Clastic sedimentary rock. Chemical sedimentary rock. Clastic sedimentary rocks What clastic rocks form from

Clastic rocks

clastic rocks, sedimentary rocks, consisting entirely or predominantly. from fragments of various rocks (igneous, metamorphic or sedimentary) and minerals (quartz, feldspars, micas, sometimes glauconite, volcanic glass, etc.). Distinguish O. of the item cemented and not cemented, friable. Carbonates (calcite, dolomite), silicon oxides (opal, chalcedony, and quartz), iron oxides (limonite, goethite, and others), clay minerals, and a number of other clay minerals serve as a binder in cemented O. G. p. often contain organic remains: shells of mollusks, etc., trunks and branches of trees, etc. The classification of O. g. p. is based on a structural feature - the size of the fragments. Coarse-clastic rocks are distinguished, or Psephites, with a fragment size of more than 1 mm(uncemented - blocks, boulders, pebbles, crushed stone, gruss, gravel; cemented - Conglomerates, breccias (See Breccia), Gravelites, etc.); sandy rocks, or psammites, with a particle size of 1-0.05 mm(sands and sandstones); silty rocks, or silts, with a particle size of 0.05-0.005 mm(siltstones and siltstones); clayey rocks, or pelites, with a particle size of less than 0.005 mm(clays, mudstones, etc.). Sometimes the boundary between silts and pelites is drawn by the particle size of 0.001 mm. Clay rocks can be of both chemical and detrital origin. There are also sedimentary deposits of mixed composition, composed of fragments of various sizes - sandy, silty, and clayey. These include widespread, especially among modern continental deposits, various loams and sandy loams. The further subdivision of the O. g. p. within the limits of structural subtypes is made according to the mineral composition of the fragments and other features. The products of volcanic eruptions also belong to volcanic eruptions: volcanic rubble, ash - loose rocks and their cemented varieties - tuffs, tuff breccias and rocks transitional between detrital and volcanogenic - tuffites and tuffaceous rocks (see Volcanic-sedimentary rocks).

With a dissected relief and high dynamics of the environment, coarse clastic rocks are formed, in conditions of a flat relief and a low speed of water and air flows, sand, silt and clay rocks are formed. Clay particles settle mainly in still water. In the coastal part of the seas and oceans, pebbles and gravel are deposited on the beach and shallow water; as they move deeper into the basin, they are replaced by sands, silts, and, finally, clayey silts at a depth below the level of action of waves and currents. However, there are pebbles and sands at great depths - the result of the action of various bottom currents and turbidity flows (See Turbidity Streams).

O. g. p. is used as a building material, sands are used in the glass and metallurgical industries. Placers of gold, platinum, precious stones, titanium minerals, tin, tungsten, rare and radioactive elements are found in river and sea sands.

Lit.: Logvinenko N.V., Petrography of sedimentary rocks (With the basics of research methods), 2nd ed., M., 1974; Rukhin L. B., Fundamentals of Lithology, 3rd ed., L., 1969.

N. V. Logvinenko.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Clastic rocks" are in other dictionaries:

Clastic rocks (a. clastic rock, fragmented rock, detrital rock; n. klastische Gesteine, Trummergesteine; f. roches detritiques, roches clastiques, roches agregees; i. rocas detriticas, rocas clasticas), sedimentary horns. breeds... Geological Encyclopedia

Rocks consisting of fragments of older rocks and minerals. According to the size of the fragments, coarse clastic (psephites), sandy (psamites), silty (siltstones, siltstones) and clayey (pelites) rocks are distinguished ... Big Encyclopedic Dictionary

Rocks consisting of fragments of older rocks and minerals. According to the size of the fragments, coarse clastic (psephites), sandy (psamites), silty (siltstones, siltstones) and clayey (pelites) rocks are distinguished. * * * CLASTIC ROCKS… … encyclopedic Dictionary

Rocks consisting of fragments of more ancient forges. rocks and minerals. According to the size of the fragments, coarse clastic (psephites), sandy (psamites), silty (siltstones, siltstones) and clayey (pelites) rocks are distinguished ... Natural science. encyclopedic Dictionary

A variety of sedimentary rocks, consisting of fragments of other rocks and minerals (usually quartz, feldspars, micas, sometimes glauconite, volcanic glass). There are cemented rocks (conglomerates and breccias), in which ... ... Geographic Encyclopedia

Natural aggregates of minerals of more or less constant composition, forming independent geological bodies that make up the earth's crust. The term "G. P." for the first time in the modern sense used (1798) Russian mineralogist and chemist V. M. Severgin ... Great Soviet Encyclopedia

Rocks formed by the accumulation of mineral substances, mainly from the aquatic environment, during their compaction and cementation. There are: chemical precipitation (gypsum, rock salt), detrital (gravel, sand, clay rocks), cemented ... ... Construction dictionary

The solid crust of the globe and its entire solid core are composed of mineral aggregates. G. rocks are those of these aggregates that play a significant role in the composition of the lithosphere, revealing in the main features the constancy of composition and structure in ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

Accumulations of destruction products of sedimentary rocks of various petrographic compositions and sizes, formed from loose or cemented fragments. Loose rocks varieties (mechanical deposits) sedimentary (boulders, ... ... Construction dictionary

Rocks that have arisen by the deposition of matter in the aquatic environment, less often from the air and as a result of the activity of glaciers. Sedimentation occurs mechanically, chemically and biogenically. Sedimentary rocks are divided into clastic, chemical and ... ... encyclopedic Dictionary

SEDIMENTARY CLASTIC, SANDY, CLAY AND MIXED (SAND-CLAY) ROCKS

Clastic rocks and their classifications

These classes include well-known loose rocks - sand, crushed stone, pebbles, gravel; cemented rocks, among which the most famous is sandstone, as well as clay rocks - clay, loam, sandy loam.

These rocks differ greatly from each other in composition and properties, but in nature the transition from clastic to clayey rocks is very gradual, with a large number of mixed varieties, which makes it necessary to consider these classes within one section.

Classification. The section considers five classes of rocks - coarse-clastic, sandy, fine-clastic, clay and mixed. For brevity, we agree to call them all clastic and argillaceous. As can be seen, they are all classified by size, clast shape, cementation, and connectivity (Table 3.5).

Sedimentary detrital, clayey and mixed rocks

Table 3.5

Structure and particle size, mm	Breed name
	Texture
	Uncemented		Cemented
	Angular	rounded	Angular	rounded
1. Coarse fragments: more than 1000			blocky	blocky conglomerate
	Neo-tanned boulders (stones)		boulder	boulder conglomerate
		gravel		Conglomerate
				gravelite
2. Medium clastic - sandy (0.05-2):	Sands (according to the predominant fraction): gravelly (rough)		Sandstones (according to the predominant fraction): gravelly (rough)
	dusty (thin)		dusty (thin)
3. Small debris - dusty: 0.002 ... 0.05			Siltstone
4. Micrograined - clayey: less than 0.002 (0.005)			Argillite
5. Mixed	Dust-clay sand with crushed stone and gravel, gravel with sandy gravel aggregate, etc.		Sandy conglomerate, sandy gravel, etc.		loam,

Compound. These rocks consist of products of mechanical and chemical destruction and transformation of other rocks on the surface of the earth. In the vast majority of cases, they are soil-forming material, most of the construction and other environmental management is carried out on them, they are often called the word "soil".

In the composition of clastic and clayey rocks, three main components are distinguished - fragments, cement and clay material.

1. debris material - the main component of clastic rocks is stone material consisting of blocks, boulders, pebbles, gravel, crushed stone, grains of sand that form sand, quartz mineral dust. All this can be represented by various rocky or semi-rocky rocks, and the name of the original rock can only be mentioned - crushed granite, limestone pebbles, quartz sand. Cobblestone, rubble, pebble, paving stones - natural or specially processed and selected stone tens of centimeters in size, used in construction for paving roads and laying foundations.

According to the shape, two main types of fragments are distinguished - angular and rounded, there are also several transitional types between them (Fig. 3.12).

Rice. 3.12. stone fragments various shapes: a- angular; b- rounded (rounded); v- semi-rounded

A widespread moraine is usually called rubble loam, while the stone inclusions present in it are closer to rounded pebbles than to angular rubble.

1.1. Fragments of an angular shape. They are formed by weathering and breaking off pieces from the bedrock monolithic rock.

In nature, this process is most intensively developed on the slopes; the debris formed as a result of it accumulates at the foot of the slopes, forming stone screes. With a horizontal relief, angular fragments remain in their place, and the weathering process quickly attenuates with depth. This is how weathering crusts are formed (Fig. 3.13).

Rice. 3.13.

Rocks of screes and weathering crusts, depending on the size of the fragments, are called blocks, crushed stone, gruss, cartilage. They can serve building material in places of its distribution, although crushed stone, boulders, etc. actually used in construction. much more often they are artificially crushed stones mined in quarries using explosions. On their basis, it is possible to obtain more durable materials for construction than when using weathered and fractured natural stone, especially since the majority of the Russian population lives in flat areas where these screes and weathering crusts are practically absent.

• 1.2. rounded (rounded) debris acquire this form as a result of treatment with water (surf, rivers, glacial streams), less often - by wind. Boulders are formed from angular blocks, pebbles from crushed stone, gravel from gruss (fine crushed stone). The smaller the fragments, the more often they are rounded. For example, sands with angular fragments are found in nature, but extremely rarely. Dusty fraction - quartz fragments 0.002-0.05 mm in size are always rounded. Due to their small size, they begin to demonstrate colloidal properties - they easily stick together, and, being stirred up, slowly settle in water.
• 2. Cement. Some rocks in nature resemble in their composition such well-known artificial materials as hardened cement mortar or concrete, in that they consist of stone fragments held together by cement. It is possible that the idea of ​​creating concrete was borrowed by people in nature. Natural cement is similar in composition to some chemical sedimentary rocks. It is carbonate, siliceous, sulphate, ferruginous and clay - then it is called clay filler. Carbonate cement is similar in composition to chemical limestone and is determined by reaction with acid. Siliceous - the most durable and hard of cements, sometimes it has oily sheen, does not react with acid. Sulfate - not durable, it is scratched with a fingernail, occasionally sugar-like crystals are visible on it. Ferrous cement is recognizable by its rusty color. Clay cement scratches with a fingernail, soaks in water.

The formation of cement is possible in two ways:

• 1) in marine conditions with simultaneous accumulation of chemical sediment along with debris;
• 2) due to precipitation chemical material from groundwater within the clastic stratum after its accumulation.

The rocks with the most common types of cementation are shown in Figs. 3.14.

Rice. 3.14. Rocks with different types of cement: a- basal cement; b - porous cement; v- contact

3. clay minerals. In coarse clastic rocks, clay minerals can play the role of a filler between stone particles and, in fact, be cement. When clay minerals are mixed with sandy and fine-clastic material, so-called clay rocks are formed - loams, sandy loams and natural clays. At the same time, clay minerals acquire the role of the main component, giving the entire mixture the properties of clay rocks, the main of which are moisture capacity, water resistance and cohesion - the ability to become plastic when wet and hard when dried.

Structure, granulometric and mineral composition. These characteristics are closely related. The structure of the material is determined depending on the particle size. Particles of a certain size are called fractions. The boundaries of the fractions are taken according to GOST 25100-2011 "Soils", they repeat the boundaries accepted in the geological literature with very slight changes, only the names of the fractions differ; geological data in parentheses (Table 3.6).

Table 3.6

Structures and approximate composition of clastic, argillaceous and mixed rocks

Structure and fraction - particle size	Approximate composition
1. Coarse-clastic (psephites) - larger than 2 mm	Fragments of any rock
2. Medium clastic - sandy (psammites) - 0.05-2 mm	Quartz predominates, feldspar may be present, there are very few other minerals
3. Small detrital - dusty (silt) - 0.002-0.05 mm	Quartz - almost the entire fraction
4. Micro-grained - clayey (pelites) - less than 0.002 mm (less than 0.005 mm)	Kaolinite, montmorillonite, glauconite and other clay minerals, quartz, limonite
5. Mixed - detrital-sandy, sandy-argillaceous, etc.	Various mixtures of particles of 1-4 fractions

It is known that the finer the material is crushed, the faster it dissolves and enters into chemical reactions. Therefore, among large-sized fragments (blocks, boulders, crushed stone, pebbles), almost all rocks are found, with the exception of the most soluble - gypsum, anhydrite, rock and other salts. Among medium-sized fragments, mainly quartz is found - the most resistant to weathering mineral, less often feldspar, and even more rarely other minerals. Medium clastic rocks are sands.

Among fine-clastic (silty) particles, there are almost no other minerals, except for quartz. Rocks - loess, silt, siltstone.

Microgranular rocks are composed of kaolinite, montmorillonite, hydromicas, and other clay minerals. The rocks are pure clays.

Mixed rocks - most often a mixture of sandy, silty and clay fractions - these are clays, loams and sandy loams. The terms "sandy-argillaceous" and "argillaceous rocks" are widely used and are used as synonyms.

The percentage by weight of particles of various fractions is called particle size distribution (grand composition). To determine it, a soil sample is passed through a set of sieves with further weighing of each fraction. Further, according to a small set of rules, the breed is given a formal correct name(Table 3.7). This applies to unconsolidated coarse clastic, sandy, and partly some clayey rocks, which will be discussed below.

Table 3.7

Subdivision of coarse and sandy soils

The correct naming of sandy and clayey soils is an important task of geology and soil science. The type of soil (in fact, the name) determines the various tabular values ​​of the parameters included in the calculations of the bases, which is important for designers. Therefore, the granular composition, along with other laboratory properties of soils, is one of the key indicators properties and is determined en masse during surveys.

Origin of clastic rocks shown schematically in fig. 3.15.

As you can see, it all starts in mountainous conditions with weathering, landslides and shedding of angular stone fragments - this is how natural lumps and rubble. In the process of weathering (chemical) are also formed clay minerals, which are easily carried away by water, and if granites and gneisses, which are very common in nature, are destroyed, detrital quartz with sandy and dusty particles is also formed.

Rice. 3.15.

Due to gravity, slope processes, temporary water flows and rivers, angular clastic material enters the sea coast. Here, material is added to it, which is formed due to the destruction of the coast by waves. In the surf zone, stone material is additionally crushed, fragments are rounded, and boulders, gravel, gravel, sand and quartz dust- material silts. Some of the material dissolves. The waves and sea currents carry the sediments to a great depth, where, perhaps, cementation and transformation into cemented analogues occur - conglomerates, gravelstones, sandstones, siltstones.

Similar processes on a smaller scale can occur due to the geological work of mountain rivers, glaciers and water glacial flows. If there is no rounding phase, then during cementation of an angular material, sedimentary breccias.

Tectonic breccias formed in zones of tectonic faults. Clastic material is obtained by moving tectonic blocks along fault planes, and cementation is obtained due to the release of chemical sediment from groundwater, which easily circulates through a fragmented zone.

Artificial gravel, artificial beach. If it is necessary to increase the area of ​​a natural pebble beach, crushed stone is brought to the coast and dumped into the surf zone. The rate of rounding of debris depends on the strength of the original rock and usually takes several months, after which the beach is again ready for use. An artificial beach must be regularly replenished with rubble and protected from erosion, since in nature there are constantly processes of grinding pebbles and carrying them away with sea currents. The expansion of sandy beaches is carried out in a similar way, but protecting them from erosion is even more difficult.

Texture of clastic, sandy and mixed rocks. The rocks of this group have a wide variety of textures and composition due to the diversity of the rocks themselves (Table 3.8).

In terms of bulk density, rocks can be dense, porous, micro- and macro-porous, fractured and weathered. Among the rocks of this group, only well-consolidated breccias, conglomerates, gravelstones, sandstones, and siltstones have dense textures. Porous due to the gaps between the fragments and particles are all non-cemented rocks - boulders, pebbles, crushed stone, gravel, sand, silt, etc. Microporous - all clay rocks due to micropores invisible to the naked eye.

The porosity of unconsolidated clastic and clayey rocks can be 20-35% and exceed 50% in loess. The terms widely used (dense clay, dense sand, etc.) are relative and refer to the minimum porosity of these rocks, which is 10-25% by volume. For sand and clay rocks, porosity is measured during surveys and is an indicator by which the compression of these rocks at the base of structures is calculated.

According to the mutual arrangement of particles, clastic rocks, like most sedimentary rocks, are layered and non-layered. Strongly compacted layered varieties are sometimes called schistous because of their external resemblance to a group of metamorphic schists. In contrast, sedimentary shale rocks get wet.

According to the bonds between the particles (this characteristic can also be attributed to the structure), clastic rocks are defined as unconsolidated (loose, loose), cemented and connected (loose). The term "connected" is used in relation to the sandy Table 3.8

Textures and some features of the composition of sedimentary detrital, clayey and mixed (detrital-clayey) rocks

Type of texture	Characteristic
1. Texture determined by the density of addition
1.1. dense	Pores are not visible, water is not absorbed into a dry sample - cemented clastic rocks
1.2. microporous	Inherent in clayey rocks. The exact porosity is determined in the laboratory. Some samples are light
1.3. porous, finely porous, cavernous	The pores are visible to the naked eye. This is inherent in weakly cemented and unconsolidated rocks.
1.4. Macroporous	The term is used only for loess, which has not only microporosity, but also visible to the naked eye pores with a diameter of about 1 mm, called macropores.
1.5. fissured	There are cracks in the rock
1.6. You are windy ah	Cracks and voids in the rock are expanded as a result of weathering processes. The breed is weakened
2. Textures determined by the mutual arrangement of particles in the rock
2.1. Layered: a) macrolayered	Visible only in the outcrop due to changes in color, composition, composition of the rock
b) finely layered	Can be seen in samples
c) slate	Fine fine lamination of clayey rocks of hard-plastic and hard consistency. Samples are broken into slab blocks by stratification
2.2. non-layered	The rocks do not have layering - loess, moraine
3. Textures determined by bonds between particles
3.1. Cemented	The rock particles are held together by cement.
3.2. Unconsolidated (loose, loose)	Rock particles are not bonded to each other
3.3. Connected (loose)	Inherent in clayey rocks. The rock is connected by colloidal bonds between particles. The rock is plastic when soaked, becomes hard when dried, but is neither monolithic nor loose material

clay rocks. They are neither rock nor loose material. They are plastic and fluid when wet and become almost solid when dry.

Hydrogeological and engineering-geological properties of cemented clastic rocks. Cemented rocks can be either dense, impermeable, or porous, permeable to water - it all depends on the ratio of the gaps between the fragments and the amount of cement. They may also be fractured, and if the cemented rock contains carbonate or sulfate constituents, karst may develop, further increasing permeability. These rocks have the usual properties of rocks and semi-rocks. As a base, they are quite strong and incompressible. As a material for crushing into crushed stone, only sandstones and siltstones are widely used, although coarse-grained rocks can also be used. To obtain beautiful facing tiles, marble breccias are used, to obtain tiles laid on the floor, sandstones and siltstones are used. Strong, well-consolidated sandstone is even used for steps, as it gives a good rough surface. Thin-layered sandstone varieties do not need to be sawn - they give natural tiles of irregular shape and are suitable for laying on paths.

Hydrogeological and engineering-geological properties of unconsolidated clastic rocks. All unconsolidated rocks have good permeability, water abundance, form aquifers suitable and convenient for exploitation. The larger the debris, the greater the permeability, the greater the filtration coefficients (see Part II, Table 8.1). Pebbles, crushed stone, gravel in their permeability are second only to highly porous, fractured and karst rocks.

Sands are also a permeable rock. The sizes of sand grains vary from 0.05 to 2 mm. Also, the filtration coefficient varies tenfold - it is maximum for gravel sands and minimum for dusty ones.

Sands are the most common among unconsolidated clastic rocks. They often lie on the surface, forming groundwater aquifers. Sands are often found in the section, and being covered from above by clayey rocks form interstratal aquifers of fresh waters. For the purposes of construction design, coarse soils and sands in accordance with GOST 25100-2011 are classified according to their granulometric composition, degree of water saturation, porosity and some other indicators determined by the laboratory.

The presence of clay or organic aggregates greatly reduces the permeability of unconsolidated rocks. Pebbles with clay filler turn, in fact, into poorly permeable rocks. The permeability of clayey sands with organic matter decreases tenfold compared to similar rocks without aggregates. As a foundation and environment for structures, unconsolidated rocks usually do not present any difficulties, with the exception of silty and fine sands, which are capable of developing quick-moving properties and frost heaving. Boulders, blocks, pebbles, crushed stone, gravel - a weakly compressible base.

Clastic rocks. They are composed of fragments of broken bedrock or minerals, sometimes with the remains of broken fossil shells. Their classification is based on the size, degree of roundness, and cementation of fragments (Table 13 and Table 14), which depend on the strength and resistance of bedrock (destroyed) rocks to weathering processes, as well as the stage of rock development: weathering, denudation, accumulation, or diagenesis. So loose rocks from angular loose fragments are the products (result) of physical weathering; from rounded - weathering, transfer (denudation) and accumulation (sedimentation) of loose deposits. The cemented clastic rocks have passed through the stage of diagenesis in their development, during which carbonate or siliceous minerals were formed between the clasts, or fine clastic minerals - clays were deposited. Loose rocks usually have a young, Quaternary age and lie near the surface, while cemented rocks are older. Most of the cemented dense clastic rocks accumulate at the bottom of the seas and oceans, where many weathering products are eventually carried away, and therefore such rocks are also called terrigenous(demolished from the continents - land). For clastic rocks, the concept of "structure" is often confused with "texture", so it is possible to characterize simply the structure of the rocks.

rubble and rubbish consist of unrounded fragments of various most durable rocks and minerals and differ in the size of the fragments. They have eluvial (rock weathering products remaining at the place of their formation) and deluvial (formed during the movement and accumulation of rock fragments on the slopes and at the foot of the hills and

Table No. 12

Characteristics of widespread sedimentary rocks and soils

Name and class (debris, chemical, biochemical)	Mineral composition (rock-forming) and chemical composition	Structure		Color and other distinctive properties	Class and varieties of soils (by granulometric composition, water permeability, strength and compressibility, softening, plasticity, salinity, solubility, etc.)
		Texture	Structure
Sand, clastic Sandstone Conglomerate Limestones of different textures diatomaceous earth rock salt Anhydrite

Executed Checked

Table 13

Sedimentary clastic rocks (key)

To size debris, mm				Cemented			minerals		Structure
	Acute-angled	rounded	Acute-angled		rounded	Structure			Texture
clastic -> 2…>100	lumps > 100 Rubble - Dresva -				Conglomerate	Various most durable breeds		The structure of cemented rocks is determined by cement		Loose, rounded or not rounded, clastic or cement
clastic,				Sandstones			quartz, olivine, feldspars, pomegranate, etc.
clastic,				Siltstones			Dust particles of quartz, etc.
clastic				Argillites			Kaolinite, montmorillonite, etc.

Table 14

Basic structures of cemented clastic rocks

Name of structure groups	Name of main structures	Features	Influence on the property of rocks
psephytic	Pebble gravel Shchebnevaya Dresvyana	Peculiar to conglomerates: rounded fragments 10…100 mm in size Peculiar to gravelites: rounded fragments from 2…10 mm in size It is observed in breccias and gruss. The unrounded form of fragments with a diameter of 10 ... 100 mm (crushed stone) and 2 ... 10 mm (grus) is characteristic	Properties and stability, in addition to the size of the fragments, depend on their mineral composition, the nature and type of cement
Psamitic	Coarse-grained medium grain fine-grained	It is observed in sandstones with a grain size	The properties and stability of rocks, in addition to the size of the fragments, depend on the mineral composition of the fragments, the nature and type of cement.
Silty	silty silty	Typical for siltstones with a grain size 0.1…0.05 mm Typical for siltstones with a grain size of 0.05 ... 0.005 mm	Not resistant to weathering: in a dry state - solid, when moistened become soft, swell in water, sometimes get soaked to the point of complete loss of cohesion
	Pelitovaya	Typical for mudstones and compacted clays less than 0.005 mm

mountains) origin, lie in the idea of ​​thin covers and plumes at the foot, covering almost the entire earth's surface. Since the most durable bedrocks are preserved in the form of crushed stone and gruss, these deposits have an average strength coefficient of 1.5.

Pebbles and gravel differ from crushed stone and gruss in the roundness of fragments, which occurs during long-term transfer over considerable distances. The degree of roundness and sorting is extremely diverse. They are divided into river, lacustrine, marine and glacial deposits occurring in the form of layers and lenses. The voids between pebbles and gravel are quite large. Pebble and gravel grains practically do not have the ability to capillary rise of water, but they are well permeable and easily give up water.

Pebbles and gravel are of great practical importance as an easily sorted and processed building material. Used for making concrete road construction and when installing filters in hydraulic structures.

Sands- loose rock, consisting of rounded or acute-angled grains of various minerals and rocks of different colors. Quartz sands predominate, but grains of feldspars, mica, magnetite and other minerals are often present with it. Sometimes there are sands consisting almost exclusively of grains of dolomite, magnetite, shales, fragments of shells or rocks. Sands according to the conditions of formation can be river, lake, sea, glacial and dune, differ in layering, roundness, mineral composition and other properties.

The porosity of sands is much less than the porosity of other clastic rocks (loess, clay); it is usually equal to 30 ... 40%. The very important properties of sand include its ability not to change volume when dried and moistened, and the ability not to absorb, pass through itself and release water. Sand saturated with water can flow and quicksands appear on the slopes. Sand saturated with water, but not able to move and be washed away, can be a reliable foundation. Sands have a small capillary rise of water. Strength coefficient 0.5 ... 0.6. Filtration coefficient 1…1400 cm/h.

Sands are of great practical importance as a material for construction purposes, for the manufacture of faience, porcelain and glass; as a material for filtering in water installations and other purposes.

Loess- yellowish-white, light, porous rock, a mixture of tiny grains (0.05 ... 0.005 mm) of quartz, clay particles and calcite, strongly pulverized, partly in the form of shell-like tiny balls, turns into powder when rubbed. It is distinguished by high adhesion of particles and can form sheer cliffs many meters long. The loess contains many thin vertical tubules with traces of plant roots; many calcareous concretions (crane or forest pupae) of bizarre shape. A typical loess is characterized by the absence of layering. It is widely distributed on the earth's surface and occupies about 4% of the land. Most scientists consider a typical loess to be an eolian formation, but there are hypotheses about its soil-eluvial, deluvial, proluvial, and even lacustrine-glacial origin. Loess belongs to specific soils due to its engineering and geological characteristics: in dry form, it can serve as a base for structures, but when wet, it is subject to strong compaction, which results in significant subsidence. The subsidence of the loess is a consequence of its high porosity and the action of water, which changes the structure of the loess. Strength coefficient 0.8, for liquefied loess 0.3. Dust filtration coefficient 0.51…1.62 cm/h.

Clay- finely dispersed rocks, which include mainly clay minerals - products of chemical decomposition (hydrolysis) of silicates, mainly feldspars. Along with clay minerals

- kaolinite, montmorillonite and others, clays contain impurities in larger or smaller quantities of particles of quartz, feldspars and other minerals, including iron hydroxides - brown limonite. Clay rocks are the most common on the earth's surface and among sedimentary rocks, accounting for 50% of their total volume.

Clay are divided into fatty and skinny. The first ones are greasy to the touch, their color is most often gray, light gray, greenish gray. The content of kaolinite in them is high - more than 40 ... 70%. These clays have great resistance at high temperatures. The second - lean clays - are less oily to the touch, and consist of the smallest particles of feldspars and quartz, as well as kaolinite in an amount of less than 40 ... 10%. They are painted mainly in yellow, yellow-brown, red-brown colors of various shades of iron oxides.

According to the formation conditions, clays are divided into primary, or residual, and secondary, or sedimentary clays. Residual clays are hydrolysis products of silicates and predominantly feldspars. Secondary clays were formed at the expense of primary clays by moving them in a horizontal direction and redepositing into reservoirs and depressions, they are distinguished by better sorting and fat content.

Clays in the dry state are hard and are a dense, powdery rock. They have considerable porosity; dry clays vigorously absorb water and, having become plastic, give this water very slowly (see Table 9). At the same time, they noticeably increase in volume - they swell. Clays are distinguished by high water absorption - they are able to contain up to 70% of their volume of water, capillary rise (up to 3 ... 7 meters) and, saturated with water, water resistance (water resistance). They contribute to the development of landslides with corresponding rather steep slopes; artesian (pressure) waters are provided as covering layers. Under the action of an external load, unconsolidated varieties of clays are strongly compressed, but this compression is very slow and can last hundreds of years. Heavy buildings built on such clays can produce significant and often uneven rainfall.

Clay soils are sandy loam, loam and clay. sandy loam is a transitional rock from sands to clays. The amount of clay particles in them is 3…10%. Wet sandy loam crumbles when rolled in the hands. Sandy loam filtration coefficient 0.01…36 cm/h. Loam contains more clay particles - 10 ... 30%, resembles clay in its properties, however, wet loam cracks when rolled and bent in hands. Loam filtration coefficient 0.06…5.0 cm/h. Clay contains more than 30% clay particles, due to which the bundle of wet clay can be rolled into a bagel. The coefficient of clay strength is 1.0. Filtration coefficient 0.000002… 0.001 cm/h. Clayey rocks are interbedded with each other and quickly wedged out over the distribution area.

Kaolin clay is used in the porcelain and stationery industry, fatty clays are used as a refractory material, and thinner clays are used for brick, tile and pottery production. Fuller clays, which are distinguished by their ability to absorb fats and oils, are used for cleaning wool, cloth, etc. From glauconite clays a good green mineral paint is obtained, from ferruginous clays - red paints, umber, sienna, ocher.

Argillite(or shale) is a very compacted fine-grained clay rock with a pronounced layering, turning into schistosity in places. It consists of the smallest particles of kaolinite, flakes of muscovite, chlorite, the smallest grains of quartz with an admixture of carbonaceous particles and iron hydroxides, therefore it often has a dark to black or brown color. Clay shales occur in the form of layers, horizontal or crumpled into folds, disturbed by faults.

Shales are common, usually in folded areas: in the Caucasus, the Urals, etc. Varieties of dark gray color, which have a thin slate separateness, are called roofing slates. Slates are black in color due to the presence of carbonaceous matter. Bituminous and oil shales are sheet rocks of black and dark gray color, rich in bitumen.

Clay shales with good fine-platy separation are used as very stable roofing material. Stair steps, skirting boards, floor tiles, window sills, panels, table boards, washbasins are made from them. Shales that do not contain impurities of ore minerals are used in electrical engineering instead of marble. Waste from slate production is used to make asphalt and artificial road stones.

Engineering-geological characteristics - clay shales differ from clays by much greater hardness. Strength coefficient of strong shale 4. Temporary compressive strength 60 ... 200 MPa.

Sandstones- cemented densely layered sands of various strengths, formed as a result of diagenesis, compaction of loose sediments under the weight of overlying sediments. By absolute size, coarse-grained, medium-grained and fine-grained sandstones are distinguished. They consist mainly of the most common and physically and chemically stable quartz. Depending on the mineralogical composition of cement, sandstones are subdivided into siliceous, calcareous, clayey, ferruginous, and gypsum (see Tables 9, 13, and 14). They occur in the form of layers and lenses.

Sandstones are widespread in Karelia, in the Central regions of Russia, in the Volga region, in the Urals. Sandstones differ in the mineral composition of sand grains: monomineral (usually quartz), polymineral arkose (consist of quartz, feldspars and mica) and greywackes (consist of fragments of various rocks, amphiboles, quartz, feldspars and mica), as well as cement (see Table 9).

Sandstones are widely used as a building material, especially where other stone building materials are not available. Sandstones rich in silicic acid (at least 97%) are used as valuable raw materials for dinas. Sandstones with siliceous cement are widely used in construction as a rubble material, some varieties are successfully used for making millstones.

Depending on porosity, humidity, cementing agent, as well as on the structure and size of the grains, the mechanical strength of sandstones varies widely (see Table 9). Porous sandstones often contain artesian waters, oil and combustible gases. The compressive strength ranges from 40…140 MPa. Strength coefficient 2…15.

Breccia and conglomerate- cemented rocks, consisting, respectively, of unrounded sharp-angled and rounded rock fragments (see Table 13) and a finer cementing substance. The composition of clasts of breccias, in comparison with conglomerates, is less complex, since the area of ​​removal of clasts that make up breccias is much smaller than that of clasts that make up conglomerates. The clasts usually belong to one or a few rock types. Fragments in conglomerates were transported over long distances for a long time from many places. The composition of cement can be different: calcareous, siliceous, ferruginous, clayey. Breccia is characterized by the heterogeneity of the composition of the cement, in contrast to the homogeneity of the composition of the clasts.

Breccia is formed during tectonic and landslide processes by the accumulation of destruction products (fragments) of rocks at the foot of the slopes. Volcanic breccias are formed by the cementation of large clastic volcanic ejecta; tuff breccia - a significant amount of ash. Conglomerates - from the debris that accumulated along the shores of the seas, mountain rivers and lakes. The fragments are cemented by various chemical compounds falling out of the water (lime, etc.) and settling small clay particles. They lie in the form of layers of small thickness - tens, sometimes the first hundreds of meters. They are distributed mainly in folded areas: in the Urals, the Caucasus, as well as in landslide zones. Due to the angular shape of the clasts, breccias are stronger than conglomerates and are more suitable as building stone. As a facing stone, they are valued for the beauty of breccia.

Thus, clastic rocks are very diverse in composition, structure, and forms of occurrence; wedged out and replace each other both along the strike of the rocks (over the area) and to the depth. Continental modern clastic usually loose rocks have a thickness of a few meters to hundreds of meters, covering the entire earth's surface. It is in these rocks, among the alternation and wedging of clastic and clay rocks, that builders often have to carry out their work. Marine terrigenous clastic rocks extending over large areas have a thickness of hundreds and even thousands of meters, as well as an older age. In flat areas within platforms, they lie under a cover of continental deposits, in folded areas they often lie near the earth's surface and fall into the field of engineering.

Table 15

Chemogenic and biogenic rocks (key)

Chemical composition	Name	Main rock-forming minerals	Structure	Texture
	Rock salt Silvinit		crystalline	massive banded layered
sulfates	Anhydrite	Anhydrite
Carbonates	Limestone	Clay minerals (40-50%)
			Biomorphic Biosomatic fine - fine - granular	Densely layered finely porous Biogenic
Siliceous rocks	diatomaceous earth	(a. clastic rock, fragmented rock, detrital rock; n. klastische Gesteine, Trummergesteine; f. roches detritiques, roches clastiques, roches agregees; i. rocas detriticas, rocas clasticas), - sedimentary rocksconsisting entirely or mainly of fragments various rocks (igneous, metamorphic or sedimentary) and minerals (feldspars, micas, sometimes glauconite, volcanic glass, etc.). There are clastic rocks cemented and non-cemented (loose). In cemented clastic rocks, carbonates (calcite, dolomite), silicon oxides (opal, chalcedony, quartz), iron oxides (limonite, goethite, etc.), clay minerals, and a number of others serve as a binder. Facing rocks often contain organic remains: whole shells or their fragments - mollusks, corals, crinoids and others, trunks and branches of trees, etc. The classification of facing rocks is based on a structural feature - the size of the fragments. There are: coarse clastic rocks, or psephites, with a fragment size of more than 1 mm (uncemented - blocks, boulders, pebbles, crushed stone, gruss, gravel; cemented - conglomerates, breccias, gravelstones, etc.); sandy rocks, or psammites, with a particle size of 1-0.05 mm, according to another classification, 1-0.1 (2-0.05 mm) (sands and sandstones); silty rocks, or siltstones, with a particle size of 0.05-0.005 mm (siltstones and siltstones); clayey rocks, or pelites, with a particle size of less than 0.005 mm (clays, mudstones, etc.). The boundary between silt and pelite is drawn by the particle size of 0.005 (0.01 in other classifications) mm. Clay rocks can be both chemical and detrital origin. There are also clastic rocks of mixed composition, composed of fragments of various sizes - sandy, silty and clayey. These include widespread, especially among modern continental deposits, various loams and sandy loams. Further subdivision of clastic rocks within structural subtypes is carried out according to the mineral composition of the fragments and other features. Clastic rocks also include products of volcanic eruptions: volcanic rubble, ash (loose rocks and their cemented varieties - tuffs), tuff breccias and rocks transitional between clastic and volcanogenic - tuffites and tuffaceous rocks (see volcanic-sedimentary rocks). With a dissected relief and high dynamics of the environment, coarse clastic rocks are formed, in conditions of a flat relief and a low speed of water and air flows, sand, silt, and clay rocks are formed. Clay particles settle mainly in calm water. In the coastal part of the seas and oceans, pebbles and gravel are deposited on the beach and shallow water, as they move deeper into the basin, they are replaced Sedimentary rocks occupy an impressive area of ​​the globe. These include most of all the minerals that our planet is so rich in. Most of the sedimentary rocks are located on the mainland, continental slope and shelf, and only a small part - on the bottom of the seas and oceans. Origin of sedimentary rocks Weathering of solid igneous rocks occurs under the destructive influence of sunlight, temperature fluctuations, and water. They form fragments of various sizes, which gradually disintegrate to the smallest particles. Wind and water carry these particles, which at some stage begin to settle, thereby forming loose accumulations on the land surface and at the bottom of water bodies. Over time, they harden, compact, acquire their own structure. This is how sedimentary rocks are formed. Rice. 1. Sedimentary rocks Like metamorphic rocks, sedimentary rocks are secondary rocks. They lie only on the surface of the earth's crust, occupying about 3/4 of the entire planet. Since almost all construction works are carried out on sedimentary rocks, it is very important to perfectly know the properties, composition and "behavior" of this type of rock. The science of engineering geology deals with these and many other issues. The main feature of sedimentary rocks is layering, which is unique for each natural compound. As a result of shifts in the earth's crust, the original forms of the occurrence of sedimentary rocks are disturbed: all kinds of gaps, cracks, faults, and folds appear. TOP 4 articleswho read along with this Rice. 2. Layering of sedimentary rocks Rock classification The deposition process can take place different ways. Depending on its specificity, several main groups of sedimentary rocks are distinguished: clastic - are formed under the influence of weathering and further transfer of particles of igneous rock; chemogenic - the result of the isolation and precipitation of substances that are formed from saturated aqueous solutions; biochemical - are formed as a result of chemical reactions with the participation of living organisms; biogenic - the result of the decomposition of the remains of plant and animal organisms. In nature, mixed groups of sedimentary rocks are often found, the formation of which was influenced by several factors at once. Thus, one of the clearest examples of sedimentary rocks of a mixed type is limestone, which can equally be of chemogenic, organogenic, biochemical, or detrital origin. Rice. 3. Limestone What have we learned? Sedimentary rocks occupy vast areas of the Earth's surface. They can be located both on land and at the bottom of the seas and oceans. Any sedimentary rock is formed from destroyed and modified igneous rocks. The classification of rocks is based on the features of the sedimentation process, which can occur under the influence of many factors. Topic quiz Report Evaluation Average rating: 4.3. Total ratings received: 331.   It might be useful to read: Offshore trap of "Crimean Titan": will the "dirty" plant be modernized?; How to choose electrodes for welding Welding a rail with steel; Production technology of fiberglass pipes Fpipes; Consumer properties of muesli bars and snack products; How to start the production of smoked fish?; Sheet metal stamping technology; From what and how are dumplings made?; The best Tabasaran carpets: description, patterns, features and reviews An excursion into history;