

















Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
I Isotope Geology & Geochemistry Quiz | Practice & Exam Preparation
Typology: Exams
1 / 25
This page cannot be seen from the preview
Don't miss anything!
Preparation
Z=Proton N=neutron Mass=A=Z+N
Nuclide Describes specific Z, N, and nucleation energy state
Electron Shells K L M N O P Q n=1 2 3 4 5 6 7 Increasing energy ’
a unit of mass used to express atomic and molecular weights, equal to one-twelfth of the mass of an atom of carbon-12. It is equal to approximately 1.66 x 10-27 kg
Preparation Basics of the Atom Isotopes
Isotopes have the same Z and charge. Also behave similarly in terms of chemical behavior. However, have ditterent mass N.
Isotopes same Z Isotones same N Isobars same Z+N=A Binding Energy Negative energy lowers the total energy (proportional to m), the energy that holds a nucleus together, equal to the mass defect of the nucleus.
and smaller nucleus
Radioactivity* Radioactive Iso- topes can achieve lower energy by α β⁻ β⁺
β⁻ n=P⁺+e⁻+v⁻ β⁺ P⁺=n+e⁻+v v & V⁻ take excess energy and nuclear spin
Radioactivity* Radioactive Iso- topes can achieve
Fission large nuclei split
Preparation
long-lived Geochem Isotopes
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller, lighter nuclei. The fission process often produces free neutrons and gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Preparation
dioactive decay* Binding energy
sured mass of ²₁H
0.1184%=2.224MeV or 1.7E14 j/kg of total mass
dioactive decay* Emission of α parti- cle
progress down the valley, results in -2p and -2n
mass of ⁴₂He`m ass ditterent in ²³⁸U->²³⁴Th it is a ditterent of .0046 amu=1.74E12 J/kg
dioactive decay* Emission of a β par- ticle and neutrino
resulting in -P and +n
Neutrinos carry excess energy and gamma rays carry excess energy
Preparation
ε=α-1, ε•1000=fractionation in parts per thousand (similar to δ values), and ε useful in radiogenic isotopes
Compares the isotopic ratio in A to a standard isotopic ratio, such as the fractionation between two phases
A-b=δA-δb
Lighter molecules are enriched in vapor, condensation and evaporation (dis- tillation)
Preparation
¹⁸O is 2X more enriched than ¹⁷O
λ characterizes the mass-dependent fractionation. λ=~.5 =~
δ¹⁷O.`5δ¹⁸O Occurs in meteorites and in zone, and sulfur in sulfides > 2.45 Ga
Nuclear Volume Ettects mass-independent isotope fractionation due to heavy element nuclear volumes
Magnetic Isotope Ettects Isotope separate by spin and magnetic moment
Isotopologues and Clumping Theory Molecules that ditter in isotopic composition. Clumped isotopes are more abundant than single substituted isotopologues, temperature dependence in clumping produces a geothermometer, higher temperature produces less clumping
Preparation
Carbon Isotope Geothermometry Often uses CO₂ as experimentally known values in minerals
Isotopic Equilibrium may not be achieved if reaction rates are slow at low temperatures kinetic fractionation competes with equilibrium fractionation systems may equilibrate during cooling
G of isotope exchange reactions are low, not readily driving the reactions to equilibrium
tope geothermom- etry*
no volume changes creates little pressure dependence , pure phases are used with little element exchange involved
The ioniziation of atomic species and acceleration through a strong magnetic field to cause separation between similar masses individual particles detect- ed.
Mass spectrometry is an analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. In simpler terms, a mass spectrum measures the masses within a sample. Mass spectrometry is used in many ditterent fields and is applied to pure samples as well as complex mixtures.
Small quantity of sample is injected and vaporized under vacuum sample bombarded with electron at 25-80 ev, the valence electron is ejected from ions, ions (+) are accelerated using an (-) anode toward the magnet each ion has
Preparation kinetic energy 1/2MV^2=Ev Ions enter magnetic field and their path is curved, radius of the curvature is smaller for lighter isotopes
Gas Duel inlet system on continuous flow systems Solid Filament with separated materials Sample La-ICP-MS on sims oxygen or ceasium beams
Peak Jumping Manually changing the magnetic field to analyze ditterent masses sequentially through a single or not enough detections.
A means to acquire a mass spectrum by jumping from one mass to charge to another; measurements are made at the mass to charge of each mass spectral peak; only ions with mass-to-charge ratios of interest are measured, skipping mass-to-charge ratios that are not of interest
General multicollectors calibrated at a specific distances from each other correction for mass fractionation, noise, and mass interference needed
SIRMS Extract oxygen from rock by reaction with bromopentafluorine cause reaction with carbon to CO2. Isolated gas is heated and frozen with liquid nitrogen to travel to a glass tube, glass tube attached to mass spec.
Preparation
terize exchange processes, track reservoir interactions, and evaluate biologic and kinetic processes
For terrestrial systems, common applications in geochronology and tracer Studies involve the following radiometric systems U-Th-Pb Rb-Sr Sm-Nd Lu-Hf Re-Os U series disequilibrium Sr, Nd, Hf, Os in seawater
In cosmochemical systems, the measurement of isotopic compositions is primarily as tracers of nucleosynthetic processes and constraining the evo- lution of the solar system. This involves measurement of the systems noted above, but also includes the decay of short lived radionuclides, as observed principally in meteorites. In addition to the systems noted above, systems of cosmochemical interest include: Fe-Ni Mn-Cr Al-Mg Zr-Mo Mo- Ru
Non-radiogenic (stable) isotope-isotope ratios are typically used to charac- terize exchange processes, track reservoir interactions, and evaluate biologic and kinetic processes: Li B Mg
Preparation
Ca Fe
Isotopic ratios are measured, not concentrations, find concentrations indirectly by isotope dilution by adding a known spike solution before ionization. Back calculate the concentrations of an in the original sample isotope ratios are measured with each element separately then calculated.
Spike: adding a known amount of a present constituent Tracer: Adding a known of a substance not already present
Quadrupole changes electrical frequencies in four rods and allows a particular mass of resonant ions to pass through to the collector
SIMS for radiogenic isotopes, primary ion beam composed of Cs or O. The instrument sputters the surface of materials and produces secondary ions to be analyzed. It is sensitive high resolution ion microprobe with smaller, shallower destructive pits.
Preparation
Elements only - useful for U-Th-Pb dating in monzanite and xenotime
Absolute precision (400±20) or relative precision (400Ma±2%) 1σ=67% chance that a value is truly in uncertainty range 2σ=95% chance that a value is truly in uncertainty range
MSWD mean square of weighted deviates
Isochron - MWSD <2. Error chron- MWSD >2.
Preparation
An atomic mass of 16 was assigned to oxygen prior to the definition of the unified atomic mass unit based upon 12C.[6] Since physicists referred to 16O only, while chemists meant the naturally-abundant mixture of isotopes, this led to slightly ditterent mass scales between the two disciplines.
Preparation
Sulfur Geothermometry fraction occurs by kinetic ettects of microbial sulfate reduction and by exchange reactions sulfate-sulfide or sulfide-suflide gives a geothermometry application
A-values known with respect to H2S a-b=AE6/T²
Organic Ettects Sulfate reducing bacteria produce ³²S-depleted sulfide bac- teria uses ³⁴S in formation of sulfide to sulfate
all four sulfur isotopes is useful for rocks >2.4 Ga due to mass independence fractionation in O2-depleted atmosphere with H2 or CH4 (reducing) atmos- phere
Carbonate Reservoirs Organic, sedimentary carbonates
carbonate fractionation occurs through exchange reactions within inorganic carbon system CO2(g) bicarbonate -carbonate or through kinetic isotope ettects in photosynthesis where ¹²C is concentrated
Carbon Geothermometry between DIC and CO2 or between minerals can be used for geothermometry
Preparation Kinetic fractionation through photosynthesis prominent C3 or C4 or CAM plants produced. Aquatic plants are more complex with DIC incorporated δ¹³C somewhat indicative of geologic reservoirs
Cosmogenic nuclides Good for young systems in surficial processes, such as glaciers, landslides, and lava flows
Cosmic rays of high energy atomic nuclei of primarily H and He encounters the earth, striking a nucleus and shattering the nucleus into pieces producing stable nuclei, unstable nuclei, protons, neutrions, muons, prion
¹⁴C comsogenic dating schemes in biological material ¹⁴N+n=¹⁴C+P ¹⁴C is incorporated into plants from CO2 updtake and consequently transferred to plant eating organisms, CO2 update and ¹⁴C decays to ¹⁴N allowing dating
In the upper atmosphere several radioactive isotopes are produced when cosmic rays collide with atmospheric molecules at high speed. These isotopes are known as cosmogenic isotopes. The production rate of the cosmogenic isotopes depends on the strength of the cosmic radiation, which again varies with the strength of the Earth magnetic field and with the solar activity. Therefore, records of cosmogenic isotope production rates are invaluable for