Bedrocks are the result of long-term geological processes. According to their origin, they are divided into igneous (igneous), sedimentary, metamorphic (modified).
Igneous rocks
Their formation occurred due to the fact that in the process of tectonic activity, the natural substance, melted in the depths of the earth, rose to the surface. As a result, the magma cooled and solidified. If it was subjected to cooling and solidification at great depths, namely slowly under the influence of high pressure, and could not get rid of gaseous inclusions, then these rocks are commonly called intrusive (deep). They have, as a rule, a coarse-grained structure.
If the magma cooled near the surface of the earth, then these rocks are called effusive. Magma,rising, subjected to cooling in a shorter period. There was little pressure on her. Gaseous products came out freely. The structure of such rocks differs from intrusive ones, despite the fact that they originally had the same composition. Effusive rocks are characterized by a fine crystalline structure or are generally amorphous.
Igneous bedrocks - granite, syenite, diabase, bas alt, gabro, andesite and others. Usually these rocks contain valuable minerals, namely platinum, chromium, titanium, nickel, cob alt, iron, etc.
Sedimentary rocks
These rocks are formed as a result of deposition on the bottom of water bodies (lake, river, sea) of organic matter and suspended minerals. Their origin is the result of weathering and destruction of igneous or older sedimentary rocks.
In geology, it is customary to divide them by origin into chemical (mineral s alt, gypsum), organic (coal, oil shale, limestone). Sedimentary rocks are also so-called clastic rocks, which include sand, gravel, crushed stone, clay, etc. The main characteristic of sedimentary rocks is their layering.
Metamorphic rocks
They owe their formation to specific chemical and physical processes. If igneous or sedimentary rocks were exposed to high temperature, gas pressure due to the recrystallization of accompanying rocks during the movement of magma. At the same time, new minerals and rocks were formed. In such processes from clayschists were created, which contain granite, mica, skarns, hornfelses, etc. Metamorphic rocks have a crystalline structure, have a banded or slate structure.
Deposits
These rocks were formed as a result of the destruction of the bedrock. They are rather loose deposits, the so-called secondary rocks. The deposits are located at the very surface of the earth, under the vegetation cover. This is a combination of sand, clay, loam, and other cracked rocks. The thickness of the outgoing rocks (thickness) is relatively small, usually ranging from a meter to 50 m.
The Earth's crust, to which mankind has access, reaches a depth of about 20 km. It consists of 95% igneous rocks, 4% metamorphic rocks and 1% sedimentary rocks. In geology, bedrocks, referring to a variety of rocks that can be used by mankind and for their own purposes, are called minerals.
The natural accumulations of these minerals in the earth's crust are mineral deposits, they can be loose and bedrock.
Gold Appearance Process
The bedrock of gold appeared in the Earth's crust as a result of magmatic processes. As a result of centuries-old manifestations of volcanic activity, rivers of red-hot magma flowed onto the earth's surface. It was a mixture of molten compounds. Their melting point is different, therefore, when magma solidifies, refractory elements first crystallize. However, inthe solidified magma continued to circulate fusible elements. Their molten consistency broke through the gaps and cracks of the solidifying magma. At the same time, veins were formed. The process of circulation of hot solutions of gold-bearing s alts continued in them. After the cooling process ended, the destruction of s alts began, the gold in the veins remained and crystallized.
Gold bedrocks were formed in many ways, but for the most part they are always located in the mountains, in those places where the rocks were formed as a result of magmatic activity.
Differences in gold deposits
Gold deposits are distinguished by the conditions of their occurrence
Primary deposits (endogenous). They arose as a result of deep processes. Their other name is ore or primary. Now the bulk of gold in the world, approximately 95-97 percent, is mined from ore deposits.
Alluvial deposits (exogenous). They appear on the earth's surface due to the destruction of the primary gold rock. Sometimes they are referred to as secondary deposits.
Deposits metamorphosed exogenous. These are conglomerates and sandstones containing gold. Appeared due to the fact that the ancient gold placers were naturally transformed. No such deposits have been found in Russia.
Gold Locations
The period of geological transformations of the Earth has millionsyears. To replace the destroyed and weathered rocks, new ones rise to its surface from the depths. The processes associated with the destruction and uplift of sections of the earth's crust are ongoing. There is a continuous renewal of the earth's surface. As a result, it is a collection of native elements, including gold. So, when rocks are destroyed, gold is released and does not disappear without a trace, like other unstable elements of bedrocks. Accumulates in placers. However, the activity of mankind has led to the fact that gold placer deposits have already been developed. Gold is now mostly mined from deep ore bedrock. The largest reserves of this noble metal are owned by several countries: Australia, South Africa, the USA, China, and Russia. About 2,500 tons of gold are mined annually in the world. Russia accounts for almost 200 tons of this metal.
