Isotope Geochemistry

E=MC²

Changes in energy state result in lower and energy, thus lower mass

*Isotope Fractionation* δ

Compares the isotopic ratio in A to a standard isotopic ratio, such as the fractionation between two phases ∆A-b=δA-δb

*Sulfur*

Converted SO2 through fluorination for analysis 34S/32S using the VCDT (canyon Diablo Triolite) standard δ³⁴S somewhat indicative of geologic reservoires

*Radioactive Decay Schemes* Branch Decay

Goes along an isobar, where stable isotopes are separated by unstable radioactive isotopes ⁴⁰K undergoes branched decay to produce 2 stable isobaric daughters

*Oxygen Isotopes* Mineral fractionation

Provide geothermometry application More positive δ18O values in all minerals from the schist belt may reflect a higher abundance of sedimentary precursor material, whereas biotites and muscovites in core and rim are indistinguishable in hydrogen isotope composition.

*Carbon*

¹²C=98.83% ¹³C=1.07% Generally measured as CO₂ after reaction with phosphoric organic compounds oxidized to form CO2

*Isotope Fractionation* α

ε=α-1, ε•1000=fractionation in parts per thousand (similar to δ values), and ε useful in radiogenic isotopes

*Basics of the Atom* •General Construction of the atom •Z= •N= •Mass=

•Composed of an *atomic nucleus* which consists of *neutrons & protons* and the outer *electron shell* Z=Proton N=neutron Mass=A=Z+N

*Mass defects in radioactive decay* Emission of α particle

•Heavy nuclei tend to decay by α decay to reduce the binding energy and progress down the valley, results in -2p and -2n mass of ⁴₂He≠mass different in ²³⁸U->²³⁴Th it is a different of .0046 amu=1.74E12 J/kg

*Inductively Coupled Plasma - Mass Spectrometry* ICPMS

•ICP-MS for radiogenic isotopes •Quadrupole single collection •Magnetic sector single and multi-collector

*Mass defects in radioactive decay* Emission of an electron and antineutrino in n→p

•Isotopes with excess neutrons go up into the valley stability along isobars , results in -n and +p Mass of P≠mass of D, it is a difference of .0003 AMU=3.0E11 J/kg

*Magnetic sector and TIMS*

•Magnetic sector similar to TIMS with a single or multi collector

*Carbonate Reservoirs*

*Carbonate Reservoirs* Organic, sedimentary carbonates

•Spike •Tracer

*Spike*: adding a known amount of a present constituent *Tracer*: Adding a known of a substance not already present

*Electron Microprobe Analysis*

Elements only - useful for U-Th-Pb dating in monzanite and xenotime

*Mass Spectrometry* •Static Measurements

General multicollectors calibrated at a specific distances from each other correction for mass fractionation, noise, and mass interference needed

*Kinetic Effects*

Isotopes may have different rates of reaction resulting in enrichment of lighter isotopes in products related to diffusion

*Half life decay* Decay Rate

T=Ln(D/(N+1)/γ Where D=radiogenic Isotopes N=remaining parent γ=Known constant Initial D₀ is possible T=Ln((D-D₀)/(N+1)/γ

Samarium-neodymium dating

This involves the alpha decay of 147Sm to 143Nd with a half-life of 1.06 x 1011 years. Accuracy levels of within twenty million years in ages of two-and-a-half billion years are achievable.[23]

*Isotope Fractionation*

aA₁+bB₂=aA+bB₁ Isotope ratio: αa-b=Ra/Rb = K^(1/n)

*10Be Cosmogenic*

*10Be Cosmogenic* cosmic rays interact with O, N in the atmosphere or with O, Ng, Si, Fe, in the crust 10Be decays to 10B immobile

*26Al 36C Cosmogenic*

*26Al 36C Cosmogenic* Cosmic rays interact with 40Ar in the atmosphere or with O, Mg, Si, Fe, in the crust. 26Al decays to 26Mg relatively immobile 36Cl decays to 36S and 26Ar mobile (useful in hydrological studies)

*Advantages of isotope geothermometry*

*Advantages of isotope geothermometry* no volume changes creates little pressure dependence , pure phases are used with little element exchange involved

*Carbon Geothermometry*

*Carbon Geothermometry* between DIC and CO2 or between minerals can be used for geothermometry

*Carbon Isotope Geothermometry*

*Carbon Isotope Geothermometry* Often uses CO₂ as experimentally known values in minerals

*Cosmogenic 18Be-26Al-26Cl*

*Cosmogenic 18Be-26Al-26Cl* can be applied to large scale problems reaching the pleistocene latitudinal variations in production and abundance

*Cosmogenic Dating sediments and sedimentation rates*

*Cosmogenic Dating sediments and sedimentation rates* 10Be and 26Al A=H/T, where a=sedimentatin rate, H=depth, T=time since deposition

*Decay Series*

radioactive parent → radioactive daughter →stable isotope

Minerals Ideal for dating

•High closure temperature •Durability •Long T½

*Mass defects in radioactive decay* Emission of a β particle and neutrino or capture of inner shell e⁻

•Isotopes with excess protons go down the valley of stability along isobars, resulting in -P and +n Neutrinos carry excess energy and gamma rays carry excess energy

*Mass defects in radioactive decay* Binding energy

•Release of binding energy ²₁H mass of measured P+N does not equal measured mass of ²₁H •Mass to energy 931.494 MeV/1V 0.1184%=2.224MeV or 1.7E14 j/kg of total mass

*Basics of the Atom* Atomic Mass in AMU

•Standardized and defined by: *¹²Cmass/12* •Total atomic mass accounts for each isotope ³⁵Cl mass • isotopic proportions ³⁷Cl mass • isotopic proportions sum both 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

*Basics of the Atom* Volume and Mass

•Volume=1/10000 of atom=volume • angstrom Mass=entire atom=1/2000 of proton mass

*Half life decay* •T½ and mean life decay •Decay Constant

•the average lifetime of a radioactive particle it is larger than T½, where the mean life equals T½/Ln2 *γ* is the decay constant which = Ln2/T½

∆¹⁷O

∆¹⁷O=δ¹⁷O-δ¹⁸O λ characterizes the mass-dependent fractionation. λ=~.5 ∆=~0

*Mass independent Effects*

∆≠0 δ¹⁷O≠.5δ¹⁸O Occurs in meteorites and in zone, and sulfur in sulfides > 2.45 Ga

*Cosmogenic* Other factors

1: Depth of rock (clay interaction) 2: Erosion rates (Reduces depth and removes cosmogenic nuclide) 3: effective range of nuclear particles 4: Density of rocks and minerals 5: Production rate (depending on latitude and elevation) 6: Topography "sheltering" area 7: weathering

*Non-radiogenic (stable)* *cosmochemical systems* *terrestrial systems*

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 evolution 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 characterize exchange processes, track reservoir interactions, and evaluate biologic and kinetic processes: Li B Mg Ca Fe

*Examples of Decay* Fission

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.

*Cosmogenic Isotopes*

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 understanding the relation between past climate change, the Earth magnetic field, and variations in the solar activity. Currently, the exact influence of past and future variations in the solar activity on climate is much debated. The cosmogenic ice core profiles provide one of the key records to resolve this controversy.

*Basics of the Atom* Isotopes

Isotopes have the same Z and charge. Also behave similarly in terms of chemical behavior. However, have different mass *N*.

*Stable Isotope Applications*

Isotopes indicate the presence and magnitude of key ecological processes. Many ecological processes produce a distinctive isotope fingerprint. The presence or absence of such processes and even their magnitude in relation to other processes are indicated by the stable isotope ratio value relative to known background values. Isotopes record biological responses to Earth's changing environmental condition. For cases in which substances or residues accumulate in an incremental fashion, such as in tree rings, animal hair and ice cores, isotope ratios can be used as a record of system response to changing environmental conditions or a proxy record for environmental change. Isotopes trace the origin and movement of key elements and substances. Owing to isotopic fractionations associated with physical and biological reactions, nutrient and element pools within and among ecosystems often differ isotopically. As a result, the source(s) of essential elements and resources acquired by an organism are easily traced using isotope ratios. Strong geographic patterns in isotope signature variation provide the means to trace the movement or origin of a substance or component at landscape to continental scales.

*Spikes and Traces*

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.

Kinetic Energy

Kinetic Energy produces radiation damage, such as: fission tacks, radiohaloes, damage to crystal lattice

*Organic Carbon*

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

*Diffusion*

Lighter isotopes are generally more mobile than heavy isotopes dependent on temperature between phases: Fluid ↔ Rock Ice ↔ Gas Mineral ↔ Mineral Other isotope fractionation influences: •pressure •chemical composition •crystal structure •sorption

*Rayleigh Fractionation*

Lighter molecules are enriched in vapor, condensation and evaporation (distillation)

*Stable Isotopes*

Low atomic mass and large mass difference between isotopes can be in multiple oxidation states and in a variety of compounds H, C, N, O, S

*Mass dependent and independent effects*

Mass dependent effects are most natural reactions ¹⁸O>>¹⁶O ¹⁷O>>¹⁶O ¹⁸O is 2X more enriched than ¹⁷O

*Oxygen*

Measurements of the ratio of oxygen-18 to oxygen-16 are often used to interpret changes in paleoclimate. The isotopic composition of oxygen atoms in the Earth's atmosphere is 99.759% 16O, 0.037% 17O and 0.204% 18O.[4] Because water molecules containing the lighter isotope are slightly more likely to evaporate and fall as precipitation,[5] fresh water and polar ice on earth contains slightly less (0.1981%) of the heavy isotope 18O than air (0.204%) or seawater (0.1995%). This disparity allows analysis of temperature patterns via historic ice cores. 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 different mass scales between the two disciplines.

*Inductively Coupled Plasma - Mass Spectrometry*

Quadrupole changes electrical frequencies in four rods and allows a particular mass of resonant ions to pass through to the collector

*Radioactive Decay Schemes* Simple Decay

Radioactive parent → stable daughter

Radiocarbon

Radiocarbon dating is also simply called Carbon-14 dating. Carbon-14 is a radioactive isotope of carbon, with a half-life of 5,730 years,[25][26] (which is very short compared with the above isotopes) and decays into nitrogen.[27] In other radiometric dating methods, the heavy parent isotopes were produced by nucleosynthesis in supernovas, meaning that any parent isotope with a short half-life should be extinct by now. Carbon-14, though, is continuously created through collisions of neutrons generated by cosmic rays with nitrogen in the upper atmosphere and thus remains at a near-constant level on Earth. The carbon-14 ends up as a trace component in atmospheric carbon dioxide (CO2). A carbon-based life form acquires carbon during its lifetime. Plants acquire it through photosynthesis, and animals acquire it from consumption of plants and other animals. When an organism dies, it ceases to take in new carbon-14, and the existing isotope decays with a characteristic half-life (5730 years). The proportion of carbon-14 left when the remains of the organism are examined provides an indication of the time elapsed since its death. This makes carbon-14 an ideal dating method to date the age of bones or the remains of an organism. The carbon-14 dating limit lies around 58,000 to 62,000 years.[28] The rate of creation of carbon-14 appears to be roughly constant, as cross-checks of carbon-14 dating with other dating methods show it gives consistent results. However, local eruptions of volcanoes or other events that give off large amounts of carbon dioxide can reduce local concentrations of carbon-14 and give inaccurate dates. The releases of carbon dioxide into the biosphere as a consequence of industrialization have also depressed the proportion of carbon-14 by a few percent; conversely, the amount of carbon-14 was increased by above-ground nuclear bomb tests that were conducted into the early 1960s. Also, an increase in the solar wind or the Earth's magnetic field above the current value would depress the amount of carbon-14 created in the atmosphere.

*Mass Spectrometry*

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 kinetic energy 1/2MV^2=Ev Ions enter magnetic field and their path is curved, radius of the curvature is smaller for lighter isotopes

*Mass Spectrometry*

The ioniziation of atomic species and acceleration through a strong magnetic field to cause separation between similar masses individual particles detected. 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 different fields and is applied to pure samples as well as complex mixtures.

*Sulfur*

The δ34S values can determine the origin source of sulfur, with heavy values typical of sulfur precipitation from sedimentary basins and marine evaporites, while lighter values are from igneous rocks

Potassium-argon dating method

This involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the closure temperature is fairly low in these materials, about 350 °C (mica) to 500 °C (hornblende)

Rubidium-strontium dating method

This is based on the beta decay of rubidium-87 to strontium-87, with a half-life of 50 billion years. This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples. Closure temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample

Uranium-lead dating

Uranium-lead radiometric dating involves using uranium-235 or uranium-238 to date a substance's absolute age. This scheme has been refined to the point that the error margin in dates of rocks can be as low as less than two million years in two-and-a-half billion years.[14][19] An error margin of 2-5% has been achieved on younger Mesozoic rocks.[20] Uranium-lead dating is often performed on the mineral zircon (ZrSiO4), though it can be used on other materials, such as baddeleyite, as well as monazite (see: monazite geochronology).[21] Zircon and baddeleyite incorporate uranium atoms into their crystalline structure as substitutes for zirconium, but strongly reject lead. Zircon has a very high closure temperature, is resistant to mechanical weathering and is very chemically inert. Zircon also forms multiple crystal layers during metamorphic events, which each may record an isotopic age of the event. In situ micro-beam analysis can be achieved via laser ICP-MS or SIMS techniques.[22] One of its great advantages is that any sample provides two clocks, one based on uranium-235's decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238's decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the sample even if some of the lead has been lost. This can be seen in the concordia diagram, where the samples plot along an errorchron (straight line) which intersects the concordia curve at the age of the sample

*Cosmogenic* Geomagnetic field

*Cosmogenic geomagnetic field* Earths magnetic field deflects cosmic rays cosmogenic nuclide production is greater towards poles, magnetic field and production changed with time, solar wind deflect cosmic rays devries effect fossil fuel burning increased atmosphere ¹²C since the industrial revolution diluting δ¹⁴C - *Suess effect* The Earth magnetic field is shielding the Earth from charged cosmic particles such that a relatively strong magnetic field reduces the production of radiogenic isotopes. The solar wind is a stream of charged particles emitted from the Sun, which varies with the solar activity. The Earth reacts to the solar wind by increasing the strength of the shielding magnetic field. Therefore, higher solar activity results in stringer shielding and thus lower production of cosmogenic isotopes. The combined magnetic field from the Earth itself and the reaction to the solar wind constitutes the Earth magnetosphere, illustrated by an artists' view below in blue. The abundance of cosmogenic isotopes in the ice cores therefore reflects past variations in both the strength of the Earth magnetic field and in the solar activity.

*Cosmogenic Nuclides*

*Cosmogenic nuclides* Good for young systems in surficial processes, such as glaciers, landslides, and lava flows

*Cosmogenic ¹⁴C dating needs calibration via tree rings or 234U-230Th coral ages*

*Cosmogenic ¹⁴C dating needs calibration via tree rings or 234U-230Th coral ages* Analytical techniques counting B-rays produced during decay acceleration mass spectrometry - higher energy ms The most well-known of the cosmogenic isotopes is probably Carbon-14 (14C) which is widely applied for radiometric dating. However, the abundance of 14C in ice sheets is very low, and 14C-measurements can generally not be used for dating of ice cores. However, two other cosmogenic isotopes, namely Beryllium-10 (10Be) and Chlorine-36 (36Cl), are deposited in measurable quantities in the ice cores and records of isotopes are obtained.

*Cosmogenic: Spallation*

*Cosmogenic: Spallation* 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

*Nuclear Stability & Radioactivity* Radioactive Isotopes can achieve lower energy by Electron Capture Fission

*Electron Capture* e⁻+p⁺=m+v *Fission* large nuclei split

*Equilibrium*

*Equilibrium* The assumption when using a geothermometer is that minerals are at complete equilibrium during or after formation

*Mass Spectrometry* •Gas •Solid •Sample

*Gas* Duel inlet system on continuous flow systems *Solid* Filament with separated materials *Sample* La-ICP-MS on sims oxygen or ceasium beams

*Geothermometers*

*Geothermometers* Is the partitioning of two stable isotopes of an element between two phases, where isotopic equilibrium is necessary, most likely to occur at high temperature. Yet at high temperature geothermometers are less sensitive than at low temperature equilibrium. •Equilibrium fractionation determined by theoretical modeling

Isochrons

*Isochrons* are cogenetic samples with different N

*Nuclear Stability & Radioactivity* Isomers

*Isomers* same Z, N, and A but differ in energy state, they are metastable and higher energy, energy loss through γ thus having a different manner of radioactive decay, and that exist for a measurable interval of time.

*Nuclide Chart* •Isotopes •Isotones •Isobars •Binding Energy

*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.

*Isotopic Equilibrium may not be achieved if*

*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

*Isotopologues and Clumping Theory*

*Isotopologues and Clumping Theory* Molecules that differ in isotopic composition. Clumped isotopes are more abundant than single substituted isotopologues, temperature dependence in clumping produces a geothermometer, higher temperature produces less clumping

*Laser Ablation*

*Laser Ablation* destructively technique leaving large and deep pits

*Mass independent Effects* Magnetic Isotope Effects

*Magnetic Isotope Effects* Isotope separate by spin and magnetic moment

*Mass independent Effects* Nuclear Volume Effects

*Nuclear Volume Effects* mass-independent isotope fractionation due to heavy element nuclear volumes

*Basics of the Atom* •Nuclide •Electron Shells

*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 →

*Sulfur* Organic Effects

*Organic Effects* Sulfate reducing bacteria produce ³²S-depleted sulfide bacteria uses ³⁴S in formation of sulfide to sulfate

*Oxygen Isotope Geothermometry*

*Oxygen Isotope Geothermometry* We assume the minerals crystallize at the same time in equilibrium and are not altered using more than one mineral can produce a more confident temperature estimate

*Oxygen Isotopes* Fluid-rock interaction

*Oxygen Isotopes* Fluid-rock interaction: solution-precipitation-chemical reaction

*Oxygen isotope fractionation with dominant inorganic carbon species relating to pH*

*Oxygen isotope fractionation with dominant inorganic carbon species relating to pH*

*Mass Spectrometry* •Peak Jumping

*Peak Jumping* Manually changing the magnetic field to analyze different 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

*Secondary Ion Mass Spectrometry* Sims (SHRIMP)

*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. Secondary-ion mass spectrometry is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions. A Faraday cup measures the ion current hitting a metal cup, and is sometimes used for high current secondary ion signals. With an electron multiplier an impact of a single ion starts off an electron cascade, resulting in a pulse of 108 electrons which is recorded directly. A microchannel plate detector is similar to an electron multiplier, with lower amplification factor but with the advantage of laterally-resolved detection. Usually it is combined with a fluorescent screen, and signals are recorded either with a CCD-camera or with a fluorescence detector.

*Stable Isotope Ratio Spectrometry* SIRMS

*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. Laser fluerinization is more modern way of releasing oxygen laser hitting a sample under a fluerinated atmosphere.

*Nuclear Stability & Radioactivity* •Stable Isotopes

*Stable Isotopes* Have lower overall energy, lower negative binding energy, and smaller nucleus

*Sulfur* Geothermometry

*Sulfur Geothermometry* fraction occurs by kinetic effects 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

*Sulfur Isotope Geothermometry*

*Sulfur Isotope Geothermometry* Sulfide and sulfate minerals can be used as a geothermometer if all minerals precipitate in equilibrium

*Thermal Ionization Mass Spectrometry* TIMS

*TIMS* for radiogeneic isotopes, extraction through liquid chromotography. HF dissolved for extraction -> evaporated and dissolved in HCl cation exchange columns "rinse" elements out deliberately. Sample evaporated and loaded on filaments for mass spec. A TIMS is a magnetic sector mass spectrometer that is capable of making very precise measurements of isotope ratios of elements that can be ionized thermally, usually by passing a current through a thin metal ribbon or ribbons under vacuum. The ions created on the ribbon(s) are accelerated across an electrical potential gradient (up to 10 KV) and focused into a beam via a series of slits and electrostatically charged plates. This ion beam then passes through a magnetic field and the original ion beam is dispersed into separate beams on the basis of their mass to charge ratio. These mass-resolved beams are then directed into collectors where the ion beam is converted into voltage. Comparison of voltages corresponding to individual ion beams yield precise isotope ratios. *Applications* •For terrestrial systems, common applications in geochronology and tracer Studies involve the following radiometric systems •In cosmochemical systems, the measurement of isotopic compositions is primarily as tracers of nucleosynthetic processes and constraining the evolution 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: •Non-radiogenic (stable) isotope-isotope ratios are typically used to characterize exchange processes, track reservoir interactions, and evaluate biologic and kinetic processes

*Time of flight Mass Spectrometer* TOF

*TOF* Ke=1/2MV^2 Ions with different masses (isotopes) will travel at different velocities when the same energy is applied The ions are introduced either directly from the source of the instrument or from a previous analyser (in the case of Q-TOF) as a pulse. This results in all the ions receiving the same initial kinetic energy. As they then pass along the field free drift zone, they are separated by their masses, lighter ions travel faster. This enables the instrument to record all ions as they arrive at the detector and so accounts for the techniques high sensitivity.

*all four sulfur isotopes*

*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) atmosphere

*Carboante Fractionation*

*carbonate fractionation* occurs through exchange reactions within inorganic carbon system CO2(g) bicarbonate -carbonate or through kinetic isotope effects in photosynthesis where ¹²C is concentrated

*¹⁴C comsogenic dating schemes in biological material*

*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

*Nuclear Stability & Radioactivity* Radioactive Isotopes can achieve lower energy by α β⁻ β⁺

*α* emission of ⁴₂He *β⁻* n=P⁺+e⁻+v⁻ *β⁺* P⁺=n+e⁻+v v & V⁻ take excess energy and nuclear spin

Uranium-thorium dating

A relatively short-range dating technique is based on the decay of uranium-234 into thorium-230, a substance with a half-life of about 80,000 years. It is accompanied by a sister process, in which uranium-235 decays into protactinium-231, which has a half-life of 32,760 years. While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments, from which their ratios are measured. The scheme has a range of several hundred thousand years. A related method is ionium-thorium dating, which measures the ratio of ionium (thorium-230) to thorium-232 in ocean sediment.

*Uncertainties* Accuracy vs. Precision MSWD

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 <2.5 Error chron- MWSD >2.5