ALBERT

Description / Table of Contents: Over the years, volumes in this series have taken a variety of forms. Many have focused on mature fields of investigation to draw together a comprehensive body of work and provide a definitive, up to date reference. A few, however, have sought to provide enough coverage of an emerging or re-emerging field to allow the reader to identify important and exciting gaps in current knowledge and opportunities for new research. This volume falls into the later category. Our primary goal in convening the short course and assembling this text it is to invigorate future research. Early “Reviews in Mineralogy” dealt with specific groups of minerals, one (or two) volumes at a time. In contrast, this volume deals explicitly with the topic of crystal size in many different systems. Until recently, the special and complicated nature of the very smallest particles rendered them nearly impossible to study by conventional methods. Even today, the challenges associated with evaluating the size-dependence of a mineral’s bulk and surface structures, properties, and reactivity are significant. However, ongoing improvements in sophisticated characterization, theory, and data analysis make particles previously described (often inaccurately) as “amorphous” (or even more mysteriously as “x-ray amorphous”) amenable to quantitative evaluation. Thermochemical, crystal chemical, and computational chemical approaches must be combined to understand particles with diameters of 1 to 100 nanometers. Determination of …

Description / Table of Contents: Micas are among the most common minerals in the Earth crust: 4.5% by volume. They are widespread in most if not all metamorphic rocks (abundance: 11%), and common also in sediment and sedimentary and igneous rocks. Characteristically, micas form in the uppermost greenschist facies and remain stable to the lower crust, including anatectic rocks (the only exception: granulite facies racks). Moreover, some micas are stable in sediments and diagenetic rocks and crystallize in many types of lavas. In contrast, they are also present in association with minerals originating from the very deepest parts of the mantle—they are the most common minerals accompanying diamond in kimberlites. The number of research papers dedicated to micas is enormous, but knowledge of them is limited and not as extensive as that of other rock-forming minerals, for reasons mostly relating to their complex layer texture that makes obtaining crystals suitable for careful studies with the modern methods time-consuming, painstaking work. Micas were reviewed extensively in 1984 (Reviews in Mineralogy 13, S.W. Bailey, editor). At that time, “Micas” volume …

Description / Table of Contents: The scientific discoveries that have been made with noble gas geochemistry are of such a profound and fundamental nature that earth science textbooks should be full of examples. Surprisingly, this really is not so. The "first discoveries" include presolar components in our _ solar system, extinct radionuclides, primordial volatiles in the Earth, the degassing history of Mars, secular changes in the solar wind, reliable present day mantle degassing fluxes, the fluxes of extraterrestrial material to Earth, groundwater paleotemperatures and the ages of the oldest landscapes on Earth. Noble gas geochemistry has scored so many such "firsts" or "home runs" that it should permeate a lot of earth science thinking and teaching. Yet rather surprisingly it does not. Noble gas geochemistry also is a broader and more versatile field than almost any other area of geochemistry. It pervades cosmochemistry, Earth sciences, ocean sciences, climate studies and environmental sciences. Yet most modern Earth, planetary and environmental science departments do not consider noble gas geochemistry to be at the top of their list in terms of hiring priorities these days. Furthermore, with the exception of Ar geochronologists, noble gas geochemists are a surprisingly rare breed. Why is the above the case? Perhaps the reasons lie in the nature of the field itself. First, although noble gas geochemists work on big problems, the context of their data is often woefully under-constrained so that it becomes hard to make progress beyond the first order fundamental discoveries. Noble gas data are often difficult to interpret. Although some concepts are straightforward and striking in their immediate implications (e.g. mantle 3He in the oceans), others are to this day shrouded in lack of clarity. The simple reason for this is that in many situations it is only the noble gases that offer any real insights at all and the context of other constraints simply does not exist. Some examples of the big issues being addressed by noble gases are as follows and I have deliberately posed these as major unresolved questions that only exist because noble gas geochemistry has opened windows through which to view large-scale issues and processes that otherwise would be obscure. (1) Is the presolar noble gas component present in a tiny fraction of submicroscopic meteoritic C or is it ubiquitously distributed? (2) How did solar noble gases get incorporated into the Earth? (3) How did solar noble gases survive the protracted accretion of the Earth via giant impacts? (4) What is the origin of the noble gas pattern in the Earth's atmosphere? (5) Why are the Earth and Mars almost opposites in terms of the relative isotopic differences between atmosphere and mantle? (6) What is the Eresent source of Earth's primordial helium? Can we ignore the core? (7) What is the 2~e/ 2Ne of the mantle, how was it acquired and why is it different from the atmosphere? (8) How does one reconcile the stronlJ fractionation in terrestrial Xe with data for other noble gases? (9) How much radiogenic Ar should the Earth have? How well do we know KIU? (10) Are the light isotopes of Xe the same in the mantle and the atmosphere? If not, why not? (11) How are noble gases transported through the creeping solid earth? (12) How does one explain the heat - helium paradox? (13) How incompatible are the noble gases during melting? (14) How are atmospheric components incorporated into volcanic samples? (15) How are the excess air components incorporated into groundwater? (16) Why are continental noble gas paleotemperature records offset from oceanic temperature records? Noble gas data tell us that the Earth and solar system represent very complex environments. When we make our simple first order conclusions and models we are only at the tip of the iceberg of discoveries that are needed to arrive at a thorough understanding of the behavior of volatiles in the solar system. Who wants to hear that things are complicated? Who wants to hire in a field that will involve decades of data acquisition and analysis in order to sort out the solar system? Sadly, too few these days. This is the stuff of deep scientific giants and bold, technically difficult long-term research programs. It is not for those who prefer superficiality and quick, glamorous, slick answers. Noble gas geochemists work in many areas where progress is slow and difficult even though the issues are huge. This probably plays a part in the limited marketability of noble gas geochemistry to the nonspecialist. Second, noble gases is a technically difficult subject. That is, noble gas geochemists need to be adept 11t technique development and this has to include skills acquired through innovation in the lab. Nobody can learn this stuff merely with a book or practical guide. Reading Zen and the Art of Motorcycle Maintenance (by Robert Pirsig) would give you a clearer picture. This magnificent MSA-GS volume is going to be enormously useful but on its own it won't make anybody into a noble gas geochemist. Although the mass spectrometry principles are not complex, the tricks involved in getting better data are often self taught or passed on by working with individuals who themselves are pushing the boundaries further. Furthermore, much of the exciting new science is linked with technical developments that allow us to move beyond the current measurement capabilities. Be they better crushing devices, laser resonance time of flight, multiple collection or compressor sources - the technical issues are central to progress. Lastly, noble gas geochemists need a broad range of other skills in order to make progress. They have to be good at mass spectrometry as already stated. However, nowadays they also need to be able to understand fields as different as mantle geochemistry, stellar evolution, cosmochemistry, crustal fluids, oceanography and glaciology. They are kind of "Renaissance" individuals. Therefore, if you are thinking broadly about hiring scientists who love science and stand a good chance of making a major difference to our understanding of the solar system, earth and its environment - I would recommend you hire a really good noble gas geochemist. However, the results may take a while. If you want somebody who will crank out papers at high speed and quickly increase the publication numbers of your department then you may need to think about somebody else. The two are not mutually exclusive but think hard about what is really important. There was no short course associated with this volume, although an attempt was undertaken to get the volume printed in time for the V. M. Goldschmidt conference in Davos, Switzerland (mid-August 2002) at which there was a major symposium on noble gases.

Description / Table of Contents: In the two decades since J. Alexander Speer's Zircon chapter in Orthosilicates (Reviews in Mineralogy, Vol. 5), much has been learned about the internal textures, trace-element and isotope geochemistry (both radiogenic and stable) and chemical and mechanical stability of zircon. The application of this knowledge and the use of zircon in geologic studies have become widespread. Today, the study of zircon exists as the pseudo-discipline of "zirconology" that involves materials scientists and geoscientists from across a range of sub-disciplines including stable and radiogenic isotopes, sedimentology, petrology, trace elements and experimental mineralogy. Zirconology has become an important field of research, so much so that coverage of the mineral zircon in a review volume that included zircon as one of many accessory minerals would not meet the needs or interests of the zirconology community in terms of depth or breadth of coverage. The sixteen chapters in this volume cover the most important aspects of zircon-related research over the past twenty-years and highlight possible future research avenues. Finch and Hanchar (Chapter 1) review the structure of zircon and other mineral (and synthetic) phases with the zircon structure. In most rock types where zircon occurs it is a significant host of the rare-earth elements, Th and U. The abundances of these elements and the form of chondrite-normalized rare-earth element patterns may provide significant information on the processes that generate igneous and metamorphic rocks. The minor and trace element compositions of igneous, metamorphic and hydrothermal zircons are reviewed by Hoskin and Schaltegger in Chapter 2. The investigation of melt inclusions in zircon is an exciting line of new research. Trapped melt inclusions can provide direct information of the trace element and isotopic composition of the melt from which the crystal formed as a function of time throughout the growth of the crystal. Thomas et a!. (Chapter 3) review the study of melt inclusions in zircon. Hanchar and Watson (Chapter 4) review experimental and natural studies of zircon saturation and the use of zircon saturation thermometry for natural rocks. Cation diffusion and oxygen diffusion in zircon is discussed by Cherniak and Watson (Chapter 5). Diffusion studies are essential for providing constraints on the quality of trace element and isotope data and for providing estimates of temperature exposure in geological environments. Zircon remains the most widely utilized accessory mineral for U- Th-Pb isotope geochronology. Significant instrumental and analytical developments over the past thirty years mean that zircon has an essential role in early Achaean studies, magma genesis, and astrobiology. Four chapters are devoted to different aspects of zircon geochronology. The first of these four, Chapter 6 by Davis et a!., reviews the historical development of zircon geochronology from the mid-1950s to the present; the following three chapters focus on particular techniques for zircon geochronology, namely ID-TIMS (Parrish and Noble, Chapter 7), SIMS (Ireland and Williams, Chapter 8) and ICP-MS (Kosier and Sylvester, Chapter 9). The application of zircon chronology in constraining sediment provenance.and the calibration ofthe geologic time-scale are reviewed by Fedo et al. (Chapter 10) and Bowring and Schmitz (Chapter 11), respectively. Other isotopic systematics are reviewed for zircon by Kinny and Maas (Chapter 12), who discuss the application of Nd-Sm and Lu-Hf isotopes in zircon to petrogenetic studies, and by Valley (Chapter 13), who discusses the importance of oxygen isotopic studies in traditional and emerging fields of geologic study. As a host of U and Th, zircon is subject to radiation damage. Radiation damage is likely responsible for isotopic disturbance and promotes mechanical instability. There is increasing interest in both the effect of radiation damage on the zircon crystal structure and mechanisms of damage and recrystallization, as well as the structure of the damaged phase. These studies contribute to an overall understanding of how zircon may behave as a waste-form for safe disposal of radioactive waste and are discussed by Ewing et a!. (Chapter 14). The spectroscopy of zircon, both crystalline and metamict is reviewed by Nadsala et a!. (Chapter 15). The final chapter, by Corfu et al. (Chapter 16), is an atlas of internal textures of zircon. The imaging of internal textures in zircon is essential for directing the acquisition of geochemical data and to the integrity of conclusions reached once data has been collected and interpreted. This chapter, for the first time, brings into one place textural images that represent common and not so common textures reported in the literature, along with brief interpretations of their significance. There is presently no comparable atlas. It is intended that this chapter will become a reference point for future workers to compare and contrast their own images against. The chapters in this volume of Reviews in Mineralogy and Geochemistry were prepared for presentation at a Short Course, sponsored by the Mineralogical Society of America (MSA) in Freiburg, Germany, April 3-4, 2003. This preceded a joint meeting of the European Union of Geology, the American Geophysical Union and the European Geophysical Society held in Nice, France, April 6-11, 2003.