Geochemistry part 1 Flashcards
Study of the nature and distribution of chemical elements in rocks and minerals
Geochemistry
geochemist who used the word “geochemistry” in his book, data of geochemistry
Frank W. Clarke
Father of Modern Geochemistry and crystal chemistry; proposed the classification of minerals according to preferred hosts
Victor M. Goldschmidt
Rock-loving minerals
Lithophile
Iron-loving minerals
Siderophile
Ore-loving minerals
Chalcophile
Gas-loving mineral
Atmophile
A model of the evolution of the universe that prostulates its origin from a hot, dense mass that expanded rapidly and cooled
Big Bang Theory
Clues of the expansion of the universe
- red shift (the use of doppler effect)
- cosmic microwave radiation
The energy of radiation produced at a specific wavelength when the universe was at temp greater than about 3000k
Cosmic Background Radiation
Hierarchy of the Universe
Clusters of Galaxy galaxy stars, pulsars, and black holes Planets Satelites Comets Asteroids Meteoroids Dust particles Molecules Atom of H and He
The basic unit in heirarchy of the universe
Stars
Produced by tcontraction of interstellar gases resulting in increase in temp
Main Sequence Stars
High luminosity and high temp 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 enrgy production shifted from the c ore to the outer shell
Red Giants
End stage of stellar evolution;
Pulsars (neutron stars), white dwarf, black hole
The theory that explains the complexation of material from the simple structure of H and deuterium (isotope of H)
Nucleosynthesis
Most abundant elements in the universe
H and He
The abundance of the first 50 elements decrease exponentially
Yaaaas
The elements with even atomic numbers are more abundant than their immediate neighbors with odd atomic numbers
Remember
Elements having atomic number higher than 50 are very low in abundance and do not vary appreciably with increasing atomic number
Ehem
The abundances of Li, Be, and B are anomalously low compared to other elements of low atomic number.
Remember natin ito
The abundance of Fe is notably higher than those of other elements with similar atomic numbers
!!!!!!!
Tc and Pm do not occur in the solars system because all of their isotopes are unstable and decay rapidly
Thechnetium
Promethium
Diffuse mas of interstellar gas and dust
The solar nebula
Condensates accreted to form larger bodies as a result of selective adhesion caused by electrostatic and magenetic forces
Planetisimals
Even atomic numbers are greater in abundance than odd atomic numbers
Oddo-Harkins effect
Volatile-rich planetisimal composed of water, amonia, and other volatiles
Cometisimals
Chunks of rock from space that land on earth
Meteorites
Common minerals found in meteorites
Kamacite Taenite Pyroxene Olivine Plagioclase
Predominantly Ni-Fe alloys with minor amounts of other minerals such as troilite (FeS)
Iron Meteorites
Chiefly silicates, mostly ferromagnesians up to 1/4 metallic Ni-Fe types
Stone meteorites
Contains chondrules composed chiefly of silicates such as olivine, pyroxene, and plagioclase or glass
Note: it also has the same composition as the sun’s atmosphere
Chondrites
Important type of chondrites, because it brought water to earth 4.4 b yrs ago
Carbonaceous chondrites - a diverse class of chondrites, they arre important because of the insights they provide into the early history of the solar system
Self-luminous gaseous spheroidal celestial body of great mass which produces energy by means of nuclear fusion reactions
Stars
A stone meteorite with no chondrules and has the same composition as terrestrial mafic and ultramafic rocks
Achondrite
Extreterrestrial olivine
A stony iron meteorite with equal proportions of pyroxene and olivine
Pallasites
Contains all the mass of an atom
Nucleus
How many times is the proton larger than the leectron
1825x
Any of the more than 1300 different atomic forms characterized by a distinct combination of protons and neutrons
Nuclide
Only 10 elements with atomic numbers. less than 27, show appreciable abundance
H, He, C, N, O, Ne, Mg, Si, S, FE
Elements adjacent to He are very low in relative abundance
Li and Be
Isotopes with mass numbers which are multiples of 4 (alpha particle mass number) have enhanced abundance
Alpha particle mass number
Plays the crucial part of overcoming the repulsive forces between protons, thus binding the nucleus to a tight structural unit
Neutrons
Refers to the number of proton in an atom of an element and serves to distinguish an element from another
Atomic Number (Z)
The ave mass of atoms of an element, the number of protons and neutrons in an atom of an element
Atomic weight (A)
Variation in atomic masses due to differences in the number neutrons of an element
Isotope
Nuclides having constant mass number but a different atomic weight
Isotones
Nuclides having the same atomic mass but different neutron number and atomic number
Isobars
A region surrounding the nucleus occupied by elevtrons having approx the same energy
electron shell
Charge deficiencies that result from substitution of ions of unequal charges must be compensated by a second substitution involving an ion having a different charge
Coupled substitution
Ions are attached on the charged surfaces of small ions; usually displayed by clay minerals
Adsorption
When minor element has the same charge and a similar atomic radius as the major eleemnt it is replacing
Camouflage
When a minor element enters a crystal preferentially because it has a higher ionic potential than the ions of the major element
Capture
The entry of a foreign ion that has a lower ionic potential that major ion because it has either a lower charge or a larger radius, or both;
Admission
Possesses lowest potential energy possible for the mineral
Stable
Possesses the highest potential enery
Unstable
Requires an energy hurdle to put in the most stable form or of lower potential energy
Metastable
Note: due to activation energy it decides if maging stable sya or hindi
Shows the ranges stability in pressure-temp space parameters
Phase diagrams
Areas representing the range of applied pressure and temp in which a mineral may exist in his stable form
Stability fields
The line separating the various stability fields and defines a restricted set of circumstances under which the separated phases 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
System
A system that is free to exchange both matter and energy to the surrounding
Open system
A system sealed with respect to the transfer of matter, but that can still exchange energies with its surrounding
Closed system
System that do not exhange matter nor energy to its surrounding
Isolated system
A part of the system occupying a specific volume and having uniform physical and chemical characteristic which distinguishes it from all other parts of a system
Phase
Comprises the minimum number of chemical species required to specify completely the compositions of all the phase present
Components
All parts of the system have the same temp; there is no 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 rate of an element in and out of the crystal are unequal
Disequilibrium
Element present the flux of atoms across the crystal boundary is the same in both directions resulting in zero 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 variance (degrees of freedom)
The Gibbs Phase Rule
By J. Willard Gibbs
0 degree of freedom
Means that the three phase equilibrium assemblage completely constrains the state of the system to a particular combination of P and T
Invariant
1 degree of freedom
Indicates that the state of the system is only unconstrained in one direction which is along the phase boundary
Univariant
2 degrees of freedom
The pressure and temp can vary independently without upsetting the equilibrium phase
Divariant
The locus of temp below which a given substance is completely solid
Solidus
The temp above which a material is completely liquid, and the max temp which crystals can coexist with the melt in thermodynamics
Liquidus
The point on the phase diagram where the max number of allowable phase are in equilibrium
Eutectic Point (invariant)
The point on a phase where a reaction takes place between a previously precipitated phase amd the liquid to produce a new solid phase.
Peritectic Point
A phase that has a composition intermediate between two other phases
Intermediate compound
Melting where in a phase melts to a liquid with the same composition as the soild
Congruent melting
Melting where in a phase melts to a liquid with composition different from the solid and produces a solid of different composition to the original solid
Incongruent Melting
Exsolution feature formed by slow cooling
Widmanstatten structure
First coined the word geochemistry
Friedrich Schonbeim
Meteorites with Equal amounts of silicate and Ni-Fe alloys
Stony-Iron Meteorites
