ALBERT

Description / Table of Contents: Contents: 1. Isotopes and radioactivity; 2. The principles o radioactive dating; 3. Radiometric dating methods; 4. Dating by cosmogenic isotopes; 5. Uncertainties and results of radiometric dating; 6. Radiogenic isotope geochemistry; 7. Stable isotope geochemistry; 8. Isotope geology and dynamic reservoir analysis

Description / Table of Contents: Microorganisms cause mineral precipitation and dissolution and control the distribution of elements in diverse environments at and below the surface of the Earth. Conversely, mineralogical and geochemical factors exert important controls on microbial evolution and the structure of microbial communities. This was the rationale for the Short Course on Geomicrobiology presented by the Mineralogical Society of America on October 18 and 19, 1997, at the Alta Peruvian Lodge in Alta, Utah. Minerals have been known and honored since humans realized their essential contributions to the "terra firma" and stone tools thrust our species on the path of cultural evolution. Microbes are the oldest living creatures, probably inhabiting at least a few salubrious environments on the earth as early as 3.8 billion years ago. At this moment in history we are only beginning to appreciate the intimate juxtaposition and interdependence of minerals and microbes. We have been nudged into this position by the realization that our earth is finite, and the recognition of many global environmental problems that minerals and microbes contribute to, both positively and negatively. In addition, our globe may not be the only site in the solar system where 'life' arose, or may persist. What all of these concerns enunciate is that we as scientists only dimly comprehend our own dynamic "terrestrial halls." This short course and volume have been generated with great enthusiasm for grasping as much as possible of the whole panorama of possibilities that involve both the inorganic and biologic realms . Over 3600 mineral species have been defined and their relationships to each other and the environments in which they form have been documented. This vast data base, collected over the past several hundred years and constantly added to and upgraded, is a monument to the research efforts of many geoscientists focused on the inorganic realm. Much of this data has come from investigators intrigued by the novelty, beauty, and versatility of minerals, direct expressions of the chemistry and physics of geologic processes. We are now adding a new dimension to questions of mineral formation, dissolution, and distribution: what were, are, and will be the contributions of microbes to these basic components of the environment. Microbes have also been known for hundreds of years. However, their small size (0.5 to 5 µm in diameter) and the difficulties associated with identifying a species unless it was grown in the laboratory (cultured), precluded thorough analysis. The advent of molecular biology has only recently made it possible to evaluate microbial evolutionary relatedness (phylogeny) and physiological diversity. These techniques are now being applied to study of microbial populations in natural environments. It is becoming very clear that the surface of Earth is populated by far more species of microbes than there are types of minerals. We are now exploring every portion of the globe and finding the relationships under the rubric "geomicrobiology." The ocean deeps are characterized by a diversity of microorganisms, including those associated with manganese nodules. The profusion and concentration of minerals created at ocean ridges and vents matches the variety of microorganisms, large animals, and plants there. The snowy tops of mountain ranges and glaciers of Antarctica harbor not just ice but whole bacterial communities whose cellular types and activities need elucidation. The equatorial jungles and the deserts, with their enormous diversity of ecological niches, further challenge us. The diversity of geographic, geologic, and biologic environments, including some contributed by humans (e.g. mines, air-conditioning equipment), can now also be explored in detail. Modern studies use protocols developed to preserve or measure in situ chemical and physical characteristics. Electron microscopes allow direct characterization of mineral and biological morphology and internal structures. Spectroscopic techniques permit complimentary chemical analysis, including determination of oxidation states, with very high spatial resolution. Other studies quantitatively measure isotopic abudances. These data serve to distinguish biologically mediated, or biologically controlled formation of the mineral from an abiotic process and mechanism. Each ecological niche requires accurate characterization of the mineralogic and biologic entities in order for us to begin to understand the range of dynamic relationships. We can pose many questions. Is the mineral only a substrate, or is its occurrence and stability impacted by microbiologic activity and metabolic requirements? Which minerals are of microbiological rather than inorganic origin and what are the mechanisms by which organisms dictate the morphology and structure of the solid phase formed? How do organic metabolic products bind metals and change their form and distribution, with implications for metal toxicity and geochemical cycles? How do inorganic reactions such as mineral dissolution and precipitation impact microbial populations through control of their physical and chemical environments? Clearly, new and excitingly research areas exist for all varieties of scientists. Although published by the Mineralogical Society of America, the authors of this volume include microbiologists, molecular biologists, biochemists, biophysicists, bioengineers as well as biomineralogists. Here, they bring together their respective expertise and perspectives to provide disciplinary and interdisciplinary background needed to define and further explore the topic of geomicrobiology. The volume is organized so as to first introduce the nature, diversity, and metabolic impact of microorganisms and the types of solid phases they interact with. This is followed by a discussion of processes that occur at cell surfaces, interfaces between microbes and minerals, and within cells, and the resulting mineral precipitation, dissolution, and changes in aqueous geochemistry. The volume concludes with a discussion of the carbon cycle over geologic time. In detail: Nealson and Stahl acquaint us with the basic properties of prokaryotes, including their size and structure. They define the types and ranges of microorganisms and their metabolisms and describe their impacts on some important biogeochemical cycles. Barns and Nierzwicki-Bauer document the phylogenetic relationships and evolution of microorganisms, begging some fundamental questions that might be now just beyond our grasp: What was the 'last common ancestor'? The physiology, biochemistry and ecology of hyperthermophilic, and the many diverse geologically important microbial species from the lithosphere and hydrosphere, as well as some of the techniques employed, are presented. Banfield and Hamers describe and integrate the processes acting on minerals and at surfaces relevant to microorganisms, examining the factors that control mineralogy, mineral forms, and the stability of phases. Surface properties and reaction rates for dissolution, precipitation, and growth of important classes of minerals are discussed. The possible role of mineral surfaces in formation of prebiotic molecules needed to explain the origin of life is examined. Little, Wagner and Lewandowski describe biofilms, an essential interface between microbes and minerals. They demonstrate that these membranes, with their unique morphological and structural attributes, are sites where much activity related to dissolution and/or formation of minerals takes place. Biology makes it possible to move molecules and elements against a gradient. Many questions regarding the transfer of elements from minerals to microbes at this important heterogeneous interface remain. Fortin, Ferris and Beveridge review surface-mediated mineral development by bacteria. Fresh or oceanic waters, anaerobic or aerobic environments provide discretely different ecologies, bacterial entities, and resulting mineralogies. It is obvious from this presentation that investigators have just scratched the surface of microbial mineralization processes. Bazlinski and Moskowitz review the magnetic biominerals and provide insights into the environmental and biological significance of these few tens of nanometer-sized mineral products. The magnetosome chemistry and biochemistry is probably the best understood of any biologically precipitated mineral. Their formation and unique properties underscore the roles these biomaterials play in the rock magnetic record and in geochemical cycles. Tebo, Ghiorse, van Waasbergen, Siering and Caspi contribute data on the roles of Mnminerals and Mn(II) oxidation in geologic environments. Their chapter encompasses molecular genetic and biochemical investigations. Manganese oxides and oxyhydroxides are notoriously difficult to identify and the crystal chemistry of these phases is a research effort on its own. The prospect of learning how microbes utilize the multiple oxidation states of Mn (2+, 3+ and 4+) as a source of energy sharpens the motivation for interdisciplinary study. Manganese is also known as a cofactor in the production and activation of the enzymes that digest large biomolecules that must be the source of the smaller molecular species and ultimately the building blocks of C, N, 0, H required by all species. How have the mechanisms identified in the bacterial systems been transferred up the phylogenetic tree to plants and humans? This is an expanding and intriguing area for further investigation. DeVrind-de Jong and de Vrind address silicate and carbonate deposition by algae (eukaryotic photosynthetic microorganisms). This chapter documents the mechanisms of biomineralization of diatoms and coccoliths. These abundant aquatic organisms are responsible for huge volumes of siliceous sediments and calcium carbonate deposits world wide. The implications of algal biomineralization for climatic variation throughout much of the Earth's history may be quite significant. Stone leads us though a quantitative approach to evaluating reactions between organic molecules and cations. He considers available extracellular organic ligands and the roles these play in uptake of metals. He documents the basic chemical speciation and complexation for several elements, making metal to metal comparisons. Remaining challenges involve coordinating the organic and inorganic results of biologic activity. Following the discussion of biomineralization and interactions between organic compounds and cations, Silver discusses the strategies microorganisms have evolved to deal with toxic metal concentrations in solution. Beyond the fundamental biological significance, this has important implications for understanding microbial populations in contaminated environments. The impact on the geochemical form (speciation) and distribution of elements is also discussed. Nordstrom and Southam summarize sulfide mineral oxidation and dissolution kinetics and devote considerable effort to describing the specific contributions of microorganisms, mostly bacteria. Despite the vast amount of accumulated information, many unanswered questions remain. Barker, Welch and Banfield address weathering of silicate minerals. This topic encompasses not only mineralogy but geomorphology, microbiology, and geochemistry. The necessary interdisciplinary mode of these investigations is highlighted by discussion of the role(s) of bacterial nutrition, groundwater chemistry, and biochemistry. There are obvious implications for hazardous waste storage, a currently daunting and politicized topic that requires predictions over thousands to millions of years. Finally, Des Marais treats the long term evolution of the carbon cycle, adopting a biogeochemical view. He discusses the sources, sinks and the transfer of the element over geologic time. Consideration of such a basic series of questions relating to the partitioning of carbon necessitate interdisciplinary crossovers. It is a fitting conclusion to a dialogue in progress.

Description / Table of Contents: This volume is a collection of papers to celebrate the life and work of Professor lan Gass. The research themes cover many of the subjects which most interested him, especially processes operating in oceanic crust. The introductory papers examine evolution of magmas from mantle melting to eruption. A central section concerns ophiolite complexes. Several papers focus on different aspects of the Troodos ophiolite complex in Cyprus, where lan first recognized that sheeted dykes within the ophiolite sequence must have formed in an oceanic spreading environment. In addition, ophiolites ,are reviewed and examined in terms of tectonics, magmatic and mantle textures, metallogenesis and hydrothermal alteration. A further section concentrates on tectonics and the genesis of magmas associated with collision and subduction. This contrasts with continental rifting and the effects of mantle plumes. This collection of papers covers a broad range of topics from processes in the mantle to those in the oceanic crust. The volume will be of interest to all scientists concerned with igneous processes and global tectonics.

Description / Table of Contents: A conference dealing with ‘Early Tertiary volcanism and the opening of the NE Atlantic’ was held at the Geological Society of London, Burlington House, London, on 18 and 19 March 1987. The meeting was supported and promoted by three of the specialist groups of the Society (Volcanic Studies, Marine Studies and Petroleum groups), and carried the endorsement of the Norsk Petroleumsforening. This broad-based support reflects the truly multidisciplinary nature of the meeting, which saw contributions from geophysicists, geochemists, geochronologists, volcanologists, petroleum geologists, structural geologists, petrologists, sedimentologists and biostratigraphers. The conference was attended by over 180 delegates from throughout the N Atlantic borderlands, who enjoyed the presentation of 34 papers and five posters, and contributed to a number of lively and spirited discussion periods. This volume contains 37 papers, four of which appear as extended abstracts, and some in forms very different to that presented at the meeting. For practical reasons some authors have combined manuscripts, some contributions presented at the meeting were not available for inclusion in this publication, and some papers have been included despite not being presented at the meeting. The papers have been grouped into six categories, essentially on the basis of structural and geographic setting, but these categories also serve to emphasize the multidisciplinary approach of the current research. Volcanic and tectonic framework The first group of papers deals with the volcanic and tectonic framework on which the subsequent regional studies are based. These papers deal not only with the regional plate-tectonic setting during the Palaeogene...

Description / Table of Contents: Unlike sedimentation and volcanism, active metamorphism is not directly observable. Metamorphic petrologists therefore must infer what constitutes the process of metamorphism by examining the products of metamorphic events. The purpose of this volume is to review the use of a powerful probe into metamorphic process: mineral assemblages and the composition of minerals. Put very simply, this volume attempts to answer the question: "What can we learn about metamorphism through the study of minerals in metamorphic rocks?" It is not an encyclopedic summary of metamorphic mineral assemblages; instead it attempts to present basic research strategies and examples of their application. Moreover, in order to limit and unify the subject matter, it concentrates on the chemical aspects of metamorphism and regrettably ignores other important kinds of studies of metamorphic rocks and minerals conducted by structural geologists, structural petrologists, and geophysicists. An overview of the chemical aspects of modern metamorphic petrology is timely because it brings together three areas of research which have reached maturity only in the last 25 years: (1) chemical analysis of minerals by microanalytical techniques; (2) application of reversible and irreversible thermodynamics to petrology; and (3) laboratory phase equilibrium experiments involving metamorphic minerals. Chemical thermodynamics is the formal mathematical framework which links measurable variables (i.e., mineral composition) to metamorphic variables which cannot be directly measured (i.e., chemical potential, pressure, temperature, fluid composition). Results of phase equilibrium studies involving metamorphic minerals at metamorphic pressures and temperatures (together with calorimetric and heat capacity data) permit these links to be quantitative. It is the union of analysis, theory, and laboratory experiment which allows the modern metamorphic petrologist to make sophisticated inferences about conditions of metamorphism and the factors which control these conditions. This union is the principal subject of the volume. The volume is organized much in the same way that one might approach a research project involving metamorphic rocks. Initially those chemical components which characterize the composition of minerals in the assemblages under consideration must be identified. In addition, the reaction relationships among components must be systematically characterized. The reaction relationships rationalize the prograde changes in mineralogy which rocks experience during metamorphism and, furthermore, form the basis for extracting information about intensive variables during metamorphism. Chapters 1-3 summarize strategies for identifying components in metamorphic minerals and for formulating chemical reactions among them. Chapter 4 develops, from classical thermodynamics, those equations which can be used to explicitly relate mineral composition to other variables of interest such as metamorphic pressure, temperature, and chemical potentials of volatile species in any metamorphic fluid phase. Chapter 5 is specifically devoted to geologic thermometry and barometry, and Chapter 6 reviews strategies for the determination of metamorphic fluid composition. Petrologists should not be content with simply calculating and cataloguing values of metamorphic pressure, temperature, and fluid composition. In order to characterize the process of metamorphism, we must try to understand what controls these measured values and the manner in which they evolve during metamorphism both as rocks are heated and buried and as rocks are cooled and uplifted. Chapter 7 explores how two concepts buffering and infiltration -- can act as general controls on fluid composition, mineral composition, and temperature during metamorphic events. In addition, this chapter develops procedures which can be used to evaluate the relative importance of buffering versus infiltration in the evolution of specific rocks. Chapter 8 demonstrates how integrated petrologic and stable isotope studies may be used, in principle, to reconstruct the prograde pressure-temperature-infiltration history of metamorphic rocks. Chapter 9 discusses the use of mineral inclusions and compositional zoning in minerals in evaluating both prograde and post-peak P-T paths of certain mineral assemblages. In addition, compositional zoning is considered as an indicator of cooling rates during post-peak uplift. Thus between Chapter I and Chapter 9 we go from the first step of describing a metamorphic mineral assemblage through a reconstruction of the physical state in which it crystallized to an analysis of what factors controlled that state and how it evolved with time. The contents of the volume reflect two themes which underlie modern research in metamorphic petrology. The first of these is an ever-increasing emphasis on the quantitative characterization of metamorphism. Current research less involves description and classification than calculation of intensive and extensive variables attained during metatamorphism. This volume hopefully serves as a text in the quantitative study of the chemical aspects of metamorphism. As a corollary to the emphasis placed on quantitative methods, we can see increasing attention paid to analytical as opposed to graphical treatments of mineral equilibria. Graphical representations, while undeniably valuable, can consider two (or at most three) independent variables. Analytical treatment of mineral equilibria is attractive because it rigorously keeps track of all variables pertinent to an equilibrium assemblage. The second theme is an increasing interest in the dynamics of metamorphism. Metamorphism obviously is not a static process -- it involves changes in pressure, temperature, mineral and fluid composition, etc. The classical static approach to quantitative metamorphic petrology, though, searches for the physical conditions of a unique pressure-temperature state which a rock or mineral assemblage records. Mineral equilibria are used to estimate single values of pressure, temperature, and fluid composition -- a sort of snapshot of what conditions were like. If mineral assemblages indeed represent a fossilized metamorphic state, then calculated P, T, Xi' however, simply represent a single point along the P-T-Xi-time path which a rock followed during metamorphism. Chapters 2, 7, 8, and 9 reflect an increasing interest among petrologists in the entire P-T-Xi-time path (or at least in more than one point along it). We can expect to see less satisfaction in the future with the snapshot model of metamorphism and more effort devoted to characterizing metamorphism as a dynamic process. Thus the volume not only summarizes time-honored current practices in quantitative metamorphic petrology, but hopefully also identifies some paths which may be followed in the future.

Description / Table of Contents: The authors of this volume presented a short course on the rare earth elements to about 80 participants in San Francisco, California, December 1-3, 1989, just prior to the fall meeting of the American Geophysical Union.