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.- 1.4.1. Simple Molecules.- 1.4.2. Simple Solids.- 1.4.3. Silicates.- 1.4.4. Carbon Polymers.- 1.4.5. Fe-Ni Alloys.- 1.5. Chemical Constitution of the Earth.- 1.5.1. The Atmosphere.- 1.5.2. The Hydrosphere.- 1.5.3. The Biosphere.- 1.5.4. The Lithosphere.- 1.6. Geochemical Classification.- 1.7. The Earth as a Chemical Factory.- 2 / The Equilibria of Phases in the Lithosphere.- 2.1. Metamorphic Equilibria.- 2.1.1. General Characteristics of Metamorphic Terrains.- 2.1.1.1. The Paragenetic Association of Metamorphic Rocks.- 2.1.1.2. Existence of Metamorphic Zones.- 2.1.2. Thermodynamic Interpretation of Metamorphic Facies.- 2.1.3. Determination of Metamorphic Phase Diagrams.- 2.1.4. Conclusions. General Characteristics of Metamorphism.- 2.2. Phase Equilibria in the Silicate Magmas.- 2.2.1. Basalts and Granites.- 2.2.2. The Genesis of Granite. Experimental Results. Study of Phase Diagrams.- 2.2.2.1. The Albite-Anorthite System.- 2.2.2.2. Quartz-Potash Feldspar System.- 2.2.2.3. The Albite-Potash Feldspar System.- 2.2.2.4. Complex Two-Component Systems.- 2.2.2.5. Total Pressure and Fluid (H2O) Pressure.- 2.2.2.6. The Ternary System Silica-Albite-Orthoclase.- 2.2.2.7. Comparison of Experiments with Field Observations.- 2.2.3. The Genesis of Basalts.- 2.2.3.1. The Evolution of Basalts and Fractional Crystallization.- 2.2.3.2. The Origin of Basaltic Magma.- 2.2.3.3. Hawaii and the Model of G. A. MacDonald.- 2.2.3.4. The Rittman-Kuno Relationship.- 2.3. Magmatism or Metamorphism. The Conditions for Their Appearance.- 3 / Chemical Equilibria in the Hydrosphere.- 3.1. Chemical Reactions in the Hydrosphere.- 3.1.1. Classification of Reactions.- 3.1.2. Acid-Base Reactions in Natural Water.- 3.1.2.1. Principal Factors.- 3.1.2.2. The Carbonate System.- 3.1.2.3. The Alkalinity.- 3.1.2.4. pH of Several Natural Environments.- 3.1.2.5. Influence of pH on the Mobility of the Elements.- 3.1.2.6. Conclusions.- 3.1.3. Oxidation-Reduction Reactions in Natural Water.- 3.1.3.1. Chief Redox Pairs in Natural Waters.- 3.1.3.2. Aerated Environments.- 3.1.3.3. Reducing Environments.- 3.1.3.4. Overall Picture of Oxidation-Reduction Phenomena at the Earth’s Surface.- 3.1.3.5. Influence of the State of Oxidation-Reduction on the Mobility of the Elements.- 3.1.4. Formation of Complexes.- 3.1.4.1. Combinations of the Major Ions in Sea Water.- 3.1.4.2. Formation of Complexes among Minor Ion Species.- 3.2. Study of the Saturation of Sea Water with Calcite.- 3.2.1. Activity Coefficients in Sea Water.- 3.2.2. Variation of the Apparent Constants as a Function of S, T, P.- 3.2.3. Experimental Studies of the ‘Carbonate System’ of the Ocean.- 3.2.4. Calcite or Aragonite.- 3.2.5. Balance of Calcium in the Ocean.- 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.- 4.1.1. Models of the Partition of the Trace Elements during the Magmatic Processes.- 4.1.1.1. Model of Fractional Crystallization.- 4.1.1.2. Model for Partial Melting.- 4.1.1.3. Mixing Model.- 4.1.2. Determination of the Partition Coefficients.- 4.1.3. Variations of the Ratio K/Rb in Nature.- 4.1.4. Differentiation of the Rare Earths.- 4.1.4.1. Diagrams by Coryell et al..- 4.1.4.2. Europium and Cerium.- 4.1.4.3. The Genesis of Basic Terrestrial Magmas.- 4.1.5. The Transition Elements.- 4.1.5.1. Use of Coryell et al.’s Diagram.- 4.1.5.2. Crystal-Field Theory.- 4.2. Trapping of Trace Elements in Sediments.- 4.2.1. Impossibility of Direct Precipitation from Sea Water for Many Elements.- 4.2.2. Precipitation in Anoxic Environments.- 4.2.3. Processes of Entrainment.- 5 / Irreversible Processes of Element Transfer.- 5.1. Evaluation of the Transfer of Elements during Irreversible Geochemical Processes.- 5.1.1. Generalities.- 5.1.2. Mobile and Inert Elements.- 5.1.3. Second Method of Helgeson.- 5.2. Box Model.- 5.2.1. Concept of Residence Time.- 5.2.2. Models of the Ocean.- 5.3. Chemical Diffusion-Reaction Coupling.- 5.3.1. Generalities.- 5.3.2. Distribution of Sulfates in the Interstitial Waters of the Santa Barbara Basin.- 5.3.3. Diffusion and Partition Coefficient.- 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.- 6.2.1. Fractionation at Equilibrium.- 6.2.2. Kinetic Fractionation.- 6.2.3. The Transition of Kinetic Fractionation to Equilibrium Fractionation: Isotopic Exchange.- 6.3. Relationship between ? and ?.- 6.3.1. Open Environment.- 6.3.2. Closed Environment.- 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.- 6.6.1. The Isotopic Functioning of Clouds and Precipitation.- 6.6.2. The Glaciers, Isotopic Record of the Quaternary Climates.- 6.6.3. Juvenile Water.- 6.6.4. Meteoritic Water ― Magma Interactions in the Genesis of Hydrothermal Deposits.- 7 / Fractionation of Radioactive Isotopes and Isotopes of Radioactive Origin.- 7.1. General Equation for the Evolution of a Radioactive System.- 7.1.1. Comments on the Conditions of Integration.- 7.1.1.1. The System is Closed.- 7.1.1.2. The System Only Loses Elements without Gaining Any.- 7.1.1.3. The Environment Gains Matter Constantly without Losing Any.- 7.2. Evaluation of the Functions G (t) and J (t) and the Potassium-Argon Time Scale.- 7.2.1. Determination of Values of G(t).- 7.2.2. Evaluation of J(t).- 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.