Most of all chemical elements, including very valuable, scattered in the rocks. Only a very small part of them concentrated in the mineral deposits. But although the content of elements in rocks is low, their total number in the earth for a Grand.
All minerals on the conditions of their formation are divided into deep and superficial. Depth of field are called endogenous (from the Greek words "edo" inside, "geos" origin), and surface - exogenous (Greek "Exo"outside).
Deep, or endogenous, deposits are formed as a result of the introduction of the earth's crust, heated underground melt or magma, and their cures. Magma penetrates through cracks in rocks. However, only a small portion of the magma in the volcano reaches the surface, forming lava flows and accumulations of volcanic ash. More magma does not reach the earth's surface and solidifies at depth, forming a deep crystalline igneous rocks, such as granite. Frozen at depth and on the surface of the Earth igneous rocks are widely used as natural stone building materials.
Due to different physical and chemical properties of the elements in the process of cooling of magmatic melts in the Earth is split and formed aggregations part of the chemical elements.
During cooling the so-called basic magmas, containing not more than 50% of silicon oxide, the process of separating substances in them is like iron smelting in blast furnaces. In the accumulations of magma that harden in depth, up pop light rock, and on the bottom of the magmatic reservoir fall of heavy minerals. These heavy minerals form magmatic ore deposits. The most significant deposits of iron and titanium, chromium and platinum, copper and Nickel. Close to its origin and field of diamonds in kimberlite pipes Siberia and South Africa, but for their education, in addition to high temperature, you need a lot of pressure.
Quite different are the valuable minerals in solidifying the so-called acidic magmas, containing more than 50% of silicon oxide. In these magmas high content of various gases, including water vapor. Gases dissolve many chemical compounds, especially metal, and not allow them to precipitate in the early stages of magma cooling. Therefore, conditions for their concentrations are in the most late, not had time to fully harden remnants of magmatic melts. Part of such residual molten magma saturated with the hot gases and dissolved valuable elements embedded in the cracks of the rocks and cooling down, forms a so-called pegmatite veins. They consist of quartz and feldspar, and sometimes contain accumulation of mica, precious stones (Topaz, aquamarine and others), minerals of beryllium and lithium, tin, tungsten, uranium.
Magmatic gases dissolved in them valuable connections not only accumulate in residual pockets of magma, but also can leak through the already hardened wall. So they penetrate into the surrounding cooling magmatic hearth breed. However, filtering hot gases and the surrounding rock can occur in a chemical reaction. Especially rapidly they occur between the hot magmatic gases and calcareous rocks. In the course of such reactions on the periphery of the arrays cooling magmatic rocks in the area of contact of them with the limestone, there are the so-called skarns. They consist of minerals, which include lime, silica and aluminum. In addition, in skarns often accumulate minerals iron, copper, lead, zinc, tungsten, and boron.
But not all of magmatic gases react on the depth with rocks. Most of them due to the high pressure rushes through cracks and pores of rocks up to the surface of the Earth. This mineralized pair gradually cooled, Sigulda and turn into hot mineral water - hydrothermal fluids. They continue to climb the porous permeable rocks. As further cooling of the hot mineral waters of diluted compounds securities and other elements precipitate. Filling in cracks of rocks, they form veins of minerals. Some items hydrothermal reacts with minerals in rocks and deposits, forming mineral deposits, replacing these rocks. These deposits are formed by deposits of mineral waters in the bowels of the Earth, called hydrothermal. With this very important group of endogenous mineral deposits are related large quantities of ores of copper, lead, zinc, tin, tungsten and other valuable items.
Exogenous deposits are formed under the influence of geological processes at the Earth's surface. They are formed during the long-term changes of rocks as they move from the interior to the surface of the Earth. Such a slow or sudden catastrophic rises in some portions of the crust occurred in all geological ages and continues today. At the Earth's surface rocks under the influence of temperature fluctuations and water flows mechanically disintegrated into small and tiny fragments. Under the influence of water, oxygen and carbon dioxide they are chemically decomposed, changing its composition. The products of such destruction are carried away by the water flow in the river and settling in their day, form the well-known river deposits of gravel, sand and clay. However, some chemical resistant, necessasy, solid and heavy minerals accumulate in the bottom bed of the river sediments, forming placers. In placers can concentrate heavy minerals with a specific gravity more than 3. Therefore, it is in the form placers are known deposits of gold, platinum, tin stone, wolframite , etc.
A significant part of the mineral mass, located in river water in the form of sludge or in a dissolved state is brought into the seas and oceans. The extent of this removal is huge. So, Volga for a year makes in the Caspian sea 25.5 million tons of suspended material, the Amu Darya into the Aral sea - 215 million tons, the Amazon into the Atlantic ocean about 1000 million tons. In the oceans and seas minerals are deposited and accumulated on the bottom. These minerals come from the continents, under the influence of gravity, as a result of chemical exposure to salty sea water, or in connection with vital activity of marine organisms. This creates strata of rocks of sedimentary origin, among which there are layers of sedimentary minerals. In addition to such well-known sedimentary rocks, as Sands, clays, limestone, widespread deposits of ores of iron, manganese, aluminum, phosphates, coal and oil.
On the Earth's surface are formed mineral deposits as a result of the dissolution and removal of part of the substance of groundwater, with the remainder accumulate difficultly soluble valuable mineral compounds. For example, in the rock consisting of calcium and aluminium, calcium minerals can be dissolved and removed with water and the residue will accumulate compounds of aluminium - bauxite - ore deposits for the production of this metal. Such deposits are called residual. Among them, in addition to bauxite, known deposits of iron ore, Nickel ore, phosphate compounds.
Of the solute can secede again under the earth from ground water, with their penetration through permeable rocks. The resulting deposits are called infiltration. Among infiltration known deposits of Nickel, copper, gold, uranium.
If rocks and prisoners among them mineral deposits, sinking into the Ground, they are subjected to the pressure resting on their masses and the internal heat of the Earth. Under their influence, rocks and minerals are changed, transformed into metamorphic rockssuch as gneiss or crystalline schist. This may occur metamorphic mineral deposits ("metamorphosis" - change). They are treated as pre-existing, but subjected to intensive change of the body, and emerged again due to metamorphism. These include, for example, deposits of marble, roofing slates, mica, graphite, garnet.