Das P{\text{ - }}T{\text{ - }}X_{{\text{CO}}_{\text{2}} } Stabilitätsfeld von Lawsonit

At pressures which are expected in the earth's crust, the high temperature border of the lawsonite stability field is marked by reaction lawsonite = zoisite + kyanite/andalusite + pyrophyllite + H₂O. (1a) The equilibrium data of reaction (1a) have been experimentally determined, and the equilibrium curve is characterized by the following P, T-data: 4 kb; 360±20° C; 5 kb; 375 ±20° C; 7kb;410±20° C. In the P, T diagram the equilibrium curve of reaction lawsonite + quartz = zoisite + pyrophyllite + H₂O (6) is very close to the curve of reaction (1a); the distance is smaller than the error stated for curve (1a), i.e. below ±20° C. The stability fields of lawsonite and anorthite + H₂O are not adjacent fields in the P, T diagram. This means that no stable reaction of lawsonite to anorthite + H₂O can exist. Thus, the CaAl-silicate formed by the decomposition of lawsonite is always zoisite. Further, as shown by experimental determination of reaction calcite + pyrophyllite + H₂O = lawsonite + quartz + CO₂, (7) lawsonite can coexist with a gas phase only if the CO₂ content of the gas phase does not exceed 3±2 Mol-%. This means, for metamorphism of lawsonite glaucophane rocks, that the fluid phase that was present during metamorphism has been quite rich in H₂O. Ernst (1971, in press) who applied a different, indirect investigation method when studying the composition of the fluid-attending Franciscan and Sanbagawa metamorphism has come to the result that during metamorphism of lawsonite-glaucophane rocks the fluid phase did not contain more than 1–3 Mol-% of CO₂.     

Geophysical Characterization of Smelting Wastes: A Case History

The thicknesses of slag piles at a smelling site in Midvale. Utah, were determined using geophysical methods; this information was needed to estimate the cost of removing or isolating slag that has the potential to contaminate ground water. From a small-scale preliminary investigation that, included terrain-conductivity profiling, low-frequency resistivity measurements, and induction logging, the electrical resistivities of the slag and the underlying sediment were determined to be approximately 100 Ω-m and 15 Ω-m, respectively. Because electromagnetic measurements are affected by such significant contrasts, terrain-conductivity profiling and time-domain electromagnetic soundings were used to determine the thicknesses of the slag piles. Generally, the estimated thicknesses from both methods were consistent and geologically plausible. In some instances, reliable estimates of the thicknesses could not be obtained because, for example, the measurements were affected by buried metal objects.
In this case study, we emphasize three principles that might help investigators at other smelter sites. First, a small-scale preliminary investigation saves time and money because those geophysical methods that have the greatest likelihood of success can be determined. Second, when the results from several geophysical methods are consistent, the confidence in the interpretation increases. Third, geophysical characterization is not always successful. Nonetheless, because of its outstanding advantages, it should be used before other more expensive characterization methods arc tried.     

Parasite findings in archeological remains: Diagnosis and interpretation

Paleoparasitology has contributed to resolving the debate about the peopling of the Americas and determining the antiquity of human parasite infection. Hookworm (Ancylostomidae) and whipworm (Trichuris trichiura) and other exclusive human intestinal parasites have been recorded in pre-Columbian America. These parasite species originated in pre-hominids and have accompanied humans across continents when people went out of Africa. However, for those human populations that crossed the Bering Land Bridge from Siberia to Alaska, cold climate conditions hampered parasite transmission. Alternative migration routes have been proposed to explain the presence of these parasites in pre-Columbian populations in the Americas. Other parasites were established in the New World long before humans entered the American continents.One such malady is Chagas disease. Chagas disease, caused by Trypanosoma cruzi, offers an example of how animals and humans have interacted in the past. Classical theory points to the origin and dispersion of human T. cruzi infection among Andean populations, starting with sedentary habits and animal domestication 6000 years ago. However, recent PCR results in mummified bodies outside the Andean region have challenged this theory. Pre-Columbian Brazilian mummies were found positive for T. cruzi infection, raising an alternative hypothesis on the antiquity of Chagas disease in the Americas. Paleoparasitology is a new tool to study past events, shedding light on human and other animal behavior, migration routes, diet, and other aspects of host–parasite environment evolution.     

Biological record of added manganese in seawater: a new efficient tool to mark in vivo growth lines in the oyster species Crassostrea gigas

The biological response of increased manganese in seawater was tested experimentally with the oyster species Crassostrea gigas by adding, once per day, a fixed quantity of MnCl₂ to the container where the oysters were living. Uptake of Mn²⁺ in the shell was traced with cathodoluminescence and quantified with a high spatial resolution proton microprobe. The daily addition of MnCl₂ resulted in the visualization of distinct growth increments seen simultaneously in both the calcitic shell and the aragonitic ligament. A relation was observed between the addition of Mn²⁺ to the seawater and incorporation of Mn in the mineral part of the shell. Thus, addition of MnCl₂ to seawater is an efficient tool to mark in vivo growth increments in bio-mineralised carbonates.     

Low-frequency variability and CO2 transient climate change

Results from a global coupled ocean-atmosphere general circulation model (GCM) are used to perform the first in a series of studies of the various time and space scales of climate anomalies in an environment of gradually increasing carbon dioxide (CO₂) (a linear transient increase of 1% per year in the coupled model). Since observed climate anomaly patterns often are computed as time-averaged differences between two periods, climate-change signals in the coupled model are defined using differences of various averaging intervals between the transient and control integrations. Annual mean surface air temperature differences for several regions show that the Northern Hemisphere warms faster than the Southern Hemisphere and that land areas warm faster than ocean. The high northern latitudes outside the North Atlantic contribute most to global warming but also exhibit great variability, while the high southern latitudes contribute the least. The equatorial tropics warm more slowly than the subtropics due to strong upwelling and mixing in the ocean. The globally averaged surface air temperature trend computed from annual mean differences for years 23–60 is 0.03 C per year. Projecting this trend to the time of CO₂ doubling in year 100 produces a warming of 2.3° C. By chance, one particular northern winter five-year average geographical difference pattern in the Northern Hemisphere from the coupled model resembles the recent observed pattern of surface temperature and sea-level pressure anomalies. This pattern is not consistent from one five-year period to the next in any season in the model. However, multidecadal averages in the coupled model show that the North Atlantic warms less than the rest of the high northern latitudes, and recent observations may be a manifestation of this phenomenon. Consistent geographic patterns of climate anomalies forced by increased CO₂ in the model are more evident with a longer averaging interval. There is also the possibility that the CO₂ climate-change signal may itself be a function of time and space. The general pattern of zonal mean temperature anomalies for all periods in the model shows warming in the troposphere and cooling in the stratosphere. This pattern (or one similar to it taking into account the rest of the trace gases) could be looked for in observations to verify the enhanced greenhouse effect. A zonal mean pattern, however, could prove scientifically satisfactory but of little value to policymakers seeking regional climate-change forecasts. These results from the coupled model underscore the difficulty in identifying a time- and space-dependent fingerprint of greenhouse warming that has some practical use from short climatic records and point to the need to understand the mechanisms of decadal-scale variability.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Zur Bildung und Zusammensetzung der brennbaren Gesteine

Zusammenfassung Vorbedingung für die Bildung von Brennsteinlagerstätten ist die Bildung von Hohlformen der Erdoberfläche. Als solche kommen in erster Linie orogene Vortiefen und Zwischensenken, sowie epirogene Senken in Frage. Je nach Schnelligkeit und Vollständigkeit der Abdichtung bleiben u. U. auch leichter zersetzliche Stoffe erhalten; dementsprechend entstehen aus meerischen Gyttjen unter zunächst oxydativen Bedingungen Brennsteine von der Art des Kuckersits, aus meerischen Sapropelen polybituminöse Gesteine und Erdöl. Festländisch bilden sich die Kohlen, zu denen auch Unterwasserablagerungen (Bogheads=Algengyttjen; Cannels = Dy, Sapropel, Gyttja; beide stets mit Dy-Grundmasse) gehören. Porphyrine und Metallgehalte gestatten eine Unterscheidung der Haupttypen der Brenngesteine und eine Zuweisung des Erdöls zu den Sapropelgesteinen.Bei der Kohlenbildung spielt das Lignin die Hauptrolle, die Zellulose wird im Torf und während früher Braunkohlenstadien abgebaut. Bei der Bildung der Kerogengesteine werden die Eiweißstoffe zersetzt, Fette und Kohlehydrate spielen wohl die Hauptrolle. Nur bei der Bildung der Sapropelite einschl. des Erdöls spielen außer Kohlehydraten (und den geringen Mengen von Fetten und Ölen) die Eiweißstoffe eine wesentliche Rolle. Die erstentstehenden Öle sind Alkane. Oberflächeneinflüsse (z. B. Tiefenstandwasser mit Sauerstoffsalzen) bewirken die Naphtenisierung; infolge der damit verbundenen Temperaturerhöhung entstehen die Aromaten, die sich später wieder in Naphtene zurückbilden.Die qualitative Geochemie verbindet die Anreicherung von Elementen und Molekülen in Gesteinen mit den Vorgängen, die im Ablagerungs- und Umbildungsraum herrschen (Fazies, Diagenese usw.). Sie führt zur Kennzeichnung der Ablagerungs- und Umbildungsräume durch typische Elemente oder Moleküle, bzw. durch deren Vergesellschaftung oder Mengenverhältnis.