Introduction to Geochemistry

TO GEOCHEMISTRY by CLAUDE-JEAN ALLEGRE Department of Earth Sciences, University of Paris 7 and GIL MICHARD Department of Chemistry, University of Paris 7 D, REIDEL PUBLISHING COMPANY DORDRECHT-HOLLAND / BOSTON-U. S. A. INTRODUCTION A LA GEOCHIMIE First published by Presses Universitaires de France, Paris, 1973 Translated/rom the French by Robert N. Varney Library of Congress Catalog Card Number 74-83871 e-ISBN -13: 978-94 -010-2261-3 ISBN -13: 978-90-277-0498-6 DOl: 10. 1007/978-94-010-2261-3 Published by D. Reidel Publishing Company, P. O. Box 17, Dordrecht, Holland Sold and distributed in the U. S. A. , Canada, and Mexico by D. Reidel Publishing Company, Inc. 306 Dartmouth Street, Boston, Mass. 02116, U. S. A. All Rights Reserved Copyright © 1974 by D. Reidel Publishing Company, Dordrecht, Holland No part of this book may be reproduced in any form, by print, photoprint, microfilm, or any other means, without written permission from the publisher TABLE OF CONTENTS PREFACE IX PREFACE BY THE TRANSLATOR XI CHAPTER 1 / THE EARTH AS A CHEMICAL SYSTEM 1 1. 1. The Earth within the Solar System 1 1. 2. The Scale of Time 1 1. 3. The Overall Chemical Composition of the Earth, the Solar System, and the Universe 2 1. 4. Chemical Compounds in the Solar System: Cosmological Minerals 5 1. 4. 1. Simple Molecules 6 1. 4. 2. Simple Solids 6 1. 4. 3. Silicates 6 1. 4. 4. Carbon Polymers 6 1. 4. 5. Fe-Ni Alloys 6 1. 5.

1 / The Earth as a Chemical System.- 1.1. The Earth within the Solar System.- 1.2. The Scale of Time.- 1.3. The Overall Chemical Composition of the Earth, the Solar System, and the Universe.- 1.4. Chemical Compounds in the Solar System: Cosmological Minerals.- 1.5. Chemical Constitution of the Earth.- 1.6. Geochemical Classification.- 1.7. The Earth as a Chemical Factory.- 2 / The Equilibria of Phases in the Lithosphere.- 2.1. Metamorphic Equilibria.- 2.2. Phase Equilibria in the Silicate Magmas.- 2.3. Magmatism or Metamorphism. The Conditions for Their Appearance.- 3 / Chemical Equilibria in the Hydrosphere.- 3.1. Chemical Reactions in the Hydrosphere.- 3.2. Study of the Saturation of Sea Water with Calcite.- 4 / The Geochemical Fractionation of Trace Elements.- Partition of a Trace Element between Two Phases.- 4.1. Fractionation of the Trace Elements in Magmatic Processes.- 4.2. Trapping of Trace Elements in Sediments.- 5 / Irreversible Processes of Element Transfer.- 5.1. Evaluation of the Transfer of Elements during Irreversible Geochemical Processes.- 5.2. Box Model.- 5.3. Chemical Diffusion-Reaction Coupling.- 5.4. Deposit of Manganese in Ocean Depths.- 6 / The Fractionation of the Light Isotopes.- 6.1. The Evidence Concerning the Natural Fractionation of Isotopes.- 6.2. The Modes of Isotopic Fractionation.- 6.3. Relationship between ? and ?.- 6.4. The 18O/16O Isotopic Composition of the Silicates and Geothermometry.- 6.5. Isotopic Composition 32S/34S of Sulfide Ore Deposits.- 6.6. Some Aspects of the Water Cycle and the Associated Isotopic Fractionation.- 7 / Fractionation of Radioactive Isotopes and Isotopes of Radioactive Origin.- 7.1. General Equation for the Evolution of a Radioactive System.- 7.2. Evaluation of the Functions G (t) and J (t) and thePotassium-Argon Time Scale.- 7.3. Isotopic Re-Equilibration of Strontium During Metamorphism.- 7.4. Loss of Radiogenic Elements in Rich Systems and Chronology of U-Th-Pb From Zircons.- 7.5. Evolution and Nature of the Earth’s Mantle.- 7.6. Evolution of the Initial Ratios of (87Sr/86Sr) and (206Pb/204Pb) in Granites and the Formation of the Continents.