This is a book about the petrology of kimberlites. It is not about upper mantle xenoliths, diamonds, or prospecting for kimberlites. The object of the book is to provide a comprehensive survey and critique of the advances which have been made in kimberlite studies over the last twenty-five years. Kimberlites are rare rock types; however, their relative obscurity is overriden by their economic and petrological importance to a degree which is not shared with the commoner varieties of igneous rocks. Kimberlites are consequently of interest to a diverse group of earth scientists, ranging from isotope g ochemists concerned with the evolution of the mantle, to volcanologists pondering the origins of diatremes, to exploration geologists seeking new occurrences of the diamondiferous varieties. A common factor essential to all of these activities is a thorough understanding of the characteristics of kimberlites. For the petrologist, kimberlites are exciting and challenging objects for study. Their petrographic diversity, complex mineralogy and geochemistry, and unusual style of intrusion provide endless opportunities for stimulating hypothesis and conjecture concerning their origin and evolution. Kimberlites are a part of a wide spectrum of continental intra-cratonic magmatism. Only by understanding all of the parts of this activity in detail may we make progress in our understanding of the whole.

In this book, the first dedicated entirely to the petrology of lamproites and their relationships to other potassium-rich rocks, the objective of the authors is to provide a comprehensive critical review of the occurrence, mineralogy, geochemistry, and petrogenesis of the clan. Although lamproites represent one of the rarest of all rock types, they are both economically and scientifically important and we believe the time is ripe for a review of the advances made in their petrology over the past two decades. Many of these advances stem from the recognition of diamond-bearing lamproites in Western Australia and the reclassification of several anomalous diamond-bearing kim berlites as lamproites. Consequently lamproites, previously of interest only to a small number of mineralogists specializing in exotica outside the mainstream of igneous petrol ogy, have become prime targets for diamond exploration on a worldwide basis. Contemporaneously with these developments, petrologists realized that lamproites possess isotopic signatures complementary to those of midoceanic ridge basalts, alkali basalts, kimberlites, and other mantle-derived melts. These isotopic studies provided new insights into the long-term development of the mantle by suggesting that the source regions of lamproites were metasomatically enriched in light rare earth and other incompatible elements up to 1-2 Ga prior to the melting events leading to generation of the magma.

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 Gar

This is a book about the petrology of kimberlites. It is not about upper mantle xenoliths, diamonds, or prospecting for kimberlites. The object of the book is to provide a comprehensive survey and critique of the advances which have been made in kimberlite studies over the last twenty-five years. Kimberlites are rare rock types; however, their relative obscurity is overriden by their economic and petrological importance to a degree which is not shared with the commoner varieties of igneous rocks. Kimberlites are consequently of interest to a diverse group of earth scientists, ranging from isotope g ochemists concerned with the evolution of the mantle, to volcanologists pondering the origins of diatremes, to exploration geologists seeking new occurrences of the diamondiferous varieties. A common factor essential to all of these activities is a thorough understanding of the characteristics of kimberlites. For the petrologist, kimberlites are exciting and challenging objects for study. Their petrographic diversity, complex mineralogy and geochemistry, and unusual style of intrusion provide endless opportunities for stimulating hypothesis and conjecture concerning their origin and evolution. Kimberlites are a part of a wide spectrum of continental intra-cratonic magmatism. Only by understanding all of the parts of this activity in detail may we make progress in our understanding of the whole.

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.

In this book, the first dedicated entirely to the petrology of lamproites and their relationships to other potassium-rich rocks, the objective of the authors is to provide a comprehensive critical review of the occurrence, mineralogy, geochemistry, and petrogenesis of the clan. Although lamproites represent one of the rarest of all rock types, they are both economically and scientifically important and we believe the time is ripe for a review of the advances made in their petrology over the past two decades. Many of these advances stem from the recognition of diamond-bearing lamproites in Western Australia and the reclassification of several anomalous diamond-bearing kim berlites as lamproites. Consequently lamproites, previously of interest only to a small number of mineralogists specializing in exotica outside the mainstream of igneous petrol ogy, have become prime targets for diamond exploration on a worldwide basis. Contemporaneously with these developments, petrologists realized that lamproites possess isotopic signatures complementary to those of midoceanic ridge basalts, alkali basalts, kimberlites, and other mantle-derived melts. These isotopic studies provided new insights into the long-term development of the mantle by suggesting that the source regions of lamproites were metasomatically enriched in light rare earth and other incompatible elements up to 1-2 Ga prior to the melting events leading to generation of the magma.