Uranium Series, Opal
Uranium series dating. A geochronological method that uses intermediate decay products in the 238U or 235U radioactive decay chains to measure the length of time required to reach the current state of radioactive disequilibrium from an initial condition.
Opal. Amorphous or only partially crystalline hydrated silicon dioxide (SiO2∙nH2O) precipitated from aqueous solutions in near-Earth-surface environments.
Mineralogy and Geochemistry of Opal
Opal is a common mineraloid found near the surface of the Earth that consists of silica containing nonstructural water (SiO2∙nH2O). Opal typically forms by precipitation of colloidal silica from silica-saturated aqueous solutions in response to decreases in temperature, neutralization of alkaline solutions, increases in salinity, or evaporative concentration. Sedimentation of colloidal microspheres (<500 nm) results in deposits of amorphous silica gel. Subsequent dewatering...
KeywordsThermal Ionization Mass Spectrometry Laser Ablation Inductively Couple Plasma Mass Spectrometry Thermal Ionization Mass Spectrometer Opal Hemisphere Isotope Dilution Thermal Ionization Mass Spectrometry
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