Sedimentary clastic rocks are examples. General grouping of sedimentary rocks. Group of 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 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 clastic 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

Clastic rocks are sedimentary rocks that arose as a result of the mechanical destruction of any rocks and the accumulation of the resulting debris. They consist of fragments of various rocks and minerals.

Classifications of clastic rocks. Classifications of clastic rocks are based on the structure of the clasts and less often on the mineral composition. Classifications are more often used, which are based on structural features - the size and shape of the fragments.

The lower boundary of detrital rocks is drawn at a size of 0.005 mm, since below this size interval, most detrital particles lose signs of primary rocks and minerals from which they are formed. And having a large total surface of particles relative to volume, they undergo oxidation, hydration, hydrolysis and replacement by newly formed minerals, mainly layered silicate-clay minerals and chlorites. These particles, lying outside the size of 0.005 mm, form sediments and rocks, the structures of which are defined as pelitic, and the sediments and rocks themselves are called pelitic through the structural name. Taking into account the newly formed, predominantly clay minerals, pelitolites are also called clay rocks.

Clastic sediments and rocks from particles larger than 0.005 mm are divided into three groups according to the size of the fragments. The smallest ones, from the term “siltstone”, received the name of siltstones and siltstones: the next in size from the term “psammite”, introduced by A.T. Brongniard in 1813 are psammites and psammitolites, most often called sands and sandstones. And the largest from the term "psephite", proposed by A.T. Brongniard in the same 1813, are psephites and psephytolites, also called coarse-clastic rocks.

The basis of coarse clastic rocks is made up of fragments of rocks of various mineral composition and genesis: igneous, metamorphic and sedimentary. Smaller ones (sands and silts) are represented by fragments of individual minerals.

According to the mineral composition, they distinguish: monomictic rocks - in which one mineral is at least 95%, oligomictic - the predominant mineral is 75-95% and polymictic - none of the minerals is 75%.

The decisive proof of the existence of real units within clastic sediments and rocks, the presence of boundaries between them and the position of the latter is the distribution of clastic rocks of different sizes in the lithosphere.

According to the size of the debris, they distinguish:

1) coarse clastic rocks (psephites), consisting mainly of fragments with a diameter of more than 2.0 mm;

2) medium clastic (psammites), consisting of fragments with a diameter of 2.0 to 0.05 mm;

3) small-clastic (siltstones), consisting of fragments with a diameter of 0.05 to 0.005 mm;

4) clayey rocks (pelites), consisting mainly of particles with a diameter of less than 0.005 mm (see table).

Table 1 - Classification of clastic rocks

Coarse clastic rocks. These include rocks consisting of fragments ranging in size from 2.0 mm to several meters in diameter. Depending on the structure and texture, the following types of rocks are distinguished.

Blocks - angular fragments over 200 mm in size, crushed stone - angular fragments from 200 to 40 mm in size and gruss - from 40 to 2.0 mm. If the fragments of the specified dimensions are rounded, then they are respectively called boulders, pebbles and gravel (see Appendix A).

Cemented crushed stone and gruss are called breccias. Ore breccias deserve special attention, in the cement of which industrial accumulations of ores of copper, lead, zinc and other metals are often present, and cemented pebbles and gravel are a conglomerate.

Conglomerates are widespread among ancient marine sediments. In conglomerates there are industrial concentrations of gold and uranium (Figure 1.2).

Figure 1.2 Glacial conglomerate and sandstone. Volozhinsky district near ag. Rakov (author's photo)

Medium clastic rocks. These include sands and sandstones that are widespread in nature. Sands are loose accumulations of debris ranging in size from 2.0 to 0.05 mm, and sandstones are fragments of the same size cemented together (see Appendix A).

Fine-clastic rocks. Fine-clastic rocks include rocks consisting of fragments ranging in size from 0.05 to 0.005 mm. Loose accumulations of such fragments are called silts, and cemented - siltstones.

One of the widespread representatives of silts is loess-light yellow rock, consisting of fragments of quartz and feldspars.

Siltstones - cemented rocks of various colors, often have a thin-layered platy structure (see Appendix B).

Mixed rocks. These include sandy loam, containing, along with sandy, up to 20-30% clay particles, and loams, in which the amount of clay particles increases to 40-50%. Accordingly, the properties of the rocks also change, which, first of all, is expressed in a decrease in plasticity when wet from clays to sands (see Appendix B).

Clay rocks. The most common sedimentary rocks are clayey, which account for more than 50% of the volume of all sedimentary rocks.

Clay rocks mainly consist of the smallest (less than 0.02 mm) crystalline grains of clay minerals. In addition, they include equally fine grains of chlorites, aluminum oxides and hydroxides, glauconite, opal, and other minerals that are products of the chemical destruction of various rocks and, to some extent, clay minerals. The third component of clay rocks is a variety of fragments smaller than 0.01 mm in size.

Clay rocks are formed as a result of chemical processes leading to the accumulation of clay minerals, and the simultaneous bringing of the smallest detrital particles.

According to the degree of lithification, clays are distinguished among clay rocks, and mudstones are highly compacted clays (see Appendix D).

Clastic rocks are one of the main representatives of sedimentary formations and make up about 20% of the volume of the Earth's sedimentary shell. Classifications of clastic rocks are based on the mineral composition and structure of the clasts. Classifications are more often used, which are based on structural features - the size and shape of the fragments. The classification is based on 2 main features: 1) the structure or dimension of the fragments 2) the mineral composition

The trace is distinguished by the dimension. types of rocks: 1) coarse clastic (1-10 mm) 2) sandy (0.1-1 mm) 3) silty (0.01-0.1) 4) pelitic (<0.01 мм)

Clastic rocks include those rocks in which the bummer. part is more than 50% of the sum of all components.

22 . Rough rocks.

Rock classification is based on clastic grain sizes and mineral composition. Add. the signs are the physical state of the rocks (scem-th, non-sem-th), the degree of roundness and sorting of grains. Clastic rocks, in which there are more than 25% of clasts > 1 mm in size along the long side, are usually called coarse clastic. Blocky rocks are found exclusively in mountainous areas. Their occurrence is associated with large earthquakes, accompanied by collapses.

Boulder rocks consist of large fragments (100-1000 mm) weakly cemented by sandy-clayey material.

Pebble and rubble rocks are an accumulation of products of mechanical destruction of various rocks - igneous, metamorphic, sedimentary. The main ones in terms of importance are fragments of 10-100 mm in size, the content of which is more than 25%. Crushed stone rocks - crushed stone and breccia, differ from each other in that in the first, the fragments are not cemented, and in the second, they are cemented.

Pebble rocks - pebble and conglomerate differ from each other in that the first is an accumulation of unconsolidated pebbles, and the second is cemented. Grus and gravel rocks are composed of fragments of various rocks and less often minerals with a predominant size of 1-10 mm. Gravel rocks consist mainly of gruss - acute-angled fragments, and gravel rocks - of rounded

23. Sand rocks.

* According to the size of the fragments, it is divided into 3 varieties: 1) coarse-grained 2 medium-grained 3) fine-grained. * By min. the composition is distinguished:

a) monomictic - one mineral makes up at least 95% of the rock b) oligomictic - one mineral makes up 75-95% of the rock c) polymictic - no mineral reaches 75%

In the polymineral class of sandstones, 2 varieties can be distinguished: 1) Arcoses - sandstones composed of quartz and a large number of PS 2) Graywackes - sandstones of very poor sorting, consist of particles of different sizes. There is little quartz and a lot of micas and other minerals; the matrix is ​​composed of clay minerals.

Sandstone deposit settings: * coastal (mostly medium to fine-grained sandstones with very little clay cement are formed here) * marine (usually homogeneous, have carbonate and clay cement) * river (sorted worse than marine, contain impurities of plant material, deltas are represented by small medium coarse-grained sandstones) * Eolian (well-rounded, homogeneous, without clay fraction)

24. Silty rocks.

Silty rocks, like sandy ones, are among the widespread sedimentary formations. Their main part, which is 50% or more, is clastic particles with a size of 0.01-0.1 mm. Loose or weakly cemented rocks are called silts, and strong, cemented rocks are called siltstones. Among them, coarse-grained, medium-grained and fine-grained are distinguished (see Table 17).

The mineral composition of the clastic part is approximately the same as in sandy rocks, but here the proportion of stable minerals is higher - quartz, muscovite, chalcedony. The role of potassium feldspars, acid plagioclases, and rock fragments in silty formations is noticeably lower. They contain more clay material, stable accessory minerals, iron oxides and hydroxides. These rocks are characterized by the presence of organic matter.* According to the mineral composition, among silty rocks, as well as among sandy ones, monomineral, oligomictic and polymictic varieties are distinguished. The structure of silty rocks (texture, structure), type and composition of cement are in many respects similar to sandy formations. Siltstones are characterized by thin horizontal bedding, less often oblique bedding is observed. The color of the rocks, depending on the impurities, can be very different - light gray, black, brick red, brown, green.

Silty rocks, like sandy ones, are formed in different paleogeographic conditions. The most common are their marine, lacustrine, river and eolian varieties. Modern representatives of the latter include some types of loess. like sandy ones, they are among the widespread sedimentary formations.

Clastic rocks are formed by the weathering of pre-existing rocks, which have been transported to different localities from where they originally were, and then turned into rocks. They have a detrital structure composed of clasts (large clasts like sand or gravel) and are classified by grain size. Table 7.1 lists the various clastic rocks along with their particle sizes.

Clastic rocks are composed of fragments of other rocks. These rock fragments originated from weathering and were then carried into lowlands or crevices, where they were trapped as sediment. If the sediment is buried deep enough, it becomes compacted and cemented, forming a sedimentary rock.

Clastic sedimentary rocks range in particle size from microscopic clay rocks to boulders. Their names are based on the size of their clasts or grains. Starting with the smallest grains, which are clays, then silts, then sand. Fragments larger than 2 mm are called pebbles or rubble.

Argillite is a rock composed mainly of clay particles, siltstone is composed of silt-sized grains, sandstone is composed of sand grains, and conglomerate is composed of pebbles covered with sand or silt.

Coarse-grained clastic rocks

Gravel (grain size greater than 2 mm; rounded fragments = conglomerate; angular fragments = breccia).

Medium-grained clastic rocks Sand (grain size from 0.05 to 2 mm).

Sandstone (mostly quartz grains = quartz sandstone or quartz arenite; mostly feldspar grains = arkose; mostly grains of sand-sized rock fragments = lithic sandstone, litharenite or gravuacca).

Cement (the glue that holds it all together) like calcite, iron oxides, silica.

Fine-grained clastic rocks

Siltstone and siltstone (grain size from 0.005 to 0.05 mm). Clay, mudstone and shale (grain size< 0,005 мм).

The deposition of these types of sedimentary rocks by various streams is something you could guess. Coarse gravel and pebbles are carried only by strong currents. There are swift mountain streams, rocky shores with high waves and melt waters of glaciers. Strong glacial flows also transport sand. This is why you usually see sand between gravel and pebbles. Pebbles and small pebbles trip over each other and become smooth very quickly, bouncing on the ground or in the water. Coastal pebbles and fragments broken glass, constantly rolled back and forth by the surf, also become smooth and rounded.

Coarse clastic rock, which is not so clearly smooth and rewashed, is not a conglomerate, but a breccia. These acute-angled rock fragments occur near their source, where the sedimentary rocks were layered on top of each other before being moved very far. Although some breccias are sedimentary in origin, others are formed from igneous rocks during volcanism. They were deposited on a layer of sedimentary rocks after the first ejection during an eruption or were instantly crushed along a fault during an earthquake.

- — Topics oil and gas industry EN rock debris … Technical Translator's Handbook

Placers of rocks and precious metals- are the result of weathering of massive rocks and their disintegration in situ into angular fragments of various sizes. R. are characteristic mainly of mountainous countries with a harsh continental climate. Water entering cracks...

DISINTEGRATION (DISAGGREGATION) OF ROCKS- their disintegration into fragments decomp. values ​​without changing the composition. Occurs under the influence of physical weathering (temperature fluctuations, cracking, under the influence of plant roots, and other causes). Geological dictionary: in 2 volumes. M.: Nedra. Under… … Geological Encyclopedia

Rock disintegration- the destruction of rocks into fragments of different sizes, without a noticeable change 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" zone. In the first… … Paleomagnetology, petromagnetology and geology. Dictionary reference.

Sedimentary rocks- ... Wikipedia

Mechanogenic sedimentary rocks- This article may contain original research. Add links to sources, otherwise it may be put up 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 Structure of the Earth, evolution of life on Earth, flora and fauna, Earth in the solar system Contents Contents Section 1. General about the planet earth. Section 2. Earth as a planet. Section 3. Structure of the Earth. Section 4.… … Encyclopedia of the investor

Glacier- or a glacier represents an icy river descending through valleys or from high mountains, or in polar countries. Mountains serve 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. Brockhaus and I.A. Efron

Books

• Set No. 1 "Flower meadow" (394001) Buy for 506 rubles
• Set No. 6 "Once upon a time there was a dog" (394006), . You will be surprised to discover how easy and entertaining the process of painting natural pebbles is. Recall that pebbles are flat fragments of mountain rocks rounded by flowing water or sea waves.