rocks are naturally occurring mineral aggregates with certain structural structures, which are the material basis of the crust and upper mantle. According to the origin, it can be divided into magmatic rocks, sedimentary rocks and metamorphic rocks. Among them, magmatic rocks are rocks formed by the condensation of molten magma at high temperature on the surface or underground, also known as igneous rocks; Sedimentary rocks are rocks formed by the products of weathering, biological action and volcanism under the surface conditions, which are transported, deposited and consolidated by external forces such as water, air and glaciers. Metamorphic rock is a rock formed by metamorphism due to the change of geological environment, which is formed by pre-existing magmatic rock, sedimentary rock or metamorphic rock.
The deep crust and the upper mantle are mainly composed of igneous rocks and metamorphic rocks. The volume of igneous rocks and metamorphic rocks within 16 kilometers from the surface accounts for 95%. The surface of the crust is dominated by sedimentary rocks, which account for about 75% of the continental area, and the ocean floor is almost completely covered by sediments.
Kuko Buchuan replied (November 21, 26):
Rock is a mineral aggregate formed by the regular combination of one or more minerals under various geological processes. For example, marble is mainly composed of calcite, while granite is composed of Shi Ying, feldspar, mica and other minerals. According to the genesis, rocks can be divided into three categories: magmatic rocks formed by magmatic activities, sedimentary rocks formed by external forces, and metamorphic rocks formed by metamorphism. It is of great significance to study rocks: a. Humans need various minerals, and certain minerals are related to certain rocks. B. rocks are the material basis for studying various geological structures and landforms. C. rocks are the basis for studying the history of the crust. A
rock is a natural mineral aggregate with a certain structural structure, which is the material basis of the crust and upper mantle. According to the origin, it can be divided into magmatic rocks, sedimentary rocks and metamorphic rocks. Among them, magmatic rocks are rocks formed by the condensation of molten magma at high temperature on the surface or underground, also known as igneous rocks; Sedimentary rocks are rocks formed by the products of weathering, biological action and volcanism under the surface conditions, which are transported, deposited and consolidated by external forces such as water, air and glaciers. Metamorphic rock is a rock formed by metamorphism due to the change of geological environment, which is formed by pre-existing magmatic rock, sedimentary rock or metamorphic rock.
The deep crust and the upper mantle are mainly composed of igneous rocks and metamorphic rocks. The volume of igneous rocks and metamorphic rocks within 16 kilometers from the surface accounts for 95%. The surface of the crust is dominated by sedimentary rocks, which account for about 75% of the continental area, and the ocean floor is almost completely covered by sediments.
Petrology mainly studies the material composition, texture, structure, classification and nomenclature, formation conditions, distribution law, genesis, metallogenic relationship and evolution process of rocks. It belongs to an important basic discipline in geological science.
at the end of 18th century, petrology was born out of mineralogy and developed into an independent discipline. In the early stage of petrology development, igneous rocks were mainly studied, and metamorphic rocks began to be systematically studied in the middle of the nineteenth century, while sedimentary rocks did not attract people's attention until the early twentieth century. At present, petrology is developing along three main branches: magmatic petrology, sedimentary petrology and metamorphic petrology.
ancient rocks all appear in the crystalline basement of the mainland. The representative rocks belong to basic and ultrabasic igneous rocks. These rocks have been transformed into metamorphic rocks rich in chlorite and amphibole due to strong metamorphism, which is usually called greenstone. For example, in 1973, granite gneiss with an isotopic age of about 3.8 billion years was discovered in West Greenland. In 1979, Batun et al. determined the age of gneiss in the middle of Bobo forest belt in South Africa about 3.9 billion years.
akasca gneiss, a metamorphic rock in northern Canada, is a well-preserved part of the ancient earth's surface. Radioactive dating shows that the Akaska gneiss is nearly 4 billion years old, which shows that some continental materials existed hundreds of millions of years after the formation of the earth.
Recently, scientists discovered a batch of the oldest rocks in southwest Australia. According to the isotope analysis results of zircon mineral crystals contained in them, it shows that their "age" is about 4.3 billion to 4.4 billion years old, which is the oldest rock sample found so far. According to this discovery, it can be inferred that when these rocks were formed, there were continents and oceans on the earth. After the earth was born 2 million to 3 million years ago, it may not be covered with hot magma as people think, but it has cooled to a temperature enough to form a solid surface and ocean. The differentiation of the earth's sphere may have been completed 4.4 billion years ago.
At present, the oldest rock found in China is the granite gneiss in eastern Hebei, in which the age of xenoliths is about 3.5 billion years.
Mineral composition of rock
The variety and content of light-colored minerals and dark-colored minerals in different igneous rocks are regular. According to color ratio, igneous rocks are divided into four categories:
The color ratio of light-colored rocks is -35; The color ratio of mesomorphic rocks is 35-65; The color ratio of dark rock is 65-9; The color ratio of dark and dark rocks is 9-1
Chemical composition of rocks < P > Magmatic rocks are mainly composed of silicate minerals, and silica is the most important component. According to its content, igneous rocks can be divided into: < P > ultrabasic rocks SiO 2 < 45%; 45 ~ 52% of basic rocks < P > 52 ~ 65% of intermediate rock SiO _ 2; Acidic rock SiO _ 2 > 65% < P > Occurrence mode of rock < P > According to its occurrence environment, it can be divided into plutonic rock, shallow rock and extrusive rock. Plutonic rocks often have holocrystalline structure, and extrusive rocks are mostly glassy or aphanitic.
Quantitative mineral composition
The variety and content of light-colored minerals and dark-colored minerals in different igneous rocks are regular. According to the color ratio, igneous rocks are divided into four categories:
The color ratio of light-colored rocks is -35; The color ratio of mesomorphic rocks is 35-65; The color ratio of dark rock is 65-9; Chemical composition of dark rock with color ratio of 9-1
Magmatic rocks are mainly composed of silicate minerals, and silica is the most important component. According to its content, igneous rocks can be divided into: < P > ultrabasic rocks with SiO _ 2 < 45%; 45 ~ 52% of basic rocks < P > 52 ~ 65% of intermediate rock SiO _ 2; Acidic rock SiO _ 2 > 65% < P > Occurrence mode of rock < P > According to its occurrence environment, it can be divided into plutonic rock, shallow rock and extrusive rock. Plutonic rocks often have holocrystalline structure, and extrusive rocks are mostly glassy or aphanitic.
A small group of glutinous rice replied (November 21, 26):
Rock is a natural mineral aggregate with a certain structure, which is the material basis of the crust and upper mantle. According to the origin, it can be divided into magmatic rocks, sedimentary rocks and metamorphic rocks. Among them, magmatic rocks are rocks formed by the condensation of molten magma at high temperature on the surface or underground, also known as igneous rocks; Sedimentary rocks are rocks formed by the products of weathering, biological action and volcanism under the surface conditions, which are transported, deposited and consolidated by external forces such as water, air and glaciers. Metamorphic rock is a rock formed by metamorphism due to the change of geological environment, which is formed by pre-existing magmatic rock, sedimentary rock or metamorphic rock.
The deep crust and the upper mantle are mainly composed of igneous rocks and metamorphic rocks. The volume of igneous rocks and metamorphic rocks within 16 kilometers from the surface accounts for 95%. The surface of the crust is dominated by sedimentary rocks, which account for about 75% of the continental area, and the ocean floor is almost completely covered by sediments.
Petrology mainly studies the material composition, texture, structure, classification and nomenclature, formation conditions, distribution law, genesis, metallogenic relationship and evolution process of rocks. It belongs to an important basic discipline in geological science.
at the end of 18th century, petrology was born out of mineralogy and developed into an independent discipline. In the early stage of petrology development, igneous rocks were mainly studied, and metamorphic rocks began to be systematically studied in the middle of the nineteenth century, while sedimentary rocks did not attract people's attention until the early twentieth century. At present, petrology is developing along the three main branches of magmatic petrology, sedimentary petrology and metamorphic petrology
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Basic definition
Rock is a natural mineral or glass aggregate with stable appearance, which is combined in a certain way. It is the material basis of the crust and upper mantle. According to the origin, it can be divided into magmatic rocks, sedimentary rocks and metamorphic rocks. Among them, magmatic rocks are rocks formed by the condensation of molten magma at high temperature on the surface or underground, also known as igneous rocks or extrusive rocks; Sedimentary rocks are rocks formed by the products of weathering, biological action and volcanism under the surface conditions, which are transported, deposited and consolidated by external forces such as water, air and glaciers. Metamorphic rock is a rock formed by metamorphism due to the change of geological environment, which is formed by pre-existing magmatic rock, sedimentary rock or metamorphic rock.
The deep crust and the upper mantle are mainly composed of igneous rocks and metamorphic rocks. The volume of igneous rocks and metamorphic rocks within 16 kilometers from the surface accounts for 95%. The surface of the crust is dominated by sedimentary rocks, which account for about 75% of the continental area, and the ocean floor is almost completely covered by sediments.
properties of rocks
the engineering properties of rocks are undoubtedly the factors of material composition (properties of particles themselves), structure (connection between particles), structure (forming environment, transformation and construction) and existing environment (stress, temperature and water). If it is a rock mass, it depends on both structural plane and rock mass. In most cases, structural plane plays a controlling role.
the history of rocks
when the earth came into being, the gravity of the core sucked the dust in the universe, and the condensed dust turned into rocks, which became rocks after weathering. Then it becomes a meteorite. When it does not fall into the earth's atmosphere, it is a stone, iron or a mixture of stone and iron that is free from outer space. If it falls into the atmosphere, it will become a meteorite we usually see when it falls to the ground without being burned by the atmosphere. Simply put, the so-called meteorite is the debris left by a miniature asteroid "hitting the earth". Hundreds of millions of years have passed and there are countless rocks in the world. Nowadays, in the field of geotechnical engineering, human beings often divide rocks into four types according to their engineering properties: extremely hard, hard, moderately hard and weak. It is developing in the quantitative direction.
ancient rocks all appear in the crystalline basement of the mainland. The representative rocks belong to basic and ultrabasic igneous rocks. These rocks have been transformed into metamorphic rocks rich in chlorite and amphibole due to strong metamorphism, which is usually called greenstone. For example, in 1973, granite gneiss with an isotopic age of about 3.8 billion years was discovered in West Greenland. In 1979, Batun et al. determined the age of gneiss in the middle of Bobo forest belt in South Africa about 3.9 billion years.
akasca gneiss, a metamorphic rock in northern Canada, is a well-preserved part of the ancient earth's surface. Radioactive dating shows that the Akaska gneiss is nearly 4 billion years old, which shows that some continental materials existed hundreds of millions of years after the formation of the earth.
Recently, scientists discovered a batch of the oldest rocks in southwest Australia. According to the isotope analysis results of zircon mineral crystals contained in them, it shows that their "age" is about 4.3 billion to 4.4 billion years old, which is the oldest rock sample found so far. According to this discovery, it can be inferred that when these rocks were formed, there were continents and oceans on the earth. After the earth was born 2 million to 3 million years ago, it may not be covered with hot magma as people think, but it has cooled to a temperature enough to form a solid surface and ocean. The differentiation of the earth's sphere may have been completed 4.4 billion years ago.
At present, the oldest rock found in China is the granite gneiss in eastern Hebei, in which the age of xenoliths is about 3.5 billion years.
the microfossils in the Warrawoona group in western Australia are relatively complete in morphology and structure. Whether they are cyanobacteria or bacteria is still difficult to determine. It is generally believed that the early stromatolite was built by cyanobacteria, and stromatolite is an indicator of the existence of cyanobacteria. If cyanobacteria appeared 3.5 billion years ago, it means that photosynthesis of releasing oxygen has already started, which leads to a question: Why didn't free oxygen accumulate in the atmosphere until 2 billion years ago? There is a gap of 1.5 billion years from 3.5 billion years ago to 2 billion years ago. Why is the accumulation of oxygen so slow? Of course, there are different explanations. For example, in recent years, it has been found that stromatolites may also be constructed entirely by photosynthetic bacteria, or even by non-photosynthetic bacteria.
The most important indirect evidences of the existence of the oldest life are the banded iron formation (BIF) and light carbon isotopes in western Greenland. If the evidence is established, it can be inferred that microorganisms that carry out oxygen-releasing photosynthesis have appeared on the earth 3.8 billion years ago, that is, organisms similar to cyanobacteria. According to Cloud's explanation, BIF is deposited by the oxidation of ferrous iron into high-valent iron due to the periodic release of oxygen by light and microorganisms. Light carbon isotopes are also indirect evidence of photosynthesis. However, the objection is that the oxygen required for the formation of BIF can be provided by the photodegradation of water molecules in the atmosphere, while the light carbon isotope may come from the thermal decomposition of carbonate.
at the end of 18th century, petrology was born out of mineralogy and developed into an independent discipline. In the early stage of petrology development, igneous rocks were mainly studied, and metamorphic rocks began to be systematically studied in the middle of the nineteenth century, while sedimentary rocks did not attract people's attention until the early twentieth century. At present, petrology is developing along three main branches: magmatic petrology, sedimentary petrology and metamorphic petrology.
application of rocks
1. rocks used as building materials
1. marble: marble has a fine texture and is often used as a wall or floor. Because marble is metamorphic from limestone, the main component is calcium carbonate, so it is also the raw material for manufacturing cement. Marble is soft and delicate, and it is a good sculpture stone. Many famous statues are made of marble, such as the famous statue of Venus. Others, such as walls or decorations, are often made of marble, such as vases, ashtrays, tables and other household items.
2. Huagangyan: The native Huagangyan can only be seen in Jinmen, so almost all the old houses in Jinmen are made of Huagangyan. Huagang Rock used in temples in Taiwan Province, which comes from Fujian, is mostly used for dragon pillars, floor tiles and stone lions in temples.
3. Slate: Because it is easy to crack into thin plates and can be easily obtained in mountainous areas, indigenous people still use slate as building materials to build stone slab houses or fences.
4. Conglomerate: Some conglomerates contain pebbles and sand, which are easily dispersed due to poor cementation. For example, this kind of conglomerate is found in the Quaternary Touji Mountain in western Taiwan, in which pebbles and sand are building materials.
5. Limestone: The most common limestone in Taiwan Province is formed by coral, commonly known as coral reef limestone. In Penghu, coral reef stone is commonly known as "stone", which is used by residents as a wall building material to shield the strong northeast monsoon and protect crops.
6. Mudstone: Because its main component is clay, it has been used as raw material for bricks and pottery since ancient times.
7. andesite: due to its hard material, it is also often used as the dragon column of temples, stone carvings of walls, tombstones, floor tiles, etc.
2. Minerals from which metals can be extracted
1. Gold deposit: After weathering and erosion of gold-bearing rocks, gold will be separated into natural gold, because gold is much heavier than sediment, and it is easy to deposit and become gold after elutriation.
2. Chalcopyrite: Chalcopyrite is the most important mineral for extracting copper.
3. galena: square