Salt Deposits Their Origin and Composition. Questo articolo non è disponibile.Salt Deposits Their Origin and Composition

Professor OTTO BRAITSCH'S Entstehung und Stoffbestand der Salz­ lagerstiitten has since its publication in 1962 enjoyed a reputation as the most complete and authoritative treatment, in any language, of the geochemistry of evaporites. The issue of this translation will now make it accessible to a much wider circle of readers. The years since first publica­ tion of the German edition have seen a great surge of discussion and research on evaporites among English-speaking geologists, and while BRAITSCH'S work was important to some of these it can now no longer be ignored by any. It may be worth pointing out that, title notwithstanding, this volume takes as its subject not only the salts but all evaporite minerals and rocks, but that it makes no attempt to go beyond the geochemical evidence in discussing the origin of these evaporites. The reader should not expect to find here any extensive discussion of paleogeography and stratigraphy, or even petrographic detail. Within its scope of geochemistry and mineral­ ogy the coverage is extensive.

A. Introduction.- 1. Outline of the Theme and Statement of the Problem.- 2. On the History of Seawater.- 3. The Zechstein Salt Succession.- 4. The Minerals of Salt Deposits.- a) The Main Components (Salt Minerals sensu stricto).- b) Accessory and Authigenic Minerals.- B. The Stability Conditions of Salt Minerals.- The Graphic Presentation of Solubility Data.- I. System CaSO4-H2O (± NaCl, etc.).- 1. Solid Phases.- 2. Temperature Dependence.- 3. The Common Ion Effect (Excluding the Formation of Compounds).- 4. Pressure Dependence.- II. System NaCI-KC1-MgCl2-H2O.- 1. Solid Phases.- 2. Stability Conditions.- a) System NaCl-H2O.- b) System NaCl-KCl-H2O.- c) System NaCl-KCl-MgCl2-H2O.- ?) Isothermal Evaporation and Solution.- ?) Temperature Dependence.- ?) Salting Out.- III. System NaCl-KCl-Na2SO4-H2O.- 1. Further Solid Phases.- 2. Stability Conditions.- IV. System NaCl-Na2SO4 MgCl2-H2O.- 1. Further Solid Phases.- 2. Stability Conditions.- 3. Crystallization Sequence (Isothermal Evaporation).- 4. Temperature Dependence.- V. The Five-Component System NaCl-KCl-MgCl2-Na2SO4-H2O.- 1. Further Solid Phases.- 2. Stability Conditions.- a) Stable Equilibria.- b) Metastable Equilibria.- 3. Crystallization Sequence.- 4. Temperature Dependence.- VI. The Five-Component System with Ca and Fe Salts.- 1. Further Solid Phases.- a) With Ca Sulphates.- b) With Ca Chlorides.- c) With Fe Chlorides.- 2. Stability Conditions.- a) With Ca Sulphates.- b) With CaCl2.- c) With FeCl2.- C. Physico-chemical Models.- I. Primary Precipitation.- 1. Static Isothermal Evaporation of Normal Seawater at 25° C.- a) Stable Equilibria without Reaction in Constant Solutions.- b) Metastable Equilibria.- c) Conditions in Reactions along Reaction Lines and at Transition Points.- 2. Altered Seawater.- a) MgSO4 Deficient.- b) Formation of Polyhalite.- 3. Primary Precipitation with a Temperature Gradient.- 4. The Effect of Pressure.- II. Thermal Metamorphism.- 1. Generalities and Calculation.- Calculation.- 2. Examples.- 3. Kainite Alteration at 72° and 83° C.- 4. Reactions in the Solid State.- 5. Geothermal Metamorphism as Defined by Borchert.- III. Solution Metamorphism.- 1. Isothermal Solution Metamorphism.- a) Incongruent Carnallite Alteration.- b) Improverishment.- c) Enrichment.- d) The Reactions of CaCl2-bearing Solutions.- e) The Formation of Kainite from Kieserite and Sylvite.- 2. Polythermal Solution Metamorphism.- IV. Dynamic Metamorphism.- V. The Behaviour of Minor Components.- 1. Bromine.- a) Theoretical Bromine Distribution.- b) The Effect of Influxes on Bromine Distribution.- c) Partition of Bromine in Thermal Metamorphism.- d) Bromine Distribution in Solution Metamorphism.- 2. Strontium.- a) Diadochically in Ca-Sulphates.- b) Sr Minerals.- c) The Sr/Ca Ratio.- D. Natural Salt Sequences and Physico-chemical Models.- I. The Main Components.- 1. Calcium Sulphate Precipitation.- a) Primary Gypsum Precipitation.- b) Anhydrite Rocks.- 2. Primary Salt Rocks.- a) MgSO4-bearing Salt Sequences.- b) MgSO4-free Salt Sequences.- ?) Without Mg Sulphate, Anhydrite Predominant.- ?) Without Mg Sulphate, Dolomite (Ankerite) Predominant.- 3. Thermally Metamorphosed Salt Rocks.- 4. Salt Rocks Altered by Solution Metamorphism.- a) Isothermal Solution Metamorphism.- ?) MgSO4-bearing Salt Sequences.- ?) MgSO4 free Salt Sequences.- b) Polythermal Solution Metamorphism.- 5. Dynamic Metamorphism of Salt Rocks.- II. Minor Components.- 1. Bromine.- a) Progressive Evaporation.- b) Varying and Recessive Concentration Changes.- c) Bromine Content and Fine Bedding.- d) Bromine Content and Water Depth.- e) Distribution of Bromine during Metamorphism.- 2. Strontium.- a) Strontium in Sulphate Rocks.- b) In Halite and Potash Salts.- E. Other Components of Salt Deposits.- 1. Boron.- a) The Behaviour of Boron during Salt Precipitation.- b) Boron Content and its Regional and Vertical Distribution.- c) Origin of the Boron.- 2. Iron.- a) The Behaviour of Iron during Salt Precipitation.- b) Distribution, Frequency, and Origin of the Iron in Salt Deposits.- 3. Salt Clays and Insoluble Residues.- a) Distribution of the Clay Minerals.- b) Chemical Characteristics of the Salt Clays.- c) Origin and Material Balance of Salt Clays.- d) Filtration Effects in Salt Clay.- e) On the Formation of Koenenite.- f) Carbonates, Fluorides, Phosphates.- F. Geological Conclusions and Problems.- 1. Normal and Altered Seawater.- 2. Rhythmic Bedding and Influxes.- 3. Temperature of Primary Precipitation.- 4. Redox Potential and Hydrogen Ion Concentrations.- 5. The Origin of the Metamorphic Solutions.- G. Review.- References.- Author and Subject Index.