![]() The type of decay determines whether the ratio of neutrons to protons will increase or decrease to reach a more stable configuration. A decay, also known as a disintegration of a radioactive nuclide, entails a change from an unstable combination of neutrons and protons in the nucleus to a stable (or more stable) combination. Reaching stability involves the process of radioactive decay. A radionuclide has an unstable combination of nucleons and emits radiation in the process of regaining stability. Remember that a radionuclide represents an element with a particular combination of protons and neutrons (nucleons) in the nucleus of the atom. ![]() What is meant by the “decay” of a radionuclide? The primary intent is to demonstrate how the half-life of a radionuclide can be used in practical ways to “fingerprint” radioactive materials, to “date” organic materials, to estimate the age of the earth, and to optimize the medical benefits of radionuclide usage. The purpose of this chapter is to explain the process of radioactive decay and its relationship to the concept of half-life. With a seawater residence time of ~10 kyr, Os isotopes from sedimentary strata can yield high-resolution chemostratigraphy that can further our understanding of processes driving OAEs ice sheet advance and retreat the transition from lacustrine to marine environments and detecting extraterrestrial impact events.Why is this chapter on half-life being presented? In addition to geochronological data, Os isotope data from sedimentary rocks can be used to track the changing redox state of the oceans from the Archean through to the modern. Os isotopes as a paleoseawater and paleoweathering proxy Coupling these ages with reservoir rock geochronology, petrography, and organic geochemistry can improve our understanding of the evolution of petroleum basins thereby greatly reducing uncertainties associated with hydrocarbon exploration. As such, the Re-Os geochronometer may yield age constraints on deposition of the source rock as well as hydrocarbon generation and migration ages. ![]() Additionally, application of the Re-Os sedimentary geochronometer has helped refine the temporal framework of the Proterozoic “Snowball Earth” events and the tempo of eukaryotic evolution.Ĭoncentrations of Re and Os in source rocks and related hydrocarbons can be much higher than average crustal rocks. Target lithologies such as black shales and organic-rich carbonates are often coincident with events such as mass extinctions, which have been dated using Re-Os geochronology. ![]() The Re-Os geochronometer has shown great promise in dating successions lacking suitable material for traditional geochronology techniques such as Ar-Ar or U-Pb zircon geochronology. Organic-rich strata are often greatly enriched in Re and Os thus providing the foundation for Re-Os sedimentary rock geochronology. ![]() Highlights in this area of research include, but are not limited to exploring the links between continental crust growth and mantle melting constraining diamond formation events and elucidating the processes driving plume magmatism and forming chemical heterogeneities in the mantle.ĭating of molybdenite and other sulfides (e.g., pyrite, arsenopyrite, bornite, marcasite) using the Re-Os geochronometer has been highly successful in providing precise and accurate age constraints on ore formation as well as associated tectonic events (e.g., fluid-flow and metamorphism) from the early Archean to younger than 1 Ma. Advances in analytical procedures and instrument development over the past 25 years have improved the reliability and accuracy of the Re-Os geochronometer with many laboratories capable of generating ages with total uncertainties <0.5%.īy coupling the Re-Os system with data from other Platinum Group Elements the techniques is routinely used to study the geochemical evolution of the terrestrial planets. ![]()
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