# Introduction to Geochronology

From Wikibooks, open books for an open world

Geochronology is the field of science concerned with determining the ages of rocks and other stuff. In this book we attempt to outline the basic principles used for the quantification of geological time focusing on the radio-isotopic dating techniques. We are attempting to be inclusive about the methodologies and applications however there is a focus on the mainstream chronometers and the application of these to the quantification of geologic time.

## Part One - Introduction

## Part Two - Principles of Radioisotopic Dating

- Introduction
- The Age Equation
- Decay Constants
- Parent/Daughter ratio
- Geochronometers - what can be dated?
- Diffusion...

## Part Three - Rocks to Ratios: Sample selection and Characterization

- Introduction: Sample Selection and Characterization
- Sample Selection
- Sample Preparation
- Sample Characterization

## Part Four - Rocks to Ratios: Analytical Approaches

- Introduction: Extracting Quantitative Isotope data From Minerals and Rocks
- Isotope dilution
- Microbeam methods
- Principles of mass spectrometry
- Thermal-ionization mass spectrometry
- Inductively-coupled plasma mass spectrometry
- Secondary ion mass spectrometry
- Gas-source mass spectrometry
- Sample introduction by laser ablation

## Part Five - Ratios to Dates: Determining P/D and Decay Constants

- Introduction: Combining Mass Spectrometry with Underpinning Calibrations
- Calibration 1: Metrology and Tracability
- Calibration 2: Relative P/D determination
- Decay Constant 1: First Principles
- Decay Constant 2: Inter-calibration

## Part Six - Dates to Ages: Considering Interpretation and Uncertainties in Geochronology

- Introduction: Combining Dates to Derive an Age
- Definitions and Concepts
- Random and/or Systematic
- Excess Variance
- Weighted means and Reduced chi-squared (MSWD)
- Isochrons and Linear Regression

## Part Seven - Commonly Used Decay Schemes

- U-Pb Decay Scheme
- U-Series Disequilibria
- (U-Th)/He
- K-Ar Decay Scheme and Ar/Ar
- Re-Os
- Rb-Sr
- Sm-Nd
- Lu-Hf

## Part Eight - Examples of Application

- Introduction
- Age of the Earth
- Tectonic Applications
- Stratigraphic Applications
- Thermochronology
- Quaternary Geochronology