What Are Iron Ore Deposits?

Iron deposits are one of the ferrous metal deposits. According to the genesis, iron ore deposits can be divided into five categories: iron deposits directly related to magmatism, contact metasomatic-gas-liquid iron deposits, iron deposits related to sedimentation, iron deposits related to surface weathering, and Iron ore deposits associated with regional metamorphism.

Late magmatic iron deposits

(1) Late magmatic heterogeneous iron deposits

It is produced in basic and ultrabasic igneous rocks such as gabbro and olivine. A single ore-bearing rock body intermittently extends from several kilometers to tens of kilometers, and is one to several kilometers wide. The ore body is relatively regular and multi-layered, and it is produced in the middle and lower part of the rock body and the bottom of the rhythm layer. The accumulated thickness of the ore body (layer) is several tens to two or three hundred meters, and the extended depth is hundreds to thousands of meters. Most of them are large-scale ore deposits. After mineralization, faults and veins develop, often destroying the continuity of the orebody's direction and tendency. The ore has a disseminated, banded, massive structure, a meteorite embedded structure, and a solid solution decomposition structure. The metal minerals are mainly titanomagnetite, followed by granular ilmenite, and contain a small amount of pyrrhotite, pyrite and other cobalt-nickel sulfides. The gangue minerals include pyroxene, basic plagioclase, olivine, apatite, and the like. Ores are generally W (TFe) 20% to 45%, W (TiO ₂ ) 3% to 16%, W (V ₂ O ₅ ) 0.15% to 0.5%, W (Cr ₂ O ₃ ) 0.1% to 0.38%, associated There are Cu, Co, Ni, Ga, Mn, P, Se, Te, Sc, and platinum group elements. All ore can be smelted only after beneficiation. Deposit example: Panzhihua Iron Mine.

(2) Late magmatic penetration deposit

Produced in gabbro and plagioclase. The ore body is distributed along certain cracks in the rock body, or it is produced in the contact zone between gabbro and plagioclase. The ore body is irregular in shape, and generally appears in lentils-like, vein-like clusters, and the geese are lined up and sideways to the deep. The length of a single ore body ranges from several meters to tens to hundreds of meters, the thickness is from several meters to tens of meters, and the depth is tens to hundreds of meters. The scale of the deposit is mostly small and medium. The ore has a compact, block-like structure. The useful mineral particles in the ore are relatively coarse, and rutile is common but ilmenite is not seen. The mineral composition and chemical composition of the ore are generally similar to those of the late magmatic heterogeneous iron ore deposits, but they often contain a large amount of plagioclase, pyroxene, cellulite, actinite, and apatite. Individual iron can be locally formed in the rock Phosphate ore body. Ore selection is easy. Example of the deposit: Damiao iron ore ^[2] .

Hydrothermal iron ore deposit

This type of deposit generally contains high iron and is widely distributed. The contact metasomatic deposits are mainly produced in the contact zone between the middle-acid intrusive body and carbonate rocks. The scale of the deposit is generally small and medium, and a few are large. Ore bodies are generally tens to hundreds of meters long, and a few are several kilometers in length, with a depth of tens to hundreds of meters and a thickness of several meters to tens of meters. The shape and distribution of the ore body are controlled by the contact zone, and there are layered, lenticular, nest-like, etc. Blind ore bodies often exist. The ore is dominated by massive structures, followed by disseminated structures, and also has breccia structures, with metasomatic and granular structures. The ore minerals are mainly magnetite, followed by pseudo hematite, and some mines have more siderites. Sulfide is mainly pyrite, and some mines have chalcopyrite, galena, sphalerite, molybdenite and so on. A few deposits contain cassiterite and "colloidal tin". The gangue minerals are mainly diopside and garnet, followed by amphibole and carbonate minerals. In some mining areas, gangue minerals have more serpentine. The total iron content of the ore is 30% to 70%, the sulfur content is generally less than 4%, the phosphorus is low, and W (SiO ₂ ) is 4% to 15%, accompanied by Cu, Co, Ni, Pb, Zn, Au, Ag, W, Sn, Mo, etc. Ores are generally well selectable, and have been widely exploited except for some unused deposits with high tin content. Ores often contain associated useful elements that can be comprehensively recovered, such as Co, Ni, Cu, Au, Ag, S, and so on. Deposit example: Daye Iron Mine.

Iron deposits associated with volcano-intrusion activities

(1) Iron ore deposits related to terrestrial volcano-intrusion

The output positions of the ore deposits in volcanic institutions can be divided into: volcano-sedimentary deposits produced in volcanic clastic rocks; iron deposits produced inside, on top of magmatic bodies and in contact with the surrounding volcanic rocks; It is produced from iron ore deposits in the contact zone between chert and surrounding sedimentary rocks. Among them, the ore body located on the top of the ocher body and its contact zone with the surrounding volcanic rocks is the largest, and the ore is relatively rich. The size of the ore bodies associated with the terrestrial volcanic invasion varies. Large ore bodies are more than a kilometer long, several tens to two or three hundred meters thick, and hundreds to thousands of meters wide. The ore body is layered, pie-shaped, lenticular, bell-shaped, ring-shaped, sac-like. The symptoms are nearly horizontal, or they are tilted around at a gentle angle. The ore minerals are mainly magnetite, pseudo-heptite, hematite, and contain pyrite. The gangue minerals include diopside, apatite, apatite, alkaline feldspar and anhydrite. Development of surrounding rock alteration. Individual pyrite and anhydrite ore bodies are sometimes formed outside the ore. The ore has lumpy, disseminated, disseminated reticulate, brecciated, patchy, and striped structures. Generally, W (TFe) is 17% 30% for disseminated ore, 35% 57% for block ore, 0.1% 1.34% for W (P), and 0.03% 8 for W (S). % Or more, W (V ₂ O ₅ ) is 0.1% to 0.3%. Deposit example: Meishan Iron Mine.

(2) Iron ore deposits related to marine volcano-intrusion activities

The ore deposit is produced near the submarine volcanic eruption center of the trough fold zone, and the ore body is present in a set of volcanic clastic rock-carbonate rock-lava (fine jadeite and horn porphyry). Ore bodies are layered, layer-like, lenticular, and a few are vein-like and sac-like, often appearing in groups. The length of a single ore body extends from several tens of meters to more than one kilometer, and it is several meters to several tens of meters thick, with a thickness of up to 100 meters, a depth of 100 meters or hundreds of meters, and a maximum of kilometers. Ore bodies are generally gentle, and small and medium ore bodies are sometimes complex. The ore structure is the same as that of the continental volcanic invasion, and it has an almond-like structure and a directional array structure. The metal minerals in the ore are mainly magnetite and hematite, and there are pseudo-like hematite, siderite and sulfide. The gangue minerals include quartz, sodium feldspar, sericite, and chlorite. The iron content of the ore is similar to that of the iron ore deposits related to the intrusive activities of terrestrial volcanoes, and it contains more Cu and Co. Most iron deposits generally have high iron grades and ore is easy to be selected, but some mines contain a certain amount of siderite, pyrite, iron silicate minerals, etc., which affect the beneficiation effect. S, P, V ₂ O ₅ , Cu, Co, etc. associated with the ore can be comprehensively recovered. Deposit example: Dahongshan Iron Mine.

Iron ore deposit

(1) shallow marine sedimentary iron deposits

Sinian sedimentary hematite and siderite deposits: Produced in the Sinian, the bottom of the ore layer is fine sandstone or sandy shale, and the top is black sandstone interbedded with thin sandstone. Generally, there are three or four layers of ore. The layer thickness is 0.7m ~ 2m. The ore type is mainly hematite, followed by siderite. The ore is mainly an oolitic structure, generally W (TFe) is 30% -50%, and the sulfur and phosphorus content is low. In local areas, small faults are more developed. Deposit example: Pangjiapu Iron Mine.

Devonian sedimentary hematite and siderite deposits: Produced in the Middle-Upper Devonian, the ore-bearing construction is mainly sand and shale, containing one to four layers of ore, the cumulative thickness is not large, but it is relatively stable. Ore types are mainly hematite and siderite, followed by oolitic ore and mixed ore. The ore is mainly of medium grade, W (TFe) is 25% 50%, and generally contains high phosphorus and low sulfur. Deposit example: Huoyaoping iron ore.

(2) Alternate sea-land lacustrine sedimentary iron deposit

Iron ore layers are often closely related to coal-bearing strata. Some ore layers are produced on the ancient erosion surface of carbonate rocks and coexist with bauxite and clay ore. The horizon is stable, and the scale of the deposit is mostly medium and small. Ore bodies are layered, layered, lenticular, or discontinuous siderite, hematite, or limonite-bearing layers composed of nodular and lenticular ore and clay shale or coal seams. Ores are dominated by siderite, hematite is dominant, or both. Veins include chlorite, quartz, and clay minerals. W (TFe) is 30% to 55%, high in phosphorus and low in sulfur, and some mines contain manganese, aluminum, and sulfur. Ore mining, beneficiation and smelting of this type of ore deposit are difficult, and oolitic ore is still difficult to use in China. Deposit example: Tutai iron ore.

Metamorphic iron ore deposit

(1) Construction of iron ore by metamorphic iron and silicon

Ore bodies are generally large and poor, with a small amount of rich ore. Material composition is generally simpler. It can be divided into three sub-categories: iron ore produced in rock strata mainly dominated by amphibole and sandwiched with rocks such as biotite granulite, sometimes with quartzite; produced from sericite green mud Iron ore in lithic phyllite and schist-dominated rock formations; iron ore produced in schist, gneiss, and meta-grained rock formations sandwiching marble. The ore-bearing zone of this type of deposits often presents complex folds in the regional structure, causing repeated occurrence of ore bodies (layers); thickening of the ore body at the axis; some deposits are affected by late denudation or faults, and are monoclinic in a local scope Or a syncline structure. There are many layers of iron ore in a mining area, and there are also one to two layers. Thick mines can reach 200-300 meters. The length of the ore body is generally several hundred meters to several kilometers, a few can reach more than ten kilometers, and the depth is hundreds of meters to more than one thousand meters. The shape of the ore body is simple, mostly layered, like layered, and the occurrence is basically consistent with the surrounding rocks. Rich ore is sometimes found in favorable parts of the lean ore layer. Individual rich ore bodies are only a few hundred meters in length, but the extension depth can reach more than a thousand meters. The ore minerals are mainly magnetite, and hematite and pseudomagnesite in a few mining areas are more. Ores generally contain a small amount of iron carbonate and iron silicate, and some mines have higher contents. The gangue minerals include quartz, chlorite, forsterite, ferro-arnet, biotite, carbonate minerals, etc., and generally contain a small amount of pyrite. The ore mostly has a striped structure, with granite and crystalline scales. The ore W (TFe) in most mining areas is 20% to 40%, and W (SiO ₂ ) is 40 to 50%. Generally, ore dressing is required; a few mining areas are rich in ore, and W (TFe) is 50% to 60%, containing sulfur. Low phosphorus, available for direct smelting. Deposit example: Anshan Iron Mine.

(2) Metamorphic carbonate iron ore

Iron ore is produced in various rock formations such as phyllite, marble, dolomitic marble, and slate, or on its contact surface. It is characterized by large changes in ore body thickness and a large proportion of rich ore. The ore body is layered, layer-like, lenticular or irregular. Ore minerals include hematite, siderite, magnetite and limonite. The gangue minerals include quartz, sericite, chlorite and carbonates. The ore structure is mainly block-shaped, followed by oolitic and band-shaped. Example of the deposit: Dalizi iron ore.

Weathered leaching type iron ore deposit

This type of deposit is formed by various types of primary iron ore, sulfide deposits, and other iron-bearing rocks enriched by weathering and leaching. It is also called a weathered crust deposit. This type of deposit is characterized by the widespread distribution of "iron caps". The shape of the ore body is affected by the terrain and structure, and it is irregular or lenticular. The ore is mainly loose and porous limonite. Veins are quartz, carbonates, clay minerals, and the like. The ore has a massive, honeycomb, grape or earthy structure. The ore W (TFe) is 35% to 60%. Most ore deposits often contain impurities such as Pb, Zn, Cu, As, Co, Ni, S, Mn, W, and Bi, depending on the different components of the original ore (rock) stone. Ore selection is difficult, there are certain limitations in industrial utilization, and it is mostly used as a matching ore. Deposit example: Dabaoshan Iron Mine.

Other types of iron ore deposits

Refers to ore deposits formed from multiple periods and multiple factors, but with major ore-forming factors and different understandings during the ore-forming period, such as iron deposits such as Hainan Shilu and Inner Mongolia Baiyun Ebo.

The stratum of the Shilu Iron Mine is mainly a set of shallow sea lagoon facies sedimentary rock series, and has experienced shallower regional metamorphism and contact metamorphism. The iron ore body mainly exists in the dolomite and dolomite crystalline limestone. The diopside or tremolite is layered or layer-like, and is produced on the two or one wing of the compound syncline. See the Mesozoic granite in the periphery of the mining area. The main ore body is 2570m long and 460m wide with a maximum vertical thickness of 430m. The ore minerals are mainly hematite and quartz, and contain a small amount of magnetite, semi-pseudohemite, iron jasper and so on. The average ore W (TFe) is 51%, W (SiO ₂ ) is 6% -33%, W (S) is 0.22% -0.6%, and W (P) is 0.01% -0.04%. W (Fe ₂ O ₃ + SiO ₂ )> 90% in the ore. There is a separate copper-cobalt orebody below the orebody floor. The iron ore produced by this iron ore is a high-quality iron-rich ore.

The strata of the Baiyun Ebo Iron Mine are pre-Cambrian shallow metamorphic quartzite, slate, and dolomite intercalated schist. The iron ore is produced in the dolomite or at the contact point between the dolomite and the siliceous slate. Layered output. The ore-bearing zone is 16 kilometers long from east to west, and 1 to 2 kilometers wide from north to south. The main ore body is 1250m long, with an average horizontal thickness of 245m, a true thickness of 99m, and a maximum extension depth of 970m. Iron ore is mainly composed of magnetite, hematite, and pseudo-like hematite. It generally contains many rare and rare earth minerals in the ore body and surrounding rocks. The gangue minerals include fluorite, sodalite, amphibole, mica, barite, dolomite, and quartz. The near-mine surrounding rocks contain rare and rare earth elements, which can sometimes constitute ore bodies alone. Iron ore W (TFe) is 27% ~ 55%, average W (TFe) is 31% ~ 36%, W (S) is 0.2% ~ 2%, W (P) is 0.3% ~ 1%, W ( F) is 2% to 10%, W (TR ₂ O ₃ ) is 2% to 8%, and the mass fraction of (Nb, Ta) ₂ O ₅ in the enriched section is 0.05% to 0.1%. Due to the complex ore composition, it is difficult to sort ore ^[3] .