ALBERT

Beschreibung / Inhaltsverzeichnis: Work carried out at the SIPRE Test Site, Site 2, on the Greenland Ice Cap,during the summer 1954, included: (1) Excavation of trenches, a circular tunnel and a deep pit; (2) Instrumentation of excavations for pressure and deformation measurements; (3) Tests on the properties of snow from the deep pit; (4) Construction of a snow house as an experimental structure and to provide a heated shelter for an observer stationed at the site for the winter. Observations and measurements over a period of five years are expected to provide sufficient information for the establishment of satisfactory design criteria for all kinds of surface and subsurface military installations on high polar ice caps.

Beschreibung / Inhaltsverzeichnis: Mining Research Corporation, Inc., under contract with Snow Ice, and Permafrost Research Establishment, Corps of Engineers, U.S. Army, conducted explosion tests in frozen Keweenaw silt, to determine; (1) the most efficient type of explosive for blasts in frozen ground, (2) the fundamental relation between weight of explosive and depth of charge, (3) the proper position of the charge relative to the frozen-ground interface, (4) the feasibility of fracturing the frozen layer by placing a charge in the underlying unfrozen material, and (5) the effect of the diameter of the borehole and of the shape of the charge upon the resultsof blasting. Information obtained from the tests applies to the specific problem of excavating in frozen ground and to fundamental explosives research. Conclusions and recommendations based on this information are presented here concerning the feasibility of using explosives for fox-holes in frozen ground; methods of placing the charge; mechanics of crater formation; the crater equation; future instrumentation; classification of explosives; and correlation of blast data.

Beschreibung / Inhaltsverzeichnis: This volume of Reviews in Mineralogy attempts to synthesize our present understanding of certain aspects of the mineralogy and chemistry of the rock-forming carbonates. Hopefully, it reflects the presently more active areas of research. This review follows, by ten years, a major assessment of (sedimentary) carbonate minerals by Lippmann (1973). There is only minor overlap of subject material, and I hope that this difference reflects fairly how this field has developed. In some respects carbonates are unique, for they are one of the few mineral groups providing an abundant record of biological, physical, and chemical processes throughout much of geologic time. Because of their relative importance in sedimentary rocks, lowtemperature examples are given more emphasis here. Moreover, the obvious correlation with energy resources has been a significant factor contributing to the current resurgence of interest in this area. However, the broader interest in carbonates is also a reflection of their widespread occurrence in vastly different geologic environments, including metamorphic and igneous settings, as well as an appreciation of their role in both atmospheric and oceanic chemistry, both past and present. In this volume, some of the papers are general (i.e., those addressing crystal chemistry and phase relations), and they provide overviews of a fundamental nature and are of interest to many. Others are more specialized in coverage and generally reflect the different approaches used in carbonate geochemistry. The final chapter introduces transmission electron microscopy, a relatively new and powerful technique for mineralogical research that has great potential in carbonate research. Owing to the short time interval between the completion of manuscripts and publication, much of the newer material in this volume is still "fresh." The various reviewers, all gratefully acknowledged, were expeditious in their efforts. A hurried schedule, however, allows for unnoticed errors to persist; these should be brought to my attention.

Beschreibung / Inhaltsverzeichnis: Post-Wisconsinian uplift of West, North and East Greenland has been estimated on the basis of information in current literature and compared to the data collected by the author in central West Greenland. For West and North Greenland the dated uplift allows an estimate to be made of the age of former shore-lines, which in turn have been used to date the stages of the extent of the Inland Ice. The results have been compared with published information on the age of glacial stages in East Greenland. The estimated ages of the ice margin stages imply a history of deglaciation in West (and North?) Greenland comparable to that of North America. In both areas the major deglaciation took place after the Younger Dryas and a marked halt took place in Boreal times. It is possible that the history of East Greenland is more closely related to that of Scandinavia where a widespread deglaciation took place prior to the Younger Dryas. The deglaciation of North Greenland was interrupted by a marked readvance or readvances during the climatic optimum. It is possible that the northward shift of the low pressure centres during this period led to an increased accumulation on the northern part of the Inland Ice.

Beschreibung / Inhaltsverzeichnis: Shell-bearing marine sediments in the Nordre Strømfjord area belong to two lithofacies, calcareous sandy gravels and calcareous muddy sands, and to four biofacies comparable to modern communities and related to the sediment lithology: epifaunal benthic and infaunal benthic facies, a current reworked 'mixed' facies and a Portlandia - Propeamussium facies. Radiocarbon dates on nine samples provide a poorly defined model of the glacio-isostatic emergence of the region. The implications of such models and their physical validity are considered in the context of these and other data, and it is suggested that curves for uplift deceleration are a useful means of obtaining the exponential constant k.

Beschreibung / Inhaltsverzeichnis: Geochemistry is a science that is based on an understanding of chemical processes in the earth. One of the principal tools available to the chemist for understanding systems at equilibrium is thermodynamics. The awareness and application of thermodynamic techniques has increased at a very fast pace in geosciences; in fact, one may be so bold as to say that thermodynamics in geology has reached the "mature" stage, although much future thermodynamic research is certainly needed. However, the natural processes in the earth are often sluggish enough that a particular system may not reach equilibrium. This observation is being supported constantly by new experimental and field data available to the geochemist e.g. the non-applicability of the phase rule in some assemblages, the compositional inhomogeneities of mineral grains, the partial reaction rims surrounding original minerals, the lack of isotopic equilibration or the absence of minerals (e.g. dolomite), which should be present according to thermodynamics. The need to apply kinetics has produced a large number of papers dealing with kinetics in geochemistry. As an initial response to this growing field, a conference on geochemical transport and kinetics was conducted at Airlie House, VA, in 1973, sponsored by the Carnegie Institution of Washington. The papers there dealt with several kinetic topics including diffusion, exsolution, metasomatism and metamorphic layering. Since 1973 the number of kinetic papers has continued to increase greatly. Therefore, the time is ripe for a Short Course in Kinetics, which brings together the fundamentals needed to explain field observations using kinetic data. It is hoped that this book may serve, not only as a reference for researchers dealing with the rates of geochemical processes, but also as a text in courses on geochemical kinetics. One of us has found this need of a text in teaching a graduate course on geochemical kinetics at Harvard and at Penn State during the past several years. Finally, it is our hope that the book may itself further even more research into the rates of geochemical processes and into the quantification of geochemical observations. The book is organized with a rough temperature gradient in mind, i.e. low temperature kinetics at the beginning and igneous kinetics at the end (no prejudices are intended with this scheme!). However, the topics in each chapter are general enough that they can be applied often to any geochemical domain: sedimentary, metamorphic or igneous. The theory of kinetics operates at two complementary levels: the phenomenological and the atomistic. The former relies on macroscopic variables (e.g. temperature or concentrations) to describe the rates of reactions or the rates of transport; the latter relates the rates to the basic forces operating between the particular atomic or molecular species of any system. This book deals with both descriptions of the kinetics of geochemical processes. Chapter one sets the framework for the phenomenological theory of reaction rates. If any geochemical reaction is to be described quantitatively, the rate law must be experimentally obtained in a kinetically sound manner and the reaction mechanism must be understood. This applies to heterogeneous fluid-rock reactions such as those occurring during metamorphism, hydrothermal alteration or weathering as well as to homogeneous reactions. Chapter 2 extends the theory to the global kinetics of geochemical cycles. This enables the kinetic concepts of stability and feedback to be applied to the cycling of elements in the many reservoirs of the earth. Chapter 3 applies the phenomenological treatment of chapter 1 to diagenesis and weathering. The rate of dissolution of minerals as well as the chemical evolution of pore waters are discussed. The atomistic basis of rates of reaction, transition state theory, is introduced in Chapter 4. Transition state theory can be applied to relate the rate constants of geochemical reactions to the atomic processes taking place. This includes not only homogeneous reactions but also reactions that occur at the surface of minerals. Chapter 5 discusses the theory of irreversible thermodynamics and its application to petrology. The use of the second law of thermodynamics along with the expressions for the rate of entropy production in a system have been used successfully since 1935 to describe kinetic phenomena. The chapter applies the concepts to the growth of minerals during metamorphism as well as to the formation of differentiated layers (banding) in petrology. Chapter 6 describes the phenomenological theory of diffusion both in aqueous solutions and in minerals. In particular, the multicomponent nature of diffusion and its consequence in natural systems is elaborated. Chapter 7 provides the atomistic basis for the rates of reactions in minerals. Understanding of the rates of diffusion, conduction, order-disorder reactions or exsolution in minerals depends on proper description of the defects in the various mineral structures. Chapter 8 provides the kinetic theory of crystal nucleation and growth. While many of the concepts in the chapter can be applied to aqueous systems, the emphasis is on igneous processes occurring during crystallization of a melt. To fully understand both the mineral composition as well as the texture of igneous rocks, the processes whereby new crystals form and grow must be quantified by using kinetic theory. Due to space and time limitations (kinetics!) some topics have not been covered in detail. In particular, the mathematical solution of diffusion or conduction equations is discussed very well by Crank in his book, Mathematics of Diffusion, and so is not covered to a great extent here. The treatment of fluid flow (e.g. convection) is also not covered in the text.