Impactites are formed when large meteorites fall to the ground. The energy that is released during this process, accompanied by an explosion, is sufficient to melt a significant mass of rocks. When a meteorite falls on the ground, a shock wave occurs, which spreads from a local source. We will quickly release energy with supersonic speed. The fragmented and molten material is thrown out from under the meteorite in the form of cumulative jets.
The fragmented and molten material of the breeds moves in the crater radially. Movements are turbulent. Mixing the fragmentation, crushed and melted material occurs; Brekty and other breeds are formed, which are mixed according to the phase state of the substance.
Then occurs the stage of the release and movement of stress metamorphism products outside the crater.
A specific form of melting impactitis is Tektites. Tektites - small (size about a few centimeters) of the body, having an elongated or rounded shape. The location of Tektites is represented by isolated scattering fields.
Until recently, various hypotheses of the origin of Tektites were expressed. One of the hypotheses suggests that Tektite is fragments of a comet that fell to the ground at great distances.
The main modern hypothesis of the origin of Tektite involves the formation of them as a result of the most distant emission of the highest -temperature portions of the impact melt at an impact event. When emissing, subsequent flight and fall in the atmosphere, they often acquire a rounded, aerodynamic shape. There are still no deposits and large blocks of textitis on Earth.
At present, eight of the flowering fields are known:
1. Central - European field (territory of the Czech Republic, Germany and Austria). Textites are common - Vltavins ( Moldavite ) along the Vltava River Czech Republic, they have the age of 15 million years. According to the geochemical and Petrographic signs of the Vltavins, their connection with the Crater Rice (Germany) has been proved.
The Ries crater impact event is believed to be the source of moldavite tektites found in Czech Republic. The tektite melt originated from a sand-rich surface layer that was ejected to distances up to 450 km.
2. Australo - Asian field: territories Indochina Peninsula, south - western part China, Australia, the islands of Indonesia and the Philippines, as well as the adjacent parts of the Indian and Pacific Oceans. Tektites - Australites, Indoshinites, Javanites, Billitonitis, Phillipinitis and some others have an age of about 0.7 million years. The crater with which Tektites are connected is not installed. It is assumed that the crater can be the basin of Lake Tonsip (Thailand). Australo - Asian field is the largest range of tcytitis spreading, reaching 4000 km transverse.
3. West - African field: the coast of the Gulf of Guinea. Tektites - ivorites (Tektites Ivory Coast). They have an age of about 1 ml. years. The connection of these textures with the impact crater of the Bosumvy (Gana) has been proven.
4. North American field: the territories of the southeast states of the United States and the islands of the Caribbean. Tektites - Bediazites (city of Bediaz, Texas) and Georgianites (Georgia, USA) have the age of 34 million years. They are associated with the formation of one -aging craters Chesapik Bay (Virginia, USA) and Tomc Canyon (New - Jersey, USA).
5. The Western - Kazakhstan Field of Tektites - Irgisites (along the Irgiz River) is associated with the crater of Zhamanshin in the Northern Aral Sea (Kazakhstan), having about 1 million age. years.
6. Single finds of Tektites - Urengoits (New Urengoy, Russia) with the age of 24 million years. They have no connection with the craters.
7. Single finds of Tektites in Guatemala (South America) with an age of about 0.8 million years. They have no connection with the craters.
8. Single finds of Tektites in the southern part of the Chelyabinsk region, Russia, having the age of 6 million years. They have no connection with the craters.
Within the scattering fields, tektites is distributed unevenly by the area: spots and stripes, while creating a radial zone of emission of the impact melt. They are formed at the initial stages of the growth of the crater from the emissions of the melt that have an intermediate speed. The melt at a speed of less than 2 km/s sets aside in a crater or near it, and thrown out at a speed of more than 11 km/s - leaves the planet.
The dimensions of tektites, on average, are several centimeters. Dimensions and mass are reduced as they move away from the crater, their shape also changes. A characteristic aerodynamic texture is observed on the surface of the tektites - furrows and rollers, and a stroke indicating the stretching of the plastic parts of the melt when flying through the atmosphere. This movement is accompanied by rotation around a long oxy. Also, micro balls are fixed on the surface of tektites, inside - hollow.
Nördlinger Ries crater is located 110 km north of the west of Munich. Its diameter is about 24 km, depth is up to 750 m. In the petrographic study of the Gneis from autigenic bracket, the Nordlingen well -73 well -shaped particles of meteorite substances were found, which
They are found in intergranium cracks in silicate minerals, as well as in the cracks of adhesion. Relatively large amount of chromium, the presence of calcium and attitude Ni \ Co = 20 are the prerequisites for the fact that a meteorite that creates a crater Ries refers to differentiated Achondrite Aubrite.
The products of distant emissions of the impact melt from the crater Ries include tektites- vltavin or Moldavite.
Moldavites belong to the central - European scattering field. The border is 256 km east of the center of the crater.
The field has a length of 150 km eastward and 32 km wide. The age of Moldavites is 15 million years.
Libyan desert glass.
Libyan glass was discovered in the south-west of Egypt (an area of 6500 km in 1932 by the Egyptiаn Desert Survey.
Libyan desert glass is unique for a given area, despite the fact that its fragments were transported by an ancient man in the territory of modern Libya, as well as to the southern part of Egypt, west of the Nile.
Its color varies from straw - yellow, light - green to gray. Transparency - from pure to muddy. Hardness, like other glasses, is 6 on the Mohs scale. The melting temperature of the Libyan glass is equal to the melting temperature of pure silica- 1727-1713 °C, higher by 500 °C than other natural glasses.
Unlike tektites, Libyan glass has no signs of ablation, which indicate their flight in the atmosphere over long distances.
There is a hypothesis that the Libyan glass is an impactite formed with rapid melting and solidification of the Nubian -rich Nubi Sandstone, which followed immediately after the impact event, but there is no evidence of this assumption.
There is also a theory that Libyan glass has volcanic genesis.
The Impact crater, which led to the formation of Libyan glass, was not scientifically confirmed, as well as signs of shock deformation in the glass itself, so a hypothesis was made that the glass was formed due to the explosion in the atmosphere. In this process, the crater and the minerals are not formed and metamorphized, but high -temperature melting of the surfaces of the rocks occurs. This theory contradict the nature of inclusions in glass, which indicate a crater -forming event.
The age of the Libyan desert glass is determined by the method of fission-track dating of 29 million years.
Physical Properties of Moldavite
Mohs Hardness 5 - 5.5
Specific gravity 2.32 - 2.40
Refractive index 1.46 - 1.51
Color: yellowish green- to greenish brown. Using magnifying devices, you can see: lechatelierite inclusions (a mineraloid as it does not have a crystal structure), gas inclusions, and flow lines.
Physical Properties of Libyan desert glass
Mohs Hardness 6 - 6.5
Specific gravity 2.2 - 2.24
Refractive index 1.46 - 1.49
Color: from light green to honey - yellow