What is Geochemistry 2017 I

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1
What Is Geochemistry?
G e o lo g y began w h e n e a r ly man f irst p icke d up a stone , considered its 
q u a l it ies , and d e c id e d th a t it was better than the stone he a lread y had. 
G o o d stones w ere use fu l and they w ere co l le c t e d , m in e d , and traded .
H en r y Fa u l a n d C a r o l Fa u l (1983, p. 1)
G eochem istry is based on the urge to understand 
why som e stones are “good” and how they 
form ed. It involves applications of the principles 
of chem istry to the solution of geological p rob 
lems and th erefo re could no t develop until 
chem istry and geology had been established as 
scientific disciplines. These applications were 
practiced first during the 16th century in the 
m ines of E u rope w here know ledge of m inerals 
and their chemical com positions was used to rec 
ognize and follow veins of ore. For exam ple, in 
1574 L azarus E rcker, the su p erin ten d en t of 
m ines for King R udolf II of A ustria, published a 
m anual in which he described ores and outlined 
procedures for their analysis (E rcker, 1951). 
How ever, several centuries passed befo re geo 
chem istry in the p resen t sense of th e word 
becam e established as an integral com ponen t of 
E arth and P lanetary Science.
1.1 Early History
Two essential prerequisites for the grow th of 
geochem istry were the discovery of the chemical 
elem ents and the developm ent of sensitive and 
accurate m ethods for the analysis o f rocks and 
minerals. U ntil the end of the 16th cen tury m at 
te r was thought to consist of earth , w ater, fire, 
and air, whose basic qualities w ere described as
warm, cold, dry, and wet. The m etals gold, silver, 
copper, iron, tin, mercury, and lead together with 
sulfur and carbon had been known for thousands 
of years bu t were not recognized as elem ents in 
the p resen t sense of the word. Antimony, arsenic, 
bism uth, and phosphorus were studied by the 
alchemists during the Middle Ages.
The developm ent of analytical chem istry 
during the 18th century resulted in the discovery 
of 46 chemical elem ents betw een 1720 and 1850. 
A fter B unsen and Kirchhoff invented the optical 
emission spectrograph, 30 additional elem ents 
w ere added from 1850 to 1925.The transuranium 
elem ents and certain other radioactive elem ents 
w ere discovered la ter in the 2 0 th cen tu ry 
(Correns, 1969).
As the num ber of known chemical elem ents 
increased during the 19th century, chem ists 
becam e aware that they could be organized into 
groups based on similarities of their chemical 
properties. These tendencies becam e the founda 
tion of the periodic table of the elem ents p ro 
posed independently by D. I. M endeleev in 1869 
and by J. L. M eyer in 1870 (Asimov, 1965). The 
cause for the periodicity of the chemical p ro p er 
ties of the elem ents was not know n then and was 
recognized only after the in ternal structure of 
atom s was w orked out during the first 30 years of 
the 2 0 th century.
2
 
1.2 G E O C H E M ISTRY IN TH E U .S .S .R . 3
The periodic tab le is a m anifestation of the 
relationship betw een the in ternal structure of 
atom s and the chem ical and physical p roperties 
of the elem ents. I t facilitates a ra tional explana 
tion of the chem ical p roperties of the elem ents 
and o f the ir observed d istribu tion in nature.
The roo ts of geochem istry lie mainly in the 
19th century, b u t it acquired its p resen t m ultifac 
eted com plexity during the 20th century. The word 
geochem istry was first used in 1838 by Christian 
F riedrich Schönbein, who was a chem istry p ro fes 
sor a t the U niversity o f B asel in Sw itzerland. The 
term was used again in 1908,70 years later, w hen 
F rank W. C larke of the U.S. G eological Survey 
published the first ed ition o f his book , The Data 
o f Geochemistry.
C larke was the Chief Chemist of the U.S. 
Geological Survey from 1884 until 1925. H e started 
the tradition for excellence in the analysis of rocks 
and m inerals tha t has helped to m ake the Survey 
one of the largest geochemical research centers in 
the world. The first edition of C larke’s book was 
amazingly m odem in its approach to geochemistry. 
H e opened with chapters on the chemical elements, 
the atm osphere, lakes and rivers, and the ocean fol 
lowed by chapters on saline lakes and springs and 
on evaporite deposits. N ext he took up volcanic 
gases, magma, rock-form ing minerals, and igneous 
rocks and then weathering, sedim entary rocks, 
m etam orphic rocks, and ore deposits. The book 
ends with chapters on fossil fuels and their origin. 
That is pretty much how we would present the data 
of geochemistry today, bu t Clarke did it this way in 
1908! M ore than 15 years passed before the great 
Soviet geochemist V. I. Vernadsky published his 
geochemistry book in 1924. Clarke was the first 
geochemist in the m odem sense of the word.
C larke’s book w ent th rough five editions, the 
last o f which appeared in 1924. I t is now being 
u pdated and expanded by the U.S. G eological 
Survey u n d er the ed itorsh ip of M ichael Fleischer. 
H ow ever, the H a n d b o o k o f Geochemistry, ed ited 
by K. H . W edepohl from 1969 to 1978, is the m ost 
com plete source of geochem ical da ta currently 
available.
1.2 Geochemistry 
in the U.S.S.R.
G eochem istry becam e an im portan t subject in 
the U.S.S.R. because of the need to develop the 
m ineral resources of the country. In 1932 Soviet 
geologists began to analyze systematically col 
lected soil samples using optical spectroscopy 
(Fersm an, 1939). In subsequent years the geolo 
gists of the C entral G eological and Prospecting 
Institu te in Moscow carried ou t extensive “m etal- 
lom etric” surveys based on soil samples in search 
of geochem ical anomalies.
G eochem istry p ro sp ered in th e U.S.S.R. 
because of the popu lar support it received partly 
in response to the rem arkable w ork of A lexander 
Fersm an (1883-1945). Fersm an studied m iner 
alogy at the U niversity of M oscow under V. I. 
Vernadsky, who took his students on m any field 
trips and encouraged them to regard m inerals as 
the products of chemical reactions. These were 
radical departures from conventional m ineralogy 
practiced at the tu rn of the century. Fersm an 
graduated in 1907 and was elected to a professor 
ship in m ineralogy in 1912 a t the age of 27. H e 
em barked on an ex traord inary career of teaching 
and research in geochem istry w ith em phasis on 
applications. H e traveled widely in the U.S.S.R. 
and explored regions rarely visited before. His 
sustained in terest in the exploration of the Kola 
Peninsula in the no rth ultim ately led to the dis 
covery of deposits of apatite and nickel ore. A s a 
result, a rem ote w ilderness area was transform ed 
into an im portant cen ter of mining and industry. 
Fersm an also explored central A sia and discov 
ered a native sulfur deposit a t K ara Kum tha t was 
actively m ined for decades.
B etw een 1934 and 1939 Fersm an published 
a com prehensive four-volum e w ork en titled 
Geochemistry in which he applied the principles 
of physical chem istry to the distribution of the 
chemical elem ents in nature. Fersm an, above all, 
aroused public in terest in geology and geochem 
istry by his inspiring lectures and popular books. 
A lexander K. Tolstoy called him a “poet of
 
4 W H A T IS G E O C H E M ISTRY?
stones.” Fersm an earned this accolade by writing 
books intended for the laym an: M ineralogy fo r 
Everyone (1928), Recollections about a Stone 
(1940), M y Travels, Stories abou t Precious Stones, 
and Geochemistry fo r Everyone (1958). The last 
two w ere published posthum ously. F ersm an’s 
convictiontha t geochem istry should serve his 
country is reflected in his words: “We cannot be 
m erely idle adm irers of our vast country; we m ust 
actively help reshape it and create a new life” 
(Shcherbakov, 1958).
The scientific legacy of Fersm an’s form er 
teacher, V ladim ir Ivanovich Vernadsky (1863- 
1945), is similarly impressive, but it has no t been 
appreciated in the w estern world. Vernadsky 
em phasized the im portance of the activities of 
living organism s in geological and geochem ical 
processes. In fact, he regarded living m atter as the 
“m ost pow erful geological fo rce” and w rote that 
the E a rth ’s crust originated from the biosphere. 
These convictions abou t the im portance of life on 
E arth were no t widely accepted by geologists in 
N orth A m erica, partly because Vernadsky wrote 
in m any languages (Russian, G erm an, French, 
Czech, Serbo-Croatian, and Japanese). His most 
im portant books (Vernadsky, 1924, 1929) were 
written in French and published in Paris. However, 
Vernadsky was also far ahead of his contem po 
raries by concluding that the biosphere may have 
controlled the environm ent on the surface of the 
E arth from the very beginning, long before the 
existence of life in Early Precam brian time was 
known (Lapo, 1986). Vernadsky’s views on this 
subject are now reflected in the “Gaia H ypothesis” 
of Lovelock (1979), m ade popular on American 
television in the “Planet E a rth ” series by the 
Public Broadcasting System. Vernadsky also iden 
tified the biosphere as the principal transform er of 
solar energy into chemical energy. This idea is now 
widely accepted. For exam ple, C loud (1983) 
described the biosphere as “a huge metabolic 
device for the capture, storage and transfer of 
energy.” Fossil fuels (coal, oil shale, petroleum , and 
natural gas) are now regarded as deposits of solar 
energy collected by the biosphere.
V ernadsky’s views on the im portance of the 
b io sphere (V ernadsky, 1945) are becom ing
ir : -asingly relevant as we attem pt to predict the 
cilimntic consequences of the “greenhouse effect” 
caused by the discharge of carbon dioxide and 
o ther gases into the atm osphere. We are carrying 
omt an experim ent on a global scale the outcome 
o f which could be de trim en ta l to life. The 
response of the biosphere to this perturbation of 
tlhe environm ent may be crucial to the ultim ate 
outcom e of this experim ent.
V. I. Vernadsky is revered in the U.S.S.R. as 
oine of the giants of science in the 2 0 th cen 
tury. His teachings still m otivate the geochem 
ists working at the V ernadsky Institu te 'of 
G eochem istry and A naly tical C hem istry in 
Moscow, which is am ong the forem ost geochem i 
cal research institutes in the world.
1.3 V. M. Goldschmidt
T he Institute of G eochem istry at the University 
o>f G öttingen in G erm any was m ade fam ous by 
tlhe work of Victor M. G oldschm idt (1888-1947). 
G oldschm idt earn ed his d o c to ra te a t the 
U niversity of Oslo in 1911 with a study of contact 
nnetam orphism based on the therm odynam ic 
p'hase rule. In the following year Max von Laue 
discovered diffraction of x-rays by crystals and 
thereby provided a m ethod for determ ining the 
crystal structure of a m ineral and the radii o f the 
ions of which it is com posed. From 1922 to 1926 
G oldschm idt and his associates at the University 
o f Oslo used x-ray diffraction to determ ine the 
crystal structures of many m inerals (Goldschm idt, 
1930). In 1930 G oldschm id t m oved to the 
Unrversity of G öttingen, w here he studied the 
distribution of the chemical elem ents using an 
optical spectrograph. From this body of da ta he 
deduced that the chemical com position of m iner 
als is determined by the requirem ents of “closest 
packing” of ions. M oreover, the substitution o f the 
ions of a major elem ent by the ions of a trace ele 
m en t depends on the similarity of their radii and 
charges. These generalizations provided a rational 
explanation for the observed distribution of the 
elem ents in the minerals of the crust of the E arth .
Goldschmidt re tu rned to Oslo in 1935 b u t 
w as unable to con tinue his w ork a fte r th e
 
1.4 M O D ER N G E O C H E M ISTRY 5
G erm an invasion of Norway in 1940. H e fled to 
Sw eden in 1942 and ultim ately m ade his way to 
E ng land , w here he w orked at the M acaulay 
In stitu te for Soil R esearch. His health had seri 
ously deterio ra ted as a consequence of im prison 
m e n t in co n cen tra tio n cam ps in Norway. 
G oldschm idt re tu rned to Oslo in 1946 bu t died 
th e re prem aturely in 1947 at the age of 59. H e left 
beh ind the m anuscrip t of a partially com pleted 
book entitled Geochemistry, which was com plet 
ed by A lex M uir and published posthum ously in 
1954. A special com m em orative issue of A pp lied 
G eochem istry (1988) was devo ted to 
G oldschm idt on the 100th anniversary of his 
birthday.
G oldschm idt’s principal contribution to geo 
chem istry is the ra tional explanation of isom or- 
phous substitu tion in crystals based on the com 
patibility of the radii and charges of the ions. H e 
thereby achieved one of the m ajor goals of geo 
chemistry. N evertheless, the urge to know and to 
understand the d istribution of the chemical ele 
m ents has continued to m otivate the work of sev 
e ra l o u ts tan d in g geochem ists, no tab ly L. H. 
A h ren s in S outh A frica , S. R. N ockolds in 
England, S. R . Taylor in Australia, K. R ankam a in 
Finland, K. H . W edepohl in G erm any, A . R 
V inogradov in the U.S.S.R., D. M. Shaw in 
Canada, and K. K. Turekian in the U nited States.
1.4 Modern Geochemistry
B eginning in the 1950s, geochem ists tu rn ed 
increasingly to the study of chemical reactions and 
processes. The roots of this line of research can be 
found in the work of A . Fersman, who used the 
concepts of therm odynam ics to study the stability 
of m inerals in their natural environment. In addi 
tion, J. H. v an ’t H off (1852-1911) studied the crys 
tallization of salts by evaporating seaw ater in 
Berlin and, in 1904, the Geophysical Laboratory 
of the C arnegie Institution of W ashington was 
founded in the U nited States. The principal objec 
tive of the G eophysical Laboratory has been to 
study the origin of igneous rocks and ore deposits 
by experim ental m ethods. The results achieved by
N. L. Bowen and his colleagues, and by their suc 
cessors, at that laboratory have becom e the foun 
dation of m odern igneous petrology. B ow en’s 
book, The Evolution o f the Igneous Rocks, pub 
lished in 1928, tu rned igneous petrology from a 
preoccupation with the description and classifica 
tion of igneous rocks tow ard a concern for their 
origin and the geochem ical differentiation of the 
E arth by m agm atic activity.
In 1952 B rian M ason published the first edi 
tion of Principles o f Geochemistry, which was 
widely used as a tex tbook at universities and 
helped to establish geochem istry as a legitim ate 
com ponent of E arth Science. In the next decade 
R obert M. Gar'rels and K onrad B. K rauskopf 
used therm odynam ics and solution chem istry to 
determ ine the stability of m inerals and the m obil 
ity of their ions at the surface of the E arth . They 
tra ined the m odern generation of geochem ists by 
their own research and through their popular 
textbooks (G arrels, 1960; G arrels and Christ, 
1965; Krauskopf, 1967).
G eochem ical prospecting, as we know it 
today, was initiated in 1947 by the U.S. G eological 
Survey (H aw kes and Lakin, 1949) and was based 
on colorimetry. The techniques developed in the 
U nited States w ere used in 1953 for soil surveys 
in the U nited K ingdom and in A frica (Webb, 
1953). Subsequently, theGeochem ical Prospecting 
R esearch C en ter a t the Im perial College of 
Science and Technology in London becam e a cen 
ter of activity in this aspect of geochemistry. 
Geochemical prospecting continues to be one of 
the most im portant practical applications of geo 
chemistry and now relies on a wide range of 
sophisticated analytical techniques.
E nv ironm en ta l geochem istry has arisen 
recently because of the need to m onitor the dis 
persion of m etals and various organic com pounds 
tha t are in troduced into the environm ent as 
anthropogenic contam inants. This new applica 
tion of geochem istry to the welfare of hum ankind 
is closely re lated to po llu tan t hydrogeology and 
medical geochemistry. G eochem ical prospecting 
and environm ental geochemistry are of param ount 
im portance because they contribute to the con 
tinued well-being of the hum an species on E arth .
 
6 W H A T IS G E O C H E M ISTRY?
Since about the middle of the 20th century 
geochemistry has becom e highly diversified into 
many subdivisions, am ong them inorganic geo 
chemistry, organic geochemistry, isotope geochem 
istry, geochem ical p rospecting , m edical geo 
chemistry, aqueous geochem istry, trace-elem ent 
geochemistry, and cosmochemistry. Each of these 
subdivisions has its own rapidly growing body of 
literature. H ow ever, the geochem ists of the world 
have organized scientific societies tha t transcend 
the boundaries of specialization and help to unify 
the field. These societies also publish journals 
tha t p rom ote the free flow of inform ation and 
ideas am ong their m em bers. For example, the 
G eochem ical Society and the M eteoritical Society 
both sponsor Geochimica et Cosmochimica Acta. 
The E uropean A ssociation for G eochem istry has 
adopted the jou rnal Chemical Geology, and the 
In ternational A ssociation of G eochem istry and 
Cosm ochem istry sponsors A p p lied Geochemistry. 
A m ong o ther journals tha t publish papers dealing 
w ith geochem istry are
Earth and Planetary Science Letters
Contributions to M ineralogy and Petrology
Journal o f Geochemical Exploration
E conom ic Geology
A m erican Journal o f Science
Nature
Science
Some journals are closely associated with certain 
regions, for example,
G eokhim ia 
D oklady (E arth 
Science Section)
Lithology and 
M ineral Resources 
Geochemistry 
International 
Geochemical Journal 
Chinese Journal 
o f Geochemistry
Russia
Japan
P eop le’s Republic 
of China
In fact, m ost E arth Science journals now publish 
papers in which geochemical data or principles 
are used to explain a geological process or to 
solve a particular problem . The strength of geo 
chem istry lies in the fact that most geological 
processes involve chemical reactions in some sig 
nificant way. G eochem istry really is for everyone, 
as Fersm an claimed in his popular book.
W hat then is geochemistry? There is no easy 
answ er to this question because geochemists con 
cern them selves with a wide range of natural phe 
nom ena and use many different techniques to 
study them . According to Fersman, “Geochemistry 
studies the history of chemical elem ents in the 
E a rth ’s crust and their behavior under different 
therm odynam ic and physicochem ical n a tu ra l 
conditions.” G oldschm idt’s definition of geo 
chem istry was “G eochem istry is concerned with 
the laws governing the distribution of the chem i 
cal elem ents and their isotopes throughout the 
E a rth ” (Correns, 1969). We could go on and on. 
G eochem istry is a highly diversified and con 
stantly evolving subject tha t can be described in 
m any different ways.
For our purposes the m ajor goals of geo 
chem ists are
1. To know the distribution of the chemical 
elem ents in the E a rth and in the solar 
system.
2. To discover the causes for the observed 
chem ical composition of terrestrial and 
ex traterrestrial materials.
3. To study chemical reactions on the surface 
of the E arth , in its interior, and in the solar 
system around us.
4 . To assem ble this inform ation into geo 
chemical cycles and to learn how these 
cycles have operated in the geologic past 
and how they may be altered in the future.
These are the lofty goals of a scientific disci 
pline. T heir intrinsic m erit is apparent. H ow ever, 
geochem ists practicing their craft today also have 
an obligation to hum ankind to assist in the devel 
 
REFERE N CES 7
opm ent and m anagem ent of natural resources, to 
m onitor the quality of the environm ent both 
locally and on a global scale, and to warn hum an 
ity against dangerous practices that may th rea ten 
the quality of life in the future.
W ith so m uch at stake it is not easy to express 
succinctly w hat geochemistry is all about. K. O.
Em ery and J. M. H un t (1974, p. 586) put it this 
way: “Studies of geochem istry ... convert idle 
speculation into ... understanding . . . ’’.T h a t will 
be the them e of this book. We can no longer 
afford idle speculation in the E arth Sciences. We 
m ust have understanding . G eochem istry can 
show us how to achieve it.
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