Basalt, mainly composed of oceanic crust, is basiclava。It's the EarthOceanic crustAnd the moonMoon SeaIt is the most important component of the earth's crust and the moon's land.In 1546, GAgricolaFor the first time in geological literaturebasaltThis word describes GermanySaxonyBlack rock.The word "basalt" in Chinese is quoted fromJapanese。Japan inHyogo CountyBlack found in Xuanwu CaveOlivine basalt, hence the name.
On October 19, 2021, the Chinese Academy of Sciences held a press conference to release the research results: Chinese scientists determined that the formation age of the basalt brought back by Chang'e-5 was 2.030 ± 0.4 billion years.[7]
Basalt is a basicExtrusive rock, its chemical composition andgabbroordiabaseSimilar, SiOtwoThe content changes between 45% and 52%, KtwoO+NatwoO content is slightly higher than that of intrusive rock, CaO, FetwoOthree+FeO and MgO content is slightly lower than that of intrusive rock.Mineral composition mainly consists of basicfeldsparandpyroxeneComposition, minor minerals includeolivine，HornblendeandBiotiteThe rocks are dark, generally black, sometimes grayish green and dark purple.presentPorphyritic structure。Stomatal structureandAlmond structureUniversal.
basaltbulk density2.8 ～ 3.3g/cmthreeDense ones have high compressive strength, up to 300MPa, sometimes higherGlassyAnd porosity, the strength decreases.Basalt has high durability, many joints, and most of the joint surfaces are pentagonal or hexagonal, forming columnar joints.Because of its brittleness, it is not easy to extract large blocks of stone. Because of the common pores and almond structures, basalt is widely distributed on the surface, but it can be used asfacing stone Not much.
The color of basalt is usually black, black brown or dark green;The basalt near the Tengchong volcanic group is mostly greenish gray, but also dark red, orange and yellow.Because of its dense texture, its specific gravity is higher than that of ordinaryGranite、limestone、Sandstone、shaleBoth are heavy.However, some basalts have reduced weight due to the large number of pores, and can even float in the water.Therefore, the basalt with light porous body is called“Pumice"In the village near the foot of the Mazhan volcano group in Tengchong, Yunnan, people call these porous light basalt" pao shi ".
By SiOtwoSaturation degree and alkalinity, basalt is divided into two categories:
①Tholeiite(i.e. subalkaline basalt) is a rock with SiO2 supersaturation or saturation.ExcludingolivineandNepheline, withOrthopyroxene、Variable pyroxeneIs a feature.Its SiOtwoThe relationship with total alkali is (NatwoO+KtwoO)/(SiOtwo-39) is less than 0.37.
②Alkaline basalt，SiOtwoUnsaturated, alkali rich.Olivine andfoid (such as nepheline)zeoliteThe latter two minerals are sometimes associated withAlkali feldsparOr potassicFeldspar, potassiumFeldsparTogether, as interstitial material produced in the matrix;No orthopyroxene, variable pyroxene, only calcium richClinopyroxene, i.eDiopsidequalityAugite。(NatwoO+KtwoO)/(SiOtwo-39) is greater than 0.37.
Tectonic environment
basalt
According to the tectonic environment, basalt can be divided into 4 types:
① Basalt developed in deep ocean ridge.Roughly 1.5 × 10 per yeartenThe ton rate gushes from the ocean ridge, which belongs to tholeiitic basalt, so it is also called deep-sea tholeiitic basalttwoO、TiOtwo, all iron and PtwoOfive, high content of CaO, which is different from other basalts.becauseSeafloor spreading, deep-sea tholeiite from oceanic ridgeOceanic crustThe main components of.
② Basalt developed in islands and seamounts in ocean basin.GenerallyTholeiiteandAlkaline basaltComposite composition, which may be caused byupper mantleHot column activities.
③ Developed inisland arcandActive continental marginBasalt.Generally, tholeiite is developed on the side of near deep trench and in the early stage, which is large in scale, widely distributed, and may be spiliteKeratophyreComponents of the series;To the mainland,Alkali contentIt is alkaline basalt, but it can also be associated with tholeiite, which is formed inisland arcAnd the final stage of orogenic activity or after stabilization, usually small and scattered.So calledHigh alumina basaltAnd symbioticAndesite、Dacite、RhyoliteIt occurs in the middle stage of island arc and orogenic belt development.ArchaeanadvancedgreenstoneThe tholeiite of the belt may be equivalent toCenozoic eraTholeiite of island arc.
④ Basalt developed in the interior of the continent.It includes large-scale flood caused by fissure eruptionTholeiiteAnd a small amount ofAlkaline basaltThey are contaminated by continental granitic materials.[1]
Lunar rocks
Lunar basalt is one of the main rocks that make up the moon. It is made of rock springs formed about 200 kilometers deep in the outer layer of the moon and crystallized (about 1050 ℃) on the moon surface after multiple eruptions (at least 5 times).It is the youngest rock on the moon, formed in 3.3-3.7 billion years ago, almost equivalent to the oldest known rock on the earth.Lunar basaltFine grain, porous, mainly composed of pyroxeneplagioclaseandilmeniteform.The pyroxene content is about 50-59%,AugiteMore than variable pyroxene;Plagioclase is about 20~29%FeldsparorAnorthite;Ilmenite content is about 10-18%.Secondary minerals include olivineChromite- Titaniumspinel、Meteorite pyrite, ironQuartzite、rutile、apatite, white phosphorite, copper, micaPentlanditeAnd some unidentified minerals.The chemical composition of lunar basalt varies greatly, especially AltwoOthreeAnd FeO, varying from 7 to 25% and 5 to 25% respectively, generally characterized by poor silicon, rich titanium and iron.
On October 19, 2021, the Chinese Academy of Sciences held a press conference to release research results: Chinese scientists found that the lunar magma activity had lasted until about 2 billion years ago through the lunar samples collected by Chang'e-5, and the life of the moon was about 800 million years longer than previously estimated.
By using the "ion probe ultra-high spatial resolution dating technology", "ultra-high spatial resolution isotope analysis technology" and "nano ion probe analysis technology", the scientific researchers of the Institute of Geology and Earth of the Chinese Academy of Sciences, the basalt brought back by Chang'e 5 was formed at an age of 2.030 ± 0.4 billion years, which means that the youngest basalt on the moon was formed 2 billion years ago.No radioactive heat generating elements such as potassium, rare earth elements, and phosphorus "Kripp substance" were found during the initial melting of basalt samples.By measuring the water content and hydrogen isotope composition of Chang'e-5 basalt, researchers found that "if the source rocks are divided into 1 million parts by weight, the water content only accounts for 1-5 parts", which indicates that the moon mantle is very "dry" and not rich in water.[7]
Mineral properties
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Because of XuanwuMagmaWith low viscosity and high fluidity, it is easy to form large-scale lava flow and lava blanket when it overflows the surface, but there are also layered intrusions, such asSillEtc.
In the ocean, it forms the ridge andisland。Related minerals include copper, cobaltSulfur、Iceland stone, gemstones, etc., which can also be acid resistantCast stoneRaw materials.
BasalticColumnar joint——In basalt lava flow, the vertical condensation surface often develops into regular hexagonal columnar joints.
It is generally believed that there are evenly distributed cooling centers (distributed in equilateral triangles, with the same distance between cooling centers) in uniform basic lava, and then the centers of each direction shrink to form hexagonal columnar joints.
Rock structure
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The crystallinity and grain size of basalt mainly depend on the cooling rate of magma.Slow cooling (such as several degrees of cooling per day) can generate crystals of several millimeters in size and the same size;Rapid cooling (e.g. 100 ℃ per minute) can generate fine needle like, plate like crystals or amorphous glass.Therefore, under the surface conditions, basalt is usually in fine-grained to aphanitic or glassy texture, and a few in medium grained texture.It often contains olivine, pyroxene and plagioclase phenocrysts, forming a porphyritic structure.Porphyritic crystals can gather in flowing magma, which is called porphyry structure.These phenocrysts were formed in the process of basalt magma rising through the crust (lasting several months to several hours), and also in the huge magma reservoir before eruption.The matrix structure changes greatly. With the thickness of rock flow, the speed of cooling and the amount of volatile components, there are various transition types between the whole crystalline and glassy, but mainly intergranular texture, interstitial texture, interstitial texture, less secondary diabase texture and diabase texture.
The basalt structure is related to its consolidation environment.The basalt formed on land often presents rope structure, block structure and columnar joint;The basalt formed underwater often has pillow structure.Porous structure and almond structure may occur in various basalts.
In explosive volcanic activity, hot basaltic lava erupted from the crater, and with the difference of its consolidation degree before landing, different shapes of volcanic bombs were formed: spindle shaped bombs, twist shaped bombs, irregular volcanic bombs, and cow dung shaped, cake shaped, straw hat shaped or snake shaped and flat splashed lava clusters.[2]
Formation process
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basalt
Is created byVolcano eruptionA kind of compact or foamy rock formed by cooling and solidifying magma.It is in the geologicalRock classificationMedium ofMagmatic rock(also called igneous rock).Magmatic rock is divided into intrusive rock andExtrusive rockTwo.The intrusive rock is the rock formed by underground magma invading the upper crust under the action of internal force, and the rock stratum is cooled and solidified. Its mineral crystal particles are large, representing that the rockGranite。The extrusive rock is the rock formed by the underground magma, under the action of internal force, ejecting from the surface along the weak zone of the crust to condense. Its mineral crystal particles are small, and some have streamline or pore structure, representing basalt.
Volcano eruptionThe temperature of the magma flowing out is as high as twelve hundred centigrade. Due to certain viscosity, the magma flows very slowly when the terrain is flat, and it flows only a few meters per minute;When encountering a steep slope, the speed will be greatly increased.In the process of flowing, it carries a large amount of water vapor and bubbles. After cooling, it forms various variant shapes.[3]
Main purpose
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basalt
Basalt is a good raw material for producing "cast stone"."Cast stone"It is a material made of basalt by melting, casting, crystallization and annealing. It is harder and more wear-resistant than alloy steel, and more resistant to corrosion than lead and rubber. Basalt is also an advanced steel casting process, playing the role of" lubricant ", which can extend the life of casting film. At the same time, Xuanwuyan can also be drawn into glass fiber, which is more than ordinaryGlass fiber clothStrong alkali resistance and high temperature resistance.
Porous basalt, also known asPumiceIt has many pores and is hard. You can mix it withconcreteIt can reduce the weight of concrete, which is not only strong and durable, but also has the characteristics of sound insulation and heat insulation. It is a high-rise buildingLightweight concreteGood aggregate.Pumice is also a good abrasive material, which can be used to grind metal and stone materials;In industry, it can also be used as filter, dryer, catalyst, etc.It is also widely used in landscape architecture, mainly forRockery, bonsai and so on, but also used in home decoration.
Basalt has excellent compression and bending resistance, good abrasion resistance and low water absorption. It is also a very good building decoration material, which can be widely used for indoor and outdoor decoration, and is mainly used as outdoor stone. Its color is natural, which can well coordinate with the surrounding landscape. It is not often suitable for outdoor landscape construction, especially the best choice of floor stone.However, as mentioned earlier, basalt is easy to form hexagonal columnar joints and brittle, so stone blocks are generally small, lacking large materials, and it is not easy to produce large size plates.
Basalt is widely used, and its application is not limited to the construction industry. For example, basalt is a good raw material for the production of "cast stone". After melting, casting, crystallization, annealing and other processes, it can form a new type of material that is hard and wear-resistant alloy steel, and more corrosion resistant than lead and rubber;Basalt can also play the role of "lubricant" in an advanced steel casting process, which can prolong the life of casting film;And basalt can also be drawn into glass fiber to make basaltGlass fiber clothIt is stronger than ordinary glass fiber cloth in alkali resistance and high temperature resistance.[4]
Basalt is the best material for repairing roads, railways and airport runways, with strong compression resistanceCrushing valueLow, strong corrosion resistance, asphalt adhesion basalt, basalt has the advantages of wear resistance, low water consumption, poor electrical conductivity, strong compression resistance, low crushing value, strong corrosion resistance, asphalt adhesion, etc., and is internationally recognized as the best cornerstone for the development of railway transportation and road transportation.
Some artists, according to pumice porous and wrinkle, leakage characteristics.It is used to build rockeries in gardens or carve small and exquisite bonsai.
In June 2024, the five-star red flag will rise on the back of the moon.This national flag is made by scientific researchers through more than a year's research and using the basalt melting wire drawing technology. It has better corrosion resistance, high temperature resistance, low temperature resistance and other excellent properties.The basalt stone comes from Yuxian County, Hebei Province. After the basalt is transported back, it should be crushed, melted and pulled into a thin wire about one-third of the diameter of the hair, and then spun into thread and woven into cloth.[8]
Eruption mode
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The occurrence of basalt shows two eruption modes:
Fissure eruption
They often form a large area of flood basalt,Fissure eruptionThe channel is often similar to the basaltDyke swarmsHowever, they are often buried by later rock flows and are not easy to find.Widely distributed in southwest ChinaMount Emei basaltIt is an example. It was formed in the Late Permian, with a distribution area of about 260000 square kilometers, a general thickness of 600~1500 meters, and the thickest part in the west of more than 3000 meters. It belongs to tholeiite, and is significantly rich in TiOtwo。In the flood basalt, the average thickness of a single rock flow is about 10~100m, and the flow distance can reach more than 100~150km.Basalt in a region is often formed by several or dozens of eruptions, and the interval between eruptions can be long or short, some as long as hundreds of thousands of years.
Central eruption
Constitute basaltVolcanic coneAnd adjacent lava flows andVolcaniclastic rock。The vast area in eastern China, starting from Heilongjiang in the north and ending at Hainan Island in the south, is a composite rock area dominated by alkaline basalt and tholeiite. It erupted in the Cenozoic era, dominated by central eruption, with hundreds of volcanic cones, especially in Heilongjiang Jilin, Inner Mongolia Plateau, Jining Datong, Nanjing, Yunnan Tengchong, GuangdongLeiqiong areaAnd Taiwan.
Domestic distribution
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Fujian ProvinceNingde Cityfuding Bai LinDazhang MountainThe reserve of basalt is 500 million cubic meters. The ore is exposed on the ground, dark black, dignified and elegant in color. It is a rare high-grade building board in China, belonging to the nationalBuilding stoneOne of the bases, named by the State Council Building Materials Administration“Fuding Black”。
Henan ProvinceLuoyang CityThe basalt in Caidian Township is in the shape of large and small blocks, with large reserves. It is widely distributed about 50 cm below the surface and can reach a depth of more than 100 meters. The ore is dark black and of good qualityHenan Communications Planning Survey and Design InstituteGeological Survey Test Center and Henan Highway Engineering Test and Testing Center have inspected various technical index requirements, and the results show that basalt stone has high hardness, high strength, good wear resistance, large anti sliding coefficient, strong adhesion with asphalt, etc., which is suitable for expressway asphalt pavementCoarse aggregateQuality requirements, it is the best stone for high-grade highway pavement, airport runway and railway ballast.
Anhui ProvinceChuzhou CityMingguang CityBasalt is rich in mineral resources, which are widely distributed in theMingguang CityChengxi Sub district Office in the west of the city, Provincial Highway 307 and 309, National Highway 104, Bengning Expressway, Tianjin Shanghai Railway run through the whole territory, and Xixu Industrial ParksandThe special wharf can berth 500 ton ships for direct navigationYangtze RiverThe location is superior and the transportation is very convenient.ProvedProspective reserves168 million tons, provenMining reserves34 million tons, the largest reserves in eastern Anhui, with an annual mining and processing capacity of more than 1 million tonsTongji UniversityThe scientific and technological detection is national first grade basalt.Basalt is producedCast stoneMain raw materials of.Cast stone has high chemical corrosion resistance and acid resistance, high hardness and mechanical strength, and is widely used in chemical industry, metallurgy, power, coal, building materials, textile and light industryindustrial sector 。Basalt is used to produce basalt paper, lime and volcanic rock without clinkercement、Decorative sheet、man-made fiberIt is also an energy-saving raw material in the ceramic industry.[5]
Basalt collection pictures of China Geological Museum
Description: Sample photos of basalt in Wenjiaqiao, Zhijin, China.khaki;SpotlessAphanitic texture；Stomatal structure almond structure;The main mineral composition is plagioclase and pyroxene.
