ALBERT

Beschreibung / Inhaltsverzeichnis: Hydrogen may be the most abundant element in the universe, but in science and in nature oxygen has an importance that is disproportionate to its abundance. Human beings tend to take it for granted because it is all around us and we breathe it, but consider the fact that oxygen is so reactive that in a planetary setting it is largely unstable in its elemental state. Were it not for the constant activity of photosynthetic plants and a minor amount of photo dissociation in the upper atmosphere, we would not have an oxygen-bearing atmosphere and we would not be here. Equally, the most important compound of oxygen is water, without which life (in the sense that we know it) could not exist. The role of water in virtually all geologic processes is profound, from formation of ore deposits to igneous petrogenesis to metamorphism to erosion and sedimentation. In planetary science, oxygen has a dual importance. First and foremost is its critical role in so many fundamental Solar System processes. The very nature of the terrestrial planets in our own Solar System would be much different had the oxygen to carbon ratio in the early solar nebula been somewhat lower than it was, because elements such as calcium and iron and titanium would have been locked up during condensation as carbides, sulfides and nitrides and even (in the case of silicon) partly as metals rather than silicates and oxides. Equally, the role of water ice in the evolution of our Solar System is important in the early accretion and growth of the giant planets and especially Jupiter, which exerted a major control over how most of the other planets formed. On a smaller scale, oxygen plays a critical role in the diverse kinds of physical evolution of large rocky planets, because the internal oxidation state strongly influences the formation and evolution of the core, mantle and crust of differentiated planets such as the Earth. Consider that basaltic volcanism may be a nearly universal phenomenon among the evolved terrestrial planets, yet there are basalts and basalts. The basalts of Earth (mostly), Earth's Moon, Vesta (as represented by the HED meteorites) and Mars are all broadly tholeiitic and yet very different from one another, and one of the primary differences is in their relative oxidation states (for that matter, consider the differences between tholeiitic and calc-alkaline magma series on Earth). But there is another way that oxygen has proven to be hugely important in planetary science, and that is as a critical scientific clue to processes and conditions and even sources of materials. Understanding the formation and evolution of our Solar System involves reconstructing processes and events that occurred more than 4.5 Ga ago, and for which the only contemporary examples are occurring hundreds of light years away. It is a detective story in which most of the clues come from the laboratory analysis of the products of those ancient processes and events, especially those that have been preserved nearly unchanged since their formation at the Solar System's birth: meteorites; comets; and interplanetary dust particles. For example, the oxidation state of diverse early Solar System materials ranges from highly oxidized (ferric iron) to so reducing that some silicon exists in the metallic state and refractory lithophile elements such as calcium exist occur in sulfides rather than in silicates or carbonates. These variations reflect highly different environments that existed in different places and at different times. Even more crucial has been the use of oxygen 3-isotope variations, which began almost accidentally in 1973 with an attempt to do oxygen isotope thermometry on high-temperature solar nebula grains (Ca-, Al-rich inclusions) but ended with the remarkable discovery of non-mass-dependent oxygen isotope variations in high-temperature materials from the earliest Solar System. The presolar nebula was found to be very heterogeneous in its isotopic composition, and virtually every different planet and asteroid for which we have samples has a unique oxygen-isotopic fingerprint. The idea for this book originated with Jim Papike, who suggested the idea of a study initiative (and, ultimately, a published volume) focused on the element that is so critically important in so many ways to planetary science. He recognized that oxygen is such a constant theme through all aspects of planetary science that the proposed initiative would serve to bring together scientists from a wide range of disciplines for the kind of cross-cutting dialogue that occurs all too rarely these days. In this sense the Oxygen Initiative is modeled on the Basaltic Volcanism Study Project, which culminated in what remains to this day a hugely important reference volume (Basaltic Volcanism Study Project 1981). After obtaining community input and feedback, primarily through the Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM) and the Management Operations Working Group for NASA's Cosmochemistry Program, a team of scientists was assembled who would serve as chapter writing leads, and the initiative was formally proposed to and accepted by the Lunar and Planetary Institute (LPI; Dr. Stephen Mackwell, Director) for sponsorship. A formal proposal was then submitted to and approved by the Mineralogical Society of America to publish the resulting volume in the Reviews in Mineralogy and Geochemistry (RiMG) series. Three open workshops were held as preludes to the book: Oxygen in the Terrestrial Planets, held in Santa Fe, NM July 20-23, 2004; Oxygen in Asteroids and Meteorites, held in Flagstaff, AZ June 2-3, 2005; and Oxygen in Earliest Solar System Materials and Processes (and including the outer planets and comets), held in Gatlinburg, TN September 19-22, 2005. The workshops were each organized around a small number of sessions (typically 4-6), each focusing on a particular topic and consisting of invited talks, shorter contributed talks, and ample time for discussion after each talk. In all of the meetings, the extended discussion periods were lively and animated, often bubbling over into the breaks and later social events. As a consequence of the cross-cutting approach, the final book spans a wide range of fields relating to oxygen, from the stellar nucleosynthesis of oxygen, to its occurrence in the interstellar medium, to the oxidation and isotopic record preserved in 4.56 Ga grains formed at the Solar System's birth, to its abundance and speciation in planets large and small, to its role in the petrologic and physical evolution of the terrestrial planets.

Beschreibung / Inhaltsverzeichnis: Fluids rich in water, carbon and sulfur species and a variety of dissolved salts are a ubiquitous transport medium for heat and matter in the Earth’s interior. Fluid transport through the upper mantle and crust controls the origin of magmatism above subduction zones and results in natural risks of explosive volcanism. Fluids passing through rocks affect the chemical and heat budget of the global oceans, and can be utilized as a source of geothermal energy on land. Fluid transport is a key to the formation and the practical utilization of natural resources, from the origin of hydrothermal mineral deposits, through the exploitation of gaseous and liquid hydrocarbons as sources of energy and essential raw materials, to the subsurface storage of waste materials such as CO2. Different sources of fluids and variable paths of recycling volatile components from the hydrosphere and atmosphere through the solid interior of the Earth lead to a broad range of fluid compositions, from aqueous liquids and gases through water-rich silicate or salt melts to carbon-rich endmember compositions. Different rock regimes in the crust and mantle generate characteristic ranges of fluid composition, which depending on pressure, temperature and composition are miscible to greatly variable degrees. For example, aqueous liquids and vapors are increasingly miscible at elevated pressure and temperature. The degree of this miscibility is, however, greatly influenced by the presence of additional carbonic or salt components. A wide range of fluid–fluid interactions results from this partial miscibility of crustal fluids. Vastly different chemical and physical properties of variably miscible fluids, combined with fluid flow from one pressure – temperature regime to another, therefore have major consequences for the chemical and physical evolution of the crust and mantle. Several recent textbooks and review articles have addressed the role and diverse aspects of fluids in crustal processes. However, immiscibility of fluids and the associated phenomena of m ultiphase fluid flow are generally dealt with only in subsections with respect to specific environments and aspects of fluid mediated processes. This volume of Reviews in Mineralogy and Geochemistry attempts to fill this gap and to explicitly focus on the role that co-existing fluids play in the diverse geologic environments. It brings together the previously somewhat detached literature on fluid–fluid interactions in continental, volcanic, submarine and subduction zone environments. It emphasizes that fluid mixing and unmixing are widespread processes that may occur in all geologic environments of the entire crust and upper mantle. Despite different P-T conditions, the fundamental processes are analogous in the different settings.

Beschreibung / Inhaltsverzeichnis: The idea for this book was conceived in early June, 2005 at a paleoaltimetry workshop held at Lehigh University, Lehigh, Pennsyalvania and organized by Dork Sahagian. The workshop was funded by the tectonics program at NSF, and was designed to bring together researchers in paleoaltimetry to discuss different techniques and focus the community on ways of improving paleoelevation estimates and consequent interpretations of geodynamics and tectonics. At this meeting, some commented that a comprehensive volume describing the different methods could help advance the field. I offered to contact the Mineralogical Society of America and the Geochemical Society about publishing a RiMG volume on paleoaltimetry. Because many of the techniques used to infer paleoelevations are geochemically-based or deal with thermodynamic principles, the GS and MSA agreed to the project. Two years and roughly 1000 e-mails later, our book has arrived. The book is organized into 4 sections: Geodynamic and geomorphologic rationale (Clark). This chapter provides the broad rationale behind paleoaltimetry, i.e., why we study it. Stable isotope proxies. These 4 chapters cover theory of stable isotopes in precipitation and their response to altitudinal gradients (Rowley), and stable isotopes sytematics in paleosols (Quade, Garzione and Eiler), silicates (Mulch and Chamberlain) and fossils (Kohn and Dettman). Proxies of atmospheric properties. These 4 chapters cover temperature lapse rates (Meyer), entropy (Forest), and atmospheric pressure proxies, including total atmospheric pressure from gas bubbles in basalt (Sahagian and Proussevitch), and the partial pressure of CO2 (Kouwenberg, Kürshner, and McElwain). Note that clumped isotope thermometry (Quade, Garzione and Eiler) also provides direct estimates of temperature. Radiogenic and cosmogenic nuclides. These 2 chapters cover low-temperature thermochronologic approaches (Reiners) and cosmogenic isotopes (Riihimaki and Libarkin). Some chapters overlap in general content (e.g., basic principles of stable isotopes in precipitation are covered to different degrees in all stable isotope chapters), but no attempt was made to limit authors' discussion of principles, or somehow attempt to arrive at a "consensus view" on any specific topic. Because science advances by critical discussion of concepts, such restrictions were viewed as counterproductive. This does mean that different chapters may present different views on reliability of paleoelevation estimates, and readers are advised to read other chapters in the book on related topics – they may be more closely linked than they might at first appear! I hope readers of this book will discover and appreciate the synergy among paleoaltimetry, climate change, and tectonic geomorphology. These interrelationships create a complex, yet rich field of scientific enquiry that in turn offers insights into climate and geodynamics.

Beschreibung / Inhaltsverzeichnis: Over 25 years ago, Volume 9 of Reviews in Mineralogy: Amphiboles and Other Hydrous Pyriboles seemed to contain all that was possible to know about this group of fascinating minerals. The subsequent twenty-five years have shown that this assessment was wrong: Nature was keeping a lot in reserve, and has since revealed considerable new complexity in the constitution and behavior of amphiboles. Some of the advances in knowledge have been due to the use of new experimental techniques, some have been due to the investigation of hitherto neglected rock-types, and some have been due to the development of new ideas. The identification and systematic investigation of variable LLE (Light Lithophile Elements), particularly Li and H, led to the identification of several new amphibole species and the recognition that variable Li and H play an important role in chemical variations in amphiboles from both igneous and metamorphic parageneses. In turn, this work drove the development of microbeam SIMS to analyze LLE in amphiboles. Detailed mineralogical work on metasyenites showed hitherto unexpected solid-solution between Na and Li at the M(4) site in monoclinic amphiboles, a discovery that has upset the current scheme of amphibole classification and nomenclature and initiated new efforts in this direction. Systematic and well-planned synthesis of amphiboles, combined with careful spectroscopy, has greatly furthered our understanding of cation and anion order in amphiboles. The use of bond-valence theory to predict patterns of SRO (Short-Range Order) in amphiboles, and use of these predictions to understand the infrared spectra of well-characterized synthetic-amphibole solid-solutions, has shown that SRO is a major feature of the amphibole structure, and has resulted in major advances in our understanding of SRO in minerals. There has been significant progress relating changes in amphibole composition and cation ordering to petrogenetic conditions and trace-element behavior. Work on the nature of fibrous amphiboles and their toxicity and persistence in living organisms has emphasized the importance of accurate mineralogical characterization in environmental and health-related problems. The current volume has taken a different approach from previous volumes concerned with major groups of rock-forming minerals. Some of the contents have previously been organized by the investigative technique or groups of similar techniques: crystal-structure refinement, spectroscopy, TEM etc. Here, we have taken an approach that focuses on aspects of amphiboles rather than experimental techniques: crystal chemistry, new compositions, long-range order, short-range order etc., and all experimental results germane to these topics are discussed in each chapter. The intent of this approach is to focus on amphiboles, and to emphasize that many techniques are necessary to fully understand each aspect of the amphiboles and their behavior in both natural and industrial processes.

Beschreibung / Inhaltsverzeichnis: The importance of sulfide minerals in ores has long been, and continues to be, a major reason for the interest of mineralogists and geochemists in these materials. Determining the fundamental chemistry of sulfides is key to understanding their conditions of formation and, hence, the geological processes by which certain ore deposits have formed. This, in turn, may inform the strategies used in exploration for such deposits and their subsequent exploitation. In this context, knowledge of structures, stabilities, phase relations and transformations, together with the relevant thermodynamic and kinetic data, is critical. As with many geochemical systems, much can also be learned from isotopic studies. The practical contributions of mineralogists and geochemists to sulfide studies extend beyond areas related to geological applications. The mining of sulfide ores, to satisfy ever increasing world demand for metals, now involves extracting very large volumes of rock that contains a few percent at most (and commonly less than one percent) of the metal being mined. This is true of relatively low value metals such as copper; for the precious metals commonly occurring as sulfides, or associated with them, the mineable concentrations (grades) are very much lower. The "as-mined" ores therefore require extensive processing in order to produce a concentrate with a much higher percentage content of the metal being extracted. Such mineral processing (beneficiation) involves crushing and grinding of the ores to a very fine grain size in order to liberate the valuable metal-bearing (sulfide) minerals which can then be concentrated. In some cases, the metalliferous (sulfide) minerals may have specific electrical or magnetic properties that can be exploited to enable separation and, hence, concentration. More commonly, froth flotation is used, whereby the surfaces of particles of a particular mineral phase are rendered water repellent by the addition of chemical reagents and hence are attracted to air bubbles pulsed through a mineral particle-water-reagent pulp. An understanding of the surface chemistry and surface reactivity of sulfide minerals is central to this major industrial process and, of course, knowledge of electrical and magnetic properties is very important in cases where those particular properties can be utilized. In the years since the publication of the first ever Reviews in Mineralogy volume (1974, at that time called MSA "Short Course Notes") which was entitled Sulfide Mineralogy, sulfides have become a focus of research interest for reasons centering on at least two other areas in addition to their key role in ore deposit studies and mineral processing technology. It is in these two new areas that much of the research on sulfides has been concentrated in recent years. The first of these areas relates to the capacity of sulfides to react with natural waters and acidify them; the resulting Acid Rock Drainage (ARD), or Acid Mine Drainage (AMD) where the sulfides are the waste products of mining, has the capacity to damage or destroy vegetation, fish and other aquatic life forms. These acid waters may also accelerate the dissolution of associated minerals containing potentially toxic elements (e.g., As, Pb, Cd, Hg, etc.) and these may, in turn, cause environmental damage. The much greater public awareness of the need to prevent or control AMD and toxic metal pollution has led to regulation and legislation in many parts of the world, and to the funding of research programs aimed at a greater understanding of the factors controlling the breakdown of sulfide minerals. We begin with a review of analytical methods for measuring and calibrating water contents in nominally anhydrous minerals by George Rossman. While infrared spectroscopy is still the most sensitive and most convenient method for detecting water in minerals, it is not intrinsically quantitative but requires calibration by some other, independent analytical method, such as nuclear reaction analysis, hydrogen manometry, or SIMS. A particular advantage of infrared spectroscopy, however, is the fact that it does not only probe the concentration, but also the structure of hydrous species in a mineral and in many cases the precise location of a proton in a mineral structure can be worked out based on infrared spectra alone. The methods and principles behind this are reviewed by Eugen Libowitzky and Anton Beran, with many illustrative examples. Compared to infrared spectroscopy, NMR is much less used in studying hydrogen in minerals, mostly due to its lower sensitivity, the requirement of samples free of paramagnetic ions such as Fe2+ and because of the more complicated instrumentation required for NMR measurements. However, NMR could be very useful under some circumstances. It could detect any hydrogen species in a sample, including such species as H2 that would be invisible with infrared. Potential applications of NMR to the study of hydrogen in minerals are reviewed by Simon Kohn. While structural models of "water" in minerals have already been deduced from infrared spectra several decades ago, in recent years atomistic modeling has become a powerful tool for predicting potential sites for hydrogen in minerals. The review by Kate Wright gives an overview over both quantum mechanical methods and classical methods based on interatomic potentials. Joseph Smyth then summarizes the crystal chemistry of hydrogen in high-pressure silicate and oxide minerals. As a general rule, the incorporation of hydrogen is not controlled by the size of potential sites in the crystal lattice; rather, the protons will preferentially attach to oxygen atoms that are electrostatically underbonded, such as the non-silicate oxygen atoms in some high-pressure phases. Moreover, heterovalent substitutions, e.g., the substitution of Al3+ for Si4+, can have a major effect on the incorporation of hydrogen. The second reason for even greater research interest in sulfide minerals arose initially from the discoveries of active hydrothermal systems in the deep oceans. The presence of life forms that have chemical rather than photosynthetic metabolisms, and that occur in association with newly-forming sulfides, has encouraged research on the potential of sulfide surfaces in catalyzing the reactions leading to assembling of the complex molecules needed for life on Earth. These developments have been associated with a great upsurge of interest in the interactions between microbes and minerals, and in the role that minerals can play in biological systems. In the rapidly growing field of geomicrobiology, metal sulfides are of major interest. This interest is related to a variety of processes including, for example, those where bacteria interact with sulfides as part of their metabolic activity and cause chemical changes such as oxidation or reduction, or those in which biogenic sulfide minerals perform a specific function, such as that of navigation in magnetotactic bacteria. The development of research in areas such as geomicrobiology and environmental mineralogy and geochemistry, is also leading to a greater appreciation of the role of sulfides (particularly the iron sulfides) in the geochemical cycling of the elements at or near the surface of the Earth. For example, the iron sulfides precipitated in the reducing environments beneath the surface of modern sediments in many estuarine areas may play a key role in the trapping of toxic metals and other pollutants. In our understanding of "Earth Systems," geochemical processes involving metal sulfides are an important part of the story. The main objective of the present text is to provide an up-to-date review of sulfide mineralogy and geochemistry. The emphasis is, therefore, on such topics as crystal structure and classification, electrical and magnetic properties, spectroscopic studies, chemical bonding, high and low temperature phase relations, thermochemistry, and stable isotope systematics. In the context of this book, emphasis is on metal sulfides sensu stricto where only the compounds of sulfur with one or more metals are considered. Where it is appropriate for comparison, there is brief discussion of the selenide or telluride analogs of the metal sulfides. When discussing crystal structures and structural relationships, the sulfosalt minerals as well as the sulfides are considered in some detail (see Chapter 2; also for definition of the term "sulfosalt"). However, in other chapters there is only limited discussion of sulfosalts, in part because there is little information available beyond knowledge of chemical composition and crystal structure. Given the dramatic developments in areas of research that were virtually non-existent at the time of the earlier reviews, major sections have been added here on sulfide mineral surface chemistry and reactivity, formation and transformation of metal-sulfur clusters and nanoparticles, modeling of hydrothermal precipitation, and on sulfides in biosystems. However, it should be emphasized that the growth in the literature on certain aspects of sulfide mineralogy over the past 20 years or so has been such that comprehensive coverage is not possible in a single volume. Thus, the general area of "sulfides in biosystems" is probably worthy of a volume in itself, and "environmental sulfide geochemistry" (including topics such as oxidative breakdown of sulfides) is another area where far more could have been written. In selecting areas for detailed coverage in this volume, we have been mindful of the existence of other relatively recent review volumes, including those in the RiMG series. It has also been our intention not to cover any aspects of the natural occurrence, textural or paragenetic relationships involving sulfides. This is published information that, although it may be supplemented by new observations, is likely to remain useful for a long period and largely not be superceded by later work. In the following chapters, the crystal structures, electrical and magnetic properties, spectroscopic studies, chemical bonding, thermochemistry, phase relations, solution chemistry, surface structure and chemistry, hydrothermal precipitation processes, sulfur isotope geochemistry and geobiology of metal sulfides are reviewed. Makovicky (Chapter 2) discusses the crystal structures and structural classification of sulfides and other chalcogenides (including the sulfosalts) in terms of the relationships between structural units. This very comprehensive survey, using a rather different and complementary approach to that used in previous review volumes, shows the great diversity of sulfide structures and the wealth of materials that remain to be characterized in detail. These materials include rare minerals, and synthetic sulfides that may represent as yet undescribed minerals. Pearce, Pattrick and Vaughan (Chapter 3) review the electrical and magnetic properties of sulfides, discussing the importance of this aspect of the sulfides to any understanding of their electronic structures (chemical bonding) and to applications ranging from geophysical prospecting and mineral extraction to geomagnetic and palaeomagnetic studies. Rapidly developing new areas of interest discussed include studies of the distinctive properties of sulfide nanoparticles. Wincott and Vaughan (Chapter 4) then outline the spectroscopic methods employed to study the crystal chemistry and electronic structures of sulfides. These range from UV-visible through infrared and Raman spectroscopies, to X-ray emission, photoemission and absorption, and to nuclear spectroscopies. Chemical bonding (electronic structure) in sulfides is the subject of the following chapter by Vaughan and Rosso (Chapter 5), a topic which draws on knowledge of electrical and magnetic properties and spectroscopic data as experimental input, as well as on a range of rapidly developing computational methods. Attention then turns to the thermochemistry of sulfides in a chapter by Sack and Ebel (Chapter 6) which is followed by discussion of phase equilibria at high temperatures in the review by Fleet (Chapter 7). Sulfides in aqueous systems, with emphasis on solution complexes and clusters, forms the subject matter of the chapter written by Rickard and Luther (Chapter 8). Sulfide mineral surfaces are the focus of the next two chapters, both by Rosso and Vaughan. The first of these chapters (Chapter 9) addresses characterization of the pristine sulfide surface, its structure and chemistry; the second (Chapter 10) concerns surface reactivity, including redox reactions, sorption phenomena, and the catalytic activity of sulfide surfaces. Reed and Palandri (Chapter 11) show in the next chapter how much can now be achieved in attempting to predict processes of sulfide precipitation in hydrothermal systems. The final chapters deal with two distinctive areas of sulfide mineralogy and geochemistry. Seal (Chapter 12) presents a comprehensive account of the theory and applications of sulfur isotope geochemistry; sulfur isotope fractionation can provide the key to understanding the natural processes of formation of sulfide deposits. In the final chapter, Posfai and Dunin-Borkowski (Chapter 13) review the rapidly developing area of sulfides in biosystems, discussing aspects of both sulfide mineral-microbe interactions and biomineralization processes involving sulfides.

Beschreibung / Inhaltsverzeichnis: As geomicrobiologists, we seek to understand how some of nature's most complex systems work, yet the very complexity we seek to understand has placed many of the insights out of reach. Recent advances in cultivation methodologies, the development of ultrahigh throughput DNA sequencing capabilities, and new methods to assay gene expression and protein function open the way for rapid progress. In the eight years since the first Geomicrobiology volume (Geomicrobiology: Interactions between microbes and minerals; volume 35 in this series) we have transformed into scientists working hand in hand with biochemists, molecular biologists, genome scientists, analytical chemists, and even physicists to reveal the most fundamental molecular-scale underpinnings of biogeochemical systems. Through synthesis achieved by integration of diverse perspectives, skills, and interests, we have begun to learn how organisms mediate chemical transformations, the ways in which the environment determines the architecture of microbial communities, and the interplay between evolution and selection that shapes the biodiversity of the planet. This volume presents chapters written by leaders in the rapidly maturing field we refer to as molecular geomicrobiology. Most of them are relatively young researchers who share their approaches and insights and provide pointers to exciting areas ripe for new advances. This volume ties together themes common to environmental microbiology, earth science, and astrobiology. The resesarch presented here, the associated short course, and the volume production were supported by funding from many sources, notably the Mineralogical Society of America, the Geochemical Society, the US Department of Energy Chemical Sciences Program and the NASA Astrobiology Institute.

Beschreibung / Inhaltsverzeichnis: The publication of this volume occurs at the one-hundredth anniversary of 1905, which has been called the annus mirabilus because it was the year of a number of enormous scientific advances. Among them are four papers by Albert Einstein explaining (among other things) Brownian motion, the photoelectric effect, the special theory of relativity, and the equation E = mc2. Also of significance in 1905 was the first application of another major advance in physics, which dramatically changed the fields of Earth and planetary science. In March of 1905 (and published the following year), Ernest Rutherford presented the following in the Silliman Lectures at Yale: "The helium observed in the radioactive minerals is almost certainly due to its production from the radium and other radioactive substances contained therein. If the rate of production of helium from known weights of the different radioelements were experimentally known, it should thus be possible to determine the interval required for the production of the amount of helium observed in radioactive minerals, or, in other words, to determine the age of the mineral." Rutherford E (1906) Radioactive Transformations. Charles Scriber's Sons, NY Thus radioisotopic geochronology was born, almost immediately shattering centuries of speculative conjectures and estimates and laying the foundation for establishment of the geologic timescale, the age of the Earth and meteorites, and a quantitative understanding of the rates of processes ranging from nebular condensation to Quaternary glaciations. There is an important subplot to the historical development of radioisotopic dating over the last hundred years, which, ironically, arises directly from the subsequent history of the U-He dating method Rutherford described in 1905. Almost as soon as radioisotopic dating was invented, it was recognized that the U-He [or later the (U-Th)/He method], provided ages that were often far younger than those allowed by stratigraphic correlations or other techniques such as U/Pb dating. Clearly, as R.J. Strutt noted in 1910, He ages only provided "minimum values, because helium leaks out from the mineral, to what extent it is impossible to say" (Strutt, 1910, Proc Roy Soc Lond, Ser A 84:379-388). For several decades most attention was diverted to U/Pb and other techniques better suited to measurement of crystallization ages and establishment of the geologic timescale. Gradually it became clear that other radioisotopic systems such as K/Ar and later fission-track also provided ages that were clearly younger than formation ages. In 1910 it may have been impossible to say the extent to which He (or most other elements) leaked out of minerals, but eventually a growing understanding of thermally-activated diffusion and annealing began to shed light on the significance of such ages. The recognition that some systems can provide cooling, rather than formation, ages, was gradual and diachronous across radioisotopic systems. Most of the heavy lifting in this regard was accomplished by researchers working on the interpretation of K/Ar and fission-track ages. Ironically, Rutherfordπs He-based radioisotopic system was one of the last to be quantitatively interpreted as a thermochronometer, and has been added to K/Ar (including 40Ar/39Ar) and fission-track methods as important for constraining the medium- to low-temperature thermal histories of rocks and minerals. Thermochronology has had a slow and sometimes fitful maturation from what were once troubling age discrepancies and poorly-understood open-system behaviors, into a powerful branch of geochronology applied by Earth scientists from diverse fields. Cooling ages, coupled with quantitative understanding of crystal-scale kinetic phenomena and crustal- or landscape-scale interpretational models now provide an enormous range of insights into tectonics, geomorphology, and subjects of other fields. At the same time, blossoming of lower temperature thermochronometric approaches has inspired new perspectives into the detailed behavior of higher temperature systems that previously may have been primarily used for establishing formation ages. Increased recognition of the importance of thermal histories, combined with improved analytical precision, has motivated progress in understanding the thermochronologic behavior of U/Pb, Sm/Nd, Lu/Hf, and other systems in a wide range of minerals, filling out the temperature range accessible by thermochronologic approaches. Thus the maturation of low- and medium-temperature thermochronology has led to a fuller understanding of the significance of radioisotopic ages in general, and to one degree or another has permeated most of geochronology. Except in rare cases, the goal of thermochronology is not thermal histories themselves, but rather the geologic processes responsible for them. Thermochronometers are now routinely used for quantifying exhumation histories (tectonic or erosional), magmatism, or landscape evolution. As thermochronology has matured, so have model and interpretational approaches used to convert thermal histories into these more useful geologic histories. Low-temperature thermochronology has been especially important in this regard, as knowledge of thermal processes in the uppermost few kilometers of the crust require consideration of coupled interactions of tectonic, geodynamic, and surface processes. Exciting new developments in these fields in turn drive improved thermochronologic methods and innovative sampling approaches. The chapters This volume presents 22 chapters covering many of the important modern aspects of thermochronology. The coverage of the chapters ranges widely, including historical perspective, analytical techniques, kinetics and calibrations, modeling approaches, and interpretational methods. In general, the chapters focus on intermediate- to low-temperature thermochronometry, though some chapters cover higher temperature methods such as monazite U/Pb closure profiles, and the same theory and approaches used in low-temperature thermochronometry are generally applicable to higher temperature systems. The widely used low- to medium-temperature thermochronometric systems are reviewed in detail in these chapters, but while there are numerous chapters reviewing various aspects of the apatite (U-Th)/He system, there is no chapter singularly devoted to it, partly because of several previous reviews recently published on this topic. Chapter 1 by Reiners, Ehlers, and Zeitler provides a perspective on the history of thermochronology, comments on modern work in this field and general lessons on the potential for noise to be turned into signal. This chapter also provides a summary of the current challenges, unresolved issues, and most exciting prospects in the field. Much of the modern understanding of kinetic controls on apparent ages, thermal histories, and sampling approaches comes from decades of progress in fission-track dating, a method that remains as essential as ever, partly because of the power of track-length measurements and the depth of (at least empirical) understanding of the kinetics of track annealing. Tagami, Donelick and OπSullivan review the fundamentals of modern fission-track dating (Chapter 2). Two of the most commonly dated, well-understood, and powerful minerals dated by fission-track methods are apatite and zircon, and the specifics of modern methods for these systems and their kinetics are reviewed by Donelick, OπSullivan, and Ketcham (Chapter 3), and Tagami (Chapter 4). Although 40Ar/39Ar and (U-Th)/He dating methods followed somewhat different paths to their modern thermochronologic incarnations, they have many features in common, especially in the kinetics of diffusion and closure. Zeitler and Harrison review the concepts underlying both 40Ar/39Ar and (U-Th)/He methods (Chapter 5). Zircon was one of the first minerals dated by the (U-Th)/He method, but has only just begun to be used for thermochronometry of both bedrock and detrital samples, as reviewed by Reiners (Chapter 6). Continuous time-temperature paths from intracrystalline variations of radiogenic Ar proven perhaps the most powerful of all thermochronologic approaches, and an innovative analogous approach in He dating (4He/3He thermochronometry) is revealing remarkably powerful constraints on the extreme low temperature end of thermal histories, as reviewed by Shuster and Farley (Chapter 7). Thermochronology of detrital minerals provides unique constraints on the long-term evolution of orogens, sediment provenance, and depositional age constraints, to name a few. Bernet and Garver (Chapter 8) review the essentials of detrital zircon fission-track dating, one of the most venerable and robust of detrital thermochronometers, and in Chapter 9, Hodges, Ruhl, Wobus, and Pringle review the use of 40Ar/39Ar dating of detrital minerals, demonstrating the power of detrital muscovite ages in illuminating variations in exhumation rates in catchments over broad landscapes. (U-Th)/He thermochronometry presents several unique interpretational challenges besides new kinetics and low temperature sensitivity. One of these is long-alpha stopping distances, and its coupling with diffusion and U-Th zonation in age corrections. Dunai reviews modeling approaches to deal with these issues in interpreting low-temperature thermal histories (Chapter 10). Ketcham (Chapter 11) reviews the theory and calibration of both forward and inverse models of thermal histories from fission-track and (U-Th)/He data, and makes some important points about the interpretations of such models. Translating thermal histories into exhumational histories and their tectonic or geomorphic significance across a landscape requires quantitative understanding of the thermal structure of the crust and how it is perturbed, a review of which is presented by Ehlers (Chapter 12). Braun (Chapter 13) illustrates the power of low-temperature thermochronometry to constrain topographic evolution of landscapes over time, using PECUBE. Gallagher, Stephenson, Brown, Holmes, and Ballester present a novel method of inverse modeling of fission-track and (U-Th)/He data for thermal histories over landscapes (Chapter 14). Continuous time-temperature paths from closure profiles or their step-heating-derived equivalents are, to some degree, the holy grail of thermochronology. Harrison, Zeitler, Grove, and Lovera (Chapter 15) provide a review of the theory, measurement, and interpretation of continuous thermal histories at both intermediate and high temperatures, derived from both K-feldspar 40Ar/39Ar and monazite U/Pb dating. Extensional orogens provide a special challenge and opportunity for thermochronometry because tectonic exhumation by footwall unroofing often outstrips erosional exhumation, and often occurs at high rates. As Stockli shows (Chapter 16) thermochronology in these setting provides opportunities to measure rates of a number of important processes, as well as obtain a snapshot of crustal thermal structure and its imprint on thermochronometers with varying closure temperatures. Spotila (Chapter 17) reviews the use of thermochronology applied to tectonic geomorphology in a wide range of orogenic settings, introducing the concept of denudational maturity. Thermochronology has found great utility in economic geology, and newly developed approaches pose great potential in this area, and shown by McInnes, Evans, Fu, and Garwin in their review of the use and modeling of thermochronology of hydrothermal ore deposits (Chapter 18). The thermal histories of sedimentary basins are also critical to understanding thermal maturation of hydrocarbons, but are also critical for understanding basin formation, erosional histories of source regions, fluid flow, and climate change and other temporal signals preserved in sedimentary rocks. Armstrong (Chapter 19) reviews these issues and the use of thermochronology in deducing the thermal histories of sedimentary basins. Drawing on large datasets of bedrock apatite fission-track dates, Kohn, Gleadow, Brown, Gallagher, Lorencak, and Noble demonstrate the power of modeling, and, importantly, effectively visualizing, integrated thermotectonic and denudational histories over large regions (Chapter 20). Thermal histories of meteorites provide constraints on a wide range of fundamentally important processes, including nebular condensation and early solar-system metamorphic histories, and the dynamics of interplanetary collisions and shock metamorphism. Min reviews thermochronologic approaches to understanding meteorite thermal histories (Chapter 21), including new methods and approaches. Finally, the importance of robust models with which to interpret thermochronologic data is underscored by the review of the Software for Interpretation and Analysis of Thermochronologic Data (Chapter 22), summarized and compiled by Ehlers, for programs associated with the work of authors in this volume and others.