Distribution of rock below surface in open pit mining

1. Sedimentary rock is one of the three main rocks that make up the earth's lithosphere (the other two are magmatic rock and metamorphic rock). It is the weathering procts of other rocks and some volcanic eruptions that are transported and deposited by water or glaciers at a place not too deep on the earth's surface In the earth's surface, 70% of the rocks are sedimentary rocks, but if the whole lithosphere from the earth's surface to the depth of 16 km is calculated, only 5% of the sedimentary rocks are sedimentary rocks. Sedimentary rocks mainly include limestone, sandstone, shale and so on

2. There are many lighting methods for open pit mining. On the one hand, it is direct mining, that is, through development, and then it is necessary to do a good job in grassroots construction, that is, to prevent denghe and so on. In other words, it's OK to use explosive photos all the time or excavate with excavators.

3. According to the geomorphic characteristics of the alpine grassland in Longli, the landform is karst landform, and the main rock type in the area shown in the figure is sedimentary rock, which is mainly eroded by water e to external forces.
therefore, D

4.

Open pit mining of mineral resources is a common method. The depth of open pit mining of some deposits in the world has exceeded 300 m. Some open-pit mines are planned to have a mining depth of 500 meters, even nearly 1000 meters. The general trend of mining instry in the world is to vigorously develop open-pit mining. At present, open-pit mining accounts for more than 90% of China's iron ore mining, non-ferrous metals account for 46%, and the proportion of open-pit mining in coal mining is also increasing

In 1979, the death rate per million tons of coal in the former Federal Republic of Germany and the United States was 0.023, while the death rate per million tons of coal in the former Federal Republic of Germany was 0.05, a difference of nearly 50 times; 035 people died per million tons of coal in American open pit mining, while 0.45 people died per million tons of coal in underground mining, the difference is more than 12 times; In China, it is about 10 times. Open pit mining has the advantages of unlimited operation space, large scale, high mechanization, high labor proctivity and low mining cost, which is about 1 / 2 of the underground mining cost. Based on the above points, it is obvious that open pit mining is better than underground mining

2.4.1 scope of rock and soil movement caused by open pit mining. Under the same mining conditions, this range is mainly related to the flexibility of surrounding rock. The flexibility of rock mass is mainly determined by the mining depth h and the slope angle, in addition to the rock composition, the development degree and position of weak plane and discontinuity α， That is, geometric conditions. According to the similarity theory, the displacement relationship between the prototype and the model under the condition of self weight is:

environmental geology and engineering

where: Δ， L， ρ， E -- displacement, characteristic size, density and elastic molus of slope body

The

subscripts h and M represent the prototype slope body and the model slope body. According to this formula, the displacement ratio of similar slopes with the same constitutive relation but different sizes is equal to the square ratio of mining depth (or slope height), that is:

environmental geology and engineering

, that is to say, the deformation of the slope body caused by the self weight volume force, for an elastic homogeneous slope, If the height of the slope increases to N times, although the stress of the corresponding point of the slope also increases n times, the corresponding displacement point will increase to n < sup > 2 < / sup > times

2.4.2 basic model curve of surface movement distribution caused by open-pit mining according to the excavation test results of soft material simulation slope and some measured data of slope deformation, the model curve and deformation diagram reflecting the basic law of slope movement and deformation under open-pit mining conditions are given in the figure

In the field measurement, it is found that the phenomenon of rock and soil movement, deformation and failure caused by mining emerge in endlessly, which are mostly affected by faults and other weak surfaces. Due to the geometric asymmetry of the rock layers and their inclinations on the two sides of the pit, the mining of the open pit slope has steps, the difference of the deformation performance of the slope sections composed of various rock groups, and the change of the slope angle (or slope curvature) on different slope sections, the actual observation curve obtained is better than the model curve in detail, Even in some big aspects, there will be some differences

for the profile parallel to the surface boundary line, or longitudinal profile, the surface and slope surface movement distribution curve should be straight under the condition of plane strain. However, e to the change of engineering geological conditions along the longitudinal section, the measured curve is always different from a straight line

in Fig. 2.14 (a), the distribution curve of subsidence or vertical displacement reflects the basic characteristics of movement and deformation of rock and soil surface after mining. The convex part of the curve indicates that the corresponding section is stretched, or the surface is stretched e to excessive compression, while the concave part indicates the surface is compressed. It can be seen that the surface deformation outside the pit caused by open pit mining is tensile deformation. The failure mode of buildings also corresponds to the deformation characteristics of the foundation. Figure 2.14 (c) shows the general characteristics of the deformation of the non toppling failure slope, which has the same place with the toppling deformation slope in some aspects, and its basic curve of movement distribution is similar

Fig. 2.14 surface deformation diagram of open-pit mining. Even after the pit is closed, the deformation still occurs. For example, Jinchuan open pit mine, a famous nickel mine in China, was closed in 1990 and transferred to underground mining. Three years later, it was found that the deformation of the slope rock mass of the open pit mine has obvious development. Rock deformation can be divided into continuous process and periodic process. In fact, the continuous process is carried out at constant speed, such as subsidence, scattering, undercurrent collapse and surface water collapse. Periodic process is carried out with variable speed, such as landslide, landslide, etc. Periodic process is the most dangerous process. In order to carry out the design work and mining work correctly, we must understand the manifestation of mobile process and be able to predict its development characteristics and possible consequences. It is also necessary to reliably determine the measures that can ensure the stability of the bench, slope and mp ring the mining period, and calculate the main parameters. The following are the main manifestations of the movement process of the open-pit mine

2.4.3.1 subsidence

under the influence of self weight, external load, rainfall immersion and dynamic load, the surface of bench platform and mp formed by natural structure or damaged structure of porous loose rock has uneven vertical subsidence. When subsidence occurs, there is no continuous slip surface. Subsidence is the least dangerous form of instability, but under certain conditions, it may seriously affect the normal work

2.4.3.2 scattered

the destruction and movement of rock near the surface of steep slope is scattered. Scattering can last for a long time (some can last for several years), and this phenomenon can occur in all kinds of mine rocks. The development of scattering may cause large-scale instability, such as landslide, rock flow and so on

2.4.3.3 rock flow

some sandy clay rocks (powdery sand and clay, macroporous sandy clay and loess) whose structures have been destroyed move in the way of flow when they are filled with water. This kind of mobile rock can move in 4 °～ six ° And a smaller angle on the step platform. Rock flow contains a lot of rock, and it develops violently, sometimes causing disasters

2.4.3.4 collapse

collapse refers to the rapid movement of rock mass or rock block and rock stratum forming slope, and part of rock mass causing movement is broken. Generally, the fracture surface of the collapsed rock is consistent with various structural surfaces of the rock mass, and the inclination angle of the failure surface is generally greater than the internal friction angle of the rock mass. When the rock mass above the failure surface overcomes the cohesive force of the rock mass, the detached rock mass cannot be supported on the fracture surface by the friction force and continue to move down the slope. Violent collapse often occurs in a blink of an eye, which has great harm to the personnel and machinery working on the lower steps

2.4.3.5 landslide

is the whole local movement of the mine rock mass forming the slope, and its movement is in the form of relative sliding between the moving rock and the fixed rock mass below. This is a common and large-scale form of slope instability. It is related to the fracture surface and weak intercalation in rock mass. Sometimes it takes a long time for landslide to form, but once it is formed, it is often sudden and disastrous, which often leads to the complete stop of open-pit work

the most serious deformation and failure forms are landslides and collapses. For example, there are 50 recorded landslides in Fushun West open pit mine, causing huge losses. Among them:

(1) in 1960, the w1200 landslide in Nanbang destroyed the main facilities of coal upgrading in xidajuan, and the state invested more than 20 million yuan in the reinforcement project of xidajuan landslide

(2) according to statistics, from 1949 to 1980, the amount of landslide clearing was 6.5% × 10 < sup > 7 < / sup > m < sup > 3 < / sup >, and the expenditure reached 100 million yuan

(3) e to the unstable slope, the northwest slope may not reach the original design level. Due to the lack of research on slope problems in the design, the refinery is built on the north side, which limits the mining and expansion in the middle of the open pit. It is necessary to pay attention to the study of slope angle in open pit mining

The control and treatment of deformation and instability of open-pit slope will not be introced in detail here

5. They are sedimentary rocks, accounting for about 70% of the earth's surface< Sedimentary rock is one of the three main rocks that make up the earth's lithosphere (the other two are magmatic rock and metamorphic rock). It is the rock formed by the weathering procts of other rocks and some volcanic eruptions, which are transported, deposited and diagenesis by water flow or glaciers at a place not too deep on the surface. On the earth's surface, 70% of the rocks are sedimentary rocks, but if the whole lithosphere from the earth's surface to the depth of 16 km is calculated, only 5% of the sedimentary rocks are sedimentary rocks. Sedimentary rocks mainly include limestone, sandstone and shale.

6. Igneous rocks are also called magmatic rocks. Molten material from the earth's interior is a rock formed by cold solidification under different geological conditions. When the lava flows out of the volcanic channel, the rock solidified on the surface is called extrusive rock or volcanic rock. The common volcanic rocks are basalt, andesite and rhyolite. When the lava rises to the surface and condenses at a certain depth in the crust, it is called intrusive rock, which can be divided into plutonic rock and hypabyssal rock. Granite, gabbro and diorite are typical plutonic rocks. Granite porphyry, gabbro porphyrite and diorite porphyrite are common hypabyssal rocks. According to the chemical composition, igneous rocks can be divided into ultrabasic rocks (SiO2, less than 45%), basic rocks (SiO2, 45% - 52%), neutral rocks (SiO2, 52% - 65%), acidic rocks (SiO2, more than 65%) and alkaline rocks (containing special alkaline minerals, SiO2, 52% - 66%). Igneous rocks account for 64.7% of the crust volume. ②
sedimentary rocks
. Layered rocks are formed by transportation, deposition and diagenesis of weathering materials, Pyroclasts, organic matter and a small amount of cosmic materials under normal temperature and atmospheric pressure. According to its genesis, it can be divided into clastic rock, clay rock and chemical rock (including biochemical rock). The common sedimentary rocks are sandstone, tuffaceous sandstone, conglomerate, clay rock, shale, limestone, dolomite, siliceous rock, ferruginous rock, phosphorous rock, etc. Sedimentary rocks account for 7.9% of the volume of the crust, but they are widely distributed on the surface of the crust, accounting for about 75% of the land area, and the seafloor is almost completely covered by sediments. There are two outstanding characteristics of sedimentary rocks: one is stratigraphy, which is called bedding structure. The interface between layers is called bedding plane. Generally, the strata below are older than those above. Second, there are fossils in many sedimentary rocks, which are the remains of "lithized" ancient organisms or traces of survival and activity. They are precious data for determining geological age and studying paleogeographic environment, and are called "pages" and "characters" for recording the history of the earth. ③
metamorphic rocks
. Rocks formed by metamorphism of original rocks. According to the different types of metamorphism, metamorphic rocks can be divided into five types: dynamic metamorphic rocks, contact metamorphic rocks, regional metamorphic rocks, migmatites and metasomatic metamorphic rocks. The common metamorphic rocks are mylonite, cataclasite, hornblende, slate, phyllite, schist, gneiss, marble, quartzite, amphibolite, schist, eclogite and migmatite. Metamorphic rocks account for 27.4% of the crust volume. Rock has specific physical properties such as specific gravity, porosity, compressive strength and tensile strength. It is a factor to be considered in construction, drilling, tunneling and other projects. It is also the carrier of various mineral resources. Different kinds of rocks contain different minerals. Taking igneous rocks as an example, basic ultrabasic rocks are related to ferrophilic elements, such as chromium, nickel, platinum group elements, titanium, vanadium and iron; Acid rocks are related to lithophile elements such as W, Sn, Mo, be, Li, Nb, Ta and U; Diamond occurs only in kimberlite and lamprophyre; Chromite occurs mostly in pure peridotite; The early Yanshanian granites in South China are rich in W-Sn deposits; Independent tin deposits and Nb, Ta, be deposits are often formed in late Yanshanian granites. Oil and coal occur only in sedimentary rocks. Iron ores in Precambrian metamorphic rocks are worldwide. Many rocks are also important instrial raw materials. For example, Han jade (a kind of white marble) in Beijing is a famous building decoration material at home and abroad. Yuhua stone in Nanjing, Shoushan stone in Fujian and Qingtian stone in Zhejiang are good arts and crafts stones. Even the river sand and pebbles that are not noticed are also very useful building materials. Many rocks are also important raw materials for traditional Chinese medicine, such as Maifanshi (a kind of intermediate acid vein rock) is a very popular medicinal rock. Rock is also an important factor of tourism resources. The world's famous mountains, Dachuan, Qifeng and Yidong are all related to rock. Our ancestors have been using rocks since the stone age. Today, with the rapid development of science and technology, people's clothing, food, housing, transportation, travel, medicine and so on can not leave the rocks. Studying, using, storing, playing and loving rocks are no longer the patents of scientists, but graally become a part of people's life.

7. Molten material from the earth's interior is a rock formed by cold solidification under different geological conditions. When the lava flows out of the volcanic channel, the rock solidified on the surface is called extrusive rock or volcanic rock. The common volcanic rocks are basalt, andesite and rhyolite. When the lava rises to the surface and condenses at a certain depth in the crust, it is called intrusive rock, which can be divided into plutonic rock and hypabyssal rock. Granite, gabbro and diorite are typical plutonic rocks. Granite porphyry, gabbro porphyrite and diorite porphyrite are common hypabyssal rocks. According to the chemical composition, igneous rocks can be divided into ultrabasic rocks (SiO2, less than 45%), basic rocks (SiO2, 45% - 52%), neutral rocks (SiO2, 52% - 65%), acidic rocks (SiO2, more than 65%) and alkaline rocks (containing special alkaline minerals, SiO2, 52% - 66%). Igneous rocks account for 64.7% of the crust volume< Common magmatic rocks:
1. Granite is the most widely distributed plutonic intrusive rock. The main mineral components are quartz, feldspar and biotite, with light color, gray white and flesh red are the most common, with isogranular and massive structure. Granite is not only beautiful, but also has high compressive strength. It is a high-quality building material< 2. One kind of peridotite intrusive rock. The main mineral composition is olivine and pyroxene, dark green or greenish black, large specific, granular structure. Nickel, diamond, asbestos, siderite and talc are also related to these rocks< Basalt is one of the most widely distributed extrusive rocks. The mineral composition is mainly plagioclase and pyroxene, black or gray black, with pore structure and almond structure. Basalt itself can be used as excellent wear-resistant raw material for casting stone<

two sedimentary rocks
layered rocks formed by weathering materials, Pyroclasts, organic matter and a small amount of cosmic materials through transportation, deposition and diagenesis under normal temperature and atmospheric pressure. According to its genesis, it can be divided into clastic rock, clay rock and chemical rock (including biochemical rock). The common sedimentary rocks are sandstone, tuffaceous sandstone, conglomerate, clay rock, shale, limestone, dolomite, siliceous rock, ferruginous rock, phosphorous rock, etc. Sedimentary rocks account for 7.9% of the volume of the crust, but they are widely distributed on the surface of the crust, accounting for about 75% of the land area, and the seafloor is almost completely covered by sediments. There are two outstanding characteristics of sedimentary rocks: one is stratigraphy, which is called bedding structure. The interface between layers is called bedding plane. Generally, the strata below are older than those above. Second, there are fossils in many sedimentary rocks, which are valuable data for determining geological age and studying paleogeographic environment< Common sedimentary rocks:

1. Conglomerate is a kind of rock cemented by pebbles, gravels and other rocks and minerals with particle diameter greater than 2 mm. It is mostly thick bedded and massive, and the bedding is not obvious, in which the arrangement of gravels has certain regularity< 2. Rock cemented by sand grains with the diameter of 0.1-2 mm. It is widely distributed, mainly composed of quartz and feldspar, and its color is usually white, gray, light red and yellow< Shale is a kind of rock formed by compaction and cementation of various clays. It is one of the most widely distributed sedimentary rocks with obvious bedding and can be split into thin sections with various colors, such as black, red, gray, yellow, etc< Limestone, commonly known as "bluestone", is a kind of gray or gray white sedimentary rock formed in the sea and lake basin. It is mainly composed of calcite particles, which will react with dilute hydrochloric acid and give off bubbles. The color of limestone is mostly white, gray and black gray, which is dense and massive

three metamorphic rocks
rocks formed by metamorphism of original rocks. According to the different types of metamorphism, metamorphic rocks can be divided into five types: dynamic metamorphic rocks, contact metamorphic rocks, regional metamorphic rocks, migmatites and metasomatic metamorphic rocks. The common metamorphic rocks are mylonite, cataclasite, hornblende, slate, phyllite, schist, gneiss, marble, quartzite, amphibolite, schist, eclogite and migmatite. Metamorphic rocks account for 27.4% of the crust volume. Rock has specific physical properties such as specific gravity, porosity, compressive strength and tensile strength. It is a factor to be considered in construction, drilling, tunneling and other projects. It is also the carrier of various mineral resources. Different kinds of rocks contain different minerals. Taking igneous rocks as an example, basic ultrabasic rocks are related to ferrophilic elements, such as chromium, nickel, platinum group elements, titanium, vanadium and iron; Acid rocks are related to lithophile elements such as W, Sn, Mo, be, Li, Nb, Ta and U; Diamond occurs only in kimberlite and lamprophyre; Chromite occurs mostly in pure peridotite; The early Yanshanian granites in South China are rich in W-Sn deposits; Independent tin deposits and Nb, Ta, be deposits are often formed in late Yanshanian granites. Oil and coal occur only in sedimentary rocks. Iron ores in Precambrian metamorphic rocks are worldwide. Many rocks are also important instrial raw materials. For example, Han jade (a kind of white marble) in Beijing is a famous building decoration material at home and abroad. Yuhua stone in Nanjing, Shoushan stone in Fujian and Qingtian stone in Zhejiang are good arts and crafts stones. Even the river sand and pebbles that are not noticed are also very useful building materials. Many rocks are also important raw materials for traditional Chinese medicine, such as Maifanshi (a kind of intermediate acid vein rock) is a very popular medicinal rock. Rock is also an important factor of tourism resources. The world's famous mountains, Dachuan, Qifeng and Yidong are all related to rock. Our ancestors have been using rocks since the stone age. Today, with the rapid development of science and technology, people's clothing, food, housing, transportation, travel, medicine and so on can not leave the rocks. Studying, using, storing, playing and loving rocks are no longer the patents of scientists, but graally become a part of people's life< Common metamorphic rocks:

1. Marble is formed by recrystallization and metamorphism of limestone or dolomite. Particle ratio: Limestone coarse, mineral composition is mainly calcite, acid violent reaction, generally white, such as containing different impurities, there are a variety of different colors. Marble is not hard and easy to carve. It is very beautiful after polishing. It is often used as decoration and building stone< 2. Slate is metamorphosed from shale and clay. The mineral composition can only be seen under the microscope. When knocking, it makes a clear sound and has obvious plate structure. The surface of the board is slightly glossy, with a variety of colors, including gray, black, gray green, purple, red, etc. it can be used as roof tile and writing slate< 3. Gneisses are mostly metamorphosed from magmatic rocks. The main mineral components are quartz, feldspar, biotite and amphibole. The mineral grains are black-and-white and arranged in continuous strips, forming gneissic structure. The lithology is hard, but it is easy to be weathered and broken

8. At present, it is more authoritative to say that surface sedimentary rocks account for 75%, magmatic rocks and metamorphic rocks account for 25%.

9.

The earth is mainly composed of solid materials except for the outer core and a small amount of melt / fluid hosted in the crust or upper mantle. On land, the volume fraction of surface sedimentary rocks is about 66%, and the rest of igneous rocks and metamorphic rocks are about half. Under the ocean, the sediments and sedimentary rocks form a thin layer covering the lower igneous and metamorphic rocks, which form the main body of the oceanic crust

The formation and differentiation of the earth is a planet in the solar system, which revolves around the sun together with other planets and has the same direction of rotation and nearly the same orbital plane. The planets in the solar system can be divided into two categories. One is terrestrial planets, which are small and composed of high density (4-5.5g / cm < sup > 3 < / sup >) rocky materials, including mercury, Venus, earth, Mars and Pluto; The other is giant planets, which are large and composed of low density (0.7-1.7g / cm < sup > 3 < / sup >) gaseous materials, including Jupiter, Saturn, Uranus and Neptune. Their characteristics are more similar to the sun and are quite different from earth like planets. According to the study of the earth, moon and meteorite samples, the mass fraction of O, Fe, Si and Mg in the earth like planets is 90%, while the mass fraction of H and he in the giant planets and the sun is 99%

the earth is an evolving planet, which has evolved from a sphere with homogeneous primitive material to a planet with stratiform structure. This process is directly related to the action of atmosphere, ocean, continent, mountain range, volcano and magnetic field. About 4.7 GA (4.7 GA) ago, the microplanet had condensed, accumulated and proliferated, mainly the oxides of Si, Fe, Mg and other chemical elements. They are cold when they condense. In the process of the earth evolution, the combined effects of (1) the kinetic energy of the impact of Planetary Materials on the earth ring the accretion process is transformed into heat energy; (2) the volume of the earth itself is reced e to the gravitational pressure, which makes the earth heated internally; and (3) the heat energy proced by the decay of radioactive elements, which causes the earth to change from cold to hot. According to Hanks and Anderson's simulation calculation of the earth's early temperature (Fig. 1-1), after the formation of the earth for 1 billion years (1gA), the temperature has reached the melting temperature of iron at 400km to 800km inside the earth. Because Fe is the heaviest element in the earth, when it melts, it forms large droplets and falls to the center of the earth, where light matter rises. It is estimated that Fe accounts for 1 / 3 of the earth's mass. The melting and sinking of Fe forms the earth's core and releases huge gravitational energy, which is finally converted into heat energy, which is similar to the principle that the drop of water is converted into electric energy. During the formation of the iron core, the average temperature of the earth rose to 2000 ℃, resulting in the melting of most of the earth's internal materials and the uniform differentiation of the earth. The melted low melting point component, which is less dense than the original material, floats upward and forms the original crust. Between the core and the crust, there is a mantle dominated by Si and Mg. The earth forms a stratospheric structure, and the same kind of material is roughly at the same depth. The formation of the crust eventually developed into a continent

Fig. 1-1 in different geological periods, the formation and degassing of the earth's oceans are also an important part of the earth's differentiation. At first, water did not exist in a free state, but existed in minerals (such as mica) as (OH) roots. When the temperature inside the earth increased and melted, water was released from it and accompanied by molten magma ejected from the earth's surface to form steam, which graally fell to the surface, forming an ocean accounting for 70% of the earth's surface area. Water vapor is accompanied by other gases, which become part of the atmosphere

The formation and differentiation of the earth is a complex process, and different scholars have different understandings on the division of stages, the change of internal temperature, the original condensation and other issues. The above is just a simple outline, interested parties can refer to the relevant reference books

2) the stratospheric structure of the earth

after differentiation, the earth has stratospheric structure. According to the geophysical data, the earth can be divided into three first-order stratospheres: the core, the mantle and the crust, in which the core accounts for (1.083 × 10 < sup > 21 < / sup > m < sup > 3 < / sup >). There are obvious discontinuities (or belts) with abrupt change of seismic wave velocity distributed among the three circles, and the chemical composition of the three circles is significantly different. Therefore, the discontinuities are mainly caused by the difference of chemical composition. The inner layer of each layer circle can be layered again. The layered interface between the core and mantle is mainly caused by the physical action, that is, the change of temperature and pressure makes the mineral phase change. The core is further divided into inner core and outer core, which are mainly composed of Fe elements, and Si and Ni are secondary components. The outer core is liquid because the temperature and pressure conditions make Fe melt. The interface between the core and mantle is Gutenberg discontinuity. The mantle can be further divided into upper mantle, transition zone and lower mantle, which are all composed of Mg rich rocks. The interface between the upper mantle and the transition zone is related to olivine phase transition β The depth of phase spinel is the same (400km); The interface between the transition zone and the lower mantle is consistent with the depth at which the minerals transform into perovskite structure (640-670km). The interface between mantle and crust is called Mohorovicic discontinuity or Moho for short. The crust is composed of feldspar and other silicate minerals, but some of them are Fe and Mg rich silicates, which are traditionally called silicomagneiss. The oceanic crust is composed of silicomagneiss. The upper part of the continental crust is composed of Al rich silicates, which is traditionally known as the silicoaluminum layer. However, the lower part of the continental crust is complex in composition, with the coexistence of igneous rocks and metamorphic rocks mainly composed of aluminosilicate and magnesiosilicate. The stratospheric structure of the earth is shown in Figure 1-2. On the right is an enlarged view of the upper mantle and crust

Fig. 1-2 diagram of the earth's stratospheric structure

from Fig. 1-2, we can see that the composition of continental crust is complex, with an average thickness of 33km; The composition of the oceanic crust is simple, with an average thickness of less than 10km. Lithosphere is a tectonic layer composed of crust and upper mantle, which is divided by the popular plate theory in recent 30 years. It has rigid characteristics. The thickness of the lithosphere is 150 km, but varies in different tectonic units, ranging from 60 km to more than 200 km. Asthenosphere is a stratosphere characterized by high temperature plasticity, in which there are not only solid mantle rocks, but also partial melting melts. Therefore, the asthenosphere has low seismic wave velocity. The thickness of the asthenosphere also varies. In some stable areas, such as the shield (craton), there is no asthenosphere, so it is difficult to show on the seismic profile. The bottom boundary of the asthenosphere is 640km in the figure, and some people have determined it as 670km, which is equivalent to the boundary between the transition zone and the lower mantle. The lower left part of the graph shows the approximate growth curve of temperature and pressure from the surface to the core. Near the surface, the ground temperature increases rapidly with the depth, that is, the ground temperature gradient is large; Within the mantle, the slope of the curve slows down. In the horizontal direction, the geothermal gradients of different tectonic positions are different. In the volcanic activity zone such as island arc volcanic area, the geothermal gradients are 30-500 ℃ / km or higher, while in the oceanic trench, the geothermal gradients are only 5-10 ℃ / km. The ground temperature of the stable continental region is generally between the above two. Under normal conditions, the earth's internal pressure can be estimated by the density of matter:

petrology

where: ρ—— Density; G - acceleration of gravity, H - depth of burial

in the crust, the relationship between pressure and depth is 0.1GPa for every 3.3km increase in depth

The distribution of the three types of rocks in the earth's surface this section introces the distribution of the three types of rocks based on the theory of plate tectonics

The theory of plate tectonics was developed in the early 1960s. Although it has obvious shortcomings in explaining continental tectonics and tectonism in geological history, it is still the best theory to explain global tectonics. According to the most basic concepts of plate tectonics, this section introces the types and combinations of the three types of rocks in different tectonic positions (Fig. 1-3), so as to enable beginners to establish an overall framework for the distribution of rocks. For a detailed introction, see Chapter 5 of this textbook

Fig. 1-3 rock association diagram of different plate parts