Kimberlites, Orangeites, and Related Rocks

ISBN-13: 9781461358220 / Angielski / Miękka / 2012 / 410 str.

Roger H. Mitchell; Roger H. Mitchell

Opis

Many people have contributed to the production of this book, and I wish to acknowledge the following colleagues who have, over the past 15 years, contributed much discussion, preprints, thin sections, rock samples, and unpublished and/or difficult-to- obtain information: Steve Bergman, Roger Clement, Howard Coopersmith, Barry Dawson, Alan Edgar, Tony Erlank, Steve Haggerty, Barry Hawthorne, Bram Janse, Viktoria Komilova, Sergei Kostrovitskii, Henry Meyer, Peter Nixon, Nick Rock, Mike Skinner, Patricia Sheahan, Simon Shee, Barbara Scott Smith, Andy Spriggs, Ken Tainton, Larry Taylor, Nikolai Vladykin, Allan Woolley, and Peter Wyllie. Special thanks go to Henry Meyer, for providing many hours of microprobe time at Purdue University, and to Mike Skinner, for samples and the opportunity to examine the Anglo-American Research Laboratory collection of orangeites. Particular thanks are expressed to Ken Tainton for permission to quote data from his Ph.D. thesis. Particular gratitude is expressed to Sam Spivak for drafting and photographic work and to Anne Hammond for preparing many polished thin sections of these difficult rocks. Their dedication, skills, and attention to detail are greatly appreciated by the author. Others from Lakehead University who helped materially during the production of this work include Reino Viitala (thin sections), Alan MacKenzie (electron microscopy), and Shelley Moogk-Pickard (trace element analysis). Carl Hager is thanked for assistance in using the Purdue microprobe.

Recenzje

`Superb...Mitchell has clearly established himself as an authority in his field. He writes with admirable clarity and his mastery of the literature of this vast subject is both encylopaedic and discerning ... [This book] is an outstanding good contribution to petrology.'
Geological Magazine

Spis treści

1. Kimberlites and Orangeites.- 1.1. Etymology of Group I and II Kimberlites.- 1.2. Definitions of Cryptogenic and Primary Phases.- 1.3. The Hybrid Nature of Kimberlites and Orangeites.- 1.4. Philosophy and Principles of Classification.- 1.4.1. Modal versus Genetic Classifications.- 1.4.2. Petrological Clans.- 1.4.3. The Lamprophyre Clan.- 1.4.4. Mineralogical—Genetic Nomenclature within Petrological Clans.- 1.5. Mineralogical Comparisons between Kimberlites and Orangeites.- 1.6. Definitions of Orangeites and Kimberlites.- 1.6.1. Orangeites.- 1.6.2. Kimberlites.- 1.7. Age and Distribution of Orangeites.- 1.8. Occurrences of Orangeites.- 1.8.1. Finsch.- 1.8.2. Barkly West Region.- 1.8.2.1. Bellsbank.- 1.8.2.2. Sover.- 1.8.2.3. Newlands.- 1.8.2.4. Pniel.- 1.8.3. Boshof District.- 1.8.3.1. Roberts Victor.- 1.8.3.2. New Elands.- 1.8.4. Winburg District.- 1.8.5. Kroonstad District.- 1.8.6. Swartruggens District.- 1.8.7. Dokolwayo.- 1.8.8. Prieska District.- 1.8.9. Summary.- 1.9. Textural—Genetic Classifications of Petrological Clans….- 1.9.1. Kimberlites.- 1.9.1.1. Crater Facies.- 1.9.1.2. Diatreme Facies.- 1.9.1.3. Hypabyssal Facies.- 1.9.1.4. Spatial Relationships between Diatreme and Hypabyssal Facies Kimberlites.- 1.9.2. Orangeites.- 1.9.3. Melilitite Clan.- 1.10. Petrographic Characteristics of Orangeite.- 1.11. Petrographic Differences with Respect to Kimberlites.- 1.12. Petrographic Differences with Respect to Lamproites.- 2. Mineralogy of Orangeites.- 2.1. Mica.- 2.1.1. Paragenesis.- 2.1.2. Composition of Primary Mica.- 2.1.2.1. Al2O3—TiO2 Variation.- 2.1.2.2. Al2O3—FeOT Variation.- 2.1.2.3. Macrocrysts versus Microphenocrysts.- 2.1.2.4. Minor Elements.- 2.1.2.5. Trace Elements.- 2.1.3. Aluminous Mica—Microxenoliths.- 2.1.4. Aluminous Biotite Macrocrysts.- 2.1.5. Micas from the Swartruggens Male Lamprophyre.- 2.1.6. Summary of Mica Compositional Variation.- 2.1.7. Solid Solutions in Orangeite Mica.- 2.1.8. Mica in Kimberlites.- 2.1.8.1. Macrocrysts.- 2.1.8.2. Primary Micas.- 2.1.8.3. Summary of Kimberlite Mica Compositional Variation.- 2.1.9. Mica in Lamproites.- 2.1.10. Mica in Minettes.- 2.1.11. Mica in Ultramafic Lamprophyres.- 2.2. Clinopyroxene.- 2.2.1. Paragenesis.- 2.2.2. Composition.- 2.2.2.1. Diopside.- 2.2.2.2. Titanian Aegirine.- 2.2.2.3. Minor Elements.- 2.2.3. Pyroxenes in the Swartruggens Male Lamprophyre..- 2.2.4. Megacrystal Pyroxenes.- 2.2.5. Comparison with Pyroxenes in Kimberlites.- 2.2.6. Comparisons with Pyroxenes in Lamproites.- 2.2.7. Comparisons with Pyroxenes in Ultramafic Lamprophyres.- 2.2.8. Comparisons with Pyroxenes from Minettes.- 2.3. Olivine.- 2.3.1. Paragenesis.- 2.3.2. Composition.- 2.3.3. Comparisons with Olivines in Kimberlites.- 2.3.4. Comparisons with Olivines in Lamproites.- 2.4. Spinel.- 2.4.1. Paragenesis.- 2.4.2. Composition.- 2.4.3. Comparisons with Kimberlite Spinels.- 2.4.4. Spinel Compositional Variation in Lamproites and Lamprophyres.- 2.5. Potassium Barium Titanates.- 2.5.1. Hollandite.- 2.5.1.1. Paragenesis.- 2.5.1.2. Composition.- 2.5.1.3. Comparison with Hollandites from Lamproites, Kimberlites, and Other Potassic Rocks.- 2.5.2. Potassium Triskaidecatitanate.- 2.5.3. Barium Pentatitanate.- 2.6. Perovskite.- 2.6.1. Paragenesis.- 2.6.2. Composition.- 2.6.3. Comparison with Perovskites from Kimberlite.- 2.6.4. Comparison with Lamproite Perovskite.- 2.7. Phosphates.- 2.7.1. Apatite.- 2.7.1.1. Paragenesis.- 2.7.1.2. Composition.- 2.7.1.3. Comparison with Kimberlite and Lamproite Apatite.- 2.7.2. Daqingshanite.- 2.7.3. Monazite.- 2.7.4. Sr—REE Phosphate.- 2.8. Amphiboles—Potassium Richterite.- 2.8.1. Paragenesis.- 2.8.2. Composition.- 2.8.3. Comparison with Potassium Richterite in Lamproite and Other Potassic Rocks.- 2.9. Potassium Feldspar.- 2.10. Ilmenite.- 2.10.1. Comparison with Groundmass Ilmenites from Kimberlites.- 2.10.2. Comparison with Ilmenites in Lamproites.- 2.11. Rutile.- 2.12. Zirconium Silicates.- 2.12.1. Zircon.- 2.12.2. Wadeite.- 2.12.3. Zirconium-Bearing Garnet.- 2.12.4. Calcium Zirconium Silicate.- 2.13. Carbonates.- 2.13.1. Calcite.- 2.13.2. Dolomite.- 2.13.3. Other Carbonates.- 2.14. Other Minerals.- 2.15. Summary.- 3. Geochemistry of Orangeites.- 3.1. Contamination and Alteration.- 3.2. Primary Magma Compositions.- 3.3. Major Element Geochemistry.- 3.3.1. Unevolved Orangeites.- 3.3.2. Mineralogical Controls on the Major Element Geochemistry.- 3.3.3. Evolved Orangeites.- 3.3.4. Comparison with Kimberlites.- 3.3.5. Comparison with Lamproites.- 3.4. First-Period Transition Elements.- 3.5. Incompatible Elements.- 3.5.1. Alkaline Earths.- 3.5.2. Second-and Third-Period Transition Elements.- 3.5.2.1. Zirconium and Hafnium.- 3.5.2.2. Niobium and Tantalum.- 3.5.3. Thorium and Uranium.- 3.5.4. Rare Earth Elements.- 3.5.5. Alkali Elements.- 3.5.6. Lead.- 3.6. Inter-Element Relationships.- 3.6.1. Extended Incompatible Element Distribution Diagrams.- 3.6.2. Ce/Y and La/Yb versus Zr/Nb.- 3.7. Peridotite Mixing and Assimilation.- 3.8. Radiogenic Isotopes.- 3.8.1. Strontium and Neodymium.- 3.8.2. Lead.- 3.9. Stable Isotopes.- 3.10. Summary.- 4. Petrogenesis of Orangeites and Kimberlites.- 4.1. Geochemical Models of Orangeite Petrogenesis Involving Limited Partial Melting of Lherzolitic Sources.- 4.1.1. Earlier Hypotheses.- 4.1.2. Melting of Enriched Mantle and Peridotite Entrainment.- 4.1.3. Three-Stage Processes—Depletion, Enrichment, and Melting.- 4.2. Experimental Evidence Pertaining to Orangeite Petrogenesis.- 4.2.1. Liquidus Experiments on Orangeite Compositions.- 4.2.2. Liquidus Experiments on Lamproite Compositions.. •.- 4.2.3. Melting of Mica Pyroxenites.- 4.2.4. Phase Relations in the System: Phlogopite–Potassium Richterite–Apatite.- 4.3. Petrogenesis of Archetypal Kimberlites—Recent Hypotheses...- 4.3.1. Carbonated Lherzolite Sources.- 4.3.1.1. Volatile Fluxing—Diapiric Model.- 4.3.1.2. Partial Melting of Magnesite Peridotite.- 4.3.1.3. Partial Melting of Carbonated Phlogopite Lherzolite.- 4.3.1.4. Carbonates in the Mantle?.- 4.3.2. Liquidus Experimental Studies at High Pressures.- 4.3.2.1. Liquidus Studies of Natural Kimberlite.- 4.3.2.2. Liquidus Studies of Synthetic Kimberlite.- 4.3.2.3. Summary—A Cautionary Note.- 4.4. Geodynamic Models of Kimberlite and Orangeite Genesis.- 4.4.1. Transition Zone Melting.- 4.4.2. Metasome Melting and Mantle Plumes.- 4.4.3. Hot-Spot Melting.- 4.4.4. Partial Melting of Heterogeneous Lithosphere.- 4.4.5. Redox Melting.- 4.5. Petrogenesis of the Orangeite Clan.- 4.5.1. Development of the Source.- 4.5.1.1. Continental Roots.- 4.5.1.2. Depth of Origin of Orangeite Magmas.- 4.5.1.3. Compositional Heterogeneities—Veined Harzburgites.- 4.5.2. Melting of the Source.- 4.5.2.1. Causes of Melting.- 4.5.2.2. Melting of Veined Lithosphere.- 4.5.3. Melt Segregation, Contamination, and Ascent.- 4.5.4. Low-Pressure and Post-Emplacement Crystallization.- 4.5.5. Summary.- 4.6. Petrogenesis of the Kimberlite Clan.- 4.6.1. Nature of the Source and Depth of Melting.- 4.6.2. The Megacryst Problem.- 4.6.3. Contamination of Kimberlites in the Mantle.- 4.6.4. Post-Emplacement Crystallization.- 4.6.5. Summary.- 4.7. Relationships of Orangeites to Kimberlites, Lamproites, and Other Ultrapotassic Magmas.- 4.7.1. Kimberlites.- 4.7.2. Lamproites.- 4.7.3. Other Ultrapotassic Magmas.- 4.7.4. Summary.- 4.8. Primary Diamond Deposits.- Postscript.- References.