Metasomatism and the Chemical Transformation of Rock*
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BOOK REVIEW METASOMATISM AND THE CHEMICAL TRANSFORMATION OF ROCK* The concept of metasomatism, or the chemical action. Touret’s pioneering research on fl uid of asteroidal parent bodies. This well-illustrated alteration of solid rocks, stems from the classical inclusions demonstrates that virtually every summary should be of considerable value to observations and interpretations of pioneering kind of rock has the remnants of mineralizing meteorite geochemists. geochemists and petrologists, starting with V. (indeed, metasomatizing) fl uids trapped in the Chapter 3 on thermodynamic modeling and M. Goldschmidt and including Hans Ramberg, minerals, including rocks of the “dry” granulite thermobarometry, by P. Goncalves, D. Marquer, Peter Misch, and D. S. Korzhinsky. Much of the facies lower crust. Recognition of metasoma- E. Oliot, and C. Durand, is a good summary of early discussion centered around the origin of tism in virtually all rocks is trundling forward the use of pseudosections as applied to meta- granite. In the middle decades of the last cen- with steamroller momentum. somatic rocks. M. Rubenach’s chapter 4, on tury, experimental studies on the melting of The treatments in this book of the various structural controls on metasomatism, gives quartzofeldspathic rocks at elevated H2O pres- topics on metasomatism refl ect the predilec- a fascinating account of deformation-related sures began to subvert earlier interpretations of tions of the authors. B. W. D. Yardley’s title mineralization in one of the world’s most metasomatism. The experiments showed that (chapter 2), “The Chemical Composition spectacular metasomatic terrains, the Mt. Isa rock melting temperatures dropped drastically o of Metasomatic Fluids in the Crust,” should Inlier of Queensland, Australia. Chapter 6 on from above 1000 ºC into the 600–800 C range have the modifi er “Upper,” since the author’s the geochronology of metasomatic events, thought to prevail during high-grade crustal emphasis is on brines of sedimentary origin. by I. M. Villa and M. L. Williams, makes the metamorphism, fostering the implication that Mineralizing fl uids of higher grade but rela- point that all isotopically datable metamor- many of the intuitive interpretations based tively shallow-seated metamorphic rocks like phic events are by defi nition metasomatic. on the textures of granites could be better skarns and greisens are briefl y addressed by This chapter is a useful discussion of the pro- explained in the larger context of magma- Yardley. The other treatments range from ele- cedures and problems of dating metasomatic tism. Andrew Putnis and Haakon Austrheim mentary, as in Pirajno’s textbook description rocks. Chapter 1, by the book’s editors, gives state the situation succinctly in chapter 5 of of ore deposits, to the dauntingly analytical thumbnail sketches of all the articles. Metasomatism and the Chemical Transformation chapter 14, by J. A. D. Connelly and Y. Y. A well-cited article in this book might prove of Rock” (p. 143). Referring to “the ultimate Podladchikov, “A Hydromechanical Model for demise of metasomatism as a large-scale pro- to be chapter 15, by M. Unsworth and S. Lower Crustal Fluid Flow,” in which they set Rondenay, on the mapping of fl uids in the cess,” they go on to say: “The magmatists won forth their mathematical theory of fl uid-fi lled the argument with the experimental work of crust and lithosphere by geophysical methods, porosity waves travelling through otherwise including seismic profi ling and electrical resis- Tuttle and Bowen (1958) and for many years impermeable rocks. metasomatism was neglected…” tivity studies. These authors make a good case Several very useful and well-written articles of for the large-scale existence of interconnected, Recent developments in chemical, isotopic, the book may be singled out. R. Klemd’s chapter saline pore fl uids in areas of the lower crust and petrographic analysis have brought meta- 10, “Metasomatism during High-Pressure undergoing thermal activation, as in the Great somatism roaring back into the vocabulary of Metamorphism: Eclogites and Blueschist Basin of the western United States. Where there petrology, as the 15 articles in this book edited Facies Rocks,” is a clear, informative, and, to are low-resistance channels there must be some by Daniel E. Harlov and H. Austrheim make this reviewer, very entertaining description of kind of conducting fl uids, and hence, probable abundantly clear. One problem has been that patently metasomatic features of rocks from metasomatic action. This and other papers of the chemical effects of metasomatic processes exposed high-pressure and ultrahigh-pressure this book (e.g. Klemd and O’Reilly and Griffi n) are often much more subtle than those of terrains. Klemd and his coworkers have con- seem to lean to the view that deep-seated fl uids igneous processes. An example is the “cryptic” centrated on the chemical relations of blue- (C–O–H fl uids and brines) result from subduc- alteration of mantle peridotites, which altera- schist-to-eclogite transitions in places like the tion of surfi cial volatiles. tion can now be apprehended by sophisticated Tianshan of western China. modern trace element and isotopic analysis. The original metasomatism controversy was Most importantly, the complex physical chem- My favorite article is chapter 12 by S. Y. O’Reilly centered around the origin of granite, whether istry of multicomponent fl uids and their inter- and W. L. Griffi n, “Mantle Metasomatism.” This or not there is an important process that could actions with rocks in reactive fl ow is orders of summary of their and many others’ research be called “granitization.” There is no discus- magnitude more diffi cult conceptually than a on mantle peridotites in the form of volcanic sion of this kind of metasomatism in Harlov ternary melting diagram; hence the former lack xenoliths and in exposed ultramafi c masses and Austrheim’s book. The commonly noted of interest in an arduous, low-reward effort to (ophiolites) reveals the profound metasoma- metasomatic phenomena of “ghost” gneissic understand it in detail. tism shown by every mantle rock, including foliation that passes seemingly uninterrupted the so-called “fertile” lherzolites, which, for so through granites and K-feldspar megacrysts that The metasomatic nature of every petrologic many years, have been thought to be pristine, grow across boundaries of mafi c inclusions in regime, from the oceanic crust (chapter 8, by undepleted potential source rocks for basalt granite seem still to be off-limits for respect- W. Bach, N. Jons, and F. Klein) to skarns and magmas. The “pyrolites” of yesteryear are now able scientists. Some day the tainted subject ore deposits (we already know those are meta- thought to be refertilized, previously depleted of granitization will also return to the realm somatic, but F. Pirajno’s descriptions in chapter dunites and harzburgites. of legitimate discussion. 7 give a nice overview), to metasomatic pro- cesses in the mantle lithosphere (chapter 12, Even extraterrestrial rocks (meteorites) show A shortcoming of my copy of this book is the O’Reilly and Griffi n) and in the deeper parts of the effects of metasomatism. Chapter 15 on low quality of many illustrations in black-and- the crust (chapter 11 by J. L. Touret and T. G. this subject, by A. J. Brearley and A. N. Krot, is white reproduction. A full-color version is now Nijland) mandate a concerted effort toward a the longest paper in the book. Some of the least available with much improved illustrations. quantitative understanding of fl uid–rock inter- thermally altered meteorites, the carbonaceous All in all though, this heavyweight book goes a chondrites, show veins containing such vola- long way toward making up for a half century tile-bearing minerals as sodalite and scapolite, of neglect of one of the principal petrogenetic and, occasionally, OH-bearing phyllosilicates. processes of the rocky universe. * Harlov DE, Austrheim H (eds) (2013) Metasomatism Even the unequilibrated ordinary chondrites and the Chemical Transformation of Rock. Springer, show evidence of fl uid-assisted metamorphism, Robert C. Newton, Dept. of Earth and Space Heidelberg, ISBN 978-3-642-28393-2 (print), ISBN Sciences, University of California at Los Angeles 978-3-642-28394-9 (online), 806 pp presumably recording processes in the regoliths ELEMENTS 155 APRIL 2014.