Isotope geochemistry is an aspect of
geology
Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
based upon the study of natural variations in the relative abundances of
isotopes
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass numbers ...
of various
elements. Variations in
isotopic abundance are measured by
isotope ratio mass spectrometry
Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample.
This technique has two different applications in the ea ...
, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
Stable isotope geochemistry is largely concerned with isotopic variations arising from mass-dependent
isotope fractionation, whereas
radiogenic isotope geochemistry is concerned with the products of natural
radioactivity.
Stable isotope geochemistry
For most stable isotopes, the magnitude of fractionation from
kinetic
Kinetic (Ancient Greek: κίνησις “kinesis”, movement or to move) may refer to:
* Kinetic theory, describing a gas as particles in random motion
* Kinetic energy, the energy of an object that it possesses due to its motion
Art and ent ...
and
equilibrium fractionation is very small; for this reason, enrichments are typically reported in "per mil" (‰, parts per thousand).
These enrichments (δ) represent the ratio of heavy isotope to light isotope in the sample over the ratio of a
standard. That is,
:
‰
Hydrogen
Carbon
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
has two
stable isotopes,
12C and
13C, and one radioactive isotope,
14C.
The stable carbon isotope ratio,
''δ''13C, is measured against Vienna Pee Dee
Belemnite
Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...
(VPDB).
The stable carbon isotopes are fractionated primarily by
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
(Faure, 2004). The
13C/
12C ratio is also an indicator of paleoclimate: a change in the ratio in the remains of plants indicates a change in the amount of photosynthetic activity, and thus in how favorable the environment was for the plants. During photosynthesis, organisms using the
C3 pathway show different enrichments compared to those using the
C4 pathway, allowing scientists not only to distinguish organic matter from abiotic carbon, but also what type of photosynthetic pathway the organic matter was using.
Occasional spikes in the global
13C/
12C ratio have also been useful as stratigraphic markers for
chemostratigraphy, especially during the
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
.
The
14C ratio has been used to track ocean circulation, among other things.
Nitrogen
Nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
has two stable isotopes,
14N and
15N. The ratio between these is measured relative to nitrogen in
ambient air.
Nitrogen ratios are frequently linked to agricultural activities. Nitrogen isotope data has also been used to measure the amount of exchange of air between the
stratosphere
The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air h ...
and
troposphere
The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. Fro ...
using data from the greenhouse gas
N2O.
Oxygen
Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
has three stable isotopes,
16O,
17O, and
18O. Oxygen ratios are measured relative to
Vienna Standard Mean Ocean Water
Vienna Standard Mean Ocean Water (VSMOW) is an isotopic standard for water. Despite the name, VSMOW is pure water with no salt or other chemicals found in the oceans. The VSMOW standard was promulgated by the International Atomic Energy Agency ( ...
(VSMOW) or Vienna Pee Dee Belemnite (VPDB).
Variations in oxygen isotope ratios are used to track both water movement, paleoclimate,
and atmospheric gases such as
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the l ...
and
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
.
Typically, the VPDB oxygen reference is used for paleoclimate, while VSMOW is used for most other applications.
Oxygen isotopes appear in anomalous ratios in atmospheric ozone, resulting from
mass-independent fractionation.
Isotope ratios in fossilized
foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...
have been used to deduce the temperature of ancient seas.
Sulfur
Sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
has four stable isotopes, with the following abundances:
32S (0.9502),
33S (0.0075),
34S (0.0421) and
36S (0.0002). These abundances are compared to those found in
Cañon Diablo troilite.
Variations in sulfur isotope ratios are used to study the origin of sulfur in an
orebody and the temperature of formation of sulfur–bearing minerals as well as a biosignature that can reveal presence of sulfate reducing microbes.
[Rollinson, H.R. (1993). ''Using Geochemical Data: Evaluation, Presentation, Interpretation'' Longman Scientific & Technical. ]
Radiogenic isotope geochemistry
Radiogenic isotopes provide powerful tracers for studying the ages and origins of Earth systems.
They are particularly useful to understand mixing processes between different components, because (heavy) radiogenic isotope ratios are not usually fractionated by chemical processes.
Radiogenic isotope tracers are most powerful when used together with other tracers: The more tracers used, the more control on mixing processes. An example of this application is to the evolution of the
Earth's crust
Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
and
Earth's mantle through geological time.
Lead–lead isotope geochemistry
Lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
has four stable
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...
s:
204Pb,
206Pb,
207Pb, and
208Pb.
Lead is created in the Earth via decay of
actinide elements, primarily
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
and
thorium
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...
.
Lead isotope
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 th ...
is useful for providing
isotopic dates on a variety of materials. Because the lead isotopes are created by decay of different transuranic elements, the ratios of the four lead isotopes to one another can be very useful in tracking the source of melts in
igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
s, the source of
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...
s and even the origin of people via
isotopic fingerprinting of their teeth, skin and bones.
It has been used to date
ice core
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ...
s from the Arctic shelf, and provides information on the source of atmospheric lead
pollution
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...
.
Lead–lead isotopes has been successfully used in
forensic science
Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...
to fingerprint bullets, because each batch of ammunition has its own peculiar
204Pb/
206Pb vs
207Pb/
208Pb ratio.
Samarium–neodymium
Samarium
Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...
–
neodymium
Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarn ...
is an isotope system which can be utilised to provide a date as well as
isotopic fingerprints of geological materials, and various other materials including archaeological finds (pots, ceramics).
147Sm decays to produce
143Nd with a half life of 1.06x10
11 years.
Dating is achieved usually by trying to produce an
isochron of several minerals within a rock specimen. The initial
143Nd/
144Nd ratio is determined.
This initial ratio is modelled relative to CHUR - the Chondritic Uniform Reservoir - which is an approximation of the chondritic material which formed the solar system. CHUR was determined by analysing
chondrite
A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form pr ...
and
achondrite
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...
meteorites.
The difference in the ratio of the sample relative to CHUR can give information on a model age of extraction from the mantle (for which an assumed evolution has been calculated relative to CHUR) and to whether this was extracted from a granitic source (depleted in radiogenic Nd), the mantle, or an enriched source.
Rhenium–osmium
Rhenium and
osmium
Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, ...
are
siderophile elements which are present at very low abundances in the crust. Rhenium undergoes
radioactive decay
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
to produce osmium. The ratio of non-radiogenic osmium to radiogenic osmium throughout time varies.
Rhenium prefers to enter
sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...
s more readily than osmium. Hence, during melting of the mantle, rhenium is stripped out, and prevents the osmium–osmium ratio from changing appreciably. This ''locks in'' an initial osmium ratio of the sample at the time of the melting event. Osmium–osmium initial ratios are used to determine the source characteristic and age of mantle melting events.
Noble gas isotopes
Natural isotopic variations amongst the noble gases result from both radiogenic and nucleogenic production processes. Because of their unique properties, it is useful to distinguish them from the conventional radiogenic isotope systems described above.
Helium-3
Helium-3
Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron (the most common isotope, helium-4, having two protons and two neutrons in contrast). Other than protium (ordinary hydrogen), helium-3 is the ...
was trapped in the planet when it formed. Some
3He is being added by meteoric dust, primarily collecting on the bottom of oceans (although due to
subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
, all oceanic
tectonic plates
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...
are younger than continental plates). However,
3He will be degassed from oceanic sediment during
subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
, so cosmogenic
3He is not affecting the concentration or
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
ratios of the
mantle
A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that.
Mantle may refer to:
*Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear
**Mantle (vesture), an Eastern Orthodox ve ...
.
Helium-3 is created by
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
bombardment, and by
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...
spallation reactions which generally occur in the crust. Lithium
spallation
Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...
is the process by which a
high-energy neutron bombards a
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...
atom, creating a
3He and a
4He ion. This requires significant lithium to adversely affect the
3He/
4He ratio.
All degassed helium is lost to space eventually, due to the average speed of helium exceeding the
escape velocity for the Earth. Thus, it is assumed the helium content and ratios of
Earth's atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
have remained essentially stable.
It has been observed that
3He is present in
volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates ...
emissions and
oceanic ridge samples. How
3He is stored in the planet is under investigation, but it is associated with the
mantle
A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that.
Mantle may refer to:
*Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear
**Mantle (vesture), an Eastern Orthodox ve ...
and is used as a marker of material of deep origin.
Due to similarities in
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
and
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
in
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
chemistry, outgassing of helium requires the loss of
volatile components (
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
,
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
) from the mantle, which happens at depths of less than 60 km. However,
3He is transported to the surface primarily trapped in the
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
lattice of minerals within
fluid inclusions.
Helium-4 is created by
radiogenic production (by decay of
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
/
thorium
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...
-series
elements). The
continental crust
Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...
has become enriched with those elements relative to the mantle and thus more He
4 is produced in the crust than in the mantle.
The ratio (R) of
3He to
4He is often used to represent
3He content. R usually is given as a multiple of the present atmospheric ratio (Ra).
Common values for R/Ra:
* Old continental crust: less than 1
*
mid-ocean ridge
A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a div ...
basalt
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...
(MORB): 7 to 9
* Spreading ridge rocks: 9.1 plus or minus 3.6
*
Hotspot rocks: 5 to 42
* Ocean and terrestrial water: 1
* Sedimentary formation water: less than 1
* Thermal spring water: 3 to 11
3He/
4He isotope chemistry is being used to date
groundwater
Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...
s, estimate groundwater flow rates, track water pollution, and provide insights into
hydrothermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
processes,
igneous
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...
geology
Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
and
ore genesis.
(U-Th)/He dating of apatite as a thermal history tool
Isotopes in actinide decay chains
Isotopes in the
decay chain
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay dire ...
s of actinides are unique amongst radiogenic isotopes because they are both radiogenic and radioactive. Because their abundances are normally quoted as activity ratios rather than atomic ratios, they are best considered separately from the other radiogenic isotope systems.
Protactinium/Thorium – 231Pa / 230Th
Uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
is well mixed in the ocean, and its decay produces
231Pa and
230Th at a constant activity ratio (0.093). The decay products are rapidly removed by
adsorption
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...
on settling particles, but not at equal rates.
231Pa has a residence equivalent to the residence time of
deep water in the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
basin (around 1000 yrs) but
230Th is removed more rapidly (centuries).
Thermohaline circulation effectively exports
231Pa from the Atlantic into the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smal ...
, while most of the
230Th remains in Atlantic sediments. As a result, there is a relationship between
231Pa/
230Th in Atlantic sediments and the rate of overturning: faster overturning produces lower sediment
231Pa/
230Th ratio, while slower overturning increases this ratio. The combination of
δ13C and
231Pa/
230Th can therefore provide a more complete insight into past circulation changes.
Anthropogenic isotopes
Tritium/helium-3
Tritium was released to the atmosphere during atmospheric testing of nuclear bombs. Radioactive decay of tritium produces the noble gas
helium-3
Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron (the most common isotope, helium-4, having two protons and two neutrons in contrast). Other than protium (ordinary hydrogen), helium-3 is the ...
. Comparing the ratio of tritium to helium-3 (
3H/
3He) allows estimation of the age of recent
ground water
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
s. A small amount of Tritium is also produced naturally by
cosmic ray spallation and
spontaneous
Spontaneous may refer to:
* Spontaneous abortion
* Spontaneous bacterial peritonitis
* Spontaneous combustion
* Spontaneous declaration
* Spontaneous emission
* Spontaneous fission
* Spontaneous generation
* Spontaneous human combustion
* Spontan ...
ternary fission
Ternary fission is a comparatively rare (0.2 to 0.4% of events) type of nuclear fission in which three charged products are produced rather than two. As in other nuclear fission processes, other uncharged particles such as multiple neutrons and ...
in natural uranium and thorium, but due to the relatively short half-life of Tritium and the relatively small quantities (compared to those from humandmade sources) those sources of Tritium usually play only a secondary role in the analysis of groundwater.
USGS Tritium/Helium-3 Dating
See also
*
Cosmogenic isotopes
*
Environmental isotopes
*
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 th ...
*
Isotopic signature
*
Radiometric dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
*
Isotope-ratio mass spectrometry
*
Sulfur isotope biogeochemistry
*
Urey-Bigeleisen-Mayer equation
Notes
References
General
*
Allègre C.J., 2008. ''Isotope Geology'' (Cambridge University Press).
*Dickin A.P., 2005. ''Radiogenic Isotope Geology'' (Cambridge University Press).
*
Faure G., Mensing T.M. (2004), ''Isotopes: Principles and Applications'' (John Wiley & Sons).
*Hoefs J., 2004. ''Stable Isotope Geochemistry'' (Springer Verlag).
*Sharp Z., 2006. ''Principles of Stable Isotope Geochemistry'' (Prentice Hall).
Stable isotopes
Environmental Isotopes (University of Ottawa)
(C. Kendall & E.A. Caldwell, chap.2 in ''Isotope Tracers in Catchment Hydrology''
dited by C. Kendall & J.J. McDonnell 1998)
Stable Isotopes and Mineral Resource Investigations in the United States (
USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
)
3He/4He
*
*
*
Re–Os
*
*
External links
National Isotope Development CenterReference information on isotopes, and coordination and management of isotope production, availability, and distribution
Isotope Development & Production for Research and Applications (IDPRA)U.S. Department of Energy program for isotope production and production research and development
{{Authority control
Geochemistry
Geophysics
Geochronological dating methods