Geochemistry

The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and their interaction with the hydrosphere and the atmosphere. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel A hydrosphere (from Greek ύδωρ - hydor, " Water " + σφαίρα - sphaira, " Sphere " An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere "

The most important fields of geochemistry are:

Isotope geochemistry: Determination of the relative and absolute concentrations of the elements and their isotopes in the earth and on earth's surface. Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their Isotopes in the A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides
Examination of the distribution and movements of elements in different parts of the earth (crust, mantle, hydrosphere etc. ) and in minerals with the goal to determine the underlying system of distribution and movement.
Cosmochemistry: Analysis of the distribution of elements and their isotopes in the cosmos . Cosmochemistry is concerned with the origin and development of the elements and their Isotopes primarily within the Solar System. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy
Organic geochemistry: A study of the role of processes and compounds that are derived from living or once-living organisms. Organic geochemistry is the study of the impacts and processes that Organisms and once-living organisms have had on the Earth.
Regional, environmental and exploration geochemistry: Applications to environmental, hydrological and mineral exploration studies.

The man considered by most to be the father of modern geochemistry was Victor Goldschmidt, and the ideas of the subject were formed by him in a series of publications from 1922 under the title ‘Geochemische Verteilungsgesetze der Elemente’. Victor Moritz Goldschmidt ( Zürich, January 27, 1888 &ndash March 20, 1947 in Oslo) was a Mineralogist considered

1 Chemical characteristics
- 1.1 Mineral constitution
- 1.2 Acid, intermediate and basic igneous rocks
2 See also
3 References
4 Further reading

Chemical characteristics

The more common rock constituents are nearly all oxides; chlorine, sulfur and fluorine are the only important exceptions to this and their total amount in any rock is usually much less than 1%. In Geology, petrology (from Greek πέτρα petra, rock and λόγος logos, knowledge is the study of rocks and the conditions on which Foundations Principles of Geology An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 F. W. Clarke has calculated that a little more than 47% of the earth's crust consists of oxygen. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the It occurs principally in combination as oxides, of which the chief are silica, alumina, iron oxides, lime, magnesia, potash and soda. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Altogether there are sixteen known Iron Oxides and oxyhydroxides Magnesia (Μαγνησία Magnisía, maɣniˈsia deriving from the tribe name Magnetes, is the name of the southeastern area of Thessaly Potash (or carbonate of potash) is an impure form of Potassium carbonate ( K 2 CO3) The silica functions principally as an acid, forming silicates, and all the commonest minerals of igneous rocks are of this nature. From a computation based on 1672 analyses of all kinds of rocks Clarke arrived at the following as the average percentage composition: SiO₂=59. 71, Al₂O₃=15. 41, Fe₂O₃=2. 63, FeO=3. 52, MgO=4. 36, CaO=4. 90, Na₂O=3. 55, K₂O=2. 80, H₂O=1. 52, TiO₂=0. 60, P₂O₅=0. 22, total 99. 22%). All the other constituents occur only in very small quantities, usually much less than 1%.

These oxides combine in a haphazard way. The potash and soda, for example, combine to produce feldspars. Feldspar is the name of a group of rock-forming Minerals which make up as much as 60% of the Earth 's crust. In some cases they may take other forms, such as nepheline, leucite and muscovite, but in the great majority of instances they are found as felspar. Nepheline, also called nephelite (from Greek: nephos, "cloud" is a Feldspathoid: a silica-undersaturated aluminosilicate Na Leucite is a rock -forming Mineral composed of Potassium and Aluminium tectosilicate K Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium The phosphoric acid with lime forms apatite. The titanium dioxide with ferrous oxide gives rise to ilmenite. Part of the lime forms lime felspar. Magnesia and iron oxides with silica crystallize as olivine or enstatite, or with alumina and lime form the complex ferro-magnesian silicates of which the pyroxenes, amphiboles and biotites are the chief. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg Enstatite is the magnesium endmember of the Pyroxene Silicate mineral series enstatite (MgSiO3 - ferrosilite (FeSiO3 The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Any excess of silica above what is required to neutralize the bases will separate out as quartz; excess of alumina crystallizes as corundum. Corundum (from Tamil kurundam குருந்தம் or kuruvindam குருவிந்தம் is a Crystalline form of These must be regarded only as general tendencies. It is possible by inspection of a rock analysis to say approximately what minerals the rock will contain, but there are numerous exceptions to any rule which can be laid down.

Mineral constitution

Hence we may say that except in acid or siliceous rocks containing 66% of silica and over, quartz will not be abundant. In basic rocks (containing 60% of silica or less) it is rare and accidental. If magnesia and iron be above the average while silica is low olivine may be expected; where silica is present in greater quantity over ferro-magnesian minerals, such as augite, hornblende, enstatite or biotite, occur rather than olivine. Unless potash is high and silica relatively low leucite will not be present, for leucite does not occur with free quartz. Nepheline, likewise, is usually found in rocks with much soda and comparatively little silica. With high alcalis soda-bearing pyroxenes and amphiboles may be present. The lower the percentage of silica and the alkalis the greater is the prevalence of t lime felspar as contracted with soda or potash felspar. Clarke has calculated the relative abundance of the principal rock-forming minerals with the following results: Apatite=0. 6, titanium minerals=1. 5, quartz=12. 0, felspars=59. 5, biotite=3. 8, hornblende and pyroxene=16. 8, total=94. 2%. This, however, can only be a rough approximation. The other determining factor, namely the physical conditions attending consolidation, plays on the whole a smaller part, yet is by no means negligible, as a few instances will prove. There are certain minerals which are practically confined to deep-seated intrusive rocks, e. g. microcline, muscovite, diallage. Leucite is very rare in plutonic masses; many minerals have special peculiarities in microscopic character according to whether they crystallized in depth or near the surface, e. g. hypersthene, orthoclase, quartz. There are some curious instances of rocks having the same chemical composition but consisting of entirely different minerals, e. g. the hornblendite of Gran, in Norway, containing only hornblende, has the same composition as some of the camptonites of the same locality which contain felspar and hornblende of a different variety. In this connection we may repeat what has been said above about the corrosion of porphyritic minerals in igneous rocks. In rhyolites and trachytes early crystals of hornblende and biotite may be found in great numbers partially converted into augite and magnetite. The hornblende and biotite were stable under the pressures and other conditions which obtained below the surface, but unstable at higher levels. In the ground-mass of these rocks augite is almost universally present. But the plutonic representatives of the same magma, granite and syenite contain biotite and hornblende far more commonly than augite.

Acid, intermediate and basic igneous rocks

Those rocks which contain most silica and on crystallizing yield free quartz are erected into a group generally designated the "acid" rocks. Those again which contain least silica and most magnesia and iron, so that quartz is absent while olivine is usually abundant, form the "basic" group. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg The "intermediate" rocks include those which are characterized by the general absence of both quartz and olivine. An important subdivision of these contains a very high percentage of alkalis, especially soda, and consequently has minerals such as nepheline and leucite not common in other rocks. Nepheline, also called nephelite (from Greek: nephos, "cloud" is a Feldspathoid: a silica-undersaturated aluminosilicate Na Leucite is a rock -forming Mineral composed of Potassium and Aluminium tectosilicate K It is often separated from the others as the "alkali" or "soda" rocks, and there is a corresponding series of basic rocks. Lastly a small sub-group rich in olivine and without felspar has been called the "ultrabasic" rocks. They have very low percentages of silica but much iron and magnesia.

Except these last practically all rocks contain felspars or felspathoid minerals. In the acid rocks the common felspars are orthoclase, which perthite, microcline, oligoclase, all having much silica and alkalis. In the basic rocks labradorite, anorthite and bytownite prevail, being rich in lime and poor in silica, potash and soda. Augite is the commonest ferro-magnesian of the basic rocks, but biotite and hornblende are on the whole more frequent in the acid.

Commonest Minerals	Acid	Intermediate		Basic	Ultrabasic
Commonest Minerals	Quartz Orthoclase (and Oligoclase), Mica, Hornblende, Augite	Little or no Quartz: Orthoclase hornblende, Augite, Biotite	Little or no Quartz: Plagioclase Hornblende, Augite, Biotite	No Quartz Plagioclase Augite, Olivine	No Felspar Augite, Hornblende, Olivine
Plutonic or Abyssal type	Granite	Syenite	Diorite	Gabbro	Peridotite
Intrusive or Hypabyssal type	Quartz-porphyry	Orthoclase-porphyry	Porphyrite	Dolerite	Picrite
Lavas or Effusive type	Rhyolite, Obsidian	Trachyte	Andesite	Basalt	Limburgite

The rocks which contain leucite or nepheline, either partly or wholly replacing felspar are not included in this table. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Syenite is a coarse-grained intrusive Igneous rock of the same general composition as Granite but with the Quartz either absent or present in relatively Diorite (ˈdaɪəraɪt is a grey to dark grey intermediate intrusive Igneous rock composed principally of Plagioclase Feldspar (typically Gabbro (ˈɡæbrəʊ is a dark coarse-grained intrusive Igneous rock chemically equivalent to Basalt. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. Quartz-porphyry, in Petrology, is the name given to a group of hemi- Crystalline Acid rocks containing Porphyritic crystals of Diabase (ˈdaɪəbeɪs or Dolerite is a Mafic, Holocrystalline, Igneous rock equivalent to Volcanic Basalt or plutonic Picrite basalt is a variety of high-magnesium olivine Basalt that is very rich in the mineral Olivine. This page is about a volcanic rock For the ghost town see Rhyolite Nevada, and for the satellite system see Rhyolite/Aquacade. Obsidian is a naturally occurring Glass formed as an extrusive Igneous rock. Trachyte is an Igneous, Volcanic rock with an Aphanitic to Porphyritic texture For the extinct cephalopod genus see Andesites. Andesite (ˈændəsaɪt is an igneous, Volcanic rock, of intermediate Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. In petrology limburgite is a dark-colored volcanic rock resembling Basalt in appearance but containing normally no Felspar. They are essentially of intermediate or of basic character. We might in consequence regard them as varieties of syenite, diorite, gabbro, etc. , in which felspathoid minerals occur, and indeed there are many transitions between syenites of ordinary type and nepheline — or leucite — syenite, and between gabbro or dolerite and theralite or essexite. But as many minerals develop in these "alcali" rocks which are uncommon elsewhere, it is convenient in a purely formal classification like that which is outlined here to treat the whole assemblage as a distinct series.

Nepheline and Leucite-bearing Rocks
Commonest Minerals	Alkali Felspar, Nepheline or Leucite, Augite, Hornblend, Biotite	Soda Lime Felspar, Nepheline or Leucite, Augite, Hornblende (Olivine)	Nepheline or Leucite, Augite, Hornblende, Olivine
Plutonic type	Nepheline-syenite, Leucite-syenite, Nepheline-porphyry	Essexite and Theralite	Ijolite and Missourite
Effusive type or Lavas	Phonolite, Leucitophyre	Tephrite and Basanite	Nepheline-basalt, Leucite-basalt

This classification is based essentially on the mineralogical constitution of the igneous rocks. Any chemical distinctions between the different groups, though implied, are relegated to a subordinate position. It is admittedly artificial by it has grown up with the grown of the science and is still adopted as the basis on which more minute subdivisions are erected. The subdivisions are by no means of equal value. The syenites, for example, and the peridotites, are far less important than the granites, diorites and gabbros. Moreover, the effusive andesites do not always correspond to the plutonic diorites but partly also to the gabbros. As the different kinds of rock, regarded as aggregates of minerals, pass gradually into one another, transitional types are very common and are often so important as to receive special names. The quartz-syenites and nordmarkites may be interposed between granite and syenite, the tonalites and adamellites between granite and diorite, the monzoaites between syenite and diorite, norites and hyperites between diorite and gabbro, and so on. ^[1].

References

^ This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petrology", a publication now in the public domain. Fred F Meissner, PE (10 November 1931 – 18 September 2007 was an American Geologist and Engineer who contributed to the fields of Geology, Geophysics, Petroleum geology refers to the specific set of geological disciplines that are applied to the search for Hydrocarbons ( Oil exploration) The Encyclopædia Britannica Eleventh Edition (1910–1911 is a 29-volume reference work that marked the beginning of the Encyclopædia Britannica The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone

Dictionary

-noun

(chemistry) The branch of chemistry that deals with the chemical composition of the Earth and other planets, and with the chemical processes that occur in the formation of rocks and minerals etc.

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Contents

Chemical characteristics

Mineral constitution

Acid, intermediate and basic igneous rocks

See also

References

Further reading

Dictionary

geochemistry

-noun