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98-510: The study is primarily focused on metallic mineral deposits and mineral resources. The techniques employed by other Earth science disciplines (such as geochemistry , mineralogy , geophysics , petrology , paleontology and structural geology ) might all be used to understand, describe and exploit an ore deposit. Economic geology is studied and practiced by geologists. Economic geology may be of interest to other professions such as engineers, environmental scientists and conservationists because of

196-443: A / k . The residence time is defined as where I and O are the input and output rates. In the above example, the steady-state input and output rates are both equal to a , so τ res = 1/ k . If the input and output rates are nonlinear functions of C , they may still be closely balanced over time scales much greater than the residence time; otherwise, there will be large fluctuations in C . In that case,

294-523: A Chemistry instructor under hydrocarbon scientist and fellow Lawrence School graduate, James Mason Crafts at the young Cornell University . Often stereotyped as a "chemist," the record shows Clarke to also have been a geologist. His short sojourn in Ithaca, New York prompted extensive surveys of local geologic forms, resumed when he taught at the University of Cincinnati . Clarke returned to Boston after

392-505: A computation based on 1672 analyses of numerous kinds of rocks Clarke arrived at the following as the average percentage composition of the Earth's crust: SiO 2 =59.71, Al 2 O 3 =15.41, Fe 2 O 3 =2.63, FeO=3.52, MgO=4.36, CaO=4.90, Na 2 O=3.55, K 2 O=2.80, H 2 O=1.52, TiO 2 =0.60, P 2 O 5 =0.22, (total 99.22%). All the other constituents occur only in very small quantities, usually much less than 1%. These oxides combine in

490-424: A concentration that is a function C ( r , t ) of position and time, but it is impractical to model the full variability. Instead, in an approach borrowed from chemical engineering , geochemists average the concentration over regions of the Earth called geochemical reservoirs . The choice of reservoir depends on the problem; for example, the ocean may be a single reservoir or be split into multiple reservoirs. In

588-472: A focus on isotope-biogeochemistry and the evidence of the earliest life processes in Precambrian . Some subfields of geochemistry are: The building blocks of materials are the chemical elements . These can be identified by their atomic number Z, which is the number of protons in the nucleus . An element can have more than one value for N, the number of neutrons in the nucleus. The sum of these

686-458: A fourth group, and in the fifth group FeO enter the magnesium silicates. The compositions of the planets and the Moon are chondritic , meaning that within each group the ratios between elements are the same as in carbonaceous chondrites. The estimates of planetary compositions depend on the model used. In the equilibrium condensation model, each planet was formed from a feeding zone in which

784-421: A haphazard way. For example, potash (potassium carbonate) and soda ( sodium carbonate ) combine to produce feldspars . 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 feldspar. Phosphoric acid with lime (calcium carbonate) forms apatite . Titanium dioxide with ferrous oxide gives rise to ilmenite . Part of

882-412: A ligand contains more than one donor atom, forming very strong complexes, also called chelates (the ligand is the chelator). One of the most common chelators is EDTA ( ethylenediaminetetraacetic acid ), which can replace six molecules of water and form strong bonds with metals that have a plus two charge. With stronger complexation, lower activity of the free metal ion is observed. One consequence of

980-430: A little more than 47% of the Earth's crust consists of oxygen . It occurs principally in combination as oxides, of which the chief are silica , alumina , iron oxides , and various carbonates ( calcium carbonate , magnesium carbonate , sodium carbonate , and potassium carbonate ). The silica functions principally as an acid, forming silicates, and all the commonest minerals of igneous rocks are of this nature. From

1078-463: A low tone with a well-modulated and quite agreeable voice, using very well-chosen language, talking good sense, but with a mild undertone of gaiety, and you find him bright and entertaining and then you find him clever . . . ." In his communications, Clarke exhibited restraint in speaking either negatively or positively of others. His praise he reserved for the individual's absence and many were advanced in his profession by Clarke's recommendation out of

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1176-439: A means of collecting peer professional efforts for common use across five successive editions. Beginning with his Constitution of silicates (1895), Clarke advanced a methodology of geochemical analysis which described a mineral's composition through fact coordination. Priority was placed on contextualizing the research by describing constitution, structure and relationship with other minerals. The mineral sample's natural history

1274-466: A new process in mineral analysis (March 1868). It was published at age 20 and during the year he went on to serve as an instructor in Chemistry at the new Cornell University. Even after he left academia, his bookish qualities were well known. He would time his Cosmos Club library visits to coincide with the librarians' opening of the periodical mail and was keen on being the first to know, rather than

1372-476: A replacement commodity substituted for those commodities which become too expensive. Additionally the fixed stock of most mineral commodities is huge (e.g., copper within the Earth's crust given current rates of consumption would last for more than 100 million years.) Nonetheless, economic geologists continue to successfully expand and define known mineral resources. Mineral resources are concentrations of minerals significant for current and future societal needs. Ore

1470-414: A result, chemical reactions show a small isotope dependence, with heavier isotopes preferring species or compounds with a higher oxidation state; and in phase changes, heavier isotopes tend to concentrate in the heavier phases. Mass-dependent fractionation is largest in light elements because the difference in masses is a larger fraction of the total mass. Ratios between isotopes are generally compared to

1568-409: A scavenged-type trace metal is aluminium , which has strong interactions with particles as well as a short residence time in the ocean. The residence times of scavenged-type trace metals are around 100 to 1000 years. The concentrations of these metals are highest around bottom sediments, hydrothermal vents , and rivers. For aluminium, atmospheric dust provides the greatest source of external inputs into

1666-508: A small sub-group rich in olivine and without feldspar has been called the "ultramafic" rocks. They have very low percentages of silica but much iron and magnesia. Except these last, practically all rocks contain felspars or feldspathoid minerals. In the acid rocks, the common feldspars are orthoclase, perthite, microcline, and oligoclase—all having much silica and alkalis. In the mafic rocks labradorite, anorthite, and bytownite prevail, being rich in lime and poor in silica, potash, and soda. Augite

1764-606: A solid core captured nebular gas. In current models, the four giant planets have cores of rock and ice that are roughly the same size, but the proportion of hydrogen and helium decreases from about 300 Earth masses in Jupiter to 75 in Saturn and just a few in Uranus and Neptune. Thus, while the gas giants are primarily composed of hydrogen and helium, the ice giants are primarily composed of heavier elements (O, C, N, S), primarily in

1862-564: A standard. For example, sulfur has four stable isotopes, of which the two most common are S and S. The ratio of their concentrations, R = S/ S , is reported as where R s is the same ratio for a standard. Because the differences are small, the ratio is multiplied by 1000 to make it parts per thousand (referred to as parts per mil). This is represented by the symbol ‰ . Equilibrium fractionation occurs between chemicals or phases that are in equilibrium with each other. In equilibrium fractionation between phases, heavier phases prefer

1960-433: A trace metal with a conservative-type distribution is molybdenum. It has a residence time within the oceans of around 8 x 10 years and is generally present as the molybdate anion (MoO 4 ). Molybdenum interacts weakly with particles and displays an almost uniform vertical profile in the ocean. Relative to the abundance of molybdenum in the ocean, the amount required as a metal cofactor for enzymes in marine phytoplankton

2058-414: A type of model called a box model , a reservoir is represented by a box with inputs and outputs. Geochemical models generally involve feedback. In the simplest case of a linear cycle, either the input or the output from a reservoir is proportional to the concentration. For example, salt is removed from the ocean by formation of evaporites , and given a constant rate of evaporation in evaporite basins,

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2156-623: Is a form of kinetic fractionation since reactions tend to be in one direction. Biological organisms prefer lighter isotopes because there is a lower energy cost in breaking energy bonds. In addition to the previously mentioned factors, the environment and species of the organism can have a large effect on the fractionation. Through a variety of physical and chemical processes, chemical elements change in concentration and move around in what are called geochemical cycles . An understanding of these changes requires both detailed observation and theoretical models. Each chemical compound, element or isotope has

2254-567: Is anomalously enriched. The pattern of elemental abundance is mainly due to two factors. The hydrogen, helium, and some of the lithium were formed in about 20 minutes after the Big Bang , while the rest were created in the interiors of stars . Meteorites come in a variety of compositions, but chemical analysis can determine whether they were once in planetesimals that melted or differentiated . Chondrites are undifferentiated and have round mineral inclusions called chondrules . With

2352-451: Is based on "educated guesses". One difficulty with this model is that there may be significant errors in its prediction of volatile abundances because some volatiles are only partially condensed. The more common rock constituents are nearly all oxides ; chlorides , sulfides and fluorides are the only important exceptions to this and their total amount in any rock is usually much less than 1%. By 1911, F. W. Clarke had calculated that

2450-479: Is classified as mineralization economically and technically feasible for extraction. Not all mineralization meets these criteria for various reasons. The specific categories of mineralization in an economic sense are: Geologists are involved in the study of ore deposits, which includes the study of ore genesis and the processes within the Earth's crust that form and concentrate ore minerals into economically viable quantities. Study of metallic ore deposits involves

2548-404: Is convenient in a purely formal classification like that outlined here to treat the whole assemblage as a distinct series. 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, but it has grown up with the growth of

2646-719: Is found in the reduced form UO 2 (s). Vanadium is in several forms in oxidation state V(V); HVO 4 and H 2 VO 4 . Its reduced forms can include VO 2 , VO(OH) 3 , and V(OH) 3 . These relative dominance of these species depends on pH . In the water column of the ocean or deep lakes, vertical profiles of dissolved trace metals are characterized as following conservative–type , nutrient–type , or scavenged–type distributions. Across these three distributions, trace metals have different residence times and are used to varying extents by planktonic microorganisms. Trace metals with conservative-type distributions have high concentrations relative to their biological use. One example of

2744-506: Is low, olivine may be expected; where silica is present in greater quantity over ferromagnesian 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 alkalis , soda-bearing pyroxenes and amphiboles may be present. The lower

2842-536: Is negligible. Trace metals with nutrient-type distributions are strongly associated with the internal cycles of particulate organic matter, especially the assimilation by plankton. The lowest dissolved concentrations of these metals are at the surface of the ocean, where they are assimilated by plankton. As dissolution and decomposition occur at greater depths, concentrations of these trace metals increase. Residence times of these metals, such as zinc, are several thousand to one hundred thousand years. Finally, an example of

2940-505: Is of prime importance to the delineation of economic reserves of petroleum and coal energy resources. Geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans . The realm of geochemistry extends beyond the Earth , encompassing the entire Solar System , and has made important contributions to

3038-480: Is possible, by rock analysis, to say approximately what minerals the rock contains, but there are numerous exceptions to any rule. Except in acid or siliceous igneous rocks containing greater than 66% of silica , known as felsic rocks, quartz is not abundant in igneous rocks. In basic rocks (containing 20% of silica or less) it is rare for them to contain as much silicon, these are referred to as mafic rocks. If magnesium and iron are above average while silica

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3136-554: Is present as the Mo(VI) oxidation state as MoO 4 (aq) in oxic environments. Mo(V) and Mo(IV) are present in reduced environments in the forms MoO 2 (aq) and MoS 2(s) . Rhenium is present as the Re(VII) oxidation state as ReO 4 within oxic conditions, but is reduced to Re(IV) which may form ReO 2 or ReS 2 . Uranium is in oxidation state VI in UO 2 (CO 3 ) 3 (aq) and

3234-401: Is that volatiles would not condense, so the planets would have no atmospheres and Earth no atmosphere. In chondritic mixing models, the compositions of chondrites are used to estimate planetary compositions. For example, one model mixes two components, one with the composition of C1 chondrites and one with just the refractory components of C1 chondrites. In another model, the abundances of

3332-427: Is the mass number , which is roughly equal to the atomic mass . Atoms with the same atomic number but different neutron numbers are called isotopes . A given isotope is identified by a letter for the element preceded by a superscript for the mass number. For example, two common isotopes of chlorine are Cl and Cl. There are about 1700 known combinations of Z and N, of which only about 260 are stable. However, most of

3430-679: Is the most common ferromagnesian in mafic rocks, but biotite and hornblende are on the whole more frequent in felsic rocks. Rocks that contain leucite or nepheline, either partly or wholly replacing felspar, are not included in this table. They are essentially of intermediate or of mafic character. We might in consequence regard them as varieties of syenite, diorite, gabbro, etc., in which feldspathoid 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 "alkali" rocks that are uncommon elsewhere, it

3528-693: The 1900 Paris Exposition . At the centennial of John Dalton 's atomic theory held at Manchester, England in 1903, Clarke delivered the Wilde Lecture. Returning to England in 1909, he presented before The Chemical Society on the subject of his mentor, Wolcott Gibbs . His forty-two year career included parallel service with the United States National Museum as 'honorary curator' of minerals. The Smithsonian Institution 's extensive mineral collection "are due in large measure to his active interest and his painstaking efforts both in

3626-545: The Earth's crust , forming silicates and other oxides. Siderophile elements ( Fe , Co , Ni , Pt , Re , Os ) have an affinity for iron and tend to concentrate in the core . Chalcophile elements ( Cu , Ag , Zn , Pb , S ) form sulfides ; and atmophile elements ( O , N , H and noble gases) dominate the atmosphere. Within each group, some elements are refractory , remaining stable at high temperatures, while others are volatile , evaporating more easily, so heating can separate them. The chemical composition of

3724-540: The University of Oslo applied these methods to many common minerals and formulated a set of rules for how elements are grouped. Goldschmidt published this work in the series Geochemische Verteilungsgesetze der Elemente [Geochemical Laws of the Distribution of Elements]. The research of Manfred Schidlowski from the 1960s to around the year 2002 was concerned with the biochemistry of the Early Earth with

3822-430: The giant planets , which are dominated by hydrogen and helium and have lower mean densities. These can be further subdivided into the gas giants ( Jupiter and Saturn ) and the ice giants ( Uranus and Neptune ) that have large icy cores. Most of our direct information on the composition of the giant planets is from spectroscopy . Since the 1930s, Jupiter was known to contain hydrogen, methane and ammonium . In

3920-439: The "mafic" group. The "intermediate" rocks include those 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. It is often separated from the others as the "alkali" or "soda" rocks, and there is a corresponding series of mafic rocks. Lastly,

4018-466: The 1960s, interferometry greatly increased the resolution and sensitivity of spectral analysis, allowing the identification of a much greater collection of molecules including ethane , acetylene , water and carbon monoxide . However, Earth-based spectroscopy becomes increasingly difficult with more remote planets, since the reflected light of the Sun is much dimmer; and spectroscopic analysis of light from

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4116-794: The AY 1868-1869, and resumed lectures at the Boston Dental College and pursued literary and journalistic endeavors, including reporting for the Boston Advertiser, through 1873. Clarke retired from the public service on January 1, 1925, having served as the Chief Chemist of the U.S. Geological Survey since 1883. Part of his Survey work included analysis of the Yellowstone geysers and their water. He also supported American contributions to many exhibitions, most notably

4214-478: The Earth and other bodies is determined by two opposing processes: differentiation and mixing. In the Earth's mantle , differentiation occurs at mid-ocean ridges through partial melting , with more refractory materials remaining at the base of the lithosphere while the remainder rises to form basalt . After an oceanic plate descends into the mantle, convection eventually mixes the two parts together. Erosion differentiates granite , separating it into clay on

4312-527: The Earth is composed of non-silicate minerals such as carbonates , oxides , and sulfides . The other determining factor, namely the physical conditions attending consolidation, plays, on the whole, a smaller part, yet is by no means negligible. Certain minerals 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

4410-587: The Periodic Table of Elements which continued until interrupted by the First World War in 1918. Prior to entering the federal service, Clarke taught chemistry and geochemistry at Howard University (1873–1874) and the University of Cincinnati (1874–1883). While at Cincinnati, he made extensive forays into Appalachia to study its geology and form. Clarke's first academic work was entitled On

4508-903: The Solar System, there could be little systematic dependence on position. Direct information on Mars, Venus and Mercury largely comes from spacecraft missions. Using gamma-ray spectrometers , the composition of the crust of Mars has been measured by the Mars Odyssey orbiter, the crust of Venus by some of the Venera missions to Venus, and the crust of Mercury by the MESSENGER spacecraft. Additional information on Mars comes from meteorites that have landed on Earth (the Shergottites , Nakhlites , and Chassignites , collectively known as SNC meteorites). Abundances are also constrained by

4606-685: The United States". It was printed by the Government Printing Office in Washington, DC. Clarke's stated purpose in writing the report was to "state the facts, and secondly, to point out defects and remedies--to show on the one hand what is, and on the other what ought to be" relative to the teaching of chemistry and physics in the United States. The report was exhaustive, spanning secondary institutions, normal schools, and more than 350 colleges and universities. In 1908

4704-448: The ages of 4.56 billion years, they date to the early solar system . A particular kind, the CI chondrite , has a composition that closely matches that of the Sun's photosphere, except for depletion of some volatiles (H, He, C, N, O) and a group of elements (Li, B, Be) that are destroyed by nucleosynthesis in the Sun. Because of the latter group, CI chondrites are considered a better match for

4802-414: The associations, alterations, and syntheses of each mineral sample. His study "Constants of Nature" (Smithsonian Institution 1876) was one of the first collections of both physical and chemical constants. The USGS's Atomic Weights series became standard references for the chemistry and geochemistry professions and academic fields. Clarke was also an academic collaborator. His Data on Geochemistry became

4900-502: The chemistry of rocks and minerals. The chief USGS chemist, Frank Wigglesworth Clarke , noted that the elements generally decrease in abundance as their atomic weights increase, and summarized the work on elemental abundance in The Data of Geochemistry . The composition of meteorites was investigated and compared to terrestrial rocks as early as 1850. In 1901, Oliver C. Farrington hypothesised that, although there were differences,

4998-596: The collection and exhibition of specimens." From 1892 to 1902, Clarke was the lone member of the American Chemical Society 's Committee on Atomic Weights. In 1902, the need for commonality between active American and German scientific committees prompted the formation of the International Commission on Atomic Weights , with Frank Clarke as its chairman. As chairman, Clarke guided the international committee in successive revisions of

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5096-495: The composition of the early Solar System. Moreover, the chemical analysis of CI chondrites is more accurate than for the photosphere, so it is generally used as the source for chemical abundance, despite their rareness (only five have been recovered on Earth). The planets of the Solar System are divided into two groups: the four inner planets are the terrestrial planets ( Mercury , Venus , Earth and Mars ), with relatively small sizes and rocky surfaces. The four outer planets are

5194-425: The compositions of solids were determined by the temperature in that zone. Thus, Mercury formed at 1400 K, where iron remained in a pure metallic form and there was little magnesium or silicon in solid form; Venus at 900 K, so all the magnesium and silicon condensed; Earth at 600 K, so it contains FeS and silicates; and Mars at 450 K, so FeO was incorporated into magnesium silicates. The greatest problem with this theory

5292-473: The convergence of knowledge; if it fulfills that purpose it is useful, even though it may be supplanted at some later day by an expression of still greater generality." Clarke authored one of the first governmental reports on the teaching of science in the United States. The report was sponsored by the US Commissioner of Education in 1878 and titled: "Report on the teaching of chemistry and physics in

5390-404: 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. Hornblende and biotite were stable under the pressures and other conditions below the surface, but unstable at higher levels. In the ground-mass of these rocks, augite is almost universally present. But

5488-481: The far-reaching impact that extractive industries have on society, the economy and the environment. The purpose of the study of economic geology is to gain understanding of the genesis and localization of ore deposits plus the minerals associated with ore deposits. Though metals, minerals and other geologic commodities are non-renewable in human time frames, the impression of a fixed or limited stock paradigm of scarcity has always led to human innovation resulting in

5586-521: The first edition of Clarke's work, The Data of Geochemistry (Survey Bulletin no. 330), was published while he was the Chief Chemist at the U.S. Geological Survey . Clarke's fifth edition of this bulletin was released in 1924; the year he retired. Clarke was also an early pioneer (1891) of work efficiency studies, using the theory of probability and least squares as the basis for work review. Clarke's parents, Henry W. Clarke and Abby (Fisher) Clarke, were residents of Boston, Massachusetts. Henry W. Clarke

5684-494: The five fractionation groups are estimated using an index element for each group. For the most refractory group, uranium is used; iron for the second; the ratios of potassium and thallium to uranium for the next two; and the molar ratio FeO/(FeO+ MgO ) for the last. Using thermal and seismic models along with heat flow and density, Fe can be constrained to within 10 percent on Earth, Venus, and Mercury. U can be constrained within about 30% on Earth, but its abundance on other planets

5782-423: The form CdCl (aq) in oxic waters or CdS(s) in a reduced environment. Thus, higher concentrations of Cd in marine sediments may indicate low redox potential conditions in the past. For copper(II), a prevalent form is CuCl (aq) within oxic environments and CuS(s) and Cu 2 S within reduced environments. The reduced seawater environment leads to two possible oxidation states of copper, Cu(I) and Cu(II). Molybdenum

5880-412: The form of water, methane, and ammonia. The surfaces are cold enough for molecular hydrogen to be liquid, so much of each planet is likely a hydrogen ocean overlaying one of heavier compounds. Outside the core, Jupiter has a mantle of liquid metallic hydrogen and an atmosphere of molecular hydrogen and helium. Metallic hydrogen does not mix well with helium, and in Saturn, it may form a separate layer below

5978-419: The forward reaction is enhanced if the humidity of the air is less than 100% or the water vapor is moved by a wind. Kinetic fractionation generally is enhanced compared to equilibrium fractionation and depends on factors such as reaction rate, reaction pathway and bond energy. Since lighter isotopes generally have weaker bonds, they tend to react faster and enrich the reaction products. Biological fractionation

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6076-484: The heavier isotopes. For two phases A and B, the effect can be represented by the factor In the liquid-vapor phase transition for water, a l-v at 20 degrees Celsius is 1.0098 for O and 1.084 for H. In general, fractionation is greater at lower temperatures. At 0 °C, the factors are 1.0117 and 1.111. When there is no equilibrium between phases or chemical compounds, kinetic fractionation can occur. For example, at interfaces between liquid water and air,

6174-506: The largest two elements by fraction of total mass are hydrogen (74.9%) and helium (23.8%), with all the remaining elements contributing just 1.3%. There is a general trend of exponential decrease in abundance with increasing atomic number, although elements with even atomic number are more common than their odd-numbered neighbors (the Oddo–Harkins rule ). Compared to the overall trend, lithium , boron and beryllium are depleted and iron

6272-421: The likely compositions. High-pressure experiments predict that hydrogen will be a metallic liquid in the interior of Jupiter and Saturn, while in Uranus and Neptune it remains in the molecular state. Estimates also depend on models for the formation of the planets. Condensation of the presolar nebula would result in a gaseous planet with the same composition as the Sun, but the planets could also have formed when

6370-456: The lime forms lime feldspar. Magnesium carbonate and iron oxides with silica crystallize as olivine or enstatite , or with alumina and lime form the complex ferromagnesian silicates of which the pyroxenes , amphiboles , and biotites are the chief. Any excess of silica above what is required to neutralize the bases will separate out as quartz ; excess of alumina crystallizes as corundum . These must be regarded only as general tendencies. It

6468-419: The lower reactivity of complexed metals compared to the same concentration of free metal is that the chelation tends to stabilize metals in the aqueous solution instead of in solids. Concentrations of the trace metals cadmium , copper , molybdenum , manganese , rhenium , uranium and vanadium in sediments record the redox history of the oceans. Within aquatic environments, cadmium(II) can either be in

6566-535: The masses of the planets, while the internal distribution of elements is constrained by their moments of inertia. The planets condensed from the solar nebula, and much of the details of their composition are determined by fractionation as they cooled. The phases that condense fall into five groups. First to condense are materials rich in refractory elements such as Ca and Al. These are followed by nickel and iron, then magnesium silicates . Below about 700 kelvins (700 K), FeS and volatile-rich metals and silicates form

6664-417: The metallic hydrogen. Terrestrial planets are believed to have come from the same nebular material as the giant planets, but they have lost most of the lighter elements and have different histories. Planets closer to the Sun might be expected to have a higher fraction of refractory elements, but if their later stages of formation involved collisions of large objects with orbits that sampled different parts of

6762-515: The mystery of the genesis of our planets and their inorganic matter may be revealed." However, for the rest of the century the more common term was "chemical geology", and there was little contact between geologists and chemists . Geochemistry emerged as a separate discipline after major laboratories were established, starting with the United States Geological Survey (USGS) in 1884, which began systematic surveys of

6860-474: The ocean floor, sandstone on the edge of the continent, and dissolved minerals in ocean waters. Metamorphism and anatexis (partial melting of crustal rocks) can mix these elements together again. In the ocean, biological organisms can cause chemical differentiation, while dissolution of the organisms and their wastes can mix the materials again. A major source of differentiation is fractionation , an unequal distribution of elements and isotopes. This can be

6958-426: The ocean. Frank Wigglesworth Clarke Frank Wigglesworth Clarke (March 19, 1847 – May 23, 1931) of Boston, Massachusetts , and Washington, D.C. was an American scientist and chemist. Sometimes known as the "Father of Geochemistry," Clarke is credited with determining the composition of the Earth's crust . He was a founder of The American Chemical Society and served as its President, in 1901. Clarke

7056-408: The one to receive, the news. Clarke was not a hearty laugher. He was known to "ripple" quietly at exceptional displays of wit or humor. Clarke's humorous use of language was compared to Lewis Carroll and the talent was renowned at Washington D.C.'s Cosmos Club . Somewhat of a gossip, he specialized in knowing not only what people were currently doing, but also what their forebears had done. Clarke

7154-462: The percentage of silica and alkali's, the greater is the prevalence of plagioclase feldspar as contracted with soda or potash feldspar. Earth's crust is composed of 90% silicate minerals and their abundance in the Earth is as follows: plagioclase feldspar (39%), alkali feldspar (12%), quartz (12%), pyroxene (11%), amphiboles (5%), micas (5%), clay minerals (5%); the remaining silicate minerals make up another 3% of Earth's crust. Only 8% of

7252-462: The planets can only be used to detect vibrations of molecules, which are in the infrared frequency range. This constrains the abundances of the elements H, C and N. Two other elements are detected: phosphorus in the gas phosphine (PH 3 ) and germanium in germane (GeH 4 ). The helium atom has vibrations in the ultraviolet range, which is strongly absorbed by the atmospheres of the outer planets and Earth. Thus, despite its abundance, helium

7350-406: The plutonic representatives of the same magma, granite, and syenite contain biotite and hornblende far more commonly than augite. Those rocks that contain the most silica, and on crystallizing yield free quartz, form a group generally designated the "felsic" rocks. Those again that contain the least silica and most magnesia and iron, so that quartz is absent while olivine is usually abundant, form

7448-607: The position of elements in the periodic table . Based on position, the elements fall into the broad groups of alkali metals , alkaline earth metals , transition metals , semi-metals (also known as metalloids ), halogens , noble gases , lanthanides and actinides . Another useful classification scheme for geochemistry is the Goldschmidt classification , which places the elements into four main groups. Lithophiles combine easily with oxygen. These elements, which include Na , K , Si , Al , Ti , Mg and Ca , dominate in

7546-416: The pressure is about equal to 1 bar , approximately Earth's atmospheric pressure at sea level . The Galileo probe penetrated to 22 bars. This is a small fraction of the planet, which is expected to reach pressures of over 40 Mbar. To constrain the composition in the interior, thermodynamic models are constructed using the information on temperature from infrared emission spectra and equations of state for

7644-427: The rate of removal of salt should be proportional to its concentration. For a given component C , if the input to a reservoir is a constant a and the output is kC for some constant k , then the mass balance equation is This expresses the fact that any change in mass must be balanced by changes in the input or output. On a time scale of t = 1/k , the system approaches a steady state in which C =

7742-419: The relative abundances should still be the same. This was the beginnings of the field of cosmochemistry and has contributed much of what we know about the formation of the Earth and the Solar System. In the early 20th century, Max von Laue and William L. Bragg showed that X-ray scattering could be used to determine the structures of crystals. In the 1920s and 1930s, Victor Goldschmidt and associates at

7840-475: The result of chemical reactions, phase changes , kinetic effects, or radioactivity . On the largest scale, planetary differentiation is a physical and chemical separation of a planet into chemically distinct regions. For example, the terrestrial planets formed iron-rich cores and silicate-rich mantles and crusts. In the Earth's mantle, the primary source of chemical differentiation is partial melting , particularly near mid-ocean ridges. This can occur when

7938-647: 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,

8036-467: The solar system is similar to that of many other stars, and aside from small anomalies it can be assumed to have formed from a solar nebula that had a uniform composition, and the composition of the Sun 's photosphere is similar to that of the rest of the Solar System. The composition of the photosphere is determined by fitting the absorption lines in its spectrum to models of the Sun's atmosphere. By far

8134-494: The solid is heterogeneous or a solid solution , and part of the melt is separated from the solid. The process is known as equilibrium or batch melting if the solid and melt remain in equilibrium until the moment that the melt is removed, and fractional or Rayleigh melting if it is removed continuously. Isotopic fractionation can have mass-dependent and mass-independent forms. Molecules with heavier isotopes have lower ground state energies and are therefore more stable. As

8232-507: 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, which contains only hornblende, has the same composition as some of the camptonites of the same locality that contain feldspar and hornblende of a different variety. In this connection, we may repeat what has been said above about

8330-420: The system is always close to a steady-state and the lowest order expansion of the mass balance equation will lead to a linear equation like Equation ( 1 ). In most systems, one or both of the input and output depend on C , resulting in feedback that tends to maintain the steady-state. If an external forcing perturbs the system, it will return to the steady-state on a time scale of 1/ k . The composition of

8428-533: The tonalites and adamellites between granite and diorite, the monzonites between syenite and diorite, norites and hyperites between diorite and gabbro, and so on. Trace metals readily form complexes with major ions in the ocean, including hydroxide , carbonate , and chloride and their chemical speciation changes depending on whether the environment is oxidized or reduced . Benjamin (2002) defines complexes of metals with more than one type of ligand , other than water, as mixed-ligand-complexes. In some cases,

8526-468: The understanding of a number of processes including mantle convection , the formation of planets and the origins of granite and basalt . It is an integrated field of chemistry and geology . The term geochemistry was first used by the Swiss-German chemist Christian Friedrich Schönbein in 1838: "a comparative geochemistry ought to be launched, before geognosy can become geology, and before

8624-447: The unstable isotopes do not occur in nature. In geochemistry, stable isotopes are used to trace chemical pathways and reactions, while radioactive isotopes are primarily used to date samples. The chemical behavior of an atom – its affinity for other elements and the type of bonds it forms – is determined by the arrangement of electrons in orbitals , particularly the outermost ( valence ) electrons. These arrangements are reflected in

8722-437: The use of structural geology , geochemistry , the study of metamorphism and its processes, as well as understanding metasomatism and other processes related to ore genesis. Ore deposits are delineated by mineral exploration , which uses geochemical prospecting, drilling and resource estimation via geostatistics to quantify economic ore bodies. The ultimate aim of this process is mining . The study of sedimentology

8820-653: The waiter has served the butter this man has said, 'Take it away, please,' and of the potatoes, 'Take that away also,' and should he be eating of sweet potato and some one has remarked to him, 'Why I thought you did not like potatoes,' he replies, 'This is not potato, it is convolvulus . . ." Anger was not a Clarke character trait. Toward the end of his life, Clarke was described as "about five feet five inches in height, one hundred and ten pounds in weight, with pale blue eyes, little hair and most of that under his ears, chewing his finger nails and apparently absorbed in thought, though really most alert." His voice delivered in ". . .

8918-579: Was a hardware merchant and dealer in iron-working machinery. Abby Clarke died when Frank Clarke was an infant of ten days. Among Clarke's New England ties were his grandfather Samuel Clarke, who served as a Unitarian minister at Princeton, New Jersey and Uxbridge, Massachusetts. Clarke was also a descendant of Col. Edward Wigglesworth, who served under General George Washington in the Continental Army, and Michael Wigglesworth, an 18th century Puritan poet who wrote "Day of Doom". Frank Clarke

9016-403: Was found to be depleted by a factor of 2 compared to solar composition and Ne by a factor of 10, a surprising result since the other noble gases and the elements C, N and S were enhanced by factors of 2 to 4 (oxygen was also depleted but this was attributed to the unusually dry region that Galileo sampled). Spectroscopic methods only penetrate the atmospheres of Jupiter and Saturn to depths where

9114-701: Was gained at a boarding school in Stoughton and several schools in Boston. He attended Boston Latin School and the English High School before matriculating to Harvard College's Lawrence Scientific School in March 1865. His Harvard mentor was Wolcott Gibbs . Clarke took his Bachelor of Science from Harvard in 1867. He then took a position as a chemistry lecturer at Boston Dental College. He then served as

9212-545: Was known for a sharp wit, sometimes employing deadpan. While attending a friend's Thanksgiving dinner, Clarke noticed the host struggling with that metric of American male performance, the carving of the turkey. Clarke "suggested that it might profit the carver to visit the National Museum, for a certain door therein bears on it the sign 'Division of Birds'." A colleague recalled his dining habits at Washington D.C.'s Cosmos Club, "[s]hould you join him at lunch and when

9310-506: Was only detected once spacecraft were sent to the outer planets, and then only indirectly through collision-induced absorption in hydrogen molecules. Further information on Jupiter was obtained from the Galileo probe when it was sent into the atmosphere in 1995; and the final mission of the Cassini probe in 2017 was to enter the atmosphere of Saturn. In the atmosphere of Jupiter, He

9408-569: Was raised by his Unitarian grandfather, Samuel Clarke, at Uxbridge until 1851. In 1851, his father Henry W. Clarke remarried, and the new family constituted itself at Woburn, Massachusetts until 1858. The Clarkes lived at Worcester, Massachusetts from 1859–1866, when they returned to Boston. After Frank left for collegiate studies, Henry Clarke moved to Watertown where he resided until his death in 1907. Clarke's primary education occurred in Woburn and Uxbridge, Massachusetts; his secondary schooling

9506-442: Was the end goal, a means of articulating the mineral's alteration products and pseudomorphs as a record of chemical change. To this record Clarke added the artificial history record available in the laboratory. The natural and artificial histories, combined, created what Clarke called the "constitution of a mineral." The constitution of a mineral was best summarized by, in the words of Clarke, "a good formula" which " . . . indicates

9604-536: Was the first theorist to advance a hypothesis regarding the evolution of elements. This concept emerged early in his intellectual career. His "Evolution and the Spectroscope" (1873) appeared in Popular Science Monthly. It noted a parallel evolution of minerals, accompanying that of plant life. He was known for pushing mineral analysis beyond analytical results. He sought compilations of

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