Rocks are clastic. Description and classification of rocks
The shell of our planet is made up of various rocks. Under the oceans their thickness is less; under the hills there are formations up to 80 km. Composition of the Earth's rocky shell (lithosphere) in different places different. More than 10% of the total is sedimentary rock. Most of all (70%) falls on igneous formations. The rest are complex rocks resulting from exposure to high pressure and temperature.
Definition
Rocks are essentially accumulations of minerals. It is believed that the earth's crust consists of more than 1,000 different formations. In simple rocks (gypsum, limestone) there is one mineral. Basalt and granite are representatives complex formations. It is the result of geological sedimentary processes.
There are igneous rocks, metamorphic and sedimentary. They differ in internal structure and have different properties, although they are often predecessors of each other.
Sedimentary rock occurs in layers. Particles are placed in it as a result of various kinds of physical phenomena. The simplest and most common of them are: destruction (breaking off, crushing), transfer, deposition and deposition. This is how clastic rock is formed. Its composition may be dominated by minerals or organic residues. Between them there can be simple or complex chemical reactions with a change in existing properties or the formation of new substances. They can occur on land or in an aquatic environment.
Circuit
Various processes are constantly taking place on our planet. During the formation of the Earth, its surface gradually cooled and a crust formed. Over time it thickened. If on the surface of the planet the temperature regime largely depends on the atmosphere, then in its depths the substances are still preserved in a molten state. Magma in the form of volcanic eruptions sometimes finds its way out and quickly cools.
Being exposed to weathering and other influences, the rock changes its properties over time. It crumbles, crumbles, fragments. Having found constancy, the particles settle, accumulate, and become denser. In moving layers they gradually sink deeper. Conditions change, temperature and pressure increase, dehydration occurs, and chemical reactions occur.
The rock changes from sedimentary to metamorphic. Typically, as a result of such processes, a change in the internal structure of minerals occurs. Substances acquire new properties: strength, strength, resistance to environmental influences. Geological processes continue. The rock descends lower into the zone high temperatures. There it first heats up, then melts and turns into magma.
The turnover occurs in a spiral. With each turn, new connections are formed due to the fact that complex transformations occur during transformations. Substances enter into chemical reactions, and during the deposition process new components are added, often serving as catalysts for new interactions.
Classification
Clastic sedimentary rock is classified according to particle size. There are four such groups. Rock particles larger than 1 mm are considered large; from 0.1 to 1 mm - sandy; 0.1-0.01 mm - silty; 0.01 - 0.001 - clayey.
Often, a division of rocks is added to the existing classification depending on the predominant minerals and their ratio. They can act as a base or a link between particles (for example, quartz sandstones).
Loose rocks can become denser if they undergo cementation. The process takes place when the base is exposed to a binder: clay, gypsum, carbonate, iron. As a result, the rock may have a complex name, for example: siliceous or calcareous sandstone. There is also a gradation by origin: river, sea, glacial.
Structure and texture
The rock, depending on the composition of minerals, can have a different structure. This or that condition is characterized by a number of features. The structure of the rock and its texture are distinguished. For the first determination, the degree of crystallinity of mineral grains, their shape and size, as well as the ratio of the constituent elements of the base and the cement substance are important.
Texture is more of an external manifestation of visible features: porosity, massiveness, schistosity or layering. Depending on the combination of these features, the rock material has a specific color, which may be decorative.
Clastic sedimentary rock (monomineral) has a more uniform texture. When two or more elements with different characteristics grow together, substances with complex chemical composition and properties are formed. Such rocks (polymineral), as a rule, have a more variegated color.
Size and shape
A clastic sedimentary rock with rounded corners and a particle size greater than 100 mm is called a boulder. The process of rounding occurs with intensive movement of material under the influence of natural forces. Fragments of the same size, but angular in shape, are usually called blocks. Particles with a size of 10-100 mm are divided according to the same principle into pebbles and crushed stone. Rounded gravel and angular debris are rocks with dimensions of 1-10 mm.
Crushing and rolling most often occurred under the influence of water. Such genesis (origin) is usually divided into river, lake and sea types. Separately, rocks processed during the movement of glaciers are distinguished.
Sands (particles 0.1-1 mm in size) are divided into large, medium and small. Loess is a porous silty polymineral rock of silty origin with fragments of 0.1-0.01 mm. The smallest particles (less than 0.01 mm) are classified as clays. About 25% of their total number have a grain size even less than 0.001 mm.
Chemical sedimentary rock
Chemogenic processes occur when various substances precipitate from aqueous solutions. The compounds of calcium and magnesium are primarily important. In addition to these processes, evaporation of solutions in a closed environment is also released. Feature rocks of chemical origin - the presence of oolite grains (oval or ellipsoidal shape) and spherulites (needle-shaped crystals). The texture and color of materials can vary and depend on the predominant minerals.
Ferrous sedimentary chemical rock is a product of weathering of basic rocks. Manganese compounds are formed due to the coagulation of colloidal solutions of hydroxides. Phosphorites and siliceous rocks were formed with the participation of microorganisms. They absorbed the main components from the water, processed them and subsequently deposited them in muddy sediments after they died. Salts were formed in a certain sequence. First, sulfates (anhydrite and gypsum) precipitated, then chlorides, and lastly, potassium and magnesium sulfate.
Limestone - sedimentary rock
This is a representative of monomineral deposits. Limestone consists of calcite and is determined by its reaction with hydrochloric acid, which has a violent manifestation. There are two types of origin: chemogenic and organogenic. If it is possible to determine what type of organic remains a rock is made of, it is given a specific name. If it is difficult to classify, such limestone is defined as shell rock.
Foraminiferal shells, protozoan algae, and deposits of powdered calcite formed the chalk. It is also a type of limestone. The material is widely used in the national economy and industry.
Chemical processes during the formation of limestone change the internal structure of the material. There are dense formations with thin crystals. Oolitic varieties have the appearance of small balls or radial rays. The minerals in them are connected to each other by carbonate cement. Calcium carbonate dissolved in groundwater, which then precipitates, turns into calcareous tuff (traverine) over time. Calcite deposits in caves form stalactites and stalagmites.
Application
Sedimentary rock is widely used in the construction industry. Boulders are crushed and processed into piece material. Gravel and crushed stone are used for reinforced concrete products and are used in laying road surfaces. Sands are not only a fine filler for concrete, but also a raw material for glass, ceramics, and bricks. Clays are used in the production of tiles, fire-resistant materials, and are also a component of alumina. Some varieties are excellent adsorbents.
Magnesites are used to make binding materials. Silicon is used as an abrasive material. Chalk is used to make lime and is also used in the production of plastics and rubber products. Marls are the best raw material for cement production.
Sedimentary clastic rocks – These are rocks that were formed as a result of the transfer and redeposition of pre-existing igneous and metamorphic rocks, as a result of physical weathering (temperature changes), the action of wind, permanent and temporary watercourses, glaciers and living organisms.
Sedimentary clastic rocks are classified by: size of the clasts , type of debris , by connection between the fragments ( particles ) .
According to the size of the debris – divided into coarse clastic , medium clastic ,
fine-clastic , fine clastic.
By connection between particles - are divided into:
loose– there is no connection between solid particles;
liaisons– rocks consist of such small particles that inter-molecular attraction forces, Vander Waals forces, arise between these particles (inherent in sedimentary fine- and fine-clastic rocks);
cemented– the pores in the rock are filled with a cementing substance, while the previously loose rock becomes rocky or semi-rocky.
By type of debris – divided into rounded and unrounded.
Consolidated clastic sedimentary rocks rocks are rocks whose pores are filled completely and partially with natural cements.
Natural cements in cemented clastic sedimentary rocks are different, for example, clayey, calcareous (carbonate), siliceous, ferruginous, phosphate, gypsum, etc. The strongest natural cement is siliceous; The weakest one is clayey.
By quantity and texture of cement distinguish clastic rocks with basal , pore and contact cement.
Basal cement is a type of cement in which individual rock fragments do not come into contact with each other.
gom, but seem to float in the mass of cement.
Pore cement is a type of cement in which all the pores are filled with a cementitious substance.
Contact cement is a type of cement in which cement is present only at the contact between solid particles.
Sedimentary clastic rocks are divided according to the size of the fragments into A:
coarse sedimentary rocks (psephites) - all sedimentary clastic rocks in which the fragments of which they consist are larger than 2 mm. These rocks can consist of rounded and unrounded fragments, and be in a loose or cemented state.
To loose rounded
boulders consisting of fragments larger than 200 mm;
pebbles, consist of fragments measuring more than 200 to 40 mm;
gravel, consist of fragments measuring more than 40 to 2 mm.
To loose, unrounded Coarse clastic rocks include:
blocks, consist of fragments larger than 200 mm;
crushed stone, consisting of fragments measuring more than 200 to 40 mm;
trees, consist of fragments measuring more than 40 to 2 mm.
To the cemented rounded coarse clastic rocks
relate:
conglomerate, consists of fragments measuring 100 -10 mm;
To the cemented unrounded Coarse clastic rocks include:
breccia, consists of fragments measuring 100 -10 mm;
gravelite, consists of fragments measuring 40 - 2 mm.
Medium clastic sedimentary rocks ( psammits ) - this is all about
brittle rocks that have a particle size of 2 - 0.05 mm. These
childbirth may be in a loose or cemented state.
Consolidated medium-clastic rocks include
sandstone.
Loose medium-clastic rocks include sand. Sand
According to grain (grain) composition, it is divided into the following types:
Gravely , consists of particles ranging in size from 2 – 1 mm;
Coarse grain , consists of particles ranging in size from 1 – 0.5 mm;
Medium-grained, consists of particles ranging in size from 0.5 – 0.25 mm;
Fine-grained, consists of particles ranging in size from 0.25 – 0.1 mm;
Fine-grained, consists of particles ranging in size from 0.1 – 0.05 mm.
Fine clastic sedimentary rocks ( silty or silty -
You ) are cohesive or cemented sedimentary rocks in which
particle size from 0.05 to 0.005 mm.
Particles with sizes from 0.05 – 0.005 are called dusty . Small-sized
brittle rocks are in a bound or cemented state -
NI. These rocks cannot be found in a loose state in their natural composition.
gut. This is explained by the small particle sizes of the components of fine fragments
ny rocks.
Cohesive fine-clastic sedimentary rocks include:
loess-like loam.
To cemented fine-clastic sedimentary rocks
include siltstone .
Fine clastic sedimentary rocks ( pelites ) - these are all mountainous
rocks that are in a bound or cemented state (not
come in loose form), and have a particle size predominantly less than 0.005 mm.
Particles smaller than 0.005 mm are called clay particles. Their
the size is so small that inter-molecular attractive forces arise between them
zheniya (Vanderwals forces), this explains the fact that these breeds cannot
walk around in a loose state.
Cohesive fine-clastic sedimentary rocks include:
sandy loam contains clay particles from 3% to 10%;
loam contains clay particles from 10% to 30%;
clay contains more than 30% clay particles.
To cemented fine-clastic sedimentary rocks
refers to – argillite .
Clay is a sedimentary fine-clastic rock that consists
of particles less than 0.01 mm in size, but among them there must be at least 30%
particles smaller than 0.005 mm.
Sandy loam is a sedimentary fine-clastic rock that
consists of sand and clay particles, but the sand particles in it should
be more than clay particles, and clay particles (less than 0.005 mm) among them
should be from 3% to 10% by weight.
Loam is a sedimentary fine-clastic rock that
which consists of sand and clay particles, but the sand particles in it
should be less than clay particles, and clay particles (less than 0.005 mm) on average
di them should be from 10% to 30% by weight.
Clay particles exhibit some specific properties of fine-
clastic rocks: plasticity , swelling ( when moisturizing ),
shrinkage ( shrink in size as it dries ), plastic , creep ,
corrosion activity, etc. .
Due to large quantity clay particles, clay is water-resistant
new rock that does not allow water to pass through it.
Fine sedimentary rocks such as loess, or loess -
visible loam have high porosity (large, coarse, vertical
closely located pores). In a dry state, these rocks have a coherent
ness (it is due to this that the vertical slope is held well), it is enough
great strength. When moistened, the connection between dust particles is
collapses, dust particles float into large pores and
the volume of the rock decreases sharply and subsidence properties appear in it.
Mineral composition of sedimentary clastic rocks
Coarse sedimentary rocks consist of different weights
form and type of igneous and metamorphic rocks, therefore they
the mineral composition corresponds to the mineral composition of those rocks from the clastic
of which they consist.
Medium clastic sedimentary rocks consist of such minerals
fish like quartz, feldspars, mica. They may contain various
colored minerals, for example glauconite.
Fine-clastic sedimentary rocks consist of finely dispersed
quartz, calcite, clay minerals, they may contain gypsum.
Fine clastic sedimentary rocks consist of:
such as sandy loam, loam - from sand and clay minerals;
such as clay - from clay minerals (kaolinite , hydromica ,
montmorillonite ) .
Structures and textures of sedimentary clastic rocks .
Coarse sedimentary rocks have a structure of coarse clastic
Medium clastic sedimentary rocks have a sandy structure (sand,
sandstone).
Fine-clastic sedimentary rocks have a silty structure
Fine-clastic sedimentary rocks have a sandy-
clayey (sandy loam), clayey-sandy (loam), clayey (clay).
Sedimentary clastic rocks are characterized by the following textures:
dense or massive;
loose or disordered;
layered;
macroporous;
microporous;
cavernous.
Sedimentary coarse and medium clastic rocks are more often
In general, they are a good basis for buildings and structures. Sedimentary
finely clastic rocks in solid, semi-solid, refractory
standing can serve as a fairly reliable foundation for buildings and structures
tions, however, when moistened, their strength and deformation characteristics
sticks decrease sharply. Sedimentary fine-clastic rocks in dry
condition, they hold the slope well, have fairly high strength
characteristics, but when moistened they soften and exhibit subsidence
ny properties.
Sedimentary clastic rocks are widely used in construction
body Crushed stone, debris - used as concrete filler, bedding
under the road surface. Consolidated sedimentary rocks are used
(conglomerate__________, breccia, sandstone) are used as building stone. Pe-
juice is used for the production of sand-lime bricks, glass, construction
solutions, as bedding under the road surface, for the installation of sandy surfaces
shower under the foundations. Loess, sandy loam, loam, clay - are used for
brick production; clay as a filler for mortars.
Sedimentary chemical rocks – these are all sedimentary rocks
genera that were formed as a result of the precipitation of salt rocks from the oversupply
pure aqueous solutions, as a result of coagulation of colloidal solutions and in
as a result of chemical weathering.
Sedimentary chemical rocks are secondary rocks.
Often sedimentary chemical rocks are monomineral.
All sedimentary chemical rocks according to the chemical composition of de-
fall into seven classes : carbonate , sulfate , halide , phosphate ,
glandular , aluminum , siliceous .
Carbonate sedimentary chemical rocks include the following rocks:
Yes, such as chemical limestone, dolomite, calcareous tuff, travertine. These
genera consist predominantly of the mineral calcite of chemical origin
Denia. Chemical limestones - formed as a result of calcium precipitation
that in closed reservoirs with increasing concentration of solutions, in warm
climate. The composition of limestones includes various impurities, most often
wet material. Dolomites are rocks consisting mainly of mineral
dolomite rocks are formed in the same way as chemical limestones. Lime
tuff - rocks that are formed at the point where underground springs emerge,
saturated with calcium carbonate, to the surface of the earth, these rocks usually
porous, spongy, often have an amorphous structure. Tuffs having
higher density and fine porosity, often crystalline structure, na-
are called travertines.
Sulfate sedimentary chemical rocks include gypsum and anhydrous
rit. They usually occur together in the earth’s crust, with anhydrite overlapping on top
is covered with a cap of plaster. These rocks are also formed as a result of the loss of
salts from supersaturated aqueous solutions. Due to the fact that anhydrite
When moisture gets into it, it turns into gypsum and increases in volume by 33%
gut, uplifts of rocks overlying anhydrite occur with their disruption
original occurrence.
Halide sedimentary rocks include rock salt and
sylvin. Rock salt - rocks that are formed as a result of precipitation
rocks of salts from supersaturated aqueous solutions, these rocks are monomine-
ral. Rock salt is made up of the mineral halite. Rock salt and sylvite
easily dissolved in water if these rocks were not covered with clayey
rocks, then they would have already dissolved under the influence of underground and surface
fresh water
Phosphate sedimentary rocks include various
phosphorites. May form as a result of chemical weathering and
precipitation of salt rocks from supersaturated aqueous solutions.
Ferrous sedimentary chemical rocks include ore rocks
Yes, for example, brown iron ore.
Aluminum sedimentary chemical rocks include bauxite
(aluminum ores). Formed as a result of chemical weathering.
Siliceous sedimentary chemical rocks include flint and
siliceous tuff.
Structures of sedimentary chemical rocks: crystalline ,
amorphous .
Textures of sedimentary chemical rocks: dense ( massive ),
banded , cavernous , spotted .
Application of sedimentary chemical rocks in construction
Sedimentary chemical rocks can be used as a base
for buildings and structures. However, due to their high solubility
cavities, voids, cracks, caves, i.e., can form in them. is happening
cause karst formation.
Karst formation is the process of dissolution of rocks
underground waters with the formation of cracks, voids, caves in them. The process of dis-
the creation of rocks proceeds the faster, the higher the filter coefficient
groundwater radios.
As a result of the presence of cracks in sedimentary chemical rocks,
voids, their strength properties are sharply reduced, and therefore, before using
To begin with, they must be examined for the presence of voids, cavities, and cracks.
In addition, sedimentary chemical rocks can be used -
as a building material, for example, dolomite - as a building stone,
limestone and siliceous tuff - as a finishing material, bauxite - for
aluminum production, brown iron ore - for the production of cast iron, iron.
Organic ( or organogenic ) sedimentary rocks
Organic or organogenic rocks are rocks that
which were formed as a result of the vital activity of living organisms.
Organogenic rocks are divided into two classes by formation:
phytogenic and zoogenic .
Phytogenic are sedimentary organic rocks that form
were called as a result of plant life.
Zoogenic are sedimentary organic rocks that form
were caused by animal activity.
According to their chemical composition, organic rocks are divided into four
class: carbonate , siliceous , carbon , glandular .
Carbonate - these include organogenic limestone, shell rock,
chalk, pearls.
Siliceous – these include diatomite, tripoli; both breeds
consists of siliceous remains of diatoms and chemical silicon
of origin (opal).
Carbon ( caustobiolites ) – these include peat, coals (stone__________-
coal, brown coal and anthracite), some types of oil.
Ferrous - these include iron baboons (found only on
the bottom of the Black Sea in the coastal strip near Kerch). This breed is educational
is due to the activity of bacteria that absorb iron from the sea
waters, and then dying off, accumulations of these bacteria fall to the bottom of the sea in
in the form of nodules containing iron of organic origin.
Structures and textures of sedimentary organic rocks
The structure of sedimentary organic rocks is determined by pre-
the property residue of the organisms from which they were formed. For example,
in chalk the structure is foraminiferal, in diatomite it is diatomaceous. Also the structure
tur in organic rocks can also be determined by the size of the fragments,
remains of living organisms from which rocks are composed. Thus,
There are three structures of sedimentary organic rocks: macroorganogen -
new , microorganogenic , detritus .
Macroorganogenic - consists of large, large remains of living
organisms (peat, brown coal, shell rock).
Microorganogenic - consists of the smallest living organisms or
their remains (chalk, organic limestone, diatomite, tripoli).
Detritus – intermediate between macro- and microorganogenic
mi structures. The composition contains large and small particles,
breakdown of living organisms.
The main textures of sedimentary organic rocks are:
dense ( massive ), striped , cavernous , loose , porous .
Mixed sedimentary rocks
Mixed sedimentary rocks are rocks that have in their
particles of organic, chemical origin, as well as detrital matter
terial. Mixed sedimentary rocks include some types of
limestone, dolomite, opoka, marl.
Opoka is a siliceous rock, it consists of diatoms and
silica of chemical origin. Marl is a carbonate rock.
It consists of calcium carbonate of chemical and organic origin and
clay particles of mechanical origin. This breed has a variety of colors
sewn, in its natural state can have significant strength, one-
but with repeated wetting and drying, it cracks, over-
moves from massive rock into separate fragments, and often into a mud-like mass.
Application in sedimentary construction
organic rocks
Sedimentary organic rocks can be used as construction
solid stone in low-rise construction. Chalk is part of the construction
ny solutions, peat is an insulating material.
12 Metamorphic rocks - origin, composition, structure, features of occurrence in the earth’s crust, physical properties and applications
Metamorphic rocks are rocks that were formed as a result of the process of metamorphism. These rocks are secondary rocks because they were formed from pre-existing rocks.
The process of metamorphism is the process of deep transformation of pre-existing sedimentary and igneous rocks under the influence of metamorphic factors.
The factors of metamorphism are high temperatures (about 1000 - 1500o C), high pressure (about 1000 atm.) and chemically active substances.
Depending on the main factor affecting rocks, the following types of metamorphism are distinguished: : contact ( contact ), dynamic ( dynamometamorphism ), regional .
Contact metamorphism is a process of deep transformation of igneous and sedimentary rocks under the influence of mainly high temperatures, as well as chemically active substances. When igneous substance is introduced into the host rocks (most often of sedimentary origin), melting occurs at the contact of these rocks. At some distance, recrystallization of rocks is observed under the influence of both high temperatures and chemically active substances coming from the magma.
The zone of distribution of contact metamorphism is several kilometers. As you move away from igneous intrusions, the rocks remain less transformed. During contact metamorphism, rocks most often change their structure, texture, and mineral composition.
Dynamic metamorphism– the process of transformation of pre-existing igneous and metamorphic rocks at great depths under the influence of high pressures (the main factor). During dynamometamorphism, the structure and texture of metamorphic rocks changes, but the mineral composition remains unchanged. Dynamometamorphism is associated with mountain-building processes.
Regional metamorphism is a process of deep transformation of rocks under the influence of all three factors: high pressure, high temperatures and chemically active substances. Distinctive feature This type of metamorphism is that it occurs at great depths and covers vast areas in the earth's crust. It is believed that this form of metamorphism is associated with the immersion of entire regions of the earth's crust to great depths in the bowels of the Earth in areas of very high temperatures. The origin of the granite-gneiss Ukrainian crystalline massif is associated with this type of metamorphism. During regional metamorphism, the structure, texture, and mineral composition of pre-existing rocks changes.
Clastic rocks. They consist of fragments of eroded bedrock or minerals, sometimes with remains of broken fossil shells. Their classification is based on the size, degree of roundness and cementation of the fragments (Table 13 and Table 14), which depend on the strength and resistance of bedrock (destroyed) to weathering processes, as well as the stage of rock development: weathering, denudation, accumulation or diagenesis. So loose rocks from angular loose fragments are products (results) of physical weathering; from rounded – weathering, transfer (denudation) and accumulation (sedimentation) of loose sediments. Cemented clastic rocks went through a stage of diagenesis in their development, during which carbonate or siliceous minerals formed between the fragments, or fine clastic minerals - clays - were deposited. Loose rocks are usually young, Quaternary in age and lie close to the surface, while cemented rocks are of an older age. Most of the cemented dense clastic rocks accumulate on the bottom of seas and oceans, where many weathering products are ultimately carried, and therefore such rocks are also called terrigenous(removed from continents - land). For clastic rocks, the concept of “structure” is often confused with “texture”, so one can simply characterize the structure of the rocks.
Crushed stone And debris 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 site of their formation) and deluvial (formed during the movement and accumulation of rock fragments on the slopes and at the foot of hills and
Table No. 12
Characteristics of widespread sedimentary rocks and soils
|
Name and class (clastic, chemical, biochemical) |
Mineral composition (rock-forming) and chemical composition |
Structure |
Color and other distinctive properties |
Class and types of soils (by particle size distribution, water permeability, strength and compressibility, softening, plasticity, salinity, solubility, etc.) |
|
|
Texture |
Structure |
||||
|
Sand, clastic Sandstone Conglomerate Limestones of different textures Diatomite Rock salt Anhydrite | |||||
Completed 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 Crushed stone – Dresva – |
Conglomerate |
different 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 |
Mudstones |
Kaolinite, montmorillonite, etc. |
|||||||||
Table 14
Basic structures of cemented clastic rocks
|
Name of structure groups |
Name of main structures |
Features |
Impact on rock properties |
|
Psephyta |
Pebble Gravel Shchebnevaya Dresvyanaya |
Characteristic of conglomerates: rounded fragments measuring 10...100 mm Characteristic of gravelites: rounded fragments ranging in size from 2…10 mm Observed in breccias and gruss forests. The unrounded shape of the fragments with a diameter of 10 ... 100 mm (crushed stone) and 2 ... 10 mm (crushed stones) is typical. |
Properties and stability, in addition to the size of the fragments, depend on their mineral composition, the nature and type of cement |
|
Psamitaceae |
Coarse grain Medium grain Fine grain |
Observed in sandstones with grain sizes |
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 |
siltstone siltstone |
Typical for siltstones with grain sizes 0.1…0.05 mm Typical for siltstones with a grain size of 0.05...0.005 mm |
Not resistant to weathering: hard when dry, hard when wet become soft, swell in water, sometimes become soaked until they completely lose cohesion |
|
Pelitic |
Typical for mudstones and compacted clays less than 0.005 mm |
mountains) origin, lie in the idea of thin covers and trails at the foot, covering almost the entire earth's surface. Since the most durable bedrock is preserved in the form of crushed stone and debris, these deposits have a strength coefficient on average of 1.5.
Pebbles and gravel They differ from crushed stone and debris by the roundness of the fragments, which occurs during long-term transport over significant distances. The degree of rounding and sorting is extremely varied. They are divided into fluvial, lacustrine, marine and glacial deposits, occurring in the form of layers and lenses. The voids between the pebbles and gravel are quite large. Pebble and gravel grains have virtually no capacity for capillary rise of water, but they are highly permeable and easily release water.
Pebbles and gravel are of great practical importance as an easily sorted and processed building material. They are used for preparing concrete, in 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, micas, magnetite and other minerals are often present along with it. Sometimes sands are found consisting almost exclusively of grains of dolomite, magnetite, shales, fragments of shells or rocks. Depending on the conditions of formation, sands can be river, lake, sea, glacial and dune; they differ in layering, roundness, mineral composition and other properties.
The porosity of sands is significantly less than the porosity of other clastic rocks (loess, clay); it is usually equal to 30...40%. Very important properties of sand include its ability not to change volume when drying and moistening and its ability to absorb, pass through and release water. Sand saturated with water can flow and quicksand appear on the slopes. Sand that is saturated with water, but does not have the ability to move and be eroded, can be a reliable foundation. Sands have a low 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 earthenware, porcelain and glass; as a material for filtering in water supply installations and other purposes.
Loess- a mixture of tiny grains (0.05...0.005 mm) of quartz, clay particles and calcite, heavily atomized, partly in the form of shell-like tiny balls, yellowish-white, light, porous rock, when ground it turns into powder. It is distinguished by high particle cohesion and can form steep multi-meter cliffs. The loess contains many thin vertical tubes with traces of plant roots; many calcareous concretions (cranes or wood pupae) of bizarre shape. Typical loess is characterized by the absence of layering. It is widespread on the earth's surface and occupies about 4% of the land. Most scientists consider typical loess to be an aeolian formation, but there are hypotheses about its soil-eluvial, deluvial, proluvial and even glaciolacustrine origin. Loess is a specific soil due to its engineering-geological characteristics: when dry, it can serve as a foundation for structures, but when moistened it is subject to strong compaction, which results in significant subsidence. The subsidence of loess is a consequence of its high porosity and the action of water, which changes the structure of the loess. The strength coefficient is 0.8, for liquefied loess 0.3. Dust filtration coefficient 0.51…1.62 cm/h.
Clays– finely dispersed rocks, which contain 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.
Clays 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 kaolinite content in them is high – from 40 to 70%. These clays are highly resistant to high temperatures. The second - lean clays - are less greasy to the touch, and consist of tiny 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 with iron oxides.
According to the conditions of formation, clays are divided into primary, or residual, and secondary, or sedimentary clays. Residual clays are products of hydrolysis of silicates and mainly feldspars. Secondary clays were formed at the expense of primary clays by moving them horizontally and redepositing into reservoirs and depressions; they are distinguished by better sorting and fat content.
Clays in the dry state are hard and represent a dense rock that can be ground into powder. They have significant porosity; dry clays vigorously absorb water and, having become plastic, release 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 - up to 70% of their volume, capillary rise and, when saturated with water, water resistance (waterproof). They contribute to the development of landslides on appropriately steep slopes; They provide artesian (pressure) water as covering layers. Under the influence of external load, unconsolidated varieties of clay are greatly compressed, but this compression occurs very slowly and can last hundreds of years. Heavy buildings erected on such clays can produce significant and often uneven settlements.
Clay soils include sandy loam, loam and clay. Sandy loam It is a transitional rock from sands to clays. The amount of clay particles in them is 3...10%. When rolled out in your hands, wet sandy loam crumbles. Sandy loam filtration coefficient 0.01…36 cm/h. Loam contains more clay particles - 10...30%, its properties resemble clay, but wet loam cracks when rolled and bent in the hands. The filtration coefficient of loam is 0.06…5.0 cm/h. Clay contains more than 30% clay particles, due to which a rope of wet clay can be rolled into a bagel. Clay strength coefficient is 1.0. Filtration coefficient 0.000002… 0.001 cm/h. Clay rocks interlayer and quickly wedge out over the area of distribution.
Kaolin clays are used in the porcelain and paper industries, fatty clays are used as refractory materials, and leaner clays are used for brick, tile and pottery production. Fulling clays, characterized by their ability to absorb fats and oils, are used for cleaning wool, cloth, etc. Glauconite clays produce good green mineral paint, and ferruginous clays produce red paints, umber, sienna, and ocher.
Argillite(or shale) is a very compacted fine-clastic clayey rock with pronounced layering, sometimes turning into foliation. It consists of tiny particles of kaolinite, flakes of muscovite, chlorite, tiny grains of quartz with an admixture of carbon particles and iron hydroxides, and therefore often has a dark to black or brownish color. Shales occur in the form of layers, horizontal or folded, broken by faults.
Clay shales are usually widespread in folded areas: in the Caucasus, the Urals, etc. Varieties of dark gray color, with thin platy structure, are called roofing shales. Slaty shales are black in color due to the presence of carbonaceous matter. Bituminous and oil shale are sheet rocks of black and dark gray color, rich in bitumen.
Clay shales with good thin-plate separation are used as a very stable roofing material. They are used to make stair steps, baseboards, floor tiles, window sills, panels, table boards, and washbasins. Shales, which do not contain admixtures of ore minerals, are used in electrical engineering instead of marble. Waste from the roofing and slate production is used to make asphalt and artificial road stones.
Engineering-geological characteristics - clayey shales differ from clays by significantly greater hardness. Strength coefficient of strong clay shale is 4. Temporary compressive strength is 60…200 MPa.
Sandstones– cemented densely layered sands of varying strength, formed as a result of diagenesis, compaction of loose sediments under the weight of overlying sediments. Based on absolute size, sandstones are classified into coarse-grained, medium-grained and fine-grained sandstones. They consist predominantly of the most common and physically and chemically stable quartz. Depending on the mineralogical composition of the cement, sandstones are divided 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, and in the Urals. Sandstones vary in the mineral composition of the sand grains: monomineral (usually quartz), polymineralic arkose (consisting of quartz, feldspars and mica) and greywacke (consisting 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 there are no other stone building materials. Varieties of sandstones rich in silicic acid (at least 97%) are used as valuable dinas raw materials. Sandstones with siliceous cement are widely used in construction as rubble material; some varieties are successfully used for making millstones.
Depending on porosity, humidity, cementing substance, as well as on the structure and size of grains, the mechanical strength of sandstones varies widely (see Table 9). Porous sandstones often contain artesian waters, oil and flammable gases. Compressive strength ranges from 40...140 MPa. Strength coefficient 2…15.
Breccia And conglomerate– cemented rocks, consisting, respectively, of unrounded acute-angled and rounded rock fragments (see Table 13) and a finer cementing substance. The composition of breccia fragments, in comparison with conglomerates, is less complex, since the area of demolition of the fragments that make up the breccias is much smaller than the fragments that are part of the conglomerates. The clasts usually belong to one or a few rock types. Debris in conglomerates was transported over long distances over long periods of time from many places. The composition of cement can be different: calcareous, siliceous, ferruginous, clayey. Breccia is characterized by heterogeneity in the composition of the cement, as opposed to the homogeneity of the composition of the fragments.
Breccia is formed during tectonic and landslide processes through the accumulation of destruction products (fragments) of rocks at the foot of the slopes. Volcanic breccias are formed by the cementation of coarse volcanic ejecta; tuff breccia - a significant amount of ash. Conglomerates are made from debris that accumulated along the shores of seas, mountain rivers and lakes. The debris is cemented by various chemical compounds falling out of the water (lime, etc.) and small clay particles settling. They occur in the form of layers of small thickness - tens, sometimes a few hundred meters. They are distributed mainly in folded areas: the Urals, the Caucasus, and also in landslide zones. Due to the angular shape of the fragments, breccias are stronger than conglomerates and are more suitable as building stone. Breccia is valued as a facing stone for its beauty.
Thus, clastic rocks are very diverse in composition, structure, and occurrence patterns; wedge out and replace each other both along the strike of the rocks (in area) and at depth. Continental modern clastic rocks, 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 pinching out of clastic and clayey 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 sediments; in folded areas they often lie close to the earth’s surface and fall within the scope of engineering activity.
Table 15
Chemogenic and biogenic rocks (key)
|
Chemical composition |
Name |
Main rock-forming minerals |
Structure |
Texture |
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|
Rock salt Silvinit |
Crystalline |
Massive Banded Layered |
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|
Sulfates |
Anhydrite |
Anhydrite |
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|
Carbonates |
Limestone |
Clay minerals (40-50%) |
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|
Biomorphic Biosomatic Fine - fine - grainy |
Densely layered, Fine porous Biogenic |
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|
Siliceous rocks |
Diatomite |
Knowledge of the composition and structure of sedimentary rocks, the ability to systematize them is one of the necessary conditions for the successful use of lithology in the study and development of the Earth's interior. Classification of sedimentary rocks. Classification of sedimentary rocks according to significance and scale are divided into general and partial. General classifications cover all sedimentary rocks, with the latter being combined into classes and subclasses based on composition, genesis and other characteristics. Particular - composed primarily of breed classes. Let's consider a relatively simple classification of sedimentary rocks proposed by M.S. Shvetsov (1934, 1968). He highlighted: a group of clastic rocks, including coarse clastic (fragments more than 1 mm), sandy (fragments 1-0.1 mm), silty (0.1-0.01 mm), pelitic (less than 0.01 mm), volcanic-sedimentary; group of clayey ones, including polymineral, hydromica, kaolite, montmorillonite; a group of chemogenic and biogenic, combining aluminium, ferruginous, manganese, siliceous, phosphate, carbonate, sulfate, halide, etc. group of caustobiolites: coals, oils, ozonerites, asphalts, oil shale. Each of the identified classes of rocks occupies an unequal position in the stratosphere. The most common clay rocks (~55-60%), approximately equal position is occupied by the class of clastic rocks and the class of chemogenic and biogenic rocks (20-25% each), a small part is accounted for by caustobiolites. Clastic rocks. Clastic (clastic or mechanical) rocks are composed of 50% or more rock or mineral fragments and are loose or cemented sediments. Their classification is based on structural features - the size and shape of the fragments. The basis of clastic rocks is made up of rock fragments of different mineral composition and genesis: igneous, metamorphic and sedimentary. The smaller ones are represented by fragments of individual minerals.
The class of coarse rocks (psephytes) includes: blocks, boulders, crushed stone, gruss, pebbles and gravel, breccias and conglomerates. In accordance with the classification of Maslov and Nalivkin, two groups of breccias are distinguished: Breccias of surface mechanical processes, among which 10 varieties are distinguished: Breccias are of volcanic origin, among which there are 5 varieties. There are all transitions between conglomerates and breccias, and some of those genetic types that were described above as breccias could (and are often done) be classified as conglomerates (coastal, glacial, silicic, volcanic, etc.). Among the conglomerates, one can distinguish between marine, river and piedmont (transitional between conglomerates and breccias), as well as transitional glacial ones, distinguished under the genetic term “moraines”. Aeolian conglomerates represent a rare case. Pseudoconglomerates are clusters of nodules formed by algae, as well as nodules. Conglomerates that occur at the base of sediment series are called basal and indicate erosion and shallow water conditions. Class of medium clastic rocks (psammites).Sands are loose rocks consisting of products of physical weathering, detrital grains of psammite size (1-0.1 mm). If the same grains are strongly enough interconnected, the rock is called sandstone. One of the significant differences between coarse-grained material and medium-grained material is that the fragments in this case are not rocks, but minerals, although fragments of fine and micro-grained rocks can be found. According to the classification scheme, sands are divided according to grain size into: coarse-grained - 1 - 0.5 mm, medium-grained - 0.5 - 0.25 mm and fine-grained - 0.25 - 0.1 mm. The initial shape of the fragments can be different - isometric, sheet, columnar, etc. During transportation, depending on the duration of transfer, the size of the grains, their mechanical and chemical stability, they are rounded to varying degrees, i.e. grains are divided according to the nature of roundness: The clastic part of sandy rocks is not the same in composition, which is determined by the difference in the source material coming from the demolition area, the degree of its processing at the stages of destruction, transport, as well as during diagenesis and catagenesis. As a result, the clastic part is enriched with minerals resistant to mechanical and chemical influence. This phenomenon is known as mineralogical maturation of clastic material. As a result, with repeated redeposition of clastic grains, only quartz is preserved from the rock-forming minerals. Composition of sand rocks. Among the rock-forming clastic minerals, quartz significantly predominates, followed by potassium feldspars, micas, chalcedony, glauconite, plagioclases, as well as hydromicas and kaolinite. The most typical in the community of accessory minerals are transparent zircon, garnets, tourmaline, staurolite, monazite, and disthene. Hornblende, pyroxenes, olivine, etc. act as accessory species. Ore opaque minerals make up up to 1 - 1.5% of the clastic part and are represented by magnetite, ilmenite, rutile, leucoxene, hematite, pyrite and marcasite. Secondary (postdiagenetic) minerals play a significant role in the structure and composition of sand rocks. Among them, the most important are regenerated quartz, microcline, orthoclase, plagioclase, as well as new formations of calcite, dolomite, chalcedony, kaolinite, hydromica, chlorite, albite, iron oxides and sulfides. According to the relationship between the main components - quartz, feldspars and rock fragments, three main groups of sandy rocks are distinguished: 1. monomineral - predominantly quartz ~ 99%, 2. oligomict - quartz 75% + impurities ~20% (pol. spar, glauconite, etc.), 3. polymict - reduced content of essential minerals (<75%), или отсутствие такового, либо нескольких минералов в одинаковом количестве. Polymictic rocks include arkoses and greywackes. Arkosic sand rocks (arkoses) - are formed due to the destruction products of granites, gneisses and other rocks similar in composition. The predominant clastic materials are quartz, less commonly feldspar; micas, iron oxides, chlorite, and glauconite are present. According to the latest data, it would be most correct to consider that arkoses consist of grains of alkali feldspar and quartz. Rock fragments may be present in small quantities (up to 15%). Arcoses are characterized by a light, pinkish-gray or grayish-yellow color, rough layering, reminiscent of the individuality of granites. They are widespread in sediments of all systems. Their appearance is always associated with uplifts of granite or gneiss massifs, the destruction of which produces typical arkoses in geosynclinal areas, and polymictic feldspathic sandstones on platforms. Graywacke sand rocks (greywackes) - just like arkoses, consist of quartz, feldspar, mica, chlorites, but unlike them contain a larger amount of clastic rocks (more than 15%), mostly dark-colored. From metamorphic rocks come fragments of clayey, clayey-siliceous, carbonaceous-siliceous shales. Igneous rocks are represented by fragments of andesites, basalts, or their deep-seated analogues. The clastic part is usually poorly sorted and poorly rounded. Color: gray, greenish-gray, dark gray to black. In foreign, most often in American, literature, the analogue of greywacke rocks is lithite rocks. Based on their mineral composition, the following groups of sandy (psammitic) rocks are distinguished. 1. Quartz sands and sandstones. Quartz - feldspar, mica, glauconite, etc. Cement - any siliceous, clayey limestone, etc. Based on the nature of the cement, sandstones are called siliceous, calcareous, clayey, carbonate-clayey, etc. 2. Magnetic and garnet sands. The grains of these minerals predominate. Rarely seen. 3. Quartz-glauconite sands and sandstones. Main components: quartz - 40-20%, glauconite - 60-80%, no more than % mica and other minerals. Depending on the amount of glauconite and its weathering, their color ranges from bright green, and with strong weathering they turn into brown ferruginous sands. 4. Ferrous sands and sandstones. They consist of quartz, the grains of which are covered with films, jackets or crusts of a brown ferruginous mineral - goethite or hydrogoethite. The sandstones are cemented by this ferruginous mineral. Color: lilac-brown to rusty-orange. 5. Arkose sands. 6. Graywackes are dark colored. Chemical composition. The chemical composition of different sand rocks is somewhat uniform. The differences lie in the quantitative ratio of individual elements. Characterized by a sharp predominance of silica SiO 2, the ratios of alumina Al 2 O 3 and iron oxides are different. In addition to the listed oxides, the presence of Na 2 O, K 2 O, MgO, MnO, S - , TiO 2, P 2 O 5, CO 2, SO 3 and others is characteristic, which are contained from fractions to 1-2%. Cementing part. The cementing part of sandy rocks is most often represented by clayey material and calcite, less often by dolomite, gypsum, anhydrite, opal, and iron oxides. There are also phosphate, siderite and other types of cement. The structures of the cementitious substance are varied. They are determined by the size and shape of the particles that make it up. The most common: 1. coarse-grained structure (particle size more than 0.5 mm), 2. medium-grained - 0.1-0.5mm, 3. fine-grained - 0.05-0.1mm, 4. fine-grained - 0.01-0.05mm, 5. microgranular or pelitomorphic - less than 0.01 mm, 6. different grain, 7. fibrous, 8. amorphous. Based on the ratio of the fragmental and cementing parts, as well as on the filling of the pore space, five types of cement are distinguished: basal, pore, contact, film, clot. For information: there are several more types of cement formed exclusively in post-sedimentation stages - regeneration, corrosion, crustification and poikilite. According to the conditions of origin, the following types of sand rocks are distinguished: coastal-marine sand rocks, marine sand rocks, river sands and sandstones, deltaic sand rocks, fluvioglacial (fluvio-glacial) sands and sandstones, aeolian Class fine-clastic rocks (siltstones and siltstones).Aleurites are loose clastic rocks, the predominant part of grains of which have a size from 0.1 to 0.01 mm and their content in the rock is 50 percent or more. Their cemented varieties are called siltstones. Sometimes divided into fractions a). 0.1-0.05 0.05-0.01, b). 0.1-0.063 0.063-0.01. In their origin, silty rocks do not differ from sandy rocks, being only a smaller part of the destruction products of the same parent rocks. Their transfer and destruction occurs under the influence of the same factors, but often with a large participation of wind. Rocks with a grain size of 0.05-0.01 mm are described as mudstones or clays, which siltstones often resemble, especially if they contain admixtures of clayey material. The mineral composition of clastic particles is approximately the same as in sandy rocks, but there is a large proportion of stable minerals - quartz, muscovite, chalcedony; the role of potassium feldspars and acid plagioclases decreases. They contain more clayey material, stable accessory minerals, iron oxides and hydroxides. Characterized by the presence of organic matter. Based on their mineral composition, they are divided into: monomineral, oligomict and polymict varieties. The structure of silty rocks (texture and structure), the type and composition of cement are in many ways similar to sand formations. Aleurites are characterized by thin horizontal layering. The color of the rocks, depending on the impurities, can be very different - light gray, black, brick red, brown, green. Silt rocks, like sand rocks, are formed under different paleogeographic conditions. The most common are marine, lacustrine, river and aeolian varieties. Modern representatives of the latter include some types of loess. In their physical and technical properties, typical silty rocks sometimes differ significantly from sandy rocks, especially if they contain a noticeable admixture of clay. They often have the property of collapsing under load, and when wetted they exhibit fluidity along with cohesion. This property leads to the formation of suffusion karst. It is the silty rocks that create the most dangerous “quicksands” for construction. - - Topics: oil and gas industry EN rock debris ... Technical Translator's Guide Placers of rocks and precious metals- are the result of weathering of massive rocks and their disintegration in situ into angular fragments of varying sizes. R. are characteristic primarily of mountainous countries with a harsh continental climate. Water getting into cracks... ... DISINTEGRATION (DISAGGREGATION) OF ROCKS- their disintegration into fragments decomposed. values without changing the composition. Occurs under the influence of physical weathering (temperature fluctuations, cracking, under the influence of plant roots, etc.). Geological Dictionary: in 2 volumes. M.: Nedra. Under… … Geological encyclopedia Disintegration of rocks- destruction of rocks into fragments of different sizes, without noticeable changes in the chemical and mineralogical composition... Explanatory dictionary of soil science MAGNETIC MINERALS OF SEDIMENTS AND SEDIMENTARY ROCKS- are formed as a result of chemical reactions at a temperature close to room temperature and a pressure of about 1 atm (authigenic minerals), both under conditions of “hematite” high oxidation (more often) and “magnetite” and even “silicate” zones. In the first… … Palaeomagnetology, petromagnetology and geology. Dictionary-reference book. Sedimentary rocks- ... Wikipedia Mechanogenic sedimentary rocks- This article may contain original research. Add links to sources, otherwise it may be set for deletion. More information may be on the talk page. (May 11, 2011) ... Wikipedia sedimentary rock Sedimentary rocks- Contents 1 Definition 2 Classification of sedimentary rocks 3 Genesis of sedimentary rocks ... Wikipedia Earth- (Earth) Planet Earth The structure of the Earth, the evolution of life on Earth, flora and fauna, Earth in the solar system Contents Contents Section 1. General information about planet earth. Section 2. Earth as a planet. Section 3. Structure of the Earth. Section 4.… … Investor Encyclopedia Glacier- or a glacier represents an icy river descending through valleys or from high mountains, or in polar countries. G. serves as one of the forms of unloading that huge supply of snow and firn, which falls in significant quantities above the snow line. For… … Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron Books
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