Principles of Geochemistry Notes

Principles of Geochemistry - Mason and Moore

Principles of Geochemistry

  • Authored by Brian Mason and Carleton B. Moore.
  • Fourth edition.
  • Published by John Wiley & Sons, New York.
  • Copyrighted in 1966, 1982.

Preface

  • Intended as an introductory text for undergraduate and graduate students in chemistry and geology, and those in other sciences.
  • Summarizes and synthesizes significant facts and ideas concerning the chemistry of the earth, and provides an account of its physical and chemical evolution.
  • Covers the entire field of geochemistry, though not always with equal detail, due to space constraints.
  • Areas of geochemical interest such as phase diagrams and ore deposits are covered by other geology courses.
  • Thermodynamics requires the depth of presentation given in physical chemistry courses.
  • The book begins with a chapter that describes the scope and subject matter of geochemistry, as well as a brief account of the field's development.
  • Followed by a chapter discussing the Earth as a planet, relating it to the solar system and the universe, and then discussing its internal structure and composition.
  • An account of the relative abundances of elements and isotopes in the Earth and in the universe is presented.
  • An attempt to give a logical account of the Earth's pregeological history is made.
  • Materials and processes at/near the Earth's surface will be covered.
  • Physicochemical principles are applied to processes on and within the Earth, particularly the chemistry of the solid-state.
  • Igneous geochemistry is covered, followed by sedimentation and sedimentary rocks.
  • A new chapter on isotope geochemistry discusses stable isotopes and geochronology.
  • Subsequent chapters discuss the atmosphere, hydrosphere, and biosphere, all of which are intertwined in terms of evolution, but also recognize material must be returned to at least a second time to properly relate it to other systems.
  • The discussion of the hydrosphere focuses on the geochemistry of seawater and the origin and evolution of the ocean.
  • The discussion of the atmosphere focuses on the nature of the primeval atmosphere and its transformations through interaction with the hydrosphere, biosphere, and lithosphere.
  • The discussion of the biosphere involves the amount and composition of organic matter and the role of organisms in element concentration and deposition.
  • Then follows a chapter on metamorphism and metamorphic rocks.
  • The final chapter is a brief summary and synthesis in terms of the geochemical cycle including environmental geochemistry
  • Emphasis is on interpretation rather than description with a focus on what is yet to be learned.
  • Awareness of gaps in geochemical knowledge exists, which can be solved by combined efforts of chemists, physicists, and geologists.
  • Acknowledges teachers of geochemistry and their own preferred approaches to the subject, but to have this text provide a useful frame upon which they may develop their chosen topics and apply their practical teaching techniques so that the field of geochemistry may continue to grow and remain vigorous.

Introduction: The Subject of Geochemistry

  • Geochemistry is defined as the science concerned with the chemistry of the Earth.
  • It involves the application of chemical principles and methods to the study of the Earth.
  • Cosmochemistry extends this study to the universe as a whole, including the chemistry of the sun, other planetary bodies, stars, and interplanetary and interstellar space.
  • Clarke defined geochemistry in a more restricted sense which is each rock may be regarded as a chemical system in which, by various agencies, chemical changes can be brought about.
  • The study of these changes is the province of geochemistry.
  • Changes which are possible include, how and when they occur, to observe the phenomena which attend them, and to describe there final results are the functions of the geochemist.
  • Geochemical studies focus on the solid crust and its reactions between essential constituents, with the aqueous envelope, and with the atmosphere.
  • V.M. Goldschmidt described geochemistry in terms of:
    • Determining quantitatively the composition of the Earth and its parts.
    • Discovering the laws that control the distribution of individual elements.
  • This requires:
    • Analytical data on terrestrial materials (rocks, waters, atmosphere).
    • Analyses of meteorites.
    • Astrophysical data on cosmic bodies.
    • Geophysical data on Earth's interior.
    • Laboratory synthesis of minerals and investigations of their formation and stability conditions.
  • The main tasks of geochemistry are:
    • Determining the relative and absolute abundances of elements and isotopes in the Earth.
    • Studying the distribution and migration of elements in the Earth's various parts (atmosphere, hydrosphere, crust, minerals, rocks) to discover governing principles.
  • The scope of geochemistry is partially defined by the historical development of geology.
  • Related subject areas such as mineralogy and petrology often cover subject matter which might well fall within the area of geochemistry.
  • Empirical geochemical studies of element distribution on Earth’s surface has led to a significant role in mineral exploration.

The History of Geochemistry

  • The science of geochemistry has largely developed during the current century, but it has older roots.
  • The term