Lamprophyres Lamproites And Related Rocks

Paleoproterozoic to Cenozoic lamprophyres, lamproites and related rock types (e.g., orangeites, kimberlites) are volatile-rich mafic magmatic rocks with a unique potential for the investigation of processes affecting mantle reservoirs. They originated from primary mantle-derived melts that intruded both cratons and off-craton regions, which were parts of former supercontinents – Columbia, Rodinia and Gondwana–Pangea. Well-known for hosting economic minerals and elements such as diamonds, base metals, gold and platinum-group elements, they are also significant for our understanding of deep-mantle processes, such as mantle metasomatism and mantle plume–lithosphere interactions, as well as large-scale geodynamic processes, such as subduction-related tectonics, and supercontinent amalgamation and break-up. This book aims to provide a timely overview of the state-of-the-art and recent advances as achieved by various research groups around the world. Mineralogical, geochemical, geochronological and isotope analyses are used to decipher the complex petrogenesis and metallogenesis of these extraordinary rocks, and unravel a complete history of tectonic events related to individual supercontinent cycles.

Following their recognition by GUmbel (1874), lamprophyres were treated for an entire century as little more than obscure curiosities. Although this situation has changed recently, with a flowering of publications and active workers, lamprophyres remain almost the only group of igneous rocks which have not yet received attention in a dedicated monograph. In five exploratory reviews (1977-1987), the writer aimed to set out what was known about these rocks. The lUGS Subcommission on igneous rock systematics had meanwhile presented its nomenclatural framework (Streckeisen 1979). All this has now been overtaken by a recent explosion of interest, epitomized not least by lamprophyres' greater prominence in the 4th International Kimberlite Conference Proceedings. More data have become available since 1985 than over the entire previous century, and it is obviously impossible for such an extraordinary outpouring to be fully reviewed in this first, preliminary book. At the risk of dissatisfying some readers, therefore, this book concentrates on factual matters, and on a broad overview rather than minutiae. Because not even a world map of known lamprophyres was previously available, almost half the book is deliberately taken up by the first global lamprophyre compilation, and its commensurately extensive Bibliography. Such a compendium of largely objective information is believed to be of more immediate interest and lasting value than a premature pottage of petrogenetic polemic. Chapters 1-7 bring previous studies up to date, and concentrate on factual information.

This remarkable volume presents the first revision to the classification system of diamond-bearing rocks in over eighty years. Presenting the latest mineralogical data, this book offers a detailed description of the mineralogy and geochemistry of kimberlites, orangeites, and lamproites. Several hundred new analyses of minerals in orangeites are included. This volume follows the publication of Kimberlites, by R.H. Mitchell, and Petrology of Lamproites, by R.H. Mitchell and S.C. Bergman, concluding the trilogy.

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.

In recent years, there has been increasing interest from geoscientists in potassic ig neous rocks. Academic geoscientists have been interested in their petrogenesis and their potential value in defining the tectonic setting of the terranes into which they were intruded, and exploration geoscientists have become increasingly interested in the association of these rocks with major epithermal gold and porphyry gold-copper deposits. Despite this current interest, there is no comprehensive textbook that deals with these aspects of potassic igneous rocks. This book redresses this situation by elucidating the characteristic features of potassic (high-K) igneous rocks, erecting a hierarchical scheme that allows interpre tation of their tectonic setting using whole-rock geochemistry, and investigating their associations with a variety of gold and copper-gold deposits, worldwide. About two thirds of the book is based on a PhD thesis by Dr Daniel Muller which was produced at the Key Centre for Strategic Mineral Deposits within the Department of Geology and Geophysics at The University of Western Australia under the supervision of Professor David Groves, the late Dr Nick Rock, Professor Eugen Stumpf!, Dr Wayne Taylor, and Dr Brendon Griffin. The remainder of the book has been compiled from the literature using the collective experience of the two authors. The book is dedi cated to the memory of Dr Rock who initiated the research project but died before its completion.

This study documents alkaline rock occurrences in British Columbia; describes their petrography, geochemistry, economic geology, and field relationships; and determines the timing and tectonic controls of emplacement, providing a basis for future, detailed studies. Work was begun in 1984 and included field mapping during the summers of 1984, 1985, and 1986. All the carbonatite-syenite localities (with the exception of the Wicheeda Lake and Mount Bisson showings) and a large number of the diatreme breccias were mapped and sampled.

Decades of field and microscope studies, and more recent quantitative geochemical analyses have resulted in a vast, and sometimes overwhelming, array of nomenclature and terminology associated with igneous rocks. This book presents a complete classification of igneous rocks based on all the recommendations of the International Union of Geological Sciences (IUGS) Subcommission on the Systematics of Igneous Rocks. The glossary of igneous terms has been fully updated since the first edition and now includes 1637 entries, of which 316 are recommended by the Subcommission. Incorporating a comprehensive bibliography of source references for all the terms included in the glossary, this book is an indispensable reference guide for all geologists studying igneous rocks, either in the field or the laboratory. It presents a standardised and widely accepted naming scheme that will allow geologists to interpret terminology in the primary literature and provide formal names for rock samples based on petrographic analyses. It is also supported by a website with downloadable code for chemical classifications.

Featuring over 250 contributions from more than 100 earth scientists from 18 countries, The Encyclopedia of Igneous and Metamorphic Petrology deals with the nature and genesis of igneous rocks that have crystallized from molten magma, and of metamorphic rocks that are the products of re-crystallization associated with increases in temperature and pressure, mainly at considerable depths in the Earth's crust. Entries range from alkaline rocks to zeolite facies - providing information on the mineralogical, chemical and textural characters of rock types, the development of concepts and the present state of knowledge across the spectrum of igneous and metamorphic petrology, together with extensive lists of both commonly used and little used terms and bibliographies.