Book Review: RiMG v. 62
Review in Mineralogy and Geochemistry, Volume 62, Water in Nominally Anhydrous Minerals edited by Hans Keppler and Joseph R. Smyth, The Mineralogical Society of America, Washington D.C., 2006, 478 pp. US $40(ISBN 093995074-X).
In the past decade, much attention has been given to water and its cycle into the deep Earth. Water, actually simple hydrogen embedded as point defects in the atomic structure of minerals, has major effects on the chemical and physical properties of Earth even at very low concentration. Hydrogen is one of the most volatile chemical components of Earth having the largest effects on its unique global geodynamique.
The present volume published by the Mineralogical Society of America (MSA) and the Geochemical Society perfectly follow and complete the past MSA volume entitled Volatiles in Magma (edited by M. R. Caroll & J. R. Holloway, review in Mineralogy, volume 30). It reviews the latest technological advances, theories, experimental results, and computer modelling methods, from the atomic scale to planetary dimensions. A short course accompanied the MSA volume, which took place in Northern Italy in October 2006. It was a pretty unique meeting where researchers of various citizenships and from very diverse locations of work (from all five continents!) were joined by a fascination with the almost puzzling incorporation of hydrogen in Nominally Anhydrous Minerals (NAMs). This volume benefited from the activities of the European network HYDROPSEC (Human Potential-research training Network, HPRN-CT-2000-0056) that ended in 2005 which focused on the speciation and mobility of the hydrogen in minerals of the earth upper mantle.
The review volume starts with an essential contribution by one of the most prominent researchers in the field, Prof. Rossman (Chapter 1), who describes the various techniques of detection, quantification and precise apparatus calibrations, which are available to study water in NAMs. It reminds us very well how difficult it is to detect hydrogen and the long work of searching for the right recipe and the right calibration (mineral-dependent!) to achieve concentration resolution close to a single ppm. The three following chapters provide theoretical background on the physical occurrence of hydrogen in NAMs, as well as fundamental technical details on the widely used Fourier-Transform Infrared Spectroscopy (FTIR) method (Chapter 2 by E. Libowitzky and A. Beran) and the less notoriously used method of Nuclear Magnetic Resonance (NMR) in Chapter 3. Chapter 4 reviews up-to-date methods of computer modelling at the atomic scale and details current limitations. Of course, this later section will be out of date pretty soon. The compilation on the occurrences of water as a trace element in almost all NAMs on and in the planet Earth are summarized in four subsequent chapters, each dedicated to a different class of minerals: the high pressure phases and oxides in Chapter 5, the crustal minerals in Chapter 6, the pyroxenes in Chapter 7 and of course olivine, garnet and accessory minerals (rutile, kyanite, coesite, spinel and zircon) in Chapter 8.
The most indispensable chapter for students, geologists, mineralogists, geochemists, as well as geophysicists and seismologists is certainly chapter 9, which explains, details and compiles the thermodynamic properties of water solubility in NAMs. This chapter gives the fundamental equations necessary to calculate the maximum water concentration (so called “solubility law”) within a crystalline solid as a function of pressure, temperature and chemical composition (for example iron in olivine and aluminium in orthopyroxene). Chapter 10 pursues this topic further by reviewing experimental results on the partitioning of water between minerals and melt. Subsequently, Chapters 11 and 12 take on the difficult task of reviewing the amount and fate of water in hydrous and anhydrous minerals in the very complex subduction factory.
Now that the occurrence of hydrogen is well evaluated and catalogued, the reader is introduced to hydrogen transport by ionic diffusion in Chapter 13 and then to the implications of the presence of hydrogen on essential physical properties of minerals. Chapter 14 provides a rigorous experimental demonstration of the effect of hydrogen on the equation of state of olivine, its fashionable polymorphs, wadsleyite and ringwoodite, as well as of the other high-pressure phases and expresses the likely possibility to quantify the hydrogen content by a seismological approach. Chapter 15 presents innovative hypotheses formulated by Prof. Karato on the enhancement of electrical conductivity of the upper mantle. In Chapter 16, Prof. Kohlstedt recalls how hydrogen, linked to silicon vacancies, significantly reduces the viscosity of olivine and other silicate minerals. Chapter 17 details the effect of water on the pressure dependence of phase transitions and demonstrates the broadening and depression of the topography of the mantle discontinuity due to water in the Transition Zone (410-660). This volume concludes with Chapter 18 on the growing implication of interplanetary dust particles in the origin of terrestrial water (now present in the ocean and the mantle) and finally, Chapter 19 relates primordial implications of the presence of water inside our planet as the necessary condition for globally active plate tectonics on Earth.
The quality of the editing and composing of the volume by H. Keppler and J. Smyth is outstanding. The book takes the reader to the atomic scale and by simply connecting the dots at each chapter finally to reach the obvious: “Earth is the water planet – not just because of its ocean, but also because of its tectonic evolution”. This RiMG volume is therefore a “must-have” to any students and researchers starting work on geological processes relating and/or potentially involving the presence water in the deep Earth.
Laboratoire Géosciences Montpellier
Université de Montpellier 2, Montpellier, France