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The role of fluids in crustal processes
Tectonophysics,
Elsevier
Science
202 (1992) 95-96
Publishers
9s
B.V.. Amsterdam
Book Review The Role of Fluids in Crustal Processes. J.D. Bredehoeft and D.L. Norton (Editors). National Academy Press, Washington, D.C. U.S.A. Marketed by John Wiley & Sons, Ltd., Chichester, U.K., 1990, hardcover, xii + 170 pp., f21.10 (ISBN 0-309-04037-x) One of the highest pursuits in the scientific study of natural phenomena is the construction of a comprehensive conceptual framework. At its best, such a framework unifies previously disparate observations and analyses, provides novel insight and understanding into the phenomena, and suggests avenues for new investigations. “The Role of Fluids in Crustal Processes” makes a surprisingly large step in this direction. The book is a collection of papers arising from a symposium at the 1986 annual meeting of the Geological Society of America. The surprise is the high degree of coherency among the chapters. Similar volumes often result in a sequence of contributions that are separate and distinct and which could just as well have been published as a special edition in a journal. “The Role of Fluids in Crustal Processess” begins with two contributions written by J.D. Bredehoeft and D.L. Norton, who are also the editors of the book. These two chapters provide an outstanding synthesis and integration of the following ten chapters. This integration is accomplished by examining the diverse driving forces for fluid flow, the physical and chemical processes which are a consequence of fluid flow in a heterogeneous crust, and the diverse couplings among these processes. Magmatic hydrothermal systems are exemplary of this integration because they form a microcosm of fluid mediated crustal processes; processes which may act individually in other environments are fully coupled in these systems. The difficulty in achieving even a modest level of coherency among such a diverse set of geologic environments, a multitude of processes, and a plethora of parameters should not be underesti0040-1951/92/$05.00
0 1992 - Elsevier
Science
Publishers
mated. The editors achieved this coherency by using the coupling among physical and chemical processes in heterogeneous environments as the foundation for their approach. The editors’ degree of success distinguishes this book from the book Fluids in the Earth’s Crust (W.S. Fyfe et al., 1978). In contrast, the earlier book seems somewhat disconnected, focussing largely on the details of chemical reactions and rock deformation related to regional metamorphism with little focus on the connections between the two processes. As Bredehoeft and Norton point out, “Recognition of the role of water as the material that controls the extent of coupling among processes shows promise of reducing the magnitude of the analytical problem to one that focuses on the controlling links of the system.” “The Role of Fluids in Crustal Processes” is informally divided into two parts, each consisting of five contributions. The first part examines processes relating to thermally induced fluid flow in neous and metamorphic systems. The second part addresses questions relating to the occurrence of high pore-fluid pressures in the lower crust. The five chapters concerning fluids in igneous and metamorphic environments form a logical progression. D.L. Norton begins by examining the interaction between large thermal perturbations, increased pore-fluid pressure, the development of fractures and mineral precipitation and/or dissolution within the fracture. S.R. Titley follows with a review of some exceptional field observations and analyses of fracture orientations, fracture abundances, and related hydrothermal alteration in and around felsic plutons. Of particular interest is how the different fracture orientations have distinctly different ages and mineral contents; this forms a unique data base for examining the time evolution of the coupled processes. A consequence of fluid flow within the fracture sets is chemical reaction with the adjacent rock. H.P. Taylor summarizes years of his laboratory research on wide spread and large scale fluid-rock
B.V. All rights
reserved
96
interaction in and around granitic plutons as preserved in the oxygen and hydrogen isotopic record. His accumulated evidence suggests that the circulation of surface fluids may occur as deep as 15 km in some cases. Two articles, one by J.V. Walther and one by S.R. Wickham and H.P. Taylor, examine larger scale thermal events as evidenced by regional metamorphism. They demonstrate that not only have fluids existed in these environments but they have flowed and, as a result, significantly modified the environment. Clearly, a quantitative examination of the fluid flow processes in metamorphic environments is needed. The final five chapters address questions relating to high pore-fluid pressures in the lower crust. While this phenomenon has received considerable attention for upper crustal environments, particularly sedimentary basins, it has mostly been ignored for greater depths. A.M. Nur and J. Walder examine the influence that the relative rates of porosity and permeability loss have on pore-fluid pressures; they propose that high pore-fluid pressures are a transient property in the lower crust. J.E. Oliver synthesizes some seismic reflection information and suggests that some deep reflectors could be caused by regions of anomalously high pore-fluid pressures. T. Engelder analyses joint patterns across the AIlegheny front (U.S.A.) and postulates that correlative patterns are caused by regional high porefluid pressures. P. Vrolijk and G. Myers use fluid inclusions in rocks from the Kodiak accretionary complex (Alaska, U.S.A.) to conclude that sub-
duction zones are characterized by anomalously high pore fluid pressures. Finally, J.D. Bredehoeft and S.E. Ingebritsen divert from water as the fluid of interest and propose that, at least in some regions, the generation of carbon dioxide by either igneous or metamorphic processes could cause high pore-fluid pressures. In summary, “The Role of Fluids in Crustal Processes” has some very positive features and can serve as a useful reference to both researchers of crustal processes and to scientists interested in following the development of a coherent conceptual framework in one aspect of the earth sciences. The books modest length, 170 pages, precludes a comprehensive coverage of all topics related to fluids and crustal processes. Notable in their absence are discussions of the chemistry of fluids and their reactions with rocks; the role of fluids in rock deformation (other than fracturing); and the influence of water on bulk crustal properties (other than seismic velocities). Perhaps the book’s greatest defect is the somewhat obscure nature of the publication. National Research Council publications are not popular resources for scientists even if, as in this case, there is much to be gained from the book. The editors’ vision and some of the book’s articles deserve a better fate. R.B.
KNAPP
(Livermore, Calif., U.S.A.)
Reference Fyfe, W.S., Price, N.J. and Thompson, A.B., 1978. Fluids in the Earth’s Crust. Elsevier, Amsterdam, 384 pp.
Erratum Borg, S.G. and DePaolo, D.J., 1991, A tectonic model of the Antarctic Gondwana margin with implications for southeastern Australia: isotopic and geochemical evidence. In: R.D. Hatcher, Jr. and L. Zonenshain (Editors), Accretionary Tectonics and Composite Continents. Tectonophysics, 196: 339-358. In Table 1, p. 343, the Sr concentration value for sample AL 1968 should read 134.28 ppm, in stead off the printed value.
Elsevier
Science
202 (1992) 95-96
Publishers
9s
B.V.. Amsterdam
Book Review The Role of Fluids in Crustal Processes. J.D. Bredehoeft and D.L. Norton (Editors). National Academy Press, Washington, D.C. U.S.A. Marketed by John Wiley & Sons, Ltd., Chichester, U.K., 1990, hardcover, xii + 170 pp., f21.10 (ISBN 0-309-04037-x) One of the highest pursuits in the scientific study of natural phenomena is the construction of a comprehensive conceptual framework. At its best, such a framework unifies previously disparate observations and analyses, provides novel insight and understanding into the phenomena, and suggests avenues for new investigations. “The Role of Fluids in Crustal Processes” makes a surprisingly large step in this direction. The book is a collection of papers arising from a symposium at the 1986 annual meeting of the Geological Society of America. The surprise is the high degree of coherency among the chapters. Similar volumes often result in a sequence of contributions that are separate and distinct and which could just as well have been published as a special edition in a journal. “The Role of Fluids in Crustal Processess” begins with two contributions written by J.D. Bredehoeft and D.L. Norton, who are also the editors of the book. These two chapters provide an outstanding synthesis and integration of the following ten chapters. This integration is accomplished by examining the diverse driving forces for fluid flow, the physical and chemical processes which are a consequence of fluid flow in a heterogeneous crust, and the diverse couplings among these processes. Magmatic hydrothermal systems are exemplary of this integration because they form a microcosm of fluid mediated crustal processes; processes which may act individually in other environments are fully coupled in these systems. The difficulty in achieving even a modest level of coherency among such a diverse set of geologic environments, a multitude of processes, and a plethora of parameters should not be underesti0040-1951/92/$05.00
0 1992 - Elsevier
Science
Publishers
mated. The editors achieved this coherency by using the coupling among physical and chemical processes in heterogeneous environments as the foundation for their approach. The editors’ degree of success distinguishes this book from the book Fluids in the Earth’s Crust (W.S. Fyfe et al., 1978). In contrast, the earlier book seems somewhat disconnected, focussing largely on the details of chemical reactions and rock deformation related to regional metamorphism with little focus on the connections between the two processes. As Bredehoeft and Norton point out, “Recognition of the role of water as the material that controls the extent of coupling among processes shows promise of reducing the magnitude of the analytical problem to one that focuses on the controlling links of the system.” “The Role of Fluids in Crustal Processes” is informally divided into two parts, each consisting of five contributions. The first part examines processes relating to thermally induced fluid flow in neous and metamorphic systems. The second part addresses questions relating to the occurrence of high pore-fluid pressures in the lower crust. The five chapters concerning fluids in igneous and metamorphic environments form a logical progression. D.L. Norton begins by examining the interaction between large thermal perturbations, increased pore-fluid pressure, the development of fractures and mineral precipitation and/or dissolution within the fracture. S.R. Titley follows with a review of some exceptional field observations and analyses of fracture orientations, fracture abundances, and related hydrothermal alteration in and around felsic plutons. Of particular interest is how the different fracture orientations have distinctly different ages and mineral contents; this forms a unique data base for examining the time evolution of the coupled processes. A consequence of fluid flow within the fracture sets is chemical reaction with the adjacent rock. H.P. Taylor summarizes years of his laboratory research on wide spread and large scale fluid-rock
B.V. All rights
reserved
96
interaction in and around granitic plutons as preserved in the oxygen and hydrogen isotopic record. His accumulated evidence suggests that the circulation of surface fluids may occur as deep as 15 km in some cases. Two articles, one by J.V. Walther and one by S.R. Wickham and H.P. Taylor, examine larger scale thermal events as evidenced by regional metamorphism. They demonstrate that not only have fluids existed in these environments but they have flowed and, as a result, significantly modified the environment. Clearly, a quantitative examination of the fluid flow processes in metamorphic environments is needed. The final five chapters address questions relating to high pore-fluid pressures in the lower crust. While this phenomenon has received considerable attention for upper crustal environments, particularly sedimentary basins, it has mostly been ignored for greater depths. A.M. Nur and J. Walder examine the influence that the relative rates of porosity and permeability loss have on pore-fluid pressures; they propose that high pore-fluid pressures are a transient property in the lower crust. J.E. Oliver synthesizes some seismic reflection information and suggests that some deep reflectors could be caused by regions of anomalously high pore-fluid pressures. T. Engelder analyses joint patterns across the AIlegheny front (U.S.A.) and postulates that correlative patterns are caused by regional high porefluid pressures. P. Vrolijk and G. Myers use fluid inclusions in rocks from the Kodiak accretionary complex (Alaska, U.S.A.) to conclude that sub-
duction zones are characterized by anomalously high pore fluid pressures. Finally, J.D. Bredehoeft and S.E. Ingebritsen divert from water as the fluid of interest and propose that, at least in some regions, the generation of carbon dioxide by either igneous or metamorphic processes could cause high pore-fluid pressures. In summary, “The Role of Fluids in Crustal Processes” has some very positive features and can serve as a useful reference to both researchers of crustal processes and to scientists interested in following the development of a coherent conceptual framework in one aspect of the earth sciences. The books modest length, 170 pages, precludes a comprehensive coverage of all topics related to fluids and crustal processes. Notable in their absence are discussions of the chemistry of fluids and their reactions with rocks; the role of fluids in rock deformation (other than fracturing); and the influence of water on bulk crustal properties (other than seismic velocities). Perhaps the book’s greatest defect is the somewhat obscure nature of the publication. National Research Council publications are not popular resources for scientists even if, as in this case, there is much to be gained from the book. The editors’ vision and some of the book’s articles deserve a better fate. R.B.
KNAPP
(Livermore, Calif., U.S.A.)
Reference Fyfe, W.S., Price, N.J. and Thompson, A.B., 1978. Fluids in the Earth’s Crust. Elsevier, Amsterdam, 384 pp.
Erratum Borg, S.G. and DePaolo, D.J., 1991, A tectonic model of the Antarctic Gondwana margin with implications for southeastern Australia: isotopic and geochemical evidence. In: R.D. Hatcher, Jr. and L. Zonenshain (Editors), Accretionary Tectonics and Composite Continents. Tectonophysics, 196: 339-358. In Table 1, p. 343, the Sr concentration value for sample AL 1968 should read 134.28 ppm, in stead off the printed value.