Composition of meteorites and their substances. Meteorites. Origin, morphology and chemical composition of real meteorites

Quite often ordinary person imagining what a meteorite looks like, he thinks about iron. And it's easy to explain. Iron meteorites are dense, very heavy, and often take on unusual, and even spectacular, shapes as they fall and melt through our planet's atmosphere. And although most people associate iron with the typical composition of space rocks, iron meteorites are one of the three main types of meteorites. And they are quite rare compared to stony meteorites, especially the most common group of them, single chondrites.

Three main types of meteorites

Exists large number types of meteorites, divided into three main groups: iron, stone, stone-iron. Almost all meteorites contain extraterrestrial nickel and iron. Those that contain no iron at all are so rare that even if we asked for help identifying possible space rocks, we likely wouldn't find anything that didn't contain large amounts of the metal. The classification of meteorites is, in fact, based on the amount of iron contained in the sample.

Iron meteorites

Iron meteorites were part of the core of a long-dead planet or large asteroid from which it is believed to have formed Asteroid Belt between Mars and Jupiter. They are the densest materials on Earth and are very strongly attracted to a strong magnet. Iron meteorites are much heavier than most Earth rocks; if you've lifted a cannonball or a slab of iron or steel, you know what we're talking about.

For most samples in this group, the iron component is approximately 90%-95%, the rest is nickel and trace elements. Iron meteorites are divided into classes based on chemical composition and structure. Structural classes are determined by studying two components of iron-nickel alloys: kamacite and taenite.

These alloys have a complex crystalline structure known as the Widmanstätten structure, named after Count Alois von Widmanstätten who described the phenomenon in the 19th century. This lattice-like structure is very beautiful and is clearly visible if the iron meteorite is cut into plates, polished and then etched in a weak solution of nitric acid. In kamacite crystals discovered during this process, the average width of the bands is measured, and the resulting figure is used to divide iron meteorites into structural classes. Iron with a fine stripe (less than 1 mm) is called “fine-structured octahedrite”, with a wide stripe “coarse octahedrite”.

Stone meteorites

The largest group of meteorites is stone, they formed from the outer crust of a planet or asteroid. Many stony meteorites, especially those found on the surface of our planet for a long time, are very similar to ordinary earthly rocks, and it takes an experienced eye to find such a meteorite in the field. Newly fallen rocks have a black, shiny surface that results from the surface burning in flight, and the vast majority of rocks contain enough iron to be attracted to a powerful magnet.

Some stony meteorites contain small, colorful, grain-like inclusions known as "chondrules." These tiny grains originated from the solar nebula, therefore predating the formation of our planet and the entire Solar System, making them the oldest known matter available for study. Stony meteorites containing these chondrules are called "chondrites".

Space rocks without chondrules are called "achondrites." These are volcanic rocks formed by volcanic activity on their “parent” space objects, where melting and recrystallization erased all traces of ancient chondrules. Achondrites contain little or no iron, making it more difficult to find than other meteorites, although specimens are often coated with a glossy crust that looks like enamel paint.

Stone meteorites from the Moon and Mars

Can we really find Moon and Martian rocks on the surface of our own planet? The answer is yes, but they are extremely rare. More than one hundred thousand lunar and approximately thirty Martian meteorites have been discovered on Earth, all of which belong to the achondrite group.

The collision of the surface of the Moon and Mars with other meteorites threw fragments into outer space and some of them fell to Earth. From a financial point of view, lunar and Martian samples are among the most expensive meteorites. In collector markets, their price reaches up to a thousand dollars per gram, making them several times more expensive than if they were made of gold.

Stony-iron meteorites

The least common of the three main types - stone-iron, accounts for less than 2% of all known meteorites. They consist of approximately equal parts of iron-nickel and stone, and are divided into two classes: pallasite and mesosiderite. Stony-iron meteorites formed at the boundary of the crust and mantle of their “parent” bodies.

Pallasites are perhaps the most alluring of all meteorites and are definitely of great interest to private collectors. Pallasite consists of an iron-nickel matrix filled with olivine crystals. When olivine crystals are clear enough to display an emerald green color, they are known as a perodot gemstone. Pallasites got their name in honor of the German zoologist Peter Pallas, who described the Russian Krasnoyarsk meteorite, found near the capital of Siberia in the 18th century. When a pallasite crystal is cut into slabs and polished, it becomes translucent, giving it an ethereal beauty.

Mesosiderites are the smaller of the two lithic-iron groups. They are composed of iron-nickel and silicates, and are usually attractive in appearance. The high contrast of the silver and black matrix, when the plate is cut and sanded, and the occasional inclusions, results in a very unusual appearance. The word mesosiderite comes from the Greek for "half" and "iron" and they are very rare. In thousands of official catalogs of meteorites, there are less than a hundred mesosiderites.

Classification of meteorites

The classification of meteorites is a complex and technical subject and the above is intended only as a brief overview of the topic. Classification methods have changed several times over the years recent years; known meteorites were reclassified into another class.

Iron meteorites represent the largest group of meteorite finds outside the hot deserts of Africa and the ice of Antarctica, as they are easily identified by non-specialists by their metallic composition and heavy weight. In addition, they weather more slowly than stone meteorites and, as a rule, have significantly larger sizes due to their high density and strength, which prevent their destruction when passing through the atmosphere and falling to the ground. Despite this fact, as well as the fact that iron meteorites have a common weighing more than 300 tons accounts for more than 80% of the total mass of all known meteorites; they are relatively rare. Iron meteorites are often found and identified, but they account for only 5.7% of all observed impacts. In terms of classification, iron meteorites are divided into groups according to two completely different principles. The first principle is a kind of relic of classical meteoritics and involves the division of iron meteorites by structure and dominant mineral composition, and the second is a modern attempt to divide meteorites into chemical classes and correlate them with certain parent bodies. Structural classification Iron meteorites are mainly composed of two iron-nickel minerals - kamasite with a nickel content of up to 7.5% and taenite with a nickel content of 27% to 65%. Iron meteorites have a specific structure, depending on the content and distribution of one or another mineral, on the basis of which classical meteorology divides them into three structural classes. OctahedritesHexahedritesAtaxitesOctahedrites
Octahedrites consist of two metal phases - kamacite (93.1% iron, 6.7% nickel, 0.2 cobalt) and taenite (75.3% iron, 24.4% nickel, 0.3 cobalt) which form a three-dimensional octahedral structures. If such a meteorite is polished and its surface treated with nitric acid, the so-called Widmanstätt structure appears on the surface, a delightful play geometric shapes. These groups of meteorites vary depending on the width of the kamasite bands: coarse-grained nickel-poor broadband octahedrites with band widths greater than 1.3 mm, medium-grained octahedrites with band widths from 0.5 to 1.3 mm, and fine-grained nickel-rich octahedrites with band widths less than 0.5 mm. Hexahedrites Hexahedrites consist almost entirely of nickel-poor kamasite and do not reveal a Widmanstätten structure when polished and etched. In many hexahedrites, after etching, thin parallel lines appear, the so-called Neumann lines, reflecting the structure of kamasite and, possibly, resulting from impact, a collision of the parent body of the hexahedrite with another meteorite. Ataxites After etching, ataxites show no structure, but, unlike hexahedrites, they are composed almost entirely of taenite and contain only microscopic kamasite lamellae. They are among the richest in nickel (the content of which exceeds 16%), but also the rarest meteorites. However, the world of meteorites is a wonderful world: paradoxically, the largest meteorite on Earth, the Goba meteorite from Namibia, weighing more than 60 tons, belongs to the rare class of ataxites.
Chemical classification In addition to the iron and nickel content, meteorites vary in the content of other minerals, as well as in the presence of traces of rare earth metals such as germanium, gallium, and iridium. Studies of the ratio of trace metals to nickel have shown the presence of certain chemical groups of iron meteorites, each of which is believed to correspond to a specific parent body. Here we will briefly touch on the thirteen identified chemical groups, it should be noted that about 15% of known iron meteorites do not fall into them meteorites, which are unique in their chemical composition. Compared to the iron-nickel core of the Earth, most iron meteorites represent the cores of differentiated asteroids or planetoids that must have been destroyed by catastrophic impact before falling to Earth as meteorites! Chemical groups:IABICIIABIICIIDIIEIIFIIIABIIICDIIIEIIIFIVAIVBUNGRIAB Group A significant part of iron meteorites belongs to this group, in which all structural classes are represented. Particularly common among meteorites of this group are large and medium-sized octahedrites, as well as iron meteorites rich in silicates, i.e. containing more or less large inclusions of various silicates, chemically closely related to uinonaites, a rare group of primitive achondrites. Therefore, both groups are considered to originate from the same parent body. Often IAB group meteorites contain inclusions of bronze-colored iron sulfide troilite and black graphite grains. Not only does the presence of these vestigial forms of carbon indicate a close relationship of the IAB group with the Carboniferous chondrites; This conclusion can also be made by the distribution of microelements. IC Group The much rarer iron meteorites of the IC group are very similar to the IAB group, with the difference that they contain less rare earth trace elements. Structurally, they belong to coarse-grained octahedrites, although IC group iron meteorites with a different structure are also known. Typical of this group is the frequent presence of dark inclusions of cementite cohenite in the absence of silicate inclusions. Group IIAB Meteorites of this group are hexahedrites, i.e. consist of very large individual kamasite crystals. The distribution of trace elements in Group IIAB iron meteorites resembles their distribution in some Carboniferous chondrites and enstatite chondrites, suggesting that Group IIAB iron meteorites originate from a single parent body. Group IIC Group IIC iron meteorites include the finest-grained octahedrites with kamasite bands less than 0.2 mm wide. The so-called “filling” plessite, a product of a particularly fine synthesis of taenite and kamasite, also found in other octahedrites in a transitional form between taenite and kamasite, is the basis of the mineral composition of iron meteorites of group IIC. Group IID Meteorites of this group occupy a middle position on the transition to fine-grained octahedrites, characterized by a similar distribution of trace elements and a very high content of gallium and germanium. Most Group IID meteorites contain numerous inclusions of the iron-nickel phosphate schreibersite, an extremely hard mineral that often makes Group IID iron meteorites difficult to cut. Group IIE Structurally, Group IIE iron meteorites belong to the class of medium-grained octahedrites and often contain numerous inclusions of various iron-rich silicates. Moreover, unlike meteorites of group IAB, silicate inclusions do not have the form of differentiated fragments, but of solidified, often clearly defined drops, which give iron meteorites of group IIE optical attractiveness. Chemically, group IIE meteorites are closely related to H-chondrites; it is possible that both groups of meteorites originate from the same parent body. Group IIF This small group includes plessitic octahedrites and ataxites, which have high nickel contents as well as very high levels of trace elements such as germanium and gallium. There is a certain chemical similarity with both the pallasites of the Eagle group and the Carboniferous chondrites of the CO and CV groups. It is possible that the pallasites of the Eagle group originate from the same parent body. Group IIIAB After group IAB, the most numerous group of iron meteorites is group IIIAB. Structurally, they belong to coarse and medium-grained octahedrites. Sometimes inclusions of troilite and graphite are found in these meteorites, while silicate inclusions are extremely rare. However, there are similarities with the main group pallasites, and both groups are now believed to be descended from the same parent body.
Group IIICD Structurally, group IIICD meteorites are the finest-grained octahedrites and ataxites, and in chemical composition they are closely related to group IAB meteorites. Like the latter, Group IIICD iron meteorites often contain silicate inclusions, and both groups are now thought to originate from the same parent body. As a result, they also have similarities with winonaites, rare group primitive achondrites. Typical of group IIICD iron meteorites is the presence of the rare mineral hexonite (Fe,Ni) 23 C 6, which is present exclusively in meteorites. Group IIIE Structurally and chemically, group IIIE iron meteorites are very similar to group IIIAB meteorites, differing from them in the unique distribution of trace elements and typical hexonite inclusions, which makes them similar to group IIICD meteorites. Therefore, it is not entirely clear whether they form an independent group descending from a separate parent body. Perhaps further research will answer this question. Group IIIF Structurally, this small group includes coarse to fine-grained octahedrites, but is distinguished from other iron meteorites by both its relatively low nickel content and the very low abundance and unique distribution of certain trace elements. Group IVA Structurally, group IVA meteorites belong to the class of fine-grained octahedrites and are distinguished by a unique distribution of trace elements. They have inclusions of troilite and graphite, while silicate inclusions are extremely rare. The only notable exception is the anomalous Steinbach meteorite, a historical German find, since it consists of almost half red-brown pyroxene in a type IVA iron-nickel matrix. The question of whether it is a product of an impact on an IVA parent body or a relative of pallasites and therefore a stony-iron meteorite is currently being vigorously debated. Group IVB
All iron meteorites of group IVB have a high nickel content (about 17%) and structurally belong to the class of ataxites. However, when observed under a microscope, one can notice that they do not consist of pure taenite, but rather have a plessite nature, i.e. formed due to the fine synthesis of kamacite and taenite. A typical example of group IVB meteorites is Goba from Namibia, the largest meteorite on Earth. UNGR Group This abbreviation, meaning “out-of-group,” refers to all meteorites that cannot be classified into the above-mentioned chemical groups. Although researchers now classify these meteorites into twenty different small groups, for a new meteorite group to be recognized, it typically requires at least five meteorites to be included, as established by the requirements of the Meteorite Society's International Nomenclature Committee. The presence of this requirement prevents the hasty recognition of new groups, which later turn out to be only an offshoot of another group.

Meteorites are small iron, stone or iron-stone space objects that regularly fall to the surface of the planets of the solar system, including the Earth. Outwardly, they are not much different from stones or pieces of iron, but they conceal many mysteries from the history of the universe. Meteorites help scientists uncover the secrets of the evolution of celestial bodies and study processes occurring far beyond our planet.

Analyzing their chemical and mineral composition, it is possible to trace patterns and connections between meteorites various types. But each of them is unique, with qualities inherent only to this body of cosmic origin.

Types of meteorites by composition:

1. Stone:

Chondrites;

Achondrites.

2. Iron-stone:

Pallasites;

Mesosiderites.

3. Iron.

Octahedrites

Ataxites

4. Planetary

Martian

Origin of meteorites

Their structure is extremely complex and depends on many factors. Studying all known varieties of meteorites, scientists came to the conclusion that they are all closely related at the genetic level. Even taking into account significant differences in structure, mineral and chemical composition, they are united by one thing - origin. All of them are fragments of celestial bodies (asteroids and planets), moving in outer space at high speed.

Morphology

To reach the surface of the Earth, a meteorite needs to travel a long way through the layers of the atmosphere. As a result of significant aerodynamic load and ablation (high-temperature atmospheric erosion), they acquire characteristic external features:

Oriented conical shape;

Melting crust;

Special surface relief.

A distinctive feature of real meteorites is the melting crust. It can differ quite significantly in color and structure (depending on the type of body of cosmic origin). In chondrites it is black and matte, in achondrites it is shiny. In rare cases, the fusion bark may be light and translucent.

With a long stay on the Earth's surface, the surface of the meteorite is destroyed under the influence of atmospheric influences and oxidation processes. For this reason, a significant part of bodies of cosmic origin after a certain time is practically no different from pieces of iron or stones.

Another distinctive external sign, which a real meteorite has, is the presence on the surface of depressions called piezoglypts or regmaglypts. Resembles fingerprints on soft clay. Their size and structure depend on the conditions of movement of the meteorite in the atmosphere.

Specific gravity

1. Iron - 7.72. The value can vary in the range of 7.29-7.88.

2. Pallasites – 4.74.

3. Mesosiderites – 5.06.

4. Stone - 3.54. The value can vary in the range of 3.1-3.84.

Magnetic and optical properties

Due to the presence of a significant amount of nickel iron, this meteorite exhibits its unique magnetic properties. This is used to verify the authenticity of a body of cosmic origin and allows indirect judgment of the mineral composition.

The optical properties of meteorites (color and reflectivity) are less pronounced. They appear only on the surfaces of fresh fractures, but over time due to oxidation they become less noticeable. Comparing the average values ​​of the brightness coefficient of meteorites with the albedo of celestial bodies of the solar system, scientists came to the conclusion that some planets (Jupiter, Mars), their satellites, as well as asteroids are similar in their optical properties to meteorites.

Chemical composition of meteorites

Considering the asteroidal origin of meteorites, their chemical composition can differ quite significantly between objects of different types. This has a significant impact on the magnetic and optical properties, as well as the specific gravity of bodies of cosmic origin. The most common chemical elements in meteorites are:

1. Iron (Fe). Is the main one chemical element. Occurs in the form of nickel iron. Even stony meteorites have an average Fe content of 15.5%.

2. Nickel (Ni). It is part of nickel iron, as well as minerals (carbides, phosphides, sulfides and chlorides). Compared to Fe, it is 10 times less common.

3. Cobalt (Co). Not found in pure form. Compared to nickel, it is 10 times less common.

4. Sulfur (S). Part of the mineral troilite.

5. Silicon (Si). It is part of the silicates that form the bulk of stone meteorites.

3. Orthorhombic pyroxene. Often found in stony meteorites, it is the second most common among silicates.

4. Monoclinic pyroxene. It is found rarely and in small quantities in meteorites, with the exception of achondrites.

5. Plagioclase. A common rock-forming mineral belonging to the feldspar group. Its content in meteorites varies widely.

6. Glass. It is the main component of stone meteorites. Contained in chondrules and also found as inclusions in minerals.

Meteorite is a solid extraterrestrial substance that was preserved during its passage through the atmosphere and reached the surface of the Earth. Meteorites are the most primitive substance of the SS, which has not experienced further fractionation since its formation. This is based on the fact that the relative distribution refractory el. in meteorites corresponds to solar distribution. Meteorites are divided into (based on metal phase content): Stone(aerolites): achondrites, chondrites, Iron-stone(siderolites), Iron(Siderites). Iron meteorites – consist of kamacite - native Fe of cosmic origin with an admixture of nickel from 6 to 9%. Stone-iron meteorites Low spread group. They have coarse-grained structures with equal weight fractions of silicate and Fe phases. (Silicate minerals - Ol, Px; Fe phase - kamacite with Widmanstätten growths). Stone meteorites – consist of Mg and Fe silicates with an admixture of metals. Divided into Chondrite, achondrite and carbonaceous.Chondrites: spheroidal segregations of a few mm or less in size, composed of silicates, less often silicate glass. Immersed in a Fe-rich matrix. The main mass of chondrites is a fine-grained mixture of Ol, Px-s (Ol-bronzite, Ol-hypersthene and Ol-pigeonite) with nickel Fe (Ni-4-7%), troilite (FeS) and plagioclase. Chondrites are crystalline. or glassy drops, cat. Image. by melting pre-existing silicate material that has been subjected to heat. Achondrites: They do not contain chondrules and have a lower content. nickel Fe and coarser structures. Their main minerals are Px and Pl, some types are enriched in Ol. In composition and structural features, achondrites are similar to terrestrial Gabbroids. The composition and structure indicate igneous origin. Sometimes bubble structures like lavas are observed. Carbonaceous chondrites (large amounts of carbonaceous matter) A characteristic feature of carbonaceous chondrites is presence of a volatile component, which indicates primitiveness (volatile elements were not removed) and did not undergo fractionation. Type C1 contains a large number chlorite(aqueous Mg, Fe aluminosilicates), as well as magnetite, water-soluble salt, nativeS, dolomite, olivine, graphite, organ. connections. Those. from the moment of their image, they are beings. at T, not > 300 0 C. In the composition chondritic meteorites lack of 1/3 chemical Email compared to composition carbonaceous chondrites, cat. are closest to the composition of protoplanetary matter. The most likely cause of the shortage of volatile electricity. - sequential condensation of electricity. and their compounds in the reverse order of their volatility.

5.Historical and modern models of accretion and differentiation of protoplanetary matter O.Yu. Schmidt in the 40s expressed the idea that the Earth and the Earth planets were formed not from hot clumps of solar gases, but through the accumulation of TV. bodies and particles - planetesimals that experienced melting later during accretion (heating due to collisions of large planetesimals, up to a few hundred km in diameter). Those. early core-mantle differentiation and degassing. Noun relates two points of view. the mechanism of accumulation and ideas about the shape of the layered structure of planets. Models homogeneous and heterogeneous accretion: HETEROGENEOUS ACCRETION 1. Short-term accretion. Early heterogeneous accretion models(Turekian, Vinogradov) assumed that the earth accumulated from material as it condensed from a protoplanetary cloud. Early models include early >T accumulation of the Fe-Ni alloy, forming the protocore of the earth, followed by lower. T by accretion of its outer parts from silicates. It is now believed that continuous change occurs during the accretion process. in the accumulating material, the Fe/silicate ratio from the center to the periphery of the forming planet. During accumulation, gold heats up, => melting of Fe, which is separated from silicates and sinks into the core. After cooling the planet, about 20% of its mass is added by material enriched in volatiles along the periphery. In the proto-earth there were no sharp boundaries between the core and the mantle, cat. established as a result of gravitational and chem. differentiation at the next stage of the planet's evolution. In early versions, differentiation occurred mainly during the formation of the Earth's Earth, and did not cover the entire Earth. HOMOGENEOUS ACCRETION 2. A longer accretion time is accepted - 10 8 years. During the accretion of the Earth and the planets of the Earth, the condensing bodies had wide variations in composition from carbonaceous chondrites enriched in volatiles to materials enriched in refractory components of the Allende type. Planets of forms. from this set of meteorite objects and their differences and similarities were determined by reference. proportions of ingredients of different composition. The same happened macroscopic homogeneity of protoplanets. The existence of a massive core suggests that the alloy originally brought by Fe-Ni meteorites, uniformly distributed throughout the entire planet, was released into the central part during its evolution. Homogeneous in composition the planet split into shells in the process of gravitational differentiation and chemical processes. Modern model of heterogeneous accretion, allowing us to explain the chemistry. the composition of the mantle is being developed by a group of German scientists (Wencke, Dreybus, Jagoutz). They found that the contents of moderately volatile (Na, K, Rb) and moderately siderophilic (Ni, Co) elements in the mantle, with different The distribution coefficients Me/silicate have the same abundance (normalized by C1) in the mantle, and the most strongly siderophile elements have excess concentrations. Those. the core was not in equilibrium with the mantle reservoir. They proposed heterogeneous accretion :1. Accretion begins with the accumulation of a highly reduced component A, devoid of volatile elements. and containing all other emails. in quantities corresponding to C1, and Fe and all siderophiles in a reduced state. As T increases, core formation begins simultaneously with accretion. 2. After accretion, more and more oxidized material, component B, begins to accumulate in 2/3 of the earth’s mass. Part of the Me component of component A is still preserved and contributes to the extraction of the most siderophilic elements. and transfer them to the nucleus. Source of moderately volatile, volatile and moderately siderophilic el. in the mantle component B, which explains their close relative prevalence. Thus, the Earth consists of 85% component A and 15% B. In general, the composition of the mantle is formed after the separation of the core by homogenization and mixing of the silicate part of component A and the substance of component B.

6. Isotopes of chemical elements. Isotopes - atoms of the same electron, but having a different number of neutrons N. They differ only in mass. Isotones - atoms of different elements, having different Z, but the same N. They are located in vertical rows. Isobars - atoms of different elements, cat. equal mass. numbers (A=A), but different Z and N. They are located in diagonal rows. Nuclear stability and isotope abundance; radionuclides The number of known nuclides is ~ 1700, of which ~ 260 are stable. On the nuclide diagram, stable isotopes (shaded squares) form a band surrounded by unstable nuclides. Only nuclides with a certain ratio of Z and N are stable. The ratio of N to Z increases from 1 to ~ 3 with increasing A. 1. Nuclides that have a cat are stable. N and Z are approximately equal. To Ca in N=Z nuclei. 2. Most stable nuclides have even Z and N. 3. Stable nuclides with even numbers are less common. Z and odd. N or even N and odd. Z. 4. P stable nuclides with odd Z and N are rare.

In kernels with even Z and N nucleons form an ordered structure, which determines their stability. The number of isotopes is smaller in light el. and took him away. in the middle part of the PS, reaching a maximum at Sn (Z=50), which has 10 stable isotopes. Elements with odd. Z stable isotopes no more than 2.

7. Radioactivity and its types Radioactivity - spontaneous transformations of the nuclei of unstable atoms (radionuclides) into stable nuclei of other elements, accompanied by the emission of particles and/or energy radiation. St. rad does not depend on chemistry. The properties of atoms are determined by the structure of their nuclei. Radioactive decay is accompanied by change. Z and N of the parent atom and leads to the transformation of an atom of one el. into the atom of another el. Also, Rutherford and other scientists have shown that he is glad. the decay is accompanied by the emission of radiation of three different types, a, b, g. a - rays - streams of high-speed particles - He nuclei, b - rays - streams e - , g - rays - electromagnetic waves with high energy and shorter λ. Types of radioactivity a-decay- decay by emission of a-particles, it is possible for nuclides with Z> 58 (Ce), and for a group of nuclides with small Z, including 5He, 5Li, 6Be. the a-particle consists of 2 P and 2N, a shift occurs by 2 positions in Z. The original isotope is called parental or maternal, and the newly formed - subsidiaries.

b-decay- has three types: regular b-decay, positronic b-decay and e – capture. Ordinary b-decay- can be considered as the transformation of a neutron into a proton and e - the latter or beta particle - is ejected from the nucleus, accompanied by the emission of energy in the form of g-radiation. The daughter nuclide is an isobar of the parent, but its charge is greater.

There is a series of decays until a stable nuclide is formed. Example: 19 K40 -> 20 Ca40 b - v- Q. Positron b-decay- emission of a positive positron particle b from the nucleus, its formation - the transformation of a nuclear proton into a neutron, positron and neutrino. The daughter nuclide is isobaric but has less charge.

Example, 9 F18 -> 8 O18 b v Q Atoms with an excess of N and located to the right of the zone of nuclear stability are b - -radioactive, because in this case, the number N decreases. Atoms to the left of the region of nuclear stability are neutron-deficient, they experience positron decay and their number N increases. Thus, during b- and b-decays there is a tendency for Z and N to change, leading to the daughter nuclides approaching the zone of nuclear stability. e – capture- capture of one of the orbital electrons. There is a high probability of capture from the K-shell, cat. closest to the core. e – capture causes emission of neutrinos from the nucleus. Daughter nuclide yavl. isobaric, and occupies the same position relative to the parent as during positron decay. There is no b - radiation, and when a vacancy in the K shell is filled, X rays are released. At g-radiation neither Z nor A change; when the nucleus returns to its normal state, energy is released in the form g-radiation. Some daughter nuclides of natural isotopes U and Th can decay either by emitting b particles or by a decay. If b-decay occurred first, then a-decay occurred, and vice versa. In other words, these two alternative decay modes form closed cycles and always lead to the same end product - stable isotopes of Pb.

8. Geochemical consequences of radioactivity of terrestrial matter. Lord Kelvin (William Thomson) from 1862 to 1899 performed a number of calculations, cat. imposed restrictions on the possible age of the Earth. They were based on consideration of the luminosity of the Sun, the influence of lunar tides and the cooling processes of the Earth. He came to the conclusion that the age of the Earth is 20-40 million years. Rutherford later performed a determination of the age of U min. and obtained values ​​of about 500 million years. Later, Arthur Holmes in his book “The Age of the Earth” (1913) showed the importance of studying radioactivity in geochronology and gave the first GHS. It was based on consideration of data on the thickness of sedimentary sediments and on the content of radiogenic decay products - He and Pb in U-containing minerals. Geochronological scale- scale of natural historical development of the Earth, expressed in numerical units of time. The age of earth's accretion is about 4.55 billion years. A period of up to 4 or 3.8 billion years is the time of differentiation of the planetary interior and the formation of the primary crust; it is called catarchaeum. The longest period of life of Z. and ZK is the Precambrian, cat. extends from 4 billion years to 570 million years, i.e. about 3.5 billion years. The age of the oldest rocks known today exceeds 4 billion years.

9. Geochemical classification of elements V.M. HolschmidtBased on: 1- electrical distribution. between different phases of meteorites - separation during the primary GC differentiation. 2- specific chemical affinity with certain elements (O, S, Fe), 3- structure of electronic shells. The leading elements composing meteorites are O, Fe, Mg, Si, S. Meteorites consist of three main phases: 1) metal, 2) sulfide, 3) silicate. All email are distributed among these three phases in accordance with their relative affinity for O, Fe and S. In Goldschmidt’s classification, the following groups of elements are distinguished: 1) Siderophilous(lovers of iron) – metal. meteorite phase: electrons that form alloys of arbitrary composition with Fe - Fe, Co, Ni, all platinoids (Ru, Rh, Pd, Pt, Re, Os, Ir), and Mo. They often have a native state. These are the transition elements of group VIII and some of their neighbors. Form the inner core of Z. 2) Chalcophilic(copper-loving) - sulfide phase of meteorites: electrons that form natural compounds with S and its analogues Se and Te, also have an affinity for As (arsenic), sometimes they are called (sulfurophilic). They easily turn into a native state. These are elements of secondary subgroups I-II and main subgroups III-VI of groups PS from 4 to 6 period S. The most famous are Cu, Zn, Pb, Hg, Sn, Bi, Au, Ag. Siderophilic el. – Ni, Co, Mo can also be chalcophile with a large amount of S. Fe under reducing conditions has an affinity for S (FeS2). In the modern model of gold, these metals form the outer, sulfur-enriched core of gold.

3) Lithophilic(stone-loving) – silicate phase of meteorites: el., having an affinity for O 2 (oxyphilic). They form oxygen compounds - oxides, hydroxides, salts of oxygen acids - silicates. In compounds with oxygen they have an 8-electron ext. shell. This is the largest group of 54 elements (C, common petrogenic - Si, Al, Mg, Ca, Na, K, elements of the iron family - Ti, V, Cr, Mn, rare - Li, Be, B, Rb, Cs, Sr , Ba, Zr, Nb, Ta, REE, i.e. all others except atmophilic ones). Under oxidizing conditions, iron is oxyphilic - Fe2O3. form the mantle Z. 4) Atmophilic(typical gaseous state) – chondrite matrix: H, N inert gases (He, Ne, Ar, Kr, Xe, Rn). They form the atmosphere of the Earth. There are also such groups: rare earth Y, alkaline, large-ion lithophile elements LILE (K, Rb, Cs, Ba, Sr), high-charge elements or elements with high field strength HFSE (Ti, Zr, Hf, Nb, Ta , Th). Some definitions of email: petrogenic (rock-forming, main) minor, rare, trace elements- from conc. no more than 0.01%. scattered– microel. not forming their own minerals accessory- form accessory min. ore- form ore mines.

10. Basic properties of atoms and ions that determine their behavior in natural systems. Orbital radii - radii of maxima of radial density e – ext. orbitals. They reflect the sizes of atoms or ions in a free state, i.e. outside chem. communications. The main factor is the e – electrical structure, and the more e – shells, the larger the size. For def. the sizes of atoms or ions in an important way. Def. distance from the center of one atom to the center of another, cat. is called the bond length. X-ray methods are used for this. To a first approximation, atoms are considered as spheres, and the “additivity principle” is applied, i.e. It is believed that the interatomic distance is the sum of the radii of the atoms or ions that make up the substance. Then knowing or accepting a certain value as the radius of one el. you can calculate the sizes of all the others. The radius calculated in this way is called effective radius . Coordination number- the number of atoms or ions located in close proximity around the atom or ion in question. CN is determined by the ratio R k /R a: Valence - the amount of e – donated or attached by an atom during the formation of a chemical. communications. Ionization potential is the energy required to remove e – from an atom. It depends on the structure of the atom and is determined experimentally. The ionization potential corresponds to the voltage of the cathode rays, which is sufficient to ionize an atom of this electron. There may be several ionization potentials, for several e - removed from the external. e – shells. Breaking off each subsequent e requires more energy and is not always possible. Usually they use the ionization potential of the 1st e – , cat. detects periodicity. On the ionization potential curve, alkali metals, which easily lose e – , occupy the minimums on the curve, and inert gases occupy the peaks. As the atomic number increases, the ionization potentials increase in a period and decrease in a group. The reciprocal is the affinity ke – . Electronegativity - the ability to attract e – when entering into connections. The halogens are the most electronegative, the alkali metals the least. Electronegativity depends on the charge of the atomic nucleus, its valency in a given compound and the structure of the e-shells. Attempts have been made repeatedly to express EO in energy units or in conventional units. The EO values ​​change naturally across PS groups and periods. EO is minimal for alkali metals and increases towards halogens. For lithophilic cations, the EO decreases. from Li to Cs and from Mg to Ba, i.e. with increased ionic radius. In chalcophilic el. EO is higher than that of lithophiles from the same PS group. For anions of group O and F, EO decreases down the group and therefore it is maximum for these elements. Email with sharply different meanings EOs form compounds with an ionic type of bond, and with close and high ones - with a covalent bond, with close and low ones - with a metallic type of bond. The Cartledge ionic potential (I) is equal to the ratio of valence to Ri, it reflects the properties of cationogenicity or ionogenicity. V.M. Golshmidt showed that the properties of cationogenicity and anionogenicity depend on the ratio of valence (W) and Ri for ions such as noble gases. In 1928, K. Cartledge called this ratio the ionic potential I. At small values ​​of I el. behaves like a typical metal and cation (alkali and alkaline earth metals), and at large - like a typical non-metal and anion (halogens). It is convenient to depict these relationships graphically. Diagram: ionic radius - valence. The magnitude of the ionic potential allows one to judge the mobility of the electron. in an aquatic environment. Email with low and high values ​​of I they are the most mobile easily (with low values ​​they pass into ionic solutions and migrate, with high values ​​they form complex soluble ions and migrate), and with intermediate values ​​they are inert. Main types of chemicals bonds, character of bonds in the main groups of minerals. Ionic– an image due to the attraction of ions with opposite charges. (with a large difference in electronegativity) Ionic bonding predominates in most min. ZK - oxides and silicates, this is the most common type of bond also in hydro- and atmospheres. The connection ensures easy dissociation of ions in melts, solutions, gases, due to which wide migration of chemicals occurs. El., their dispersion and concentration in the earth's geospheres. Covalent – noun due to the interaction of e – used by different atoms. Typical for email. with an equal degree of attraction e –, i.e. EO. Characteristic for liquid and gaseous substances (H2O, H2, O2, N2) and less for crystals. Covalent bonds characterize sulfides, related compounds As, Sb, Te, as well as monoel. non-metal compounds - graphite, diamond. Covalent compounds are characterized by low solubility. Metal- a special case of a covalent bond, when each atom shares its e - with all neighboring atoms. e – capable of free movement. Typical for native metals (Cu, Fe, Ag, Au, Pt). Many min. have a connection, cat. refers partly to ionic, partly to covalent. In sulfide min. The covalent bond is maximally manifested; it occurs between the metal atoms and S, and the metal bond occurs between the metal atoms (metal luster of sulfides). Polarization - This is the effect of distortion of the e-cloud of an anion by a small cation with a high valence so that the small cation, attracting a large anion to itself, reduces its effective R, itself entering its e-cloud. Thus, the cation and anion are not regular spheres, and the cation causes deformation of the anion. The higher the charge of the cation and the smaller its size, the stronger the polarization effect. And the larger the size of the anion and its negative charge, the more it is polarized - deformed. Lithophilic cations (with 8 electron shells) cause less polarization than ions with complementary shells (such as Fe). Chalcophile ions with large ordinal numbers and high valence call the strongest polarization. This is associated with the formation of complex compounds: 2-, , 2-, 2-, cat. soluble and yavl. the main transporters of metals in hydrothermal solutions.

11.State (form of location) email. in nature. In GC the following are distinguished: min. (crystalline phases), impurities in min., various forms of dispersed state; email location form in nature carries information about the degree of ionization, chemical characteristics. email connections in phases, etc. In-vo (el.) is in three main forms. The first is the end atoms, the image. stars are different. types, gas nebulae, planets, comets, meteorites and cosmos. TV particles in. Concentration degree The substance is different in all bodies. The most diffuse states of atoms in gaseous nebulae are held by gravitational forces or are on the verge of overcoming them. The second is scattered atoms and molecules, an image of interstellar and intergalactic gas, consisting of free atoms, ions, molecules, e – . The amount of it in our Galaxy is significantly less than that which is concentrated in stars and gaseous nebulae. Interstellar gas is located at different levels. stages of rarefaction. The third is intensively migrating atomic nuclei and elementary particles flying at enormous speed that make up cosmic rays. V.I. Vernadsky identified the main four forms of occurrence of chemicals. Email in the Earth's Earth and on its surface: 1. rocks and minerals (solid crystalline phases), 2. magma, 3. dispersed state, 4. living matter. Each of these forms is distinguished by a special state of their atoms. Noun and other selection of forms of location of email. in nature, depending on specific holy elements themselves. A.I. Perelman highlighted mobile and inert forms finding chemical Email in the lithosphere. By his definition, movable form represents such a state of chemistry. Email in gp, soils and ores, being in the cat. Email can easily move into the solution and migrate. Inert form represents such a state in mineral deposits, ores, weathering crust and soils, in cat. Email in this situation, it has a low migration ability and cannot move into the region and migrate.

12.Internal factors of migration.

Migration- movement of chemicals Email in geospheres Z, leading to their dispersion or conc. Clarke - medium conc. in the main types of gp ZK of each chemical. Email can be considered as the state of its equilibrium under the conditions of a given chemical. environment, deviation from cat. is gradually reduced by the migration of this electricity. Under terrestrial conditions, the migration of chemicals. Email occurs in any medium - TV. and gaseous (diffusion), but easier in a liquid medium (in melts and aqueous solutions). At the same time, the forms of migration of chemicals. Email are also different - they can migrate in atomic (gases, melts), ionic (solutions, melts), molecular (gases, solutions, melts), colloidal (solutions) forms and, in the form of clastic particles (air and water environment ). A.I. Perelman distinguishes four types of chemical migration. El.: 1.mechanical, 2.physical-chemical, 3.biogenic, 4.technogenic. The most important internal factors: 1. Thermal properties of electricity, i.e. their volatility or refractoriness. El., having a condensation temperature of more than 1400 o K are called refractory platinoids, lithophilic - Ca, Al, Ti, Ree, Zr, Ba, Sr, U, Th), from 1400 to 670 o K - moderately volatile. [lithophilic – Mg, Si (moderately refractory), many chalcophilic, siderophilic – Fe, Ni, Co ],< 670 o K – летучими (атмофильные). На основании этих св-в произошло разделение эл. по геосферам З. При магм. процессе в условиях высоких Т способность к миграции будет зависеть от возможности образования тугооплавких соединений и, нахождения в твердой фазе. 2. Хим. Св-ва эл. и их соединений. Атомы и ионы, обладающие слишком большими или слишком малыми R или q, обладают и повышенной способностью к миграции и перераспределению. Хим. Св-ва эл. и их соединений приобретают все большее значение по мере снижения T при миграции в водной среде. Для литофильных эл. с низким ионным потенциалом (Na, Ca, Mg) в р-рах хар-ны ионные соединения, обладающие высокой раствор-ю и высокими миграционными способностями. Эл. с высокими ионными потенциалами образуют растворимые комплексные анионы (С, S, N, B). При низких Т высокие миграционные способности газов обеспечиваются слабыми молекулярными связями их молекул. Рад. Св-ва, опред-ие изменение изотопного состава и появление ядер других эл.

Instructions

All meteorites are divided into iron, stony-iron and stone, depending on their chemical composition. The first and second have a significant percentage of nickel content. They are found infrequently, because having a gray or brown surface, they are indistinguishable by eye from ordinary stones. The best way to look for them is with a mine detector. However, when you pick one up, you will immediately realize that you are holding metal or something similar to it.

Iron meteorites have high specific gravity and magnetic properties. Fallen long ago, they acquire a rusty tint - this is their distinctive feature. Most iron and stony meteorites are also magnetized. The latter, however, are significantly less. It is quite easy to detect a recently fallen one, since a crater usually forms around the place where it fell.

As the meteorite moves through the atmosphere, it becomes very hot. In those that have recently fallen, a melted shell is noticeable. After cooling, regmaglypts remain on their surface - depressions and protrusions, as if from fingers, and fur - traces reminiscent of burst bubbles. Meteorites are often shaped like a slightly rounded head.

Sources:

• Committee on Meteorites of the Russian Academy of Sciences

– celestial stones or pieces of metal flying from space. They are quite inconspicuous in appearance: gray, brown or black. But meteorites are the only extraterrestrial substance that can be studied or at least held in one's hands. With their help, astronomers learn the history of space objects.

You will need

• Magnet.

Instructions

The simplest, but also the best indicator that the average person can get is a magnet. All sky stones contain iron, which... A good option is something like a horseshoe with four pounds of tension.

After such initial testing, the possible one should be sent to the laboratory to confirm or refute the authenticity of the find. Sometimes these tests last about a month. Cosmic rocks and their terrestrial brothers are composed of the same minerals. They differ only in the concentration, combination and mechanics of the formation of these substances.

If you think that what you have in your hands is not a ferrous meteorite, but a meteorite, testing with a magnet will be pointless. Examine it carefully. Rub your find thoroughly, focusing on a small area about the size of a coin. This way you will make it easier for yourself to study the stone matrix.

They have small spherical inclusions that resemble freckle spots of solar iron. This is a distinctive feature of “traveler” stones. This effect cannot be produced artificially.

Video on the topic

Sources:

• The shape and surface of meteorites. in 2019

The meteorite can be distinguished from an ordinary stone right at the place of discovery. According to the law, a meteorite is considered a treasure and the finder receives a reward. Instead of a meteorite, there may be other natural wonders: a geode or an iron nugget, even more valuable.

This article tells you how to determine right at the place of discovery whether it is a simple cobblestone, a meteorite or another natural rarity mentioned later in the text. Equipment and tools you will need are paper, a pencil, a strong (at least 8x) magnifying glass and a compass; preferably a good camera and GSM navigator. Also - a small garden or sapper. No chemicals or a hammer and chisel are required, but a plastic bag and soft packaging material are required.

What is the essence of the method

Meteorites and their “simulators” have enormous scientific value and are considered treasures by Russian legislation. The finder, after being assessed by experts, receives a reward.

However, if the find was subjected to chemical, mechanical, thermal and other unauthorized influences before being delivered to a scientific institution, its value decreases sharply, several times or tens of times. For scientists, the rare sinter minerals on the surface of the sample and its interior preserved in its original form may be of greater importance.

Treasure hunters-“predators”, who independently clean their finds to a “marketable” state and break them into souvenirs, not only harm science, but also greatly deprive themselves. Therefore, it is further described that there is over 95% confidence in the value of what was discovered, without even touching it.

External signs

Meteorites fly into the earth's atmosphere at a speed of 11-72 km/s. At the same time, they melt. The first sign of the extraterrestrial origin of the find is the melting crust, which differs in color and texture from the interior. But in iron, iron-stone and stone meteorites different types melting crust is different.

Small iron meteorites entirely take on a streamlined or ogival shape, somewhat reminiscent of a bullet or artillery shell (item 1 in the figure). In any case, the surface of the suspicious “stone” is smoothed, as if sculpted from, pos. 2. If the sample also has a bizarre shape (item 3), then it may turn out to be both a meteorite and a piece of native iron, which is even more valuable.

Fresh melting bark is blue-black (Pos. 1,2,3,7,9). In an iron meteorite that has lain in the ground for a long time, it oxidizes over time and changes color (Pos. 4 and 5), and in an iron-stone meteorite it can become similar to ordinary rust (Pos. 6). This often misleads seekers, especially since the melting relief of a stony-iron meteorite that flew into the atmosphere at a speed close to the minimum can be poorly expressed (Pos. 6).

In this case, a compass will help out. Bring it to, if the arrow points to a “stone”, then it is most likely an iron-containing meteorite. Iron nuggets are also “magnetic”, but they are extremely rare and do not rust at all.

In stony and stony-iron meteorites, the melting crust is heterogeneous, but in its fragments some elongation in one direction is already visible to the naked eye (Pos. 7). Rocky meteorites often break up while still in flight. If the destruction occurred in the final section of the trajectory, their fragments, which do not have a melting crust, may fall to the ground. However, in this case, their internal structure, unlike any earthly minerals (Pos. 8).

If a sample is chipped, then in mid-latitudes you can determine whether it is a meteorite or not at first glance: the melting crust is sharply different from the interior (Pos. 9). It will accurately show the origin of the bark under a magnifying glass: if a streaky pattern is visible on the bark (Pos. 10), and so-called organized elements are visible on the chip (Pos. 11), then this is most likely a meteorite.

In the desert, the so-called stone tan can be misleading. Also in deserts, wind and temperature erosion are strong, which is why the edges of ordinary stone can be smoothed out. In a meteorite, the influence of the desert climate can smooth out the streaky pattern, and the desert tan can tighten the chip.

In the tropical zone, external influences on rocks are so strong that meteorites on the ground surface soon become difficult to distinguish from simple stones. In such cases, approximate specific gravity after removal from the deposit can help to gain confidence in the find.

Documentation and seizure

In order for a find to retain its value, its location before removal must be documented. To do this:

· Via GSM, if you have a navigator, and record the geographical coordinates.
· We take photographs from different sides, from far and near (from different angles, as photographers say), trying to capture in the frame everything remarkable near the sample. For scale, next to the find we place a ruler or an object of known size (lens cap, matchbox, tin can, etc.)
· We draw croques (plan diagram of the find site without scale), indicating compass azimuths to the nearest landmarks ( settlements, geodetic signs, noticeable hills, etc.), with an eye assessment of the distance to them.

Now you can start withdrawing. First, we dig a trench on the side of the “stone” and watch how the type of soil changes along its length. The find must be removed along with the deposits around it, and in any case, in a soil layer of at least 20 mm. Scientists often value the chemical changes around a meteorite more than the meteorite itself.

Having carefully dug up, we put the sample in a bag and estimate its weight with our hands. Light elements and volatile compounds are “swept out” of meteorites in space, so their specific gravity is greater than that of terrestrial rocks. For comparison, you can dig up and weigh a similar-sized cobblestone in your hands. The meteorite, even in a layer of soil, will be much heavier.

What if it’s a geode?

Geodes—crystallization “nests” in terrestrial rocks—are often similar in appearance to meteorites that have lain in the ground for a long time. The geode is hollow, so it will be lighter than even an ordinary stone. But don't be disappointed: you're just as lucky. Inside the geode is a nest of natural piezoquartz, and often precious stones (Pos. 12). Therefore, geodes (and iron nuggets) are also considered treasures.

But under no circumstances should you split the object into a geode. In addition to the fact that it will depreciate significantly, the illegal sale of gems entails criminal liability. The geode must be taken to the same facility as the meteorite. If its contents have jewelry value, the finder, by law, has the right to an appropriate reward.

Where to take it?

The find must be delivered to the nearest scientific institution, at least to a museum. You can also go to the police; the regulations of the Ministry of Internal Affairs provide for such a case. If the find is too heavy, or the scientists and the police are not very far away, it is better not to seize it at all, but to call one or the other. This does not detract from the rights of the finder and the reward, but the value of the find increases.

If you still have to transport it yourself, the sample must be provided with a label. In it you need to indicate the exact time and place of discovery, all significant, in your opinion, circumstances of the discovery, your full name, time and place of birth and permanent residence address. Crocs and, if possible, photographs are attached to the label. If the camera is digital, then the files from it are downloaded to the media without any processing, preferably in addition to the computer, directly from the camera to a flash drive.

For transportation, the sample in a bag is wrapped in cotton wool, synthetic padding or other soft padding. It is also advisable to place it in a strong wooden box, securing it from shifting during transportation. In any case, you need to deliver it yourself only to a place where qualified specialists can arrive.