Pore-forming mineral for igneous, sedimentary and metamorphic rocks

For the most part, the rock-forming mineral is one of the main components of the earth's crust - rock. The most common are quartz, mica, feldspars, amphiboles, olivine, pyroxenes and others. Meteorites and lunar rocks are also referred to them. Any rock-forming mineral belongs to one or another class - to the main ones, which are more than ten percent, secondary - up to ten percent, accessory - less than one percent. The main, that is, the main ones, are silicates, carbonates, oxides, chlorides or sulfates.

Differences

The pore-forming mineral can be light (leucocratic, salic), such as quartz, feldspathoids, feldspars and the like, and dark colors (melanocratic, mafic), like olivine, pyroxenes, amphiboles, biotite and others. They are also distinguished by their composition. Pore-forming mineral is of silicate, carbonate or halogen rocks. Paragenesis - a combination of different types, defining the name, called the cardinal. For example, oligoclase, microcline or quartz is combined with granites.

Groups of rock-forming minerals that give place to the rock in petrographic taxonomy are diagnostic or symptomatic. These are quartz, feldspathoids and olivine. Also, the minerals are primary, syngenetic, forming the entire breed, and secondary, arising during the transformation of the rock. The constituent main rock-forming minerals chemical elements are called petrogenic. These are O, H, F, S, C, Cl, Mg, Fe, Na, Ca, Si, Al, K.

Properties of minerals

The crystal structure and chemical composition determine all the properties of minerals. Diagnosis is performed using a variety of analytical methods - spectral analysis, chemical, electron microscopy, X-ray diffraction. In field practice, the simplest (diagnostic) properties of minerals are determined purely visually, by eye. Most of them are physical. However, accurate determination of the mineral requires a whole range of diagnostic methods. Some properties of different minerals may coincide, while others may not.

This depends on the presence of mechanical impurities, chemical composition and forms of excretion. Rarely, the main properties are so characteristic that they can accurately diagnose any rock. Diagnostic properties are divided into three groups. Optical and mechanical groups due to their properties allow the determination of properties for all without stones. The third group is the others, with the properties used to diagnose highly specific minerals.

Monomineral and polymineral rocks

Rock rocks are accumulations of natural mineral masses covering the surface of the Earth, taking part in the construction of its crust. Here, as already mentioned, completely different substances are involved in the chemical composition. Those rocks, whose composition is one single mineral, are called monomineral, and all others, consisting of two kinds of rocks and more are polymineral. For example, limestone is entirely calcite, so it is monomineral. But granites are diverse. They include quartz, and mica, and feldspar, and many other things.

Mono- and polyminality depends on which geological processes occurred in the area. You can take any rock and determine the exact region, even the area where it was taken. They are similar to each other, and at the same time almost never repeat themselves. These are all studied rocks. There are a lot of stones, all seem to be identical, but their chemical properties were formed as a result of different processes.

Origin

According to the conditions in which the formation of mountains occurred, sedimentary, metamorphic and igneous rocks are distinguished. Magmatic rocks include the one that was formed from the eruption of magma. The hot, melted stone, cooling down, turned into a solid crystalline mass. This process is still in our days.

In molten magma, a huge number of chemical compounds, which are affected by high pressure and temperature, while many compounds are in the gaseous state. The pressure pushes the magma to the surface or comes close to it and begins to cool down. The more heat is lost, the sooner the mass crystallizes. The rate of crystallization determines the size of the crystals. On the surface, the cooling process is rapid, the gases evaporate, so the stone is fine-grained, and in the depths large crystals are formed.

Fouled and deep crystalline rocks

Crystallized magma is divided into two main features, which give groups names. The magmatic rocks include a group of effusive, that is, poured out, as well as a group of intrusive - deep crystallization. As already mentioned, magma cools under different conditions, and therefore the rock-forming mineral turns out to be different. Discharged with the volatilization of gases is enriched by chemical compounds and becomes poorer for others. The crystals are small. In deep magma, chemical compounds do not find new ones, the heat is lost slowly, and therefore the crystals are large in structure.

The poured rocks are represented by basalts and andesites, almost half of them, less often there is a liparite, all other rocks in the earth's crust are insignificant. In the depths porphyry and granites are most often formed, they are twenty times larger than all the others. Primary igneous rocks, depending on the composition of quartz, are divided into five groups. Crystalline rocks include a lot of impurities, among which there are various micro- and ultramicroelements, thanks to which all kinds of plants cover the earth's crust.

Magma

Magma contains practically the entire periodic table, where Ti, Na, Mg, K, Fe, Ca, Si, Al predominate, and various volatile components - chlorine, fluorine, hydrogen, hydrogen sulphide, carbon and its oxides, and so on, plus water in the form couple. When the magma moves up to the surface, the number of the latter decreases significantly. When cooling, magma forms a silicate - a mineral, which is a different compound of silica. Silicates are called all such plan minerals - with salts of silicic acids. Aluminosilicates contain salts of aluminum-silicic acids.

Basalt magma is basic, it is the most widespread and consists of half of silica, the remaining fifty percent is magnesium, iron, calcium, aluminum (significantly), phosphorus, titanium, potassium, sodium (less). Basaltic magmas are subdivided into a supersaturated silica - tholeiitic and enriched with alkali olivine-basalt. Granite magma is acidic, rhyolitic, it has even more silica, up to sixty percent, but in density it is more viscous, less mobile and heavily saturated with gases. Any volume of magma is constantly evolving, under the influence of chemical processes.

Silicates

This is the most widespread class of natural minerals - more than seventy-five percent of the Earth's crust mass, as well as one-third of all known minerals. Most of them are rock-forming and magmatic, and of metamorphic origin. Silicates are also found in sedimentary rocks, and some of them serve man as jewels, ore for the production of metals (silicate of iron, for example) and are mined as minerals.

They have a complex structure and chemical composition. The structural lattice is characterized by the presence of an ionic tetravalent group SiO ₄ - a double tetraerd. Silicates are island, ring, chain, ribbon, sheet (layer), frame. This separation depends on the combination of silicon-oxygen tetraerides.

Classification of rocks

Modern systematics in this field began in the nineteenth century, and in the twentieth, it developed tremendously as the science of petrography-petrology. In 1962 the Petrographic Committee was first created in the USSR. Now this institution is located in Moscow IGEM RAS.

The degree of secondary changes of effusive rocks differ as Cenotypic - young, unchanged, and paleotypic - ancient, which over time, recrystallized. This rocks are volcanogenic, detrital, which formed during the eruption and consist of pyroclasts (debris). Chemical classification implies the division into groups depending on the content of silica. Magmatic rocks in composition can be ultrabasic, basic, medium, acidic and ultra-acidic.

Batholiths and rods

Very large, irregularly shaped massifs of intrusive rocks are called batholiths. The area of such formations can be estimated in many thousands of square kilometers. These are the central parts of the folded mountains, where the batholiths extend to the whole mountain system. They are composed of coarse-grained granites with outgrowths, sprouts and protrusions, formed from the introduction of granite magma.

The rod is elliptical or round in cross-section. They are smaller than batholiths in size - often a little less than a hundred square kilometers, sometimes - all two hundred, but the rest of the properties are similar. Many rods stand out from the mass of the batholith like a dome. Their walls are steeply falling, the outlines are wrong.

Laccoliths, ethmolites, lopolites, dikes

Mushroom or dome-shaped formations, formed by viscous magmas, are called laccoliths. Meet more often in groups. They are small in size - up to several kilometers in diameter. The breed of laccoliths, growing under the pressure of magma, is lifted, without disturbing the stratification of the earth's crust. Than are very similar to mushrooms. Etmolites, on the contrary, are funnel-shaped, with a thin part down. Apparently, the narrow opening served as the outlet of the magma.

Lopolytes have bodies saucer-shaped, convex down and with raised edges. They also seem to grow out of the earth, not breaking the earth's surface, but as if stretching it. In the rocks, sooner or later, cracks appear - for various reasons. Magma feels weak places and under pressure begins to fill all the gaps and cracks, at the same time absorbing surrounding rocks under the influence of huge temperatures. So dykes are formed. They are small - in diameter from half a meter to hundreds of meters, but not even six kilometers. Since the magma in the cracks cools rapidly, the dikes are always fine-grained. If there are narrow ridges in the mountains, rocks are probably dikes, because they are more resistant to erosion than the surrounding rocks.