Lithosphere, main elements

Minerals are solid, inorganic compounds found in nature. They have distinct crystalline structures and chemical compositions. Minerals of various elements are found in the lithosphere mainly as oxides, carbonates, and sulfides. 

Thus, the chemical reactivity of the elements in seawater is reflected by the residence time. It is important to note, however, that while residence times tell us something about the relative reactivities, they also tell us nothing about the nature of the reactions. The best source of clues for imderstanding these reactions is to study the shape of dissolved profiles of the different elements. When we do this we find that there are six main characteristic types of profiles as described in Table 10-8. Notice that most of these reactions occur at the phase discontinuities between the atmosphere, biosphere, hydrosphere, and lithosphere. 

Mercury is a relatively rare chemical element. In the lithosphere it occurs mainly as sulfides, HgS. Mercury sulfide comes in two forms cinnibar, which is black, and vermillion. In some places mercury exists in a small proportion as free chemical species. 

Silicon is next to oxygen the most abundant element in the lithosphere the average content amounts about 30% by weight. Inorganic silicon compounds such as silica and silicates form the basis of most of the rocks forming the earth s crust. In the atmosphere, there is no silicon present, except as dust of cosmic and terrestrial origin. The silicon content in the hydrosphere, mainly in form of dissolved silica (silicic acid), is also very small. 

Clay is found everywhere on earth, usually as part of the outer layer of the earth s crust, the lithosphere. In a few places clay is also found and mined below the surface. Clay is an erosion product of magma or sedimentary rock. Before entering into the phenomenon erosion , first some information about the various kinds of rocks of which the earth s surface is built up. By now we know that the elements O, Si, Al, Fe, Ca, Na, K and Mg mainly occur in rocks (see Geology /Mineralogy). 

A main concern of geochemistiy is the investigation of the abundance and the distribution of the elements on the surface and in deeper layers of the earth, and of transport processes. The components of the geosphere are the lithosphere, the hydrosphere and the atmosphere. The relative abundance of the elements on the surface of the earth is plotted in Fig. 15.1 as a function of the atomic number. This relative abundance is similar within the solar system. The elements H, O, Si, Ca and Fe exhibit the highest abundances and maxima are observed at the magic numbers Z = 8, 20, 50 and 82. The abundances of the elements and their isotopes are determined by the nuclear reactions by which they have been produced and by their nuclear properties, whereas the chemical properties of the elements are only responsible for distribution and fractionation processes. 

Sulphur (0.052% of the lithosphere) occurs mainly as the element and in sulphides and sulphates. 

Iodine (10 % of lithosphere) is obtained mainly from iodates present in Chilean nitrates. lodate-rich solutions are reduced with sodium bisulphite to hberate the element ... 

Fig. 2.3 Distribution of elements in the four main environmental materials, lithosphere, hydrosphere, atmosphere and biosphere. The elements are shown in their actual form as compounds, ions or molecules as appropriate. The main components of each material are shown in boxes, other major constituents are shown outside the boxes.

In any given time the vast majority of S is in the lithosphere. However, the main transport of this element occurs in the atmosphere, hydrosphere, and biosphere. The role of the biosphere often involves reactions that result in the movement of sulfur from one reservoir to another. 

Of approximately 80 elements found in soils, 17 are used by plants to grow. These are called the essential elements and include H, C, O, N, P, S, K, Mg, Ca, B, Cl, Mn, Fe, Cu, Zn, Mo, and Co. Hydrogen and O are derived from the hydrosphere, C from the atmosphere, N from the biosphere, and the remaining 13 from the lithosphere or the mineral soil. Soil is mainly an O-Si-Al-Fe matrix containing relatively small amounts of the other essential... 

Our own solar system was formed ca. 4.5 billion years ago out of matter from supernovas and other interstellar substances, and the earth is one of the nine planets in this system. The different zones within the planet are shown in Figure 3.2. The mantle constitutes ca. 83% of the earth s total volume and consists mainly of iron and magnesium silicates. The lithosphere is the sohd portion of the earth as contrasted with the atmosphere and the hydrosphere. It includes the earth crust and the upper mantle. Between 100 and 400 km depth in the upper mantle is a plastic shell, the partially molten asthenosphere. Currents in that medium cause the movements of the continents. The core is believed to consist of an alloy of iron and nickel, and to contain also up to 10% of a lighter element, perhaps sulfur or oxygen. The inner central core is solid, the outer fluid. The temperature in the center is about 4000°C. 

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