ALBERT

Beschreibung / Inhaltsverzeichnis: Several years ago, John Rakovan and John Hughes (colleagues at Miami of Ohio), and later Matt Kohn (at South Carolina), separately proposed short courses on phosphate minerals to the Council of the Mineralogical Society of America (MSA). Council suggested that they join forces. Thus this volume, Phosphates: Geochemical, Geobiological, and Materials Importance, was organized. It was prepared in advance of a short course of the same title, sponsored by MSA and presented at Golden, Colorado, October 25-27. We are pleased to present this volume entitled Phosphates: Geochemical, Geobiological and Materials Importance. Phosphate minerals are an integral component of geological and biological systems. They are found in virtually all rocks, are the major structural component of vertebrates, and when dissolved are critical for biological activity. This volume represents the work of many authors whose research illustrates how the unique chemical and physical behavior of phosphate minerals permits a wide range of applications that encompasses phosphate mineralogy, petrology, biomineralization, geochronology, and materials science. While diverse, these fields are all linked structurally, crystal-chemically and geochemically. As geoscientists turn their attention to the intersection of the biological, geological, and material science realms, there is no group of compounds more germane than the phosphates. The chapters of this book are grouped into five topics: Mineralogy and Crystal Chemistry, Petrology, Biomineralization, Geochronology, and Materials Applications. In the first section, three chapters are devoted to mineralogical aspects of apatite, a phase with both inorganic and organic origins, the most abundant phosphate mineral on earth, and the main mineral phase in the human body. Monazite and xenotime are highlighted in a fourth chapter, which includes their potential use as solid-state radioactive waste repositories. The Mineralogy and Crystal Chemistry section concludes with a detailed examination of the crystal chemistry of 244 other naturally-occurring phosphate phases and a listing of an additional 126 minerals. In the Petrology section, three chapters detail the igneous, metamorphic, and sedimentary aspects of phosphate minerals. A fourth chapter provides a close look at analyzing phosphates for major, minor, and trace elements using the electron microprobe. A final chapter treats the global geochemical cycling of phosphate, a topic of intense, current geochemical interest. The Biomineralization section begins with a summary of the current state of research on bone, dentin and enamel phosphates, a topic that crosses disciplines that include mineralogical, medical, and dental research. The following two chapters treat the stable isotope and trace element compositions of modern and fossil biogenic phosphates, with applications to paleontology, paleoclimatology, and paleoecology. The Geochronology section focuses principally on apatite and monazite for U-ThPb, (U- Th)/He, and fission-track age determinations; it covers both classical geochronologic techniques as well as recent developments. The final section-Materials Applications-highlights how phosphate phases play key roles in fields such as optics, luminescence, medical engineering and prosthetics, and engineering of radionuclide repositories. These chapters provide a glimpse of the use of natural phases in engineering and biomedical applications and illustrate fruitful areas of future research in geochemical, geobiological and materials science. We hope all chapters in this volume encourage researchers to expand their work on all aspects of natural and synthetic phosphate compounds.

Beschreibung / Inhaltsverzeichnis: Exactly 100 years before the publication of this volume, the first paper which calculated the half-life for the newly discovered radioactive substance U-X (now called 234Th), was published. Now, in this volume, the editors Bernard Bourdon, Gideon Henderson, Craig Lundstrom and Simon Turner have integrated a group of contributors who update our knowledge of U-series geochemistry, offer an opportunity for non-specialists to understand its basic principles, and give us a view of the future of this active field of research. In this volume, for the first time, all the methods for determining the uranium and thorium decay chain nuclides in Earth materials are discussed. It was prepared in advance of a two-day short course (April 3-4, 2003) on U-series geochemistry, jointly sponsored by GS and MSA and presented in Paris, France prior to the joint EGS/AGU/EUG meeting in Nice. The discovery of the 238U decay chain, of course, started with the seminal work of Marie Curie in identifying and separating 226Ra. Through the work of the Curies and others, all the members of the 238U decay chain were identified. An important milestone for geochronometrists was the discovery of 230Th (called Ionium) by Bertram Boltwood, the Yale scientist who also made the first age determinations on minerals using the U-Pb dating method (Boltwood in 1906 established the antiquity of rocks and even identified a mineral from Sri Lanka-then Ceylon as having an age of 2.1 billion years!) The application of the 238U decay chain to the dating of deep sea sediments was by Piggott and Urry in 1942 using the "Ionium" method of dating. Actually they measured 222Ra (itself through 222Rn) assuming secular equilibrium had been established between 230Th and 226Ra. Although 230Th was measured in deep sea sediments by Picciotto and Gilvain in 1954 using photographic emulsions, it was not until alpha spectrometry was developed in the late 1950's that 20Th was routinely measured in marine deposits. Alpha spectrometry and gamma spectrometry became the work horses for the study of the uranium and thorium decay chains in a variety of Earth materials. These ranged from 222Rn and its daughters in the atmosphere, to the uranium decay chain nuclides in the oceanic water column, and volcanic rocks and many other systems in which either chronometry or element partitioning, were explored. Much of what we learned about the 238U, 235U and 232Th decay chain nuclides as chronometers and process indicators we owe to these seminal studies based on the measurement of radioactivity. The discovery that mass spectrometry would soon usurp many of the tasks performed by radioactive counting was in itself serendipitous. It came about because a fundamental issue in cosmochemistry was at stake. Although variation in 235U/238U had been reported for meteorites the results were easily discredited as due to analytical difficulties. One set of results, however, was published by a credible laboratory long involved in quality measurements of high mass isotopes such as the lead isotopes. The purported discovery of 235U/238U variations in meteorites, if true, would have consequences in defining the early history of the formation of the elements and the development of inhomogeneity of uranium isotopes in the accumulation of the protoplanetary materials of the Solar System. Clearly the result was too important to escape the scrutiny of falsification implicit in the way we do science. The Lunatic Asylum at Caltech under the leadership of Jerry Wasserburg took on that task. Jerry Wasserburg and Jim Chen clearly established the constancy and Earth-likeness of 235U/238U in the samplable universe. In the hands of another member of the Lunatic Asylum, Larry Edwards, the methodology was transformed into a tool for the study of the 238U decay chain in marine systems. Thus the mass spectrometric techniques developed provided an approach to measuring the U and Th isotopes in geological materials as well as cosmic materials with the same refinement and accommodation for small sample size. Soon after this discovery the harnessing of the technique to the measurement of all the U isotopes and all the Th isotopes with great precision immediately opened up the entire field of uranium and thorium decay chain studies. This area of study was formerly the poaching ground for radioactive measurements alone but now became part of the wonderful world of mass spectrometric measurements. (The same transformation took place for radiocarbon from the various radioactive counting schemes to 'accelerator mass spectrometry.) No Earth material was protected from this assault. The refinement of dating corals, analyzing volcanic rocks for partitioning and chronometer studies and extensions far and wide into ground waters and ocean bottom dwelling organisms has been the consequence of this innovation. Although Ra isotopes, 210Pb and 210Po remain an active pursuit of those doing radioactive measurements, many of these nuclides have also become subject to the mass spectrometric approach. In this volume, for the first time, all the methods for determining the uranium and thorium decay chain nuclides in Earth materials are discussed. The range of problems solvable with this approach is remarkable-a fitting, tribute to the Curies and the early workers who discovered them for us to use.

Beschreibung / Inhaltsverzeichnis: This volume highlights some of the frontiers in the study of plastic deformation of minerals and rocks. The research into the plastic properties of minerals and rocks had a major peak in late 1960s to early 1970s, largely stimulated by research in the laboratory of D. T. Griggs and his students and associates. It is the same time when the theory of plate tectonics was established and provided a first quantitative theoretical framework for understanding geological processes. The theory of plate tectonics stimulated the study of deformation properties of Earth materials, both in the brittle and the ductile regimes. Many of the foundations of plastic deformation of minerals and rocks were established during this period. Also, new experimental techniques were developed, including deformation apparatus for high-pressure and high-temperature conditions, electron micros-copy study of defects in minerals, and the X-ray technique of deformation fabric analysis. The field benefited greatly from materials science concepts of deformation that were introduced, including the models of point defects and their interaction with dislocations. A summary of progress is given by the volume Flow and Fracture of Rocks: The Griggs Volume, published in 1972 by the American Geophysical Union. Since then, the scope of Earth sciences has greatly expanded. Geodynamics became concerned with the Earth's deep interior where seismologists discovered heterogeneities and anisotropy at all scales that were previously thought to be typical of the crust and the upper mantle. Investigations of the solar system documented new mineral phases and rocks far beyond the Earth. Both domains have received a lot of attention from mineralogists (e.g., summarized in MSA's Reviews in Mineralogy, Volume 36, Planetary Materials and Volume 37, Ultra-High Pressure Mineralogy). Most attention was directed towards crystal chemistry and phase relations, yet an understanding of the deformation behavior is essential for interpreting the dynamic geological processes from geological and geophysical observations. This was largely the reason for a rebirth of the study of rock plasticity, leading to new approaches that include experiments at extreme conditions and modeling of deformation behavior based on physical principles. A wide spectrum of communities emerged that need to use information about mineral plasticity, including mineralogy, petrology, structural geology, seismology, geodynamics and engineering. This was the motivation to organize a workshop, in December 2002 in Emeryville, California, to bridge the very diverse disciplines and facilitate communication. This volume written for this workshop should help one to become familiar with a notoriously difficult subject, and the various contributions represent some of the important progress that has been achieved. The spectrum is broad. High-resolution tomographic images of Earth's interior obtained from seismology need to be interpreted on the bases of materials properties to understand their geodynamic significance. Key issues include the influence of deformation on seismic signatures, such as attenuation and anisotropy, and a new generation of experimental and theoretical studies on rock plasticity has contributed to a better understanding. Extensive space exploration has revealed a variety of tectonic styles on planets and their satellites, underlining the uniqueness of the Earth. To understand why plate tectonics is unique to Earth, one needs to understand the physical mechanisms of localization of deformation at various scales and under different physical conditions. Also here important theoretical and experimental studies have been conducted. In both fields, studies on anisotropy and shear localization, large-strain deformation experiments and quantitative modeling are critical, and these have become available only recently. Complicated interplay among chemical reactions (including partial melting) is a key to understand the evolution of Earth. This book contains two chapters on the developments of new techniques of experimental studies: one is large-strain shear deformation (Chapter 1 by Mackwell and Paterson) and another is deformation experiments under ultrahigh pressures (Chapter 2 by Durham et al.). Both technical developments are the results of years of efforts that are opening up new avenues of research along which rich new results are expected to be obtained. Details of physical and chemical processes of deformation in the crust and the upper mantle are much better understood through the combination of well controlled laboratory experiments with observations on "real" rocks deformed in Earth. Chapter 3 by Tullis and Chapter 4 by Hirth address the issues of deformation of crustal rocks and the upper mantle, respectively. In Chapter 5 Kohlstedt reviews the interplay of partial melting and deformation, an important subject in understanding the chemical evolution of Earth. Cordier presents in Chapter 6 an overview of the new results of ultrahigh pressure deformation of deep mantle minerals and discusses microscopic mechanisms controlling the variation of deformation mechanisms with minerals in the deep mantle. Green and Marone review in Chapter 7 the stability of deformation under deep mantle conditions with special reference to phase transformations and their relationship to the origin of intermediate depth and deep-focus earthquakes. In Chapter 8 Schulson provides a detailed description of fracture mechanisms of ice, including the critical brittle-ductile transition that is relevant not only for glaciology, planetology and engineering, but for structural geology as well. In Chapter 9 Cooper provides a review of experimental and theoretical studies on seismic wave attenuation, which is a critical element in interpreting distribution of seismic wave velocities and attenuation. Chapter 10 by Wenk reviews the relationship between crystal preferred orientation and macroscopic anisotropy, illustrating it with case studies. In Chapter 11 Dawson presents recent progress in poly-crystal plasticity to model the development of anisotropic fabrics both at the microscopic and macroscopic scale. Such studies form the basis for geodynamic interpretation of seismic anisotropy. Finally, in Chapter 12 Montagner and Guillot present a thorough review of seismic anisotropy of the upper mantle covering the vast regions of geodynamic interests, using a global surface wave data set. In Chapter 13 Bercovici and Karato summarize the theoretical aspects of shear localization. All chapters contain extensive reference lists to guide readers to the more specialized literature. Obviously this book does not cover all the areas related to plastic deformation of minerals and rocks. Important topics that are not fully covered in this book include mechanisms of semi-brittle deformation and the interplay between microstructure evolution and deformation at different levels, such as dislocation substructures and grain-size evolution ("self-organization"). However, we hope that this volume provides a good introduction for graduate students in Earth science or materials science as well as the researchers in these areas to enter this multidisciplinary field.

Beschreibung / Inhaltsverzeichnis: Until only a few years ago, I would never have imagined that a volume on the stable isotope geochemistry of elements like Mg, Fe or Cu would be written. In fact, a comic book of blank pages entitled The Stable Isotope Geochemistry of Fluorine would have been a more likely prospect. In volume 16 of this series, published in 1986, I wrote: Isotopic variations have been looked for but not found for heavy elements like Cu, Sn, and Fe .... Natural variations in isotopic ratios of terrestrial materials have been reported for other light elements like Mg and K, but such variations usually turn out to be laboratory artifacts. I am about ready to eat those words. We have known for many years that large isotopic fractionations of heavy elements like Pb develop in the source regions of TIMS machines. Nonetheless, most of us held fast to the conventional wisdom that no significant mass-dependent isotopic fractionations were likely to occur in natural or laboratory systems for elements that are either heavy or engaged in bonds with a dominant ionic character. With the relatively recent appearance of new instrumentation like MC-ICP-MS and heroic methods development in TIMS analyses, it became possible to make very precise measurements of the isotopic ratios of some of these non-traditional elements, particularly if they comprise three or more isotopes. It was eminently reasonable to reexamine these systems in this new light. Perhaps atomic weights could be refined, or maybe there were some unexpected isotopic variations to discover. There were around the turn of the present century, reports began appearing of biological fractionations of about 2-3 per mil for heavy elements like Fe and Cr and attempts were made to determine the magnitude of equilibrium isotope effects in these systems, both by experiment and semi-empirical calculations. Interest emerged in applying these effects to the study of environmental problems. Even the most recalcitrant skeptic now accepts the fact that measurable and meaningful variations in the isotopic ratios of heavy elements occur as a result of chemical, biological and physical processes. Most of the work discussed in this volume was published after the year 2000 and thus the chapters are more like progress reports rather than reviews. Skepticism now focuses on whether isotopic variations as small as 0.1 per mil are indeed as meaningful as some think, and the fact that measured isotopic fractionations of these non-traditional elements are frequently much smaller than predicted from theoretical considerations. In fact the large fractionations suggested by the calculations provide much of the stimulus for working in this discipline. Clearly some carefully designed experiments could shed light on some of the ambiguity. My optimism for the future of this burgeoning new field remains high because it is in very good hands indeed. Approximately three-quarters of the elements in the Periodic Table have two or more isotopes. RiM 16 and RiMG 43 were devoted to H, C, 0, and S isotope variations, and B isotope variations were discussed in RiM 33. The importance of these elements to geochemistry may be illustrated by a GeoRef search of 0 isotope publications, which yields over 25,000 papers, theses, and abstracts spanning over five decades. Isotopic variations of the remaining 56 elements that have two or more isotopes, however, remains relatively little explored, but is gaining rapid attention, in part driven by advances in analytical instrumentation in the last 5-10 years. Our goal for this volume was to bring together a summary of the isotope geochemistry of non-traditional stable isotope systems as is known through 2003 for those elements that have been studied in some detail, and which have a variety of geochemical properties. In addition, recognizing that many of these elements are of interest to workers who are outside the traditional stable isotope fields, we felt it was important to include discussions on the broad isotopic variations that occur in the solar system, theoretical approaches to calculating isotopic fractionations, and the variety of analytical methods that are in use. We hope, therefore, that this volume proves to be useful to not only the isotope specialist, but to others who are interested in the contributions that these non-traditional stable isotopes may make toward understanding geochemical and biological cycles.