What Is the Mantle Zone?

The mantle is between the Moho and Gutenberg surfaces, the thickness is above 2800km, the average density is 4.59g / cm³, the volume accounts for 82.26% of the earth's volume, and the mass of the mantle accounts for 67.0% of the total mass of the earth , To a large extent affected the overall composition of the earth's matter. The lateral change of the mantle is relatively uniform. According to the change of the seismic wave velocity, the 1000km surge zone is taken as the interface (Lepoti plane), and the upper and lower mantles are further divided into two sub-layers. ^[1]

(A) the crust

(1) Inferred from the comparison of the density and seismic wave velocity of each circle with the relevant properties of the surface rocks or minerals.

(2) Based on the pressure and temperature of each rim, the high temperature and high pressure simulation experiments are used to make an estimation.

(3) Inferred from materials from deep underground. Volcanic eruption and tectonic movement can sometimes bring deep underground materials (such as the upper mantle) to the surface, providing a basis for our understanding of deep materials.

(4) Compare with the results of meteorite research. ,

Meteorites are fragments of celestial bodies from the solar system space. According to the large number of meteorite obtained, they can be divided into three types according to their composition:

Stone meteorite is composed of olivine, pyroxene (iron, magnesium silicate) minerals, and its composition is approximately equivalent to that of superbasic rocks seen on the surface. The metal state of iron and nickel has very few components and density. 3-3.5g / cm³ or more.

Iron meteorite (ironmeteorite) is a natural alloy mainly composed of iron and nickel in the metal state, with a density of 8-8.5g / cm³ or greater;

The iron stone meteorite is a transition type of the above two types of meteorites, in which iron, magnesium silicate minerals, and iron and nickel components in the metal state each occupy a part.

Modern astronomy and astrogeological studies have shown that: These meteorites should come from celestial bodies or asteroids in the solar system. When they enter the gravitational field of the earth, they are attracted by the earth, and a considerable part of them are rubbed by the atmosphere. Into the ground. It is extremely unlikely that matter outside the solar system will enter the earth through distant space. The material composition, formation and evolution within the solar system are uniform "Lu, especially when humans land on the moon and obtain similar solidity on the moon s surface rocks and certain rocks on the earth s surface, which further establishes the belief in the unity of the solar system s matter, so it can be used The characteristics of the meteorite infer the state of matter inside the earth.

The basement structure of the upper mantle is composed of refractory peridotite layers of different thicknesses and transitions down to the mantle rock (Figure 5-1). The main characteristic of rocks close to the mantle composition is that they can crystallize in the following four different mineral combinations (Ringwood, 1962a, b; Green and Ringwood, 1963):

Peridotite amphibole

Mantle petrology is a petrology that focuses on the mantle. The research contents include the composition of the upper mantle (rock, minerals, geochemistry) and its vertical and horizontal heterogeneity; the role of molten magma in the upper mantle and the source of magma chemical storage Reservoir; rheological and dynamic characteristics of the upper mantle; thermal state of the upper mantle; evolution of the mantle and other geological effects (such as metasomatism) in the mantle. At the surface, samples of the upper mantle can be obtained from the upper mantle inclusions in the Kimberlite and alkaline basalts, the metamorphic peridotite in the Alpine-type intrusive rocks, and the ophiolite mantle, providing compositional data. However, in order to build a complete model, the interpenetration of geophysics, physical chemistry, and experimental petrology can provide more constraints. ^[4]