Underground streams

What crystallizes most minerals and ore deposits? It turns out that in these processes the main role is played by hydrothermal solutions and underground streams. But what are they?

It turns out that in these processes the main role is played by hydrothermal solutions and underground streams

To begin with, in the cycle water not only participate ocean (hydrosphere) and atmosphere, but also the earth's crust (lithosphere). All of it is "infiltrated" by cold and hot underground streams. Cold - in their upper parts, hot - in deeper, warmer. From lakes, seas and rivers, water enters the crust through cracks and begins a long circulation there. Submerged, underground streams heat up, dissolve their enclosing rocks, are saturated with a variety of substances and become potentially ore-bearing.

When moving magma, superheated water vapor with dissolved them elements that rush up, cool down and turn into hot mineralized underground streams.

These underground streams are filtered through porous sections of rocks and for long millions of years there are colossal chemical changes on their scale and deposited, the masses of new minerals crystallize.

Iron and manganese, lead and zinc, copper and bismuth, niobium and tantalum - all these metals are part of underground flows. Of course, in some particular underground stream there are not all these substances, but only some of them. The composition of the streams depends on two main reasons: on the composition of the parent magma and on the interaction of the streams with the host rocks, as a result of which the rocks are dissolved and absorbed by the stream.

What chemical compounds are the substances carried by the underground stream? How and by what means is some chemical element contained in the earth's crust in insignificant quantities, and in some places it concentrates 100-1000 or more times, forming large deposits?

On the composition of ancient underground streams, plausible assumptions can be made on the basis of the composition of gas-liquid inclusions in minerals. But the form of chemical compounds - carriers of ore matter - is very difficult to judge. Here is the area of hypotheses and guesses.

In nature, ore veins are widely distributed, for example, by the sulphides of various metals: pyrite, chalcopyrite, galena and sphalerite. Perhaps, the substance of these minerals was transferred in the form of sulfides? But, alas, their solubility in water is minimal. Simple calculations have shown that the formation of a small sulfide ore vein requires literally the oceans of water.

However, nature prompted a way out of the impasse. It turns out that metals precipitate in the form of sulphides, only when mixing metal-containing subterranean streams with hydrogen sulfide streams. One can come to the conclusion that in the underground streams, not those compounds that we observe in the form of minerals in ores were transported at all.

Therefore, ore minerals are nothing but difficult-to-dissolve products of chemical reactions that occur in underground streams when they interact with other subterranean streams or solid rock.