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Alkaline igneous rocks
Lithos, 24 (1989) 81-82
81
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Book Review Alkaline Igneous Rocks, edited by J.G. Fitton and B.G.J. Upton. Geological Society Special Publication No. 30. Blackwell Scientific Publications, London, 1987, x v i + 5 6 8 pp. Price: U K £65.00 (hardback). "In the present state of petrographical nomenclature the student will be saved much trouble if he will fix his attention on the rocks themselves instead of on the names which have been used in different senses by different writers." (J.J. Harris Teall, 1888. ) Less than 1% of all igneous rocks are alkaline; but these alkaline rocks account for more than 50% of all igneous rock names. This reflects their wide range of compositions and exotic mineralogy. In the last century, when geology remained very largely a descriptive subject, geologists generated a plethora of names for different igneous rock types. The practice was to name a "new" rock after a place where it occurred - - the type locality. Jacuparungite and tinguzite (from Brazil), uncompahrite (Zaire), kajanite (Borneo), gaussbergite (Antarctica), cancarixite (Spain), madupite (U.S.A.), cocite (Vietnam) and kakortokite (Greenland) are some of the wonderful names concocted for igneous rocks of the alkaline type. Furthermore, in the old days essentially similar rocks from d~fferent localities were given diffi~rent names: this led to great confusion. Although there has been a real effort in recent years to simplify and standardise the nomenclature and classification (see P.A. Sabine's recent review in Episodes, Vol. 12, 1989: "Setting standards in Petrology"), there remains much to be done. That much is clear from this book too: different authors have different opinions, viz. the classification of the same rocks, because their own definitions of these rocks differ. For example, S.C. Bergman writes "'Lamproites should not be included in the Lamprophyre clan'" (p. 170 ) whilst 21 pages later N.M.S. Rock states "'Lamproites are the fourth branch of the Lamprophyre clan".
If you are not primarily interested in alkaline-igneous rocks, but wish to know more about them in order to get a better understanding of, for example,
large-scale Earth science processes (i.e. tectonics), then you usually have a difficult task ahead of you, because the literature on these rocks is widely scattered about. This book will go a long way towards helping you. It is a collection of 25 papers which were presented at a symposium held in 1984, ten years after the publication of The Alkaline Rocks edited by H. Sorensen. The understanding of these rocks has vastly improved; and this book provides the evidence thereof. However, inevitably the coherence of the subject is somewhat lost, as is the way with edited books. Alkaline igneous rocks occur in every major tectonic environment. They may host a number of important economic mineral deposits (including diamonds) and lately have been linked with certain Archaean gold deposits. They play a major role in deciphering the chemical geodynamics of our planet: asthenosphere-lithosphere interaction and differentiation, melting and crystallization processes, degassing, recycling, craton formation, etc. About one-third of the book deals with principles of alkaline magma genesis and evolution: mantle metasomatism (D.K. Bailey) mantle xenoliths and isotope fingerprinting (M. Menzies) experimental studies (A.D. Edgar), the origin of nephelinites, carbonatites, kimberlites, lamproites and lamprophyres (M.J. Le Bas, J.D. Twyman and J. Grittins, J.B. Dawson, S.C. Bergman and N.M.S. Rock, respectively; several of these rock clans were not covered in Sorensen's book). These are very thorough and comprehensive overviews. The seventeen papers of the second part (about two-thirds) of the book provide reviews of classic alkaline provinces: Ocean Islands (Hawaii; the south and central Atlantic), the East African rift (Kenya and Malawi ), West Africa (the Cameroon line; the Niger-Nigerian complexes; Mali), southern and northeastern U.S.A. (Tres Picos, Texas; the Monteregian HillsWhite Mountains), the Kola Peninsula, southern and eastern Greenland (including the Garder province, and the Ilimaussaq intrusion), the Massif Central, and the recently (1977) discovered Velasio province in Bolivia. This part of the book provides a wealth of chemical data, field observations, petrography, mineralogy and general petrogenetic insights. The entire volume is produced in the meticulous
82
BOOKREVIEW
way that one has become accustomed to expect from the Special Publications o f Geological Society of L o n d o n . There are h u n d r e d s o f diagrams a n d beautifully draughted maps; a n d a wealth o f geochemical data in tables. The editing has been masterly. The book has a good subject index ( i n c l u d i n g references to the figures a n d tables), a n d a c o m p r e h e n s i v e overview o f the entire book by the two Editors. This book should n o d o u b t be acquired by all alkaline igneous petrologists, it will surely also become a s t a n d a r d reference text for petrology students. It could also be useful to those not specialized in alkaline rocks: for example, most papers have explicit a n d implicit i m p l i c a t i o n s for tectonophysics. U n f o r t u n a t e l y for the non-specialists the messages are often cryptic, a n d both specialist a n d non-specialist would do well to reread parts of J.J. Harris Teall's Introduction to British Petrography written in 1888 ( q u o t e d b e l o w ) , a n d p o n d e r as to whether we are getting our scientific messages clearly across to each other:
any clearness of view. The more rocks are studied the less they seem to me to adapt themselves to any classification at all comparable in definiteness with the classifications of organic bodies and mineral substances. Rock-masses often vary so much in composition and structure that any scheme of classification based on work done in the laboratory is unsuitable for the expression of broad geological facts. It is absolutely impossible to map the different varieties recognized by modern petrographers. The conclusion at which I have arrived is that the necessity for giving names to rocks arises rather from work done in the field than from work done in the laboratory. Rock-specimens are mineral-aggregatesand may be described as such. Rockmasses are integral portions of the earth's crust and possess a certain amount of individuality in virtue of their mode of occurrence. "It will be understood from these remarks that I attach very little importance to any of the rock-names used in the present work. My object has been to describe the structure and composition of the rocks; not to introduce new names or to add to the confusion already existing by giving new definitions of old names." Despite this reservation, or perhaps because of it,
Alkaline Igneous Rocks should be in every geoscience library.
"'As regards the classification of rocks I am sorry to say that increasing knowledge has not tended to bring about
MAARTEN J. DE WIT (Rondebosch)
81
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Book Review Alkaline Igneous Rocks, edited by J.G. Fitton and B.G.J. Upton. Geological Society Special Publication No. 30. Blackwell Scientific Publications, London, 1987, x v i + 5 6 8 pp. Price: U K £65.00 (hardback). "In the present state of petrographical nomenclature the student will be saved much trouble if he will fix his attention on the rocks themselves instead of on the names which have been used in different senses by different writers." (J.J. Harris Teall, 1888. ) Less than 1% of all igneous rocks are alkaline; but these alkaline rocks account for more than 50% of all igneous rock names. This reflects their wide range of compositions and exotic mineralogy. In the last century, when geology remained very largely a descriptive subject, geologists generated a plethora of names for different igneous rock types. The practice was to name a "new" rock after a place where it occurred - - the type locality. Jacuparungite and tinguzite (from Brazil), uncompahrite (Zaire), kajanite (Borneo), gaussbergite (Antarctica), cancarixite (Spain), madupite (U.S.A.), cocite (Vietnam) and kakortokite (Greenland) are some of the wonderful names concocted for igneous rocks of the alkaline type. Furthermore, in the old days essentially similar rocks from d~fferent localities were given diffi~rent names: this led to great confusion. Although there has been a real effort in recent years to simplify and standardise the nomenclature and classification (see P.A. Sabine's recent review in Episodes, Vol. 12, 1989: "Setting standards in Petrology"), there remains much to be done. That much is clear from this book too: different authors have different opinions, viz. the classification of the same rocks, because their own definitions of these rocks differ. For example, S.C. Bergman writes "'Lamproites should not be included in the Lamprophyre clan'" (p. 170 ) whilst 21 pages later N.M.S. Rock states "'Lamproites are the fourth branch of the Lamprophyre clan".
If you are not primarily interested in alkaline-igneous rocks, but wish to know more about them in order to get a better understanding of, for example,
large-scale Earth science processes (i.e. tectonics), then you usually have a difficult task ahead of you, because the literature on these rocks is widely scattered about. This book will go a long way towards helping you. It is a collection of 25 papers which were presented at a symposium held in 1984, ten years after the publication of The Alkaline Rocks edited by H. Sorensen. The understanding of these rocks has vastly improved; and this book provides the evidence thereof. However, inevitably the coherence of the subject is somewhat lost, as is the way with edited books. Alkaline igneous rocks occur in every major tectonic environment. They may host a number of important economic mineral deposits (including diamonds) and lately have been linked with certain Archaean gold deposits. They play a major role in deciphering the chemical geodynamics of our planet: asthenosphere-lithosphere interaction and differentiation, melting and crystallization processes, degassing, recycling, craton formation, etc. About one-third of the book deals with principles of alkaline magma genesis and evolution: mantle metasomatism (D.K. Bailey) mantle xenoliths and isotope fingerprinting (M. Menzies) experimental studies (A.D. Edgar), the origin of nephelinites, carbonatites, kimberlites, lamproites and lamprophyres (M.J. Le Bas, J.D. Twyman and J. Grittins, J.B. Dawson, S.C. Bergman and N.M.S. Rock, respectively; several of these rock clans were not covered in Sorensen's book). These are very thorough and comprehensive overviews. The seventeen papers of the second part (about two-thirds) of the book provide reviews of classic alkaline provinces: Ocean Islands (Hawaii; the south and central Atlantic), the East African rift (Kenya and Malawi ), West Africa (the Cameroon line; the Niger-Nigerian complexes; Mali), southern and northeastern U.S.A. (Tres Picos, Texas; the Monteregian HillsWhite Mountains), the Kola Peninsula, southern and eastern Greenland (including the Garder province, and the Ilimaussaq intrusion), the Massif Central, and the recently (1977) discovered Velasio province in Bolivia. This part of the book provides a wealth of chemical data, field observations, petrography, mineralogy and general petrogenetic insights. The entire volume is produced in the meticulous
82
BOOKREVIEW
way that one has become accustomed to expect from the Special Publications o f Geological Society of L o n d o n . There are h u n d r e d s o f diagrams a n d beautifully draughted maps; a n d a wealth o f geochemical data in tables. The editing has been masterly. The book has a good subject index ( i n c l u d i n g references to the figures a n d tables), a n d a c o m p r e h e n s i v e overview o f the entire book by the two Editors. This book should n o d o u b t be acquired by all alkaline igneous petrologists, it will surely also become a s t a n d a r d reference text for petrology students. It could also be useful to those not specialized in alkaline rocks: for example, most papers have explicit a n d implicit i m p l i c a t i o n s for tectonophysics. U n f o r t u n a t e l y for the non-specialists the messages are often cryptic, a n d both specialist a n d non-specialist would do well to reread parts of J.J. Harris Teall's Introduction to British Petrography written in 1888 ( q u o t e d b e l o w ) , a n d p o n d e r as to whether we are getting our scientific messages clearly across to each other:
any clearness of view. The more rocks are studied the less they seem to me to adapt themselves to any classification at all comparable in definiteness with the classifications of organic bodies and mineral substances. Rock-masses often vary so much in composition and structure that any scheme of classification based on work done in the laboratory is unsuitable for the expression of broad geological facts. It is absolutely impossible to map the different varieties recognized by modern petrographers. The conclusion at which I have arrived is that the necessity for giving names to rocks arises rather from work done in the field than from work done in the laboratory. Rock-specimens are mineral-aggregatesand may be described as such. Rockmasses are integral portions of the earth's crust and possess a certain amount of individuality in virtue of their mode of occurrence. "It will be understood from these remarks that I attach very little importance to any of the rock-names used in the present work. My object has been to describe the structure and composition of the rocks; not to introduce new names or to add to the confusion already existing by giving new definitions of old names." Despite this reservation, or perhaps because of it,
Alkaline Igneous Rocks should be in every geoscience library.
"'As regards the classification of rocks I am sorry to say that increasing knowledge has not tended to bring about
MAARTEN J. DE WIT (Rondebosch)