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This text describes and provides ready access to the literature for all known occurrences of alkaline igneous rocks and carbonatites of Africa. Over 1000 occurrences are described from 40 countries. The descriptions include geographical co-ordinates and information of structure, general geology, rock types, petrography, mineralogy, ages, economic aspects and principal references. There are 348 geological and distribution maps and a locality index.
Phoscorites are dark, often very handsome, sometimes economically valuable, magnetite-apatite-silicate rocks, almost always associated with carbonatite. They are key to understanding the longstanding question of how carbonate and carbonate-bearing magmas rise to the crust and the Earths surface. Despite this, they have been given little attention; a search on geological literature databases will produce thousands of references to carbonatite (up to 4125 on Georef) but not more than thirty references to phoscorite. This book goes some way to redress this balance. Over recent years many European and North American scientists have studied Kola rocks in collaboration with Russian colleagues. The idea for this book came from one such project funded by the European organisation, INTAS (Grant No 97-0722). The Kola Peninsula is one of the outstanding areas in the World for the concentration and economic importance of alkaline rocks. However, Russian work on the Kola complexes is still relatively unknown and a particular aim of this book, as well as presenting current research, is to make this knowledge accessible to English language readers. A large exploration programme on Kola alkaline rocks was active from 1950 to 1990 and involved teams of geologists who studied many kilometres of drill core and carried out detailed mineralogical and petrological studies.
The alkaline igneous rocks and carbonatites are compositionally and mineralogically the most diverse of all igneous rocks and, apart from their scientific interest, are of major, and growing, economic importance. They are important repositories of certain metals and commodities, indeed the only significant sources of some of them, and include Nb, the rare earths, Cu, V, diamond, phosphate, vermiculite, bauxite, raw materials for the manufacture of ceramics, and potentially Th and U. The economic potential of these rocks is now widely appreciated, particularly since the commencement of the mining of the Palabora carbonatite for copper and a host of valuable by-products. Similarly, the crucial economic dominance of rare earth production from carbonatite-related occurrences in China, has stimulated the world-wide hunt for similar deposits. This volume describes and provides ready access to the literature for all known occurrences of alkaline igneous rocks and carbonatites of Antarctica, Asia and Europe excluding the former USSR, Australasia and oceanic islands. More than 1,200 occurrences from 59 countries are outlined together with those of 57 oceanic islands and island groups. The descriptions include geographical coordinates and information on general geology, rock types, petrography, mineralogy, age and economic aspects with the principal references cited. There are 429 geological and distribution maps and a locality index. As has been demonstrated by the three earlier volumes, the present book is likely to be of considerable interest to mineral exploration companies, as there are no comprehensive published reviews of the economic aspects of the alkaline rocks. It will also interest research scientists in the fields of igneous petrology and volcanology, and geologists concerned with the regional distribution of igneous rocks and their geodynamic relationships.
During the last few years, carbonatites have received a considerable amount of attention. Some of this interest was no doubt kindled by the importance of volatiles in the Earth's mantle, particularly CO , by the fact that carbonatites 2 can be used to monitor the chemical evolution of the sub-continental upper mantle, and by the fact that carbonatites may be effective metasomatizing agents at both mantle and crustal levels. The interest in Oldoinyo Lengai has extended over at least 100 years, but it was not until the eruptions of 1960, when the unique carbonatitic nature of its lavas was recognized, that the volcano took on special significance in volcanology and igneous petrology. The recognition of carbonatitic flows coin cided with the first successful laboratory experiments carried out on carbonatitic melts. Since then, Oldoinyo Lengai has formed a cornerstone in all carbonatite discussions. It is probably true to say that the findings from Oldoinyo Lengai have dominated our ideas about carbonatites, in spite of the fact that the alkali rich, natrocarbonatitic lavas of Oldoinyo Lengai are markedly different from other carbonatites.
This vivid introduction to economic geology not only describes the most important deposit types, but also the processes involved in their formation. Magmatic, hydrothermal and sedimentary processes as well as weathering and alteration are explained in the framework of plate tectonics and the history of the Earth. The chapter about fossil fuels includes unconventional deposits and the much-debated fracking. Other topics covered are exploration, mining and economic aspects like commodity prices.
Geologic setting, production, reserves, outlook for future supply, and relation of fluorspar deposits to rift structures and carbonatites.
All the solid fuels fossil energy and mineral commodities we use come out of the Earth. Modern society is increasingly dependent on mineral and fossil energy sources. They differ in availability, cost of production, and geographical distribution. Even if solid fuels, fossil energy resources and mineral commodities are non-renewable, the extracted metals can to a large extent be recycled and used again and again. Although the stock of these secondary resources and their use increases, the world still needs and will continue to need primary mineral resources for the foreseeable future. Growing demands have begun to restrict availability of these resources. The Earth is not running out of critical mineral resources – at least for the near future – but the ability to explore and extract these resources is being restricted in many regions by competing land use, as well as political and environmental issues. Extraction of natural resources requires a clear focus on sustainable development, involving economic, environmental and socio-cultural aspects. Although we do not know what the most important resources will be in 100 years from now, we can be quite certain that society will still need energy and a wide range of raw materials. These resources will include oil and gas, coal, uranium, thorium, geothermal, metallic minerals, industrial and specialty minerals, including cement, raw materials, rare-earth elements. A global approach for assessing the magnitude and future availability of these resources is called for – an approach that, with appropriate international collaboration, was started within the triennium of the International Year of Planet Earth. Some global mineral resource assessments, involving inter-governmental collaboration, have already been initiated. The International Year of Planet Earth helped to focus attention on how the geosciences can generate prosperity locally and globally, as well as sustainability issues in both developed and developing countries.
In 1978, Fred Hoyle proposed that interstellar comets carrying several viruses landed on Earth as part of the panspermia hypotheses. With respect to life, the origin of homochirality on Earth has been the greatest mystery because life cannot exist without molecular asymmetry. Many scientists have proposed several possible hypotheses to answer this long-standing L-D question. Previously, Martin Gardner raised the question about mirror symmetry and broken mirror symmetry in terms of the homochirality question in his monographs (1964 and 1990). Possible scenarios for the L-D issue can be categorized into (i) Earth and exoterrestrial origins, (ii) by-chance and necessity mechanisms, and (iii) mirror-symmetrical and non-mirror-symmetrical forces as physical and chemical origins. These scenarios should involve further great amplification mechanisms, enabling a pure L- or D-world.