Geochemistry Flashcards
The study of the nature and distribution of chemical elements in rock and minerals
Geochemistry
The application of basic chemistry to earth sciences
Geochemistry
It is used for dating rocks by using the radioactivity of elements
Geochronology or Isotope Geochemistry
Geochemistry was first coined by
Christian Friedrich Schonbein
Chemistry professor from University of Basel in Switzerland, in 1838
Christian Friedrich Schonbein
The first geochemist in the modern sense of the world of USGS in 1908
Frank W. Clarke
Book written by Frank Clarke
The Data of Geochemistry
He correlated the mineral formation and structure to its chemical composition
Victor M. Goldschmidt
Victor M. Goldschmidt studied at
University of Gottingen in Germany
He stated the rational explanation of isomorphous substitution in crystals based on the capability of the radii and charges of the ions
Victor M. Goldschmidt
Father of modern chemistry and crystal chemistry
Victor M. Goldschmidt
He proposed the classification of minerals according to preferred hosts
Victor M. Goldschmidt
it is a rock loving mineral
Lithophile
It is an iron loving mineral
Siderophile
It is an ore loving mineral
Chalcophile
It is a gas loving mineral
Atmophile
Goals of Geochemistry
- To know the distribution of the chemical element in the Earth and in the solar system
2 . To discover the causes for the observed chemical composition of terrestrial and extraterrestrial materials - To study the chemical reactions on the surface of the earth, in its interior and in the solar system around us
- To assemble this information into geochemical cycles and to learn how this cycle operated in the geologic past and how they maybe altered in the future
A model of the evolution of the universe that postulates its origin from a hot, dense mass that expanded rapidly and cooled
Big Bang Theory
In the Big Bang Theory the fundamental composition that eventually combined or nucleated to become organized into the nuclei of H and He
Quark Soup
Clues of “expanding Universe”
- The “red shift” of spectral light emitted by distant galaxies - the use of “doppler Effect” calculations
2.The “cosmic Microwave Radiation” which is the energy of radiation produced at a specific wavelength when the universe was at temperatures greater than about 3000oK
Hierarchy of Heavenly Bodies
> Cluster of Galaxies
Galaxies
Stars, Pulsars, and Black Holes
Planets
Satellites
Comets
Asteroids
Meteoroids
Dust Particles
Molecules
Atoms of H and He
basin unit in the hierarchy
Star
Produced by contraction of interstellar gases resulting in increase in temperature
Main Sequence Stars
Energy production by H fusion becomes possible and thus produces star
Main Sequence Stars
High Luminosity and High temperature stars
Blue Giants
Stars less massive than the sun
Red Dwarfs
Bigger than the sun and is formed by depletion of H in the core during the main phase; the energy production shifted from the core to the outer shell
Red Giants
How Red Giants are formed?
formed by depletion of H in the core during the main phase; the energy production shifted from the core to the outer shell
End stage of stellar evolution
Pulsars (neutron stars), White Dwarf and Black Holes
Contraction leads to the increase in core temperature and eventually explodes to form the supernova
Pulsars (neutron stars), White Dwarf and Black Holes
The star cycle begins again
Pulsars (neutron stars), White Dwarf and Black Holes
The theory that explains the complexation of material from the simple structure of H and deuterium (isotope of H)
Nucleosynthesis
First 4 statement in Nucleosynthesis
- H and He are the most abundant isotopes in the universe
- The abundances of the first 50 elements decreases exponentially
- The abundances of the elements having atomic numbers greater than 50 are very low and do not vary appreciably with increasing atomic number
- Elements with even atomic numbers are more abundant than immediate neighbors with odd atomic numbers
Last 4 statements in Nucleosynthesis
- The abundances of Li, Be, and B are anomalously low compared to other elements of low atomic number
- The abundance of Fe is notably higher than those of other elements with similar atomic numbers
- Tc and Pm do not occur in the solar system because all of their isotopes are unstable and decay rapidly
- The elements having atomic number greater than 83 (Bi) have no stable isotopes, but occur naturally at very low abundances because they are daughters of long - lived radioactive isotopes of U and Th
Diffuse mass of interstellar gas and dust
Solar Nebula
Condensates accreted to form larger bodies as a result of selective adhesion caused by electrostatic and magnetic forces
Planetisimals
High density, small planets
Terrestrial planets
Low Density, Large planets
Jovian Planets
Volatile rich planetisimals composed of water, ammonia, methane and other volatiles
Cometisimals
Diagram that shows the luminosity and temperature of the star
Hertzsprung-Russell Diagram
Chuck of rock from space that land on Earth
Meteorites
Kind of Meteorites
> Iron
Stones
Stony-irons
Predominantly Ni-Fe alloys Minor amounts of other minerals such as Troilite (FeS)
Iron Meterorites
Iron meteorites are classified according to ________________
% of Ni
Hexahedrite, Octahedrite and Ataxite are examples of what meteorite
Iron Meteorites
Chiefly Silicates, mostly ferromagnesian Up to 1/4 metallic
Stony Meteorites
Types of stone meteorites
- Chondrites
- Achondrites
Meteorites that contain chondrules
Chondrites
Meteorite composed chiefly of silicates such as olivine pyroxene, and plagioclase or glass important type
Carbonaceous Chondrite
High content of volatiles, including water and non biogenic carbon (will later show how determined to be non-biogenic)
Chondrites
Meteorite that have some composition as Sun’s atmosphere
Chondrites
Meteorite that has no chondrules
Achondrites
Meteorite that has the same composition as terrestrial mafic and ultramafic rocks
Achondrites
Most __________ are breccias
Achondrites
Equal amounts of silicates and Ni-Fe alloys
Stony-iron meteorites
Many are crystallized silicates which have been brecciated, then invaded by metallic and sulfide melts
Stony-iron meteorites
Stony- iron meteorites classified according to kind of silicates: Olivine
Pallasite
Stony- iron meteorites classified according to kind of silicates: Plagioclase, Pyroxene
Mesosiderite
Components of an atom
- A nucleus at the center, containing nearly all of the mass of their atom but accounting for only ten- thousandth of its diameter
- A family of electrons gathered around the nucleus, forming three dimensional clouds that makes up the volume of an atom
Protons are ___________X more massive than electron
1825X
Denotes any of the more than 1300 different atomic forms characterized by a distinct combination of protons and neutrons
Nuclide
Only about 270 of which are stable
Nuclide
Composed of positively charged protons and neutrons, particles of nearly equal mass but of zero charge
Nucleus
First 3 general facts about atomic structure and property
- Only 10 elements - H, He, C, N, O, Ne, Mg, Si, S, and Fe - all with atomic numbers less than 27, shows appreciable abundance. Of these H and He far outweigh the other 8
- Abundance show a rapid exponential decrease for elements of the lower atomic numbers, followed by an almost constant value for heavier elements
- Elements adjacent to Helium like Li and Be are very low in relative abundance
Last 3 general facts about atomic structure and property
- Elements of even atomic number are more abundant than those of odd atomic number on either side. This regularity was first coined by Oddo and Harkins and is sometimes referred to as the Oddo Harkins Rule
- Isotopes with mass numbers which are multiples of 4 (alpha particle mass number) have enhanced abundances
- There is a pronounced abundance peak at atomic number 26 and smaller peaks at several other heavier atomic numbers such as oxygen
Elements of even atomic number are more abundant than those of odd atomic number on either side.
Oddo-Harkins Effect
Play the crucial role of overcoming the repulsive forces between protons, thus binding the nucleus to a tight structure.
Neutron
Refers to the number of proton in an atom of an element; it is the same for any atom of the element; this number serves to distinguish an element from another
Atomic Number (Z)
The average mass of the atoms of an element; to a close approximation, the number of protons plus the number of neutrons in an atom of an element
Atomic Mass (A)
The sum of the masses of its naturally occurring isotopes weighted in accordance with their abundances
Atomic Weight
Variation in atomic masses due to difference in the number of neutrons of an element
Isotopes
Nuclides having constant mass number but a different atomic number
Isotones
Nuclides having the same atomic mass but different neutron number and atomic number
Isobars
A region surrounding the nucleus occupied by electrons having approximately the same energy
Electron shell
Charge deficiencies that result from the substitution of ions of unequal charges must be compensated by a second substitution involving an ion having a different charge; the processes contributed to the diversification of chemical composition of many minerals
Coupled Substitution
An alternative to coupled substitution in which ions are attached on the charged surfaces of small ions; usually displayed by the clay minerals.
Adsorption
This occurs when the minor element has the same charge and a similar atomic radius as the major element it is replacing
Camouflage
This takes place when a minor element enters a crystal preferentially because it has a higher ionic potential than the ions of the major element
Capture
This involves the entry of a foreign ion that has a lower ionic potential than the major ion because it has either a lower charge or a larger radius, or both
Admission
The extent to which ions are admitted into a particular lattice site decreases as the difference in radii of competing ions increases
Admission
Possesses lowest potential energy possible for the mineral
Stable
Possesses the highest potential energy
Unstable
Requires an energy hurdle to put in the most stable form or of lower potential energy.
Metastable
Reveals or shows the ranges of stability in
pressure-temperature space (or in any possible physical , chemical, or mineralogical) parameters.
Phase Diagram
Areas representing the range of applied pressure and temperature in which a mineral may exist in its stable form.
Stability Fields
The line separating the various stability fields and defines a restricted set of circumstance under which the separated phase coexist in equilibrium.
Phase Boundary
Energy required for transformation to take place and is represented by the height of the energy hurdle.
Activation Energy
Concerned on the free energy changes associated with chemical equilibrium between phases, and provides the tools for working out which mineral assemblages will be stable under which conditions.
Thermodynamics
Deals with the mechanics of the reactions that lead to equilibrium, and the rates at which they occur.
Chemical Kinetics
A part of the universe which we wish to confine attention or whose properties are under consideration; the system is separated from its surroundings by a boundary whose properties
can be defined.
System
One that is free to exchange both matter and energy with the surroundings.
Open System
One that is sealed with respect to the transfer of matter, but that can still exchange energies with its surroundings.
Closed System
One that is capable of exchanging neither mass or energy with its surroundings.
Isolated System
A part or parts of a system occupying a specific volume and having uniform physical and chemical characteristics which distinguishes it from all other parts of the system.
Phase
Comprise the minimum number of chemical (atomic and molecular) species required to specify completely the compositions of all the phases present.
Components
All parts of the system have the same temperature; there is no net transfer of heat.
Thermal Equilibrium
The distribution of components among the phases of a system has become constant, showing no net change with time.
Chemical Equilibrium
The diffusion rates of an element in and out of the crystal are unequal; there will be a net change of composition of each phase with time.
Disequilibrium
For every element present the flux of atoms across the crystal boundary is the same in both directions resulting in zero net flow, and no change of composition in time.
Equilibrium
A formula which expresses the number of phases that can coexist in mutual equilibrium in terms of the number of components in the system and another property of the equilibrium called the variance; the variance is also known as the number of degrees of freedom.
The Phase Rule
(Variance of 0) Means that the three phase equilibrium assemblage completely constrains the state of the system to a particular combination of P and T.
Invariant
One degree of freedom indicates that the state of the system is only unconstrained in one direction which is along the phase boundary.
Univariant
The pressure and the temperature can vary independently (two degrees of freedom) without upsetting the equilibrium phase
assemblage.
Divariant
Is the locus of temperatures (a curve on a phase diagram) below which a given substance is completely solid (crystallized).
Solidus
The temperature above which a material is completely liquid, and the maximum temperature at which crystals can co- exist
with the melt in thermodynamic equilibrium
Liquidus
The point on a phase diagram where the maximum number of allowable phases are in equilibrium.
Eutectic Point
When this point is reached, the temperature must remain constant until one of the phases disappears
Eutectic Point
A eutectic is a/an ______________ point
Invariant
The point on a phase diagram where a reaction takes place between a previously precipitated phase and the liquid to produce a new solid phase.
Peritectic Point
When this point is reached, the temperature
must remain constant until the reaction has
run to completion.
Peritectic Point
Peritectic is a/an ________ point
Invariant
A phase that has a composition intermediate between two other phases
Intermediate Compound
melting wherein a phase melts to a
liquid with the same composition as the solid
Congruent Melting
melting wherein a phase melts to a liquid with a composition different from the solid and produces a solid of different composition to the original solid.
Incongruent melting
Usually measured in percentage (either mass or molar), and are commonly above 1% of the chemical composition of the material
Major Elements
Elements that occur in such small concentrations that they do not change the essence of what a material is. usually < 0.1%
Trace Elements
Are everything in between. Technically, this means things between 1% and 0.1%.
Minor Elements
Ions that do not fit into the structure of the rock-forming minerals or minerals precipitating in the magma at the time when ions are present and therefore accumulate as
in the residual magma
Incompatible Elements
______________ are concentrated in the late-stage differentiates of magmas, including aplites dikes, pegmatites, and hydrothermal veins.
Incompatible Elements
ions easily accommodated in the mineral structure
Compatible Elements
Magma derived from the mantle with Fo# 88
to 92, Mg # of 65 and above, and low Cr#
Primitive Magma
First magma derived from primitive magma.
Primary Magma
Primary Magma can be classified as
Parental Magma
Derived primarily by partial melting of the same source and have no characteristics that reflect the subsequent effects of differentiation
Primary Magma
Are not necessarily primitive nor primary but
where other magmas derived.
Parental Magma
In Rb/Sr the one incompatible to melt is _______
Rb
In Sm/Nd the one compatible to melt is _______
Sm
Fertile Unaltered mantle
Lherzolite
Refractory residuum after basalt has been extracted by partial melting
Dunite and Harzburgite
High concentration of NiO in magma composition shows
Mantle origin
Low concentration of NiO in magma composition shows
Cumulate
High concentration of TiO2 in magma composition shows
MOR derived or Mid Oceanic Ridges Derived
Low concentration of TiO2 in magma composition shows
Island Arc Derived
Separates the subalkaline from the
alkaline fields at low P
Thermal Divide
Cannot cross this divide by fractional crystallization; cannot derive one series from the other (at least via low-P fractional crystallization)
Thermal Divide
when plagioclase is a fractionating phenocryst or a residual solid in source
Europium Anomaly
a non-destructive analytical technique used to determine the elemental composition of materials.
XRF or X-ray Fluorescence
It determines the chemistry of a sample by measuring the secondary X-ray emitted form a sample when it is excited by a primary X-ray source
XRF or X-ray Fluorescence
Application of XRF
- research in Igneous, Sedimentary and Metamorphic Petrology
- Mining (measuring the grade of ore)
- Cement Production
- Ceramic and Glass Manufacturing
- Metallurgy (Quality Control)
- Environmental Studies (Analyses of particulate matter on air filters)
- Petroleum Industry (Sulfur Content of Crude Oils and Petroleum Products)
- Field Analysis in geological and environmental Studies (using portable, handheld XRF spectometers)
XRF is particularly well suited for investigations that involve
- Bulk chemical analyses of major elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P) in rock and sediment
- Bulk chemical analyses of trace elements (in abundance > 1 ppm ; Ba, Ce, Co, Cr, Ga, La, Ni, Rb, Sc, Sr, Rh, U, V, Y, Zr, Zn) in rock and sediment - detection limits for trace elements are typically on the order of a few parts per million
XRF is limited to analysis of
- relatively large samples, typically >1
- materials that can be prepared in powder form and effectively homogenized
- materials for which compositionally similar, well-characterized standards are available
- materials containing high abundances of elements for which absorption and fluorescence effects are reasonably well understood
the primary, non destructive tool for identifying and quantifying the mineralogy of crystalline compounds in rocks, soils and particulates
XRD or X-ray Diffraction
Every mineral or compound has a characteristic _______________ pattern whose fingerprint can be matched against a database of over 250,000 recorded phases
XRD or X-ray Diffraction
________________ can interpret the diffraction traces produced by individual constituents and highly complex mixtures
Modern Computer- Controlled diffraction Systems
An essential technique for identifying and characterizing the nature of clay minerals, providing information which cannot be determined by any other method
XRD or X-ray Diffraction
Application of XRD
- characterization of lithologies intended for radioactive waste disposal and carbon dioxide capture/storage
- researching changes in soil clay mineralogy with different land management practices
- determining the contribution of clay minerals to the engineering behavior of rocks and soils
- distinguishing natural and anthropogenic sources of toxic elements in brown field sites
- providing forensic evidence
- providing indicators of geological history, basin maturity and low grade metamorphism
A spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state
AAS or Atomic Absorption Spectroscopy
In analytical chemistry it is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed
AAS or Atomic Absorption Spectroscopy
Used to determine over 70 different elements in solution or directly in solid samples
AAS or Atomic Absorption Spectroscopy
An analytical technique used for elemental determinations
ICP - MS or Inductively Coupled Plasma Mass Spectrometry
It is accomplished by counting the number ions at a certain mass of the elements
ICP - MS or Inductively Coupled Plasma Mass Spectrometry
most samples analyzed by ICP-MS are ___________
Liquid
Solid samples for ICP-MS must be ___________ before measuring
Liquefied
Gas samples In ICP-MS can be ____________
measured directly
