Strontium Isotope Geology (Minerals, Rocks and Mountains)

Since the end of World War II isotope geology has grown into a diversi­ fied and complex discipline in the earth sciences. It has progressed by the efforts of a relatively small number of specialists, many of whom are physi­ cists, chemists, or mathematicians who were attracted to the earth sciences by the opportunity to measure and to interpret the isotopic compositions of certain chemical elements in geological materials. The phenomenal growth of isotope geology during the last 25 years is an impressive indi­ cation of the success of their efforts. We have now entered into a new phase of development of isotope geology which emphasizes the application of the new tools to the solution of specific problems in the earth and planetary sciences. This requires the active participation of a new breed of geologists who understand the nature and complexity of geological problems and can work toward their solution by a thoughtful application of the principles of isotope geology. It is there­ fore necessary to explain these principles to earth scientists at large to enable them to make use of the new information which isotope geology can offer them.

I. The Geochemistry of Rubidium and Strontium.- 1. Introduction.- 2. Rubidium.- 3. Strontium.- 4. The Rubidium/Strontium Ratio.- 5. Summary.- II. Measurement of Geologic Time by the Rubidium-Strontium Method.- 1. Introduction.- 2. Radioactive Decay of 87Rb to 87Sr.- 3. The Half-life of 87Rb.- 4. The Growth of Radiogenic 87Sr in Rocks and Minerals.- 5. The Rubidium-Strontium Isochron Method of Dating.- 6. A Useful Approximation.- 7. Analytical Methods.- 8. Summary.- III. Uses of Strontium Isotopes in Petrogenesis.- 1. Introduction.- 2. Evolution of Strontium in the Continental Crust and the Upper Mantle.- 3. Applications to Petrology.- 4. Summary.- IV. Volcanic Rocks.- 1. Introduction.- 2. The Strontium Isotopic Data for Volcanic Rocks.- a) General Comment.- b) Basaltic Rocks from Oceanic Islands.- c) Sea-Floor Basalts.- d) Andesites of Volcanic Arcs.- e) Antarctic and Tasmanian Dolerites.- 3. Variations in the Initial 87Sr/86Sr Ratio among and within Geologic Provinces.- a) Oceanic Islands.- b) Continental Volcanic Rocks.- 4. Possible Causes of Variations in Isotopic Composition among Cogenetic Rocks.- 5. Summary.- V. Granitic Rocks.- 1. Introduction.- 2. The Granite Problem.- 3. Observed Initial 87Sr/86Sr Ratios of Granitic Rocks.- 4. Interpretation and Discussion of Initial 87Sr/86Sr Ratios of Granites.- a) Granites with Initial Ratios within the Basalt Field.- The Salisbury Pluton, North Carolina.- b) Granites with High Initial 87Sr/86Sr Ratios.- The Heemskirk Granite, Western Tasmania.- c) Granites with Intermediate Initial 87Sr/86Sr Ratios.- The Isle of Skye.- Phanerozoic Batholiths of North America.- 5. Summary.- VI. Alkalic Rocks and Carbonatites.- 1. Introduction.- 2. Carbonatites.- 3. Alkalic Rocks.- a) Potassic Rocks.- b) Sodic Rocks.- c) Comparison of North American and African Alkalic Rocks.- 4. Summary.- VII. Ultramafic and Related Rocks.- 1. Introduction.- 2. 87Sr/86Sr Ratios of Ultramafic Rocks.- a) The Layered Gabbro-Norite-Peridotite Association in Major Intrusions.- Anorthosites.- b) The Alpine-Type Peridotite-Serpentinite Association.- c) Ultramafic Rocks in Differentiated Basic Sills and in Minor Intrusions.- d) Kimberlites.- e) Ultramafic Nodules.- 3. Summary.- VIII. Sedimentary Rocks and the Oceans.- 1. Introduction.- 2. Marine Carbonate Rocks and the Oceans.- 3. Marine Evaporites.- 4. Dating of Detrital Sedimentary Rocks.- 5. Glauconite.- 6. Nonmarine Carbonate Rocks.- 7. Summary.- IX. Isotopic Homogenization of Strontium in Open Systems.- 1. Introduction.- 2. Contact Metamorphism.- 3. Regional Metamorphism.- 4. Open-System Behavior of Total-Rock Samples.- 5. Chemical Weathering.- 6. Summary.- X. Meteorites.- 1. Introduction.- 2. Rubidium and Strontium in Stony Meteorites.- 3. The Ages of Stony and Iron Meteorites.- 4. The Initial 87Sr/86Sr Ratios of Stony Meteorites.- 5. Summary.- XI. The Moon.- 1. Introduction.- 2. Lunar Basalt.- 3. Initial 87Sr/86Sr Ratios.- 4. Luny Rock 1 and Sample 12013.- 5. The Soil.- 6. Luna 16.- 7. Summary.- XII. The Evolution of the Isotopic Composition of Terrestrial Strontium.- 1. Introduction.- 2. Evolution of Strontium in the Mantle.- 3. Initial 87Sr/86Sr Ratios of Gabbro and Basalt.- 4. Continental Growth.- 5. Summary.- References for Appendix.- Author Index.