Methods and Applications of Geochronology

Front Cover -- Methods and Applications of Geochronology -- Methods and Applications of Geochronology -- Copyright -- Dedication -- Contents -- Contributors -- Preface -- 1 - Introduction to methods and applications of geochronology: A perspective on geological time -- 1. Introduction -- 2. Awareness and observation of geological and biological time: pre-20th century -- 2.1 Quod tempus est? -- 2.2 The journey into deep time -- 2.3 Uniformitarianism and the geological timescale -- 3. In search of an absolute time -- 3.1 The modern approach -- References -- 2 - High-precision CA-ID-TIMS U-Pb geochronology of zircon: Materials, methods, and interpretations -- 1. Introduction -- 2. Establishing a U-Pb dating infrastructure and installing best practices -- 2.1 Sample preparation and mineral separation -- 2.1.1 Crushing -- 2.1.2 Shaking table separation -- 2.1.3 Magnetic separation -- 2.1.4 Density separation -- 2.1.5 Optical separation and selection -- 2.2 Sample imaging (and in situ analyses) (Fig. 2.1B) -- 2.3 Chemical abrasion (Fig. 2.1C) -- 2.4 Low-level Pb, clean air chemistry -- 2.4.1 Low procedural Pb blank -- 2.4.2 Isotopic tracers ("spikes") -- 2.4.3 Clean air environment -- 2.4.4 Clean materials -- 2.4.5 Elemental separation workflow -- 2.5 Mass spectrometry (Fig. 2.1E) -- 2.6 Data treatment -- 3. Quality assessment -- 3.1 Precision -- 3.1.1 Analytical variation during the acquisition of mass spectrometry data -- 3.1.2 Fractionation of measured Pb or U isotope ratios -- 3.1.3 Correction for common Pb in analysis -- 3.2 Accuracy -- 3.3 Repeatability -- 3.4 Reproducibility -- 4. Interpretation of high-precision U-Pb zircon dates -- 4.1 Which geological event or moment is zircon dating? -- 4.2 Do all zircon crystals in an igneous rock sample reproduce the same age? -- 4.3 Reasons of age scatter -- 4.3.1 Protracted growth.