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Geochemistry and mineral formation in the earth surface
2552
Book Reviews
Ma& Dyke Swarms, H. C. Halls and W. F. Fahrig, editors. Geological Association of Canada, Special Paper 34, 1987, 5Olp., with map folder, $65.00 (GAC members), $79.00 (non-members) (plus $3.00 postage and handling) (ISBN O-9192 16-33-I). IN THE SUMMER of 1985, Halls convened a conference on Mafic Dyke Swarms at the Erindale Campus of the University of Toronto. This volume is one result. The best place to start reading is the last chapter, where HALLSsimultaneously summarizes the proceedings and emphasizes problems more-or-less solved and problems still unresolved. One can then better select a thread to follow. Intrusion mechanics and magma transfer are concerns of the first six papers. POLLARDstresses the value of fracture mechanics in understanding the general propagation mechanism, and his views are augmented by ~IJRCO~E et al. At Spanish Peaks Colorado (SMITH), and in Skye (PLATTENand WATTERSON)there is ample fabric evidence to support the idea of substantial lateral movement of lava and growth of dykes. This idea has been contitmed in Iceland (SICURDSSON),as in Hawaii, by tracking the location of seismic activity during dyke propagation. And DELANEYtackles the tricky problem of heat transfer and its effects on the cooling histories of dykes, and on their capacity to act as conduits over extensive periods of time. The next seven papers treat geochemistry and geochronology. Crustal contamination of mantle-derived magmas is favoured for sheet intrusions (MoHR); however, it seems likely also that the chemistry of Proterozoic dykes-at least those of the Scourie swarmmay reelect the composition of tbe sub-continental lithosphere, rather than assimilation (TARNEYand WEAVER).Analyses of dykes from a wider time and space-Archaean to Middle Proterozoic of the Canadian Shield-suggest secular changes in dyke bulk compositions (CONDIEet al.), and imply hetrogeneous mantle sources, and possible increased recycling of sediments to the mantle by the Mid-Proterozoic. This theme of dyke variability is further emphasized by study of the Mackenzie and Sudbuty dyke swarms (GIBSONet al.). Density stratification in the Great Abitibi Dyke is inferred (ERNST et al.), as is the emplacement of the dyke in response to the major impingement of the Grenville Province on the Superior Province. One paper deals with high-precision U-Pb dating of six different sets of Canadian basic intrusions, using baddelyite as well as zircon (RRCCH et a/.);
Geochemistry aad Mineral Formation in the Earth Surface edited by R. Rodriguez-Clemente and Yves Tardy. Proceedings of the International Meeting ‘Geochemistry of the Earth Surface and processeS of Mineral Formation’ held in Granada (Spain) 16-22 March 1986, CSIC, Madrid, l987,893p., 7000 pesetas (ISBN 84-00-06683-9). THIS VOLUMECONTAINS59
papers which represent part of the 16 1 contributions (lectures and posters) presented in Grenada in 1986. The papers are collected together under seven headings viz. global cycles and isotope geochemistry, weathering, supergene ore formation, recent sediments, organic geochemistry and biogeochemistry, clay formation and diagenesis, and mineral formation and crystal growth. In collections of this kind the quality of the papers is commonly uneven. Here, a surprisingly high quality is generally maintained. Unfortunately, two of the best papers given in Grenada, by Jan Veizer and by Bob Bemer, respectively, am not represented. One suspects
just as valuable are the dates derived from Ar-Ar techniques (HAN@ which have great utility in paleomagnetic work also. Various uses of paleomagnefism of dykes are dealt with in the next seven papers. Can we believe the paleomagnetism of dykes? EVANS answers “yes”! which is a comfort for the other papers, the subjects of which range from downward modelling of dykes (SCHWARZet al.), implying dykes extending at least 15 km down, through the use of magnetic anomalies for identification of dyke swarms even when exposure is poor to non-existent (TUCKERand BOYD;HALL-Set al., DRUECKERand GAY), and discussion ofthe Apparent Polar Wander Path derived from Fennoscandian dykes (BYLUND and FESONEN), to determination oftemperature profiles across dykes from remanent magnetism (BUCHAN and SCHWARZ). As one might expect, there are several papers which attempt to relate dyke intrusion and tectonics, especially rifting, of which the most entertaining is the paper by FAHRIG,on failed arms and passive margins. Finally, twelve papers present the absolutely essential cataloguing of mafic dyke swarms worldwide. Every continent, if not already dealt with elsewhere, appears here. For the Canadian Shield, there is a superb map of diabase dyke swarms (FAHRIGand WEST).But there are gaps. There is no mention of the near and middle East; and Africa is represented only by Zimbabwe, and the area south of 18” south, in addition to an earlier mention of Tanzania. This is a book well worth acquiring if you have an interest in what the nature of magma sources may be like, the kinds of mechanisms by which magma may be transferred to its final site, and what may happen to it as it travels and cools. There is also the matter of relating all this to plate movements of the past, for which there is much implicit in this volume. Halls and Fahrig are to be commended for their zeal in assembling these papers: a great deal of new work is being encouraged as a result. Orders can be sent to the Geological Association of Canada, Department of Earth Sciences, Memorial University of Newfoundland. St. John’s, Newfoundland, Canada, A 1B 3X5. Department ofGeolog1 M&aster University Hamilton, Ontario Canada, L8S 4Ml
Paul M. Clifford
that the authors got fed up of waiting the almost two years for the volume to appear. The fact that some of the ideas presented seem old hat by now (I’m thinking par&l&y of the paper on podzohsation in the “weathering” section) is also a function of this unacceptably long lag in publication. Apart from this, the main criticism I have is that the production quality is poor. Transmission electron micrographs (for example on pages 5 15 and 834) have lost much of their definition in the reproduction process. Still, it’s a good book for the research library, for earth surface groupies, and for aficionados of the idiosyncratic use of prepositions. (The book can beordered through Servicio de Publicaciones, Del Conseio Sunerior de Investigaciones Cientificas, Bitrubio no. 6, Madrid~2&%6,~Spain.) Department of Land Resource Science University of Guelph Guelph, Ontario, Canada, NIG 2 WI
Ward Chesworth
Book Reviews
Ma& Dyke Swarms, H. C. Halls and W. F. Fahrig, editors. Geological Association of Canada, Special Paper 34, 1987, 5Olp., with map folder, $65.00 (GAC members), $79.00 (non-members) (plus $3.00 postage and handling) (ISBN O-9192 16-33-I). IN THE SUMMER of 1985, Halls convened a conference on Mafic Dyke Swarms at the Erindale Campus of the University of Toronto. This volume is one result. The best place to start reading is the last chapter, where HALLSsimultaneously summarizes the proceedings and emphasizes problems more-or-less solved and problems still unresolved. One can then better select a thread to follow. Intrusion mechanics and magma transfer are concerns of the first six papers. POLLARDstresses the value of fracture mechanics in understanding the general propagation mechanism, and his views are augmented by ~IJRCO~E et al. At Spanish Peaks Colorado (SMITH), and in Skye (PLATTENand WATTERSON)there is ample fabric evidence to support the idea of substantial lateral movement of lava and growth of dykes. This idea has been contitmed in Iceland (SICURDSSON),as in Hawaii, by tracking the location of seismic activity during dyke propagation. And DELANEYtackles the tricky problem of heat transfer and its effects on the cooling histories of dykes, and on their capacity to act as conduits over extensive periods of time. The next seven papers treat geochemistry and geochronology. Crustal contamination of mantle-derived magmas is favoured for sheet intrusions (MoHR); however, it seems likely also that the chemistry of Proterozoic dykes-at least those of the Scourie swarmmay reelect the composition of tbe sub-continental lithosphere, rather than assimilation (TARNEYand WEAVER).Analyses of dykes from a wider time and space-Archaean to Middle Proterozoic of the Canadian Shield-suggest secular changes in dyke bulk compositions (CONDIEet al.), and imply hetrogeneous mantle sources, and possible increased recycling of sediments to the mantle by the Mid-Proterozoic. This theme of dyke variability is further emphasized by study of the Mackenzie and Sudbuty dyke swarms (GIBSONet al.). Density stratification in the Great Abitibi Dyke is inferred (ERNST et al.), as is the emplacement of the dyke in response to the major impingement of the Grenville Province on the Superior Province. One paper deals with high-precision U-Pb dating of six different sets of Canadian basic intrusions, using baddelyite as well as zircon (RRCCH et a/.);
Geochemistry aad Mineral Formation in the Earth Surface edited by R. Rodriguez-Clemente and Yves Tardy. Proceedings of the International Meeting ‘Geochemistry of the Earth Surface and processeS of Mineral Formation’ held in Granada (Spain) 16-22 March 1986, CSIC, Madrid, l987,893p., 7000 pesetas (ISBN 84-00-06683-9). THIS VOLUMECONTAINS59
papers which represent part of the 16 1 contributions (lectures and posters) presented in Grenada in 1986. The papers are collected together under seven headings viz. global cycles and isotope geochemistry, weathering, supergene ore formation, recent sediments, organic geochemistry and biogeochemistry, clay formation and diagenesis, and mineral formation and crystal growth. In collections of this kind the quality of the papers is commonly uneven. Here, a surprisingly high quality is generally maintained. Unfortunately, two of the best papers given in Grenada, by Jan Veizer and by Bob Bemer, respectively, am not represented. One suspects
just as valuable are the dates derived from Ar-Ar techniques (HAN@ which have great utility in paleomagnetic work also. Various uses of paleomagnefism of dykes are dealt with in the next seven papers. Can we believe the paleomagnetism of dykes? EVANS answers “yes”! which is a comfort for the other papers, the subjects of which range from downward modelling of dykes (SCHWARZet al.), implying dykes extending at least 15 km down, through the use of magnetic anomalies for identification of dyke swarms even when exposure is poor to non-existent (TUCKERand BOYD;HALL-Set al., DRUECKERand GAY), and discussion ofthe Apparent Polar Wander Path derived from Fennoscandian dykes (BYLUND and FESONEN), to determination oftemperature profiles across dykes from remanent magnetism (BUCHAN and SCHWARZ). As one might expect, there are several papers which attempt to relate dyke intrusion and tectonics, especially rifting, of which the most entertaining is the paper by FAHRIG,on failed arms and passive margins. Finally, twelve papers present the absolutely essential cataloguing of mafic dyke swarms worldwide. Every continent, if not already dealt with elsewhere, appears here. For the Canadian Shield, there is a superb map of diabase dyke swarms (FAHRIGand WEST).But there are gaps. There is no mention of the near and middle East; and Africa is represented only by Zimbabwe, and the area south of 18” south, in addition to an earlier mention of Tanzania. This is a book well worth acquiring if you have an interest in what the nature of magma sources may be like, the kinds of mechanisms by which magma may be transferred to its final site, and what may happen to it as it travels and cools. There is also the matter of relating all this to plate movements of the past, for which there is much implicit in this volume. Halls and Fahrig are to be commended for their zeal in assembling these papers: a great deal of new work is being encouraged as a result. Orders can be sent to the Geological Association of Canada, Department of Earth Sciences, Memorial University of Newfoundland. St. John’s, Newfoundland, Canada, A 1B 3X5. Department ofGeolog1 M&aster University Hamilton, Ontario Canada, L8S 4Ml
Paul M. Clifford
that the authors got fed up of waiting the almost two years for the volume to appear. The fact that some of the ideas presented seem old hat by now (I’m thinking par&l&y of the paper on podzohsation in the “weathering” section) is also a function of this unacceptably long lag in publication. Apart from this, the main criticism I have is that the production quality is poor. Transmission electron micrographs (for example on pages 5 15 and 834) have lost much of their definition in the reproduction process. Still, it’s a good book for the research library, for earth surface groupies, and for aficionados of the idiosyncratic use of prepositions. (The book can beordered through Servicio de Publicaciones, Del Conseio Sunerior de Investigaciones Cientificas, Bitrubio no. 6, Madrid~2&%6,~Spain.) Department of Land Resource Science University of Guelph Guelph, Ontario, Canada, NIG 2 WI
Ward Chesworth