, central Shandong, northwest Anhui, Xinyu, Jiangxi, Hanzhong, Shaanxi, Hunan and other places. According to the type of ore in the deposit, the rock and mineral combination of the ore-bearing metamorphic rock series and other geological characteristics, it is divided into the following two categories. 1. Modified iron-silica constructed iron deposits Typical iron deposits are distributed in the Anshan-Benxi area of Liaoning. Therefore, they are generally called “Anshan-style” iron deposits. This type of iron ore is an iron ore deposit that is subject to different degrees of regional metamorphism and is related to the formation of volcanic-iron siliceous deposits. Roughly equivalent to foreign Algoma-type iron ore. Mainly formed in the precambrian (mostly concentrated in 2000-3000Ma) old metamorphic rock area. Iron ore deposits are mainly produced in different layers in Liaoning, Hebei, Shandong, Henan, Anhui and other places in the Taikoo Yu Anshan Group, Qianxi Group, Taishan Group, Dengfeng Group, Huoqiu Group and their equivalent metamorphic rock series; Shanxi In the Wutai Group, Luliang Group and their equivalent metamorphic rock strata in the Paleoproterozoic, Inner Mongolia, most of the metamorphism belongs to the greenschist to amphibolite facies, and some are produced in the granulite facies. Hunan, Jiangxi and other provinces are produced in the Banxi Group or the Sinian Songshan Group. The iron-bearing metamorphic rock series in most areas are subject to mixed petrification and granitization to varying degrees. The iron ore layer in the metamorphic iron-silicon construction is multi-layered, and there are also 1 to 2 layers, which are layered, layered, and lenticular. The thickness of the ore bed is generally tens to hundreds of meters, and the thickest can reach about 350m. The extension is relatively stable, and the length of individual ore beds can reach more than tens of kilometers. Most of the deposits are large or extra large.
The composition of iron minerals and quartz in the ore has a black-and-white striped and striped structure, and when the degree of metamorphism is high, it transitions to a gneiss-like structure. The ore is magnetite quartzite, hematite quartzite, chlorite magnetite quartzite, and amphibolite quartzite. Mainly lean ore, the iron content is generally 25% to 40%. In lean ore, there are also iron-rich ore with iron grades of 50% to 60% of different scales and different origins. 2. Iron ore deposits constructed by metamorphic carbonates Typical ore deposits are located in Da Lizi, Jilin, so it is called the “Da Lizi” iron ore. This type of iron ore is a carbonate-type sedimentary iron ore deposit subject to slight regional metamorphism. Mainly produced in the Proterozoic strata. The ore-bearing rock series is mainly composed of clastic-carbonate rocks, such as sandstone, mudstone, and limestone. There are not many known mineral deposits, mainly in the Paleoproterozoic Liaohe Group phyllite and carbonate rocks in southeastern Jilin; Yunnan Yimen and Eshan iron deposits are produced in the Kunyang Group carbonate rocks in the lower part of the Neoproterozoic middle. The ore body is layered, layered, lentil-like, sweet potato-like, and irregular in shape. The ore body is generally 100-300m long along the strike, 200-500m deep on the slope, the slant length is greater than the strike length, and the thickness varies greatly. The ore minerals include hematite, magnetite, siderite, limonite, etc. The ore is dominated by massive and banded structures, followed by oolitic structures. The ore types are hematite, magnetite, siderite, and secondary limonite. The surrounding rocks of magnetite type and hematite type ore are mostly phyllite, while the surrounding rocks of siderite type ore are mostly marble. Rich iron ore occupies a relatively large proportion. For example, Yunnan Huanian Iron Mine, half of its reserves are ore containing alkaline iron smelting. (2) Late magmatic iron deposits This is a type of deposits related to basic, basic-ultrabasic magmatism. Its iron minerals are rich in vanadium and titanium, and are usually called vanadium-titanium magnetite deposits. Reserves account for 11.6%. According to the method of mineralization, it can be divided into two categories: 1. Late magma fractionated iron deposits. Deposits formed by the late fractionation of magma crystallization and rich in iron, vanadium, titanium and other residual magma condensed. my country was first discovered in the Panzhihua area of Sichuan Province, so it is often called the “Panzhihua” iron deposit in China. The deposits are produced in basic-ultrabasic rock masses such as gabbro-peridotite. The rock masses are mostly distributed on the edge of the ancient land uplift zone and are controlled by deep faults. The length of the ore-bearing rock mass can reach several tens of kilometers and the width is one to several kilometers. The rock mass is well differentiated, with obvious facies and clear rhythm. According to the rock combination, it can be divided into gabbro type, gabbro-sulfurite type, gabbro-trocite type, gabbro-plagioclase type, gabbro-pyroxenite-gravelite type and diabase type. Phase combination type. Iron ore bodies are mostly layered, distributed in the dark facies zone at the bottom of the middle or lower rhythm layer of the rock mass, and interbed parallel to the rhythm layer of the rock mass.
Mineral deposits are often composed of several to dozens of parallel ore bodies, with a cumulative thickness of from tens to two to three hundred meters, and an extension of more than one kilometer. The main ore minerals include granular ilmenite, magnetite, ilmenite, magnesia-aluminum spinel, etc., with a small amount of pyrrhotite, pyrite, and sulfides of cobalt, nickel, and copper. The ore has a meteoric iron structure and an inlaid structure. The ore is densely massive, banded and disseminated in structure. The ore contains 20%-45% TFe, 3%-16% TiO2, 0.15%-0.5% V2O5, 0.1%-0.38% Cr2O3, and trace amounts of Cu, Co, Ni, Ga, Mn, P, Se, Te, Sc and Pt group elements can be comprehensively utilized. Most of these deposits are large in scale and are important sources of iron, vanadium, and titanium metals. They are mainly distributed in Sichuan in China The Pan (Zhihua) West (Chang) area of the province. 2. Late magmatic penetrating iron ore deposits are formed by penetrating iron-bearing liquid from the late magmatic phase differentiation along the fracture or contact zone in the rock mass. my country was first discovered in Damiao, Hebei Province, so it is often called the “Damiao-style” iron deposit. Iron ore deposits are produced in plagioclase and gabbro rock masses. Basic rock masses are distributed along the east-west fault zone in a belt shape. The ore body is formed by penetrating along the cracks of the rock mass or the contact zone of the above two magmatic rocks. The ore bodies are irregular in shape, mostly in the shape of lentils or veins, appearing in groups and arranged in geese. The boundary between the ore body and the surrounding rock is clear, and the occurrence is steep. From the surface to the deep, branching and compounding are common in ore bodies, mostly blind ore bodies. A single ore body is several hundreds of meters long, several tens of meters thick, and tens to hundreds of meters deep. The main minerals are magnetite, ilmenite, hematite, rutile and pyrite. Gangue minerals include plagioclase, pyroxene, chlorite, actinolite, phomphibole and apatite. The structure of the ore is uniform, and the structure of meteorite is common. With disseminated and massive structure. There are rich and poor ore, containing vanadium, titanium, nickel, cobalt, platinum and other sulfides. Amphibole, chlorite, and zoisite alterations are common in surrounding rocks near the mine. The useful mineral particles are large and the ore is easy to select. The size of the deposits is generally medium to small, mainly distributed in Damiao and Heishan areas in Chengde area, Hebei Province. (3) Contact metasomatic-hydrothermal iron deposits Contact metasomatic deposits, often called skarn deposits. It mainly occurs in or near the contact zone between intermediate-acid-medium-basic intrusive rocks and carbonate rocks (calcium-magnesia-containing rocks). Such deposits generally have a typical skarn mineral combination (calcaluminate-wroughtite garnet series, diopside-porthoproxene series), and they have certain origins and spatial distribution with skarn. relation. The formation ages of magmatic rock intrusions range from Caledonian, Hercynian, Indosinian, to Yanshanian. The Yanshanian period is the most important in our country. The generation age of carbonate rocks ranges from the pre-Sinian to the Jurassic, and the lithology is also very different. As far as the known domestic skarn type iron ore surrounding rocks are concerned, they include limestone, marble, dolomitic limestone, marl, various impure limestones, and dolomite; some of the surrounding rocks can be hornstones. , Schist, slate, sandstone or tuff, etc. From the perspective of lithological age, the Proterozoic (including the Sinian) are mostly siliceous limestone; the Cambrian-Ordovician are mostly pure limestone or magnesite-bearing limestone; the Carboniferous-Permian Mostly limestone containing mud and organic matter. The Cambrian-Ordovician limestone is the most favorable for the formation of contact metasomatic iron deposits in the north of my country, and the Triassic Daye limestone and the Early Permian Qixia limestone in the south. Most of the contact metasomatic iron ore is formed in the contact zone, and some ore bodies can extend into non-skarn surrounding rocks. The ore bodies often appear in groups, with complex shapes, mostly lenticular, cystic, and irregular. And veins, etc., the mineral composition of the ore is more complicated. Iron ore is dominated by massive structures, followed by disseminated, spotted, massive and breccia structures. This type of iron ore is often associated with comprehensive utilization of copper, cobalt, gold, silver, tungsten, lead, zinc, etc.; it even forms common (associated) deposits such as iron-copper, iron-copper-molybdenum, iron-boron, iron-tin, iron-gold, etc. . The size of the deposits is mainly small and medium-sized, and there are also large-scale deposits. This type of iron ore is widely distributed in my country, mainly concentrated in the Handan (Dan)-Xing (Taiwan) region of Hebei Province, eastern Hubei, southern Shanxi, western Henan, central Shandong, northern Jiangsu, southern Fujian, northern Guangdong, and southwest Sichuan and Yunnan. West and other places are an important source of iron-rich ore in my country. According to the conditions of magmatic rock and surrounding rock, it is often divided into Hanxing type, Daye type and Huanggang type iron ore in industry.
The surrounding rocks of the Hanxing-type iron mine are mainly limestone of the Middle Ordovician Majiagou Formation, and the ore bodies are often stratified. The surrounding rocks of Daye-type iron ore deposits are mainly Triassic Daye limestone, with irregular ore bodies. Huanggang-type iron ore-forming rock bodies are granite and baigangite, and the surrounding rocks are Paleozoic carbonate rock intercalated with volcanic rock series. Hydrothermal iron deposits are obviously controlled by structure, some are controlled by faults, some are controlled by folds, and some are controlled by a combination of faults and folds. The relationship between hydrothermal iron deposits and magmatic rocks often varies from place to place, and most ore bodies are at a certain distance from the rock masses. High-temperature hydrothermal magnetite and hematite deposits are often related to alkaline granite, granodiorite, and diorite, while mid-low-temperature hydrothermal hematite deposits are often related to smaller intermediate-acid intrusions. People should keep a certain distance. There is no obvious relationship between the mid-low temperature hydrothermal siderite deposit and the intrusive body. The control effect of surrounding rock conditions on hydrothermal iron ore is not obvious. Wall rock alteration is a significant feature of hydrothermal iron ore. Diopside, tremolization, biotization, epidoteification, etc. are common in high-temperature deposits; chlorite, sericitization, silicification, and carbon are common in medium- and low-temperature deposits. Acidification and so on. Most hydrothermal iron ore bodies are small and often appear in groups. The ore bodies are vein-shaped, lenticular-shaped, and lentil-shaped, with branching and compounding, expansion and contraction, and recurrence of pinching. The combination of ore is simple, and the grade of ore is generally high. The size of the deposit is mainly small and medium-sized. Distributed in Inner Mongolia, Jilin, Shandong, Hubei, Guangdong, Guizhou and Yunnan provinces and autonomous regions. However, there are also large deposits, such as the Wendeng iron deposit in the Upper Cambrian-Middle Ordovician carbonate rocks in the Zihe area of Shandong. The deposit is composed of 22 ore bodies, which are layered and lenticular, overlapping and distributed in parallel. The main ore body is 7000m long, 12-36m thick, and 100-470m deep. The main ore minerals are limonite and siderite. The ore grade TFe averages 41% (limonite) and 30% (siderite), and the proven iron ore reserves are 116 million tons, of which iron smelting <
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