Crust main elements

Knowledge of the 90 chemical elements and their properties in compounds led to the construction, by man, of a unique table of elements, the Periodic Table, of 18 Groups in six periods in a pattern fully explained by quantum theory, described in Chapter 2. There is then a huge variety of chemical combinations possible on the Earth and limitations on what is observable are related to element position in this Table. It also relates to the thermodynamic and/or kinetic stability of particular combinations of them in given physical circumstances (Table 11.3). The initial state of the surface of the Earth with which we are concerned was a dynamic water layer, the sea, covering a crust mainly of oxides and some sulfides and with an atmosphere of NH3, HCN, N2, C02(C0, CH4), H20, with some H2 but no 02. This combination of phases and their contents then produced an aqueous solution layer of particular components in which there were many concentration restrictions between it and the components of the other two layers due to thermodynamic stability, equilibria, or kinetic stability of the chemicals trapped in the phases. It is the case that equilibrium... 

A very small amount of the matter in the earth s crust, oceans, and atmosphere is involved in living matter. The main element in living matter is carbon, but only a tiny... 

The elements beryllium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, molybdenum, silver, cadmium, tin, thallium, lead, and bismuth mainly occur in the crystal structures of rock-forming silicates and oxides of the common rocks in the Earths crust. These elements - with the exception of magnesium, iron, titanium, chromium, and zirconium - are trace elements in the minerals. They follow certain rules as reported by Goldschmidt (1954) in their ten-... 

Table 1.1 also contains data for average concentrations of the 25 selected elements in the oceanic crust. As a first approximation, we have assumed for this part of the compilation that the oceanic crust mainly consists of the so-called ocean ridge basalt (MORE). Large volumes of this basaltic ocean crust have undergone hydrothermal alteration connected with a gain of H2O, CO2, Na, Mg and S from heated sea water and losses of Si, Ca, Ee, Mn, etc. from the altered basalt to the ocean water reservoir. 

Sources and Production Potassium is highly reactive and does not occur in nature as a free metal. The abundance of potassium in the 16 km-thick Earths crust - mainly in silicates (feldspars, micas) - is 25.9 g kg k In the frequency list of the elements, potassium occupies seventh place. Its abundance in sea vater is almost as great, due to the veathering of potassium-containing minerals. After veathering of the rocks, potassium is bound by the calcium zeolites of the soils, and only part of it reaches the sea (0.38 g sea water). 

A very small amount of the matter in the earth s crust, oceans, and atmosphere is involved in living matter. The main element in living matter is carbon, but only a dny fraction of the carbon in the environment occurs in living organisms. More than one-quarter of the total mass of the earth s crust, oceans, and atmosphere is made up of silicon, yet it has almost no biological role. 

Calcium, as noted above, is the fifth most abundant element in the earth s crust and hence the third most abundant metal after A1 and Fe. Vast sedimentary deposits of CaC03, which represent the fossilized remains of earlier marine life, occur over large parts of the earth s surface. The deposits are of two main... 

Niobium and tantalum are rare elements. The content of niobium and of tantalum in the Earth s crust is lxl0"3 and 2x1 O 4 wt. %, respectively [21]. Niobium and tantalum are encountered in nature together, mostly in the form of oxides that are derived from orthoniobic (orthotantalic), metaniobic (metatantalic) and pyroniobic (pyrotantalic) acids. The main minerals are listed in Table 2, which reveals that the most important source of tantalum and niobium is tantalite-columbite, (Fe,Mn)(Nb,Ta)206. 

Polonium, completing the elements of Group 16, is radioactive and one of the rarest naturally occurring elements (about 3 x 10 " % of the Earth s crust). The main natural source of polonium is uranium ores, which contain about lO g of Po per ton. The isotope 210-Po, occurring in uranium (and also thorium) minerals as an intermediate in the radioactive decay series, was discovered by M. S. Curie in 1898. 

The outer crust of earth has provided the solid foundation for the evolution of human beings, who are the prime focus of interest and concern to archaeology. The main components of this crust are minerals and rocks, some consolidated and others occurring as sediments, nonconsolidated deposits, created by weathering processes from the minerals and rocks. All these minerals, rocks, and sediments, as well as everything else in the universe, are made up from just over 100 chemical elements listed in Appendix I. Most of the elements in the crust of the earth occur in extremely low relative amounts, and only a few, listed in Table 1, make up almost 99% of its total bulk (Bloom 1969). 

Carbon, a common element in the outer crust of the earth, and the main component of all biological and organic substances, occurs in three isotopic forms carbon-12 or C-12 for short (whose chemical symbol is 12C), carbon-13 or C-13 (13C), and carbon-14 or C-14 (14C) (see Fig. 8 and Table 66). 

The two rare earth elements niobium (Nb) and tantalum (Ta) were the main subject of study in the investigation referred to. Both elements have very similar properties and almost always occur together in our solar system. However, the silicate crust of the Earth contains around 30% less niobium (compared to its sister tantalum). Where are the missing 30% of niobium They must be in the Earth s FeNi core. It is known that the metallic core can only take up niobium under huge pressures, and the conditions necessary for this may have been present on Earth. Analyses of meteorites from the asteroid belt and from Mars show that these do not have a niobium deficit. 

Occurrence. Silicon is the second most abundant element in the earth s crust, after oxygen (about 28% by weight). It occurs mainly in oxides (quartz, agate, opal, etc.) and a great variety of silicate minerals (feldspar, clay, mica, olivine, etc.). 

We know a great deal about the nature of the universe. For instance, the element hydrogen makes up about 75% of all the mass in the universe. In terms of number, about 90% of all atoms in the universe are hydrogen atoms, and most of the rest of the atoms in the universe are helium. All the other heavier elements make up just one to two percent of the total. Interestingly, the most abundant element on Earth (in number of atoms) is oxygen (O ). Oxygen accounts for about 50% of all the elements found in the Earth s crust, and silicon, the second most abundant element, makes up about 25%. Silicon dioxide (SiO ) accounts for about 87% of the total Earth s mass. Sfiicon dioxide is the main chemical compound found in sand and rocks. 

The stable form of Cs-133 is the 48th most abundant element on Earth, but because it is so reactive, it is always in compound form. The Earths crust contains only about 7 ppm of Cs-133. Like the other alkali metals, it is found in mixtures of complex minerals. Its main source is the mineral pollucite (CsAlSi Og). It is also found in lepidohte, a potassium ore. Pollucite is found in Maine, South Dakota, Manitoba, and Elba and primarily in Rhodesia, South Africa. 

Thallium is the 59th most abundant element found in the Earths crust. It is widely distributed over the Earth, but in very low concentrations. It is found in the mineral/ores of crooksite (a copper ore CuThSe), lorandite (TLAsS ), and hutchinsonite (lead ore, PbTl). It is found mainly in the ores of copper, iron, sulfides, and selenium, but not in its elemental metallic state. Significant amounts of thallium are recovered from the flue dust of industrial smokestacks where zinc and lead ores are smelted. 

Rhenium was the last naturally occurring chemical element to be discovered in 1925 by Noddack, Tacke, and Berg in the mineral gadolinite. The name of this extremely rare element (the estimated occurrence in the earth s crust is about 0.7 ppb ) is derived from the Rhine river. Residues from the processing of molybdenum ores represent the main source of the metal. 

Average ratios for Si, Al, K, Ca, and Ti to Fe approximate earth crust ratios, indicated by arrows at left. These elements occur mainly in coarse particles (Figures 3 and 4). The Mn/Fe ratio is somewhat greater and Zn/Fe is 20 times greater than earth crust ratios. These two elements have appreciable fine-mode concentrations (Figure 4). All 8 elements may occur characteristically in continental air masses. 

Mossbauer spectroscopy is a selective tool for the quantitative analysis and spe-ciation of a very limited number of elements. It has been mainly used to study iron compounds—e.g., ceramics, as it gives valuable information about iron-bearing oxide and silicate minerals. This technique has been applied to the identification of the provenance of clay and used raw materials—the manufacturing method employed in pottery and, to a lesser extent, to the characterization of pigments and weathering crusts formed on stone monuments [23]. 

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