Many interesting and perplexing questions arise in connection with the highly potassic volcanic associa tion dominated by mafic and ultramafic rocks contain ing leucite. Its occurrence is very restricted as compar ed with the olivine-basalt trachyte kindred, but it is distributed at widely scattered points on all the conti nents, and its chemical and petrographic individuality is both remarkable and constant. A considerable litera ture is available related to the mineralogy, petrology, geochemistry, phase chemistry, distribution, and origin of this interesting suite of rocks. It seemed that there was a genuine need for a review-synthesis of all these data, which would be intelligible to a wide spectrum of advanced students and professionals in the earth sciences. The monograph may be divided into two parts. The first part consists of six chapters in which the mineralogical and chemical peculiarities of leucite bearing rocks and their nomenclature, petrology, min eralogy, distribution, and physical and chemical condi tions of formation are discussed. Phase equilibria stud ies on many leucite-bearing ternary, pseudoternary, quaternary, and pseudoquaternary joins and systems, studied by different investigators at variable tempera tures in air, are described in the second part in Chap ters 7 to 12. Survival of leucite and formation of pseu doleucite is discussed in Chapter 13. Leucite-bearing synthetic and natural rock systems studied at different temperatures under variable pressures in presence or absence of water, are summarized in Chapters 14 and 15.

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1 Introduction.- 1.1 Basalt and its Relation to Leucite-Bearing Mafic and Ultramafic Rocks.- 1.2 Mineralogical Composition and Other Geochemical Peculiarities of Leucite-Bearing Rocks.- 1.3 A Brief Summary of the Hypotheses of Origin of Leucite-Bearing Rocks.- 1.4 Objective of This Study.- 2 Nomenclature and Petrography of Leucite-Bearing Rocks.- 2.1 Nomenclature.- 2.1.1 Italite.- 2.1.2 Leucitite.- 2.1.3 Olivine Leucitite.- 2.1.4 Melilite Leucitite.- 2.1.5 Katungite.- 2.1.6 Leucite Tephrite.- 2.1.7 Leucite Basanite.- 2.1.8 Melilite-Nepheline Leucitite.- 2.1.9 Jumillite.- 2.1.10 Verite.- 2.1.11 Wolgidite.- 2.1.12 Fitzroyite.- 2.1.13 Mamilite.- 2.1.14 Cedricite.- 2.1.15 Wyomingite.- 2.1.16 Orendite.- 2.1.17 Madupite.- 2.1.18 Potassium-Rich Ankaratrite.- 2.1.19 Mafurite.- 2.1.20 Shonkinite.- 2.1.21 Absarokite, Banakite, and Shoshonite.- 3 Mineralogical Composition of Leucite-Bearing Rocks.- 3.1 Leucite.- 3.2 Nepheline.- 3.3 Kalsilite.- 3.4 Kaliophilite.- 3.5 Sanidine.- 3.6 Plagioclase.- 3.7 Pyroxene.- 3.8 Olivine.- 3.9 Mica.- 3.10 Potash Richterite.- 3.11 Melilite.- 3.12 Analcite.- 3.13 Accessory Minerals.- 3.13.1 Sodalite.- 3.13.2 Apatite.- 3.13.3 Priderite.- 3.13.4 Wadeite.- 3.13.5 Other Minerals.- 4 Minor and Trace Element Geochemistry, Initial 87Sr/86Sr Ratios and Oxygen Isotopic Ratios of Leucite-Bearing Rocks.- 4.1 Trace Element Geochemistry.- 4.2 The Initial 87Sr/S6Sr Ratios of Highly Potassic Lavas and Other Rock Types.- 4.3 ? 18O-contents of Leucite-Bearing Rocks.- 5 Distribution of Leucite-Bearing Rocks.- 5.1 Volcanic Fields, East and Southeast of Ruwenzori, Uganda.- 5.2 Birunga Volcanic Province.- 5.3 Leucite-Bearing Rocks of West Kimberley, Australia.- 5.4 Leucite-Bearing Rocks of New South Wales, Australia.- 5.5 Leucite-Bearing Rocks of Indonesia.- 5.6Volcanic Fields of Highwood Mountains, Montana (USA).- 5.7 Potassic Rocks of Navajo-Hopi Province (USA).- 5.8 Leucite-Bearing Rocks of Leucite Hills, Wyoming (USA).- 5.9 Leucite-Bearing Rocks of Italy.- 5.9.1 Monti Vulsini.- 5.9.2 Vico Volcanic Complex.- 5.9.3 Monti Sabatini.- 5.9.4 Colli Albani (Alban Hills).- 5.9.5 Phlegrean Fields.- 5.9.6 Somma-Vesuvius.- 5.9.7 Roccamonfina.- 5.9.8 Volcanic Activity in the Eolian Arc Region.- 5.10 Volcanic Provinces of Spain.- 5.11 Leucite-Bearing Lamprophyres of Eastern India.- 5.12 Leucite-Bearing Rocks of the Laacher See and Other Areas of West Germany.- 5.13 Leucite-Bearing Rocks of the Tristan da Cunha Islands.- 5.14 Leucite-Bearing Rocks of Manchuria, China.- 5.14.1 Wu-ta-lien-chih.- 5.14.2 Erh-Ko.- 5.14.3 Chi-hsing Shan.- 5.15 Leucite Bearing Rocks of Utsuryo Island (Ullung-do), Korea.- 6 Conditions of Formation of Leucite-Bearing Mafic and Ultramafic Rocks.- 6.1 Chemical Conditions.- 6.2 Silica Activity in Leucite-Bearing Rocks.- 6.3 Physical Conditions.- 7 Leucite-Bearing Ternary Joins and Systems.- 7.1 The System Nepheline-KalsiliteSiO2.- 7.2 The System Diopside-Leucite-SiO2.- 7.3 The System Anorthite-Leucite-SiO2.- 7.4 The System Diopside-Sanidine-Albite.- 7.5 The System Diopside-Nepheline-Sanidine.- 7.6 The System Nepheline-Leucite-Anorthite.- 8 Leucite-Albite Incompatibility.- 8.1 The Join Leucite-Albite.- 8.1.1 Composition of Alkali Feldspars in the Leucite-Albite-Join.- 8.2 The Join Leucite-Albite-Anorthite.- 8.2.1 Compositions of Ternary Feldspars in the Leucite-Albite-Anorthite Join.- 8.3 Petrological Implications.- 9 Leucite- and Feldspar-Bearing Quaternary Joins and Systems.- 9.1 The System Forsterite-Diopside-Leucite-Anorthite.- 9.1.1 The Join Forsterite-Diopside-Anorthite.- 9.1.2 The Join Forsterite-Anorthite-Leucite.- 9.1.3 The Join Diopside-Leucite-Anorthite.- 9.1.4 Paragenesis.- 9.2 The System Diopside-Leucite-Anorthite-SiO2.- 10 The System Forsterite-Diopside-Akermanite-Leucite.- 10.1 The Join Diopside-Akermanite-Leucite.- 10.2 The Join Forsterite-Diopside-Leucite.- 10.3 The Join Forsterite-Akermanite-Leucite.- 10.4 The Join Forstente-Diopside-Akermanite.- 10.5 The Join Diopside-Akermanite-Leucite with 3% Forsterite.- 10.6 Paragenesis.- 10.6.1 Melilite Leucitite.- 10.6.2 Olivine Leucitite.- 10.6.3 Katungite.- 10.6.4 Olivine Melilitite.- 10.7 Course of Crystallization of Liquid in the System Forsterite-Diopside-Akermanite-Leucite.- 11 The System Diopside-Nepheline-Akermanite-Leucite.- 11.1 The Join Diopside-Nepheline-Akermanite.- 11.2 The Join Diopside-Nepheline-Leucite.- 11.3 The Join Nepheline-Akermanite-Leucite.- 11.4 The Join (Di38AK3Ne59)100?x-Lcx.- 11.5 Course of Crystallization of Liquid Within the System Diopside-Nepheline-Akermanite-Leucite.- 11.6 Paragenesis.- 11.7 Melilite-Plagioclase Incompatibility Problem in Leucite-Bearing Lavas.- 12 Solubility of KFe3+Si2O6 in Leucite.- 13 Survival of Leucite.- 13.1 Alteration of Leucite to Analcite.- 13.2 Pseudoleucite and its Genesis.- 14 Study of Leucite-Bearing Systems Under Different Pressures and the $${{P}{{{{H}{2}}O}}} - T$$ Stabilities of Phlogopite, Potassium-Rich Richtente, and Kaersutite.- 14.1 Leucite-Bearing System Under Different Pressures.- 14.2 The System KAlSiO4-Mg2SiO4 SiO2-H2O.- 14.3 Phlogopite Stability.- 14.4 Potassic Richterite and Kaersutite as Possible Sources of Potassium in the Upper Mantle.- 14.4.1 Stability of Potassic Richterite.- 14.4.2 Stability of Kaersutite.- 15 Study of Leucite-Bearing Rocks in Air and Under Various PT Conditions.- 15.1 One-Atmospheric Studies on Leucite-BearingRocks.- 15.2 Studies of Synthetic and Natural Leucite-Bearing Rock Systems Under Different P-T Conditions.- 15.2.1 Experiments Under Low Water Pressures (up to 10 kb).- 15.2.2 Thermodynamic Considerations for the Conversion of a Katungite to a Phlogopite Pyroxenite at High Pressures.- 15.2.3 Study of a Synthetic Biotite Mafurite Glass at High Pressures.- 15.2.4 Study of a Synthetic Leucite Basanite and a Melilite-Nepheline Leucitite Between 10 and 25 kb.- 16 Leucite-Bearing Rocks and Their Relation to Kimberlites.- 16.1 Comparison of the Chemistry of Kimberlites and Leucite-Bearing Rocks.- 16.2 Possible Genetic Connection Between Potassic Rocks and Kimberlites.- 16.3 Experimental Study of a Synthetic Katungite Under $${{P}{{{{H}{2}}O}}} - T$$ and $${{P}{{C{{O}{2}}}}}$$ in Relation to Kimberlite Genesis.- 16.4 Experimental Study of Two Picrites with Reference to the Genesis of Kimberlite and Potassium-Rich Magma.- 17 Structural and Tectonic Control of Alkali Magmatism with Special Reference to Leucite-Bear…