Volatile emissions and gas geochemistry of Hot Spring Basin,Yellowstone National Park,USA

We characterize and quantify volatile emissions at Hot Spring Basin (HSB), a large acid-sulfate region that lies just outside the northeastern edge of the 640 ka Yellowstone Caldera. Relative to other thermal areas in Yellowstone, HSB gases are rich in He and H₂, and mildly enriched in CH₄ and H₂S. Gas compositions are consistent with boiling directly off a deep geothermal liquid at depth as it migrates toward the surface. This fluid, and the gases evolved from it, carries geochemical signatures of magmatic volatiles and water–rock reactions with multiple crustal sources, including limestones or quartz-rich sediments with low K/U (or ^40?Ar/^4?He). Variations in gas chemistry across the region reflect reservoir heterogeneity and variable degrees of boiling. Gas-geothermometer temperatures approach 300 °C and suggest that the reservoir feeding HSB is one of the hottest at Yellowstone. Diffuse CO₂ flux in the western basin of HSB, as measured by accumulation-chamber methods, is similar in magnitude to other acid-sulfate areas of Yellowstone and is well correlated to shallow soil temperatures. The extrapolation of diffuse CO₂ fluxes across all the thermal/altered area suggests that 410 ± 140 t d^− 1 CO₂ are emitted at HSB (vent emissions not included). Diffuse fluxes of H₂S were measured in Yellowstone for the first time and likely exceed 2.4 t d^− 1 at HSB. Comparing estimates of the total estimated diffuse H₂S emission to the amount of sulfur as SO₄²⁻ in streams indicates ~ 50% of the original H₂S in the gas emission is lost into shallow groundwater, precipitated as native sulfur, or vented through fumaroles. We estimate the heat output of HSB as ~ 140–370 MW using CO₂ as a tracer for steam condensate, but not including the contribution from fumaroles and hydrothermal vents. Overall, the diffuse heat and volatile fluxes of HSB are as great as some active volcanoes, but they are a small fraction (1–3% for CO₂, 2–8% for heat) of that estimated for the entire Yellowstone system.     

Possible contribution of leakage currents from the Atlantic Ocean to the magnetic-field variations observed in Devon

It is suggested that leakage currents flow across Devon, north of Exeter, from large-scale electric-current systems induced in the Atlantic Ocean by the geomagnetic variations incident on the Atlantic Ocean from the ionosphere. This model can account for the variation with period of the contribution of induced current flow to the differences in the magnetic H variations of period > 30 s observed at Exeter and Sidmouth.     

HYDROLOGIC TEST SYSTEM FOR FRACTURE FLOW STUDIES IN CRYSTALLINE ROCK

Abstract. A hydrologic test system has been designed to measure the intrinsic permeabilities of individual fractures in crystalline rock. This report contains the design schematics and specifications necessary to build and/or modify this test system for other similar field applications. This system is used to conduct constant pressure/declining flow rate and pressure pulse hydraulic tests. The system is composed of four distinct units: (1) The Packer System, (2) Injection System, (3) Collection System, and (4) Electronic Data Acquisition System. The apparatus is built in modules so it can be easily transported and reassembled. It is also designed to operate over a wide range of pressures (0–300 psig) and flow rates (0.2–1.0 gal/min). This system has proved extremely effective and versatile in its use at the Climax Facility, Nevada Test Site.     

Age and isotope geochemistry of the Archaean Pongola and Usushwana suites in Swaziland, southern Africa: a case for crustal contamination of mantle-derived magma

The igneous rocks of the Pongola Supergroup (PS) and Usushwana Intrusive Suite (UIS) represent a case of late Archaean continental magmatism in the southeastern part of the Kaapvaal craton of South Africa and Swaziland.

U-Pb dating on zircons from felsic volcanic rocks of the PS yields a concordia intercept age of 2940 ± 22Ma that is consistent with a Sm-Nd whole rock age of 2934 ± 114Ma determined on the PS basalt-rhyolite suite. The initial ε_Nd of−2.6 ± 0.9 is the lowest value so far reported for Archaean mantle-derived rocks. Rb-Sr whole rock dating of the PS yields a younger isochron age of 2883 ± 69Ma, which is not significantly different form the accepted U-Pb zircon age.

An internal (cpx-opx-plag-whole rock) isochron for a pyroxenite from the younger UIS yields an age of 2871 ± 30 Ma and initial ¹⁴³Nd/¹⁴⁴Nd that lies off the CHUR growth curve by ε_Nd −2.9 ± 0.2. However, Sm-Nd whole-rock data for the UIS yield an excessively high age of 3.1 Ga that conflicts with firm geological evidence showing the UIS to be intrusive into the PS.

The negative deviations of initialε_Nd from the chondritic Nd evolution curve suggest significant contamination of the PS and UIS melts by older continental crust. A mixing process with continental crust after magma segregation is supported by a high initial ⁸⁷Sr/⁸⁶Sr ratio of0.703024 ± 24 for a clinopyroxene sample from a UIS pyroxenite, compared with an expected value of 0.701 for the 2.9 Ga mantle. We therefore interpret the linear array of data points for the UIS gabbros as a mixing line between 2.87 Ga old magma and older continental crust.

Parallel LREE-enriched REE patterns, negative Nb-Ti anomalies, a distinctive and uniform ratio of Ti/Zr 46 and a narrow span of initial Nd indicate a common source for both the PS and UIS suites which is different from primitive mantle.     

Zum Umweltverhalten von Fluortensiden Teil 1: Prüfung auf Aquatoxizität

Poecilia reticulata PETERS (guppy) and the green alga Monoraphidium griffithii were used for testing of different fluorotensides. After the representation of the methods of investigation and the definition of criteria of toxicity the obtained results of investigation are discussed. In general, the toxicity of the four investigated fluorotensides to algae was lower than to fish. The anionic fluorotenside CF₃—(CF₂)n—CFH—COONa was an exception. In tables and diagrams the results are summarized. Finally, for the condition of the receiving-water biocenosis class “2” the respective still permissible matter concentrations are proposed. They vary between 0.05 and 0.2 mg/1.     

Further investigations of the fog in the photo-electric condensation nucleus counter

Summary The effect on extinction of isothermal distillation, shrinking of the droplets by evaporation without recondensation of the liberated water vapour, coagulation and differential settling of the fog droplets which take place in the fog of a photo-electric nucleus counter and which can produce a small additional extinction («creep») in the first seconds after its formation, were numerically examined. The relative contribution of each process to the total creep observed is assessed. It is found that isothermal distillation can produce amounts of creep (up to 1.70%) which exceed considerably those caused by evaporation or coagulation. The results of these computations explain the occurrence of creep with concentrations greater than approx. 25 000 nuclei/cm³ in fog-tubes of 3.85 cm air-column diameter.That the disappearance of creep in fog-tubes of diameters 2.5 cm and less is due to the accelerated heat-flow from the walls of the narrow fog-tube was previously proved by reducing appropriately the diameter of the light pencil through the fog. In order to meet the objection that by restricting the cross section of the light pencil the fine structure of the fog comes into play, the increase in the travel time of the heat from the walls was achieved this time by using a photo-electric counter with a fog-tube of 8 cm diameter and a light beam of 2.8 cm diameter as in the «Standard Counter 1946». As expected, creep was found in every single measurement up to readings of 53%. Typical examples of the galvanometer pointer-movement and photographic records of the extinction during fog formation in such a wide fog-tube for readings between approx. 10 and 76% are given and their peculiarities discussed.The extinction over the range from 175 000 to 20 000 nuclei/cm³ was also measured with a red and a blue monochromatic interference filter and the results contrasted against the computed extinctions for these two wave lengths. It was ascertained that for the same number of nuclei the extinction for red light is in general larger than that for blue; the difference between the observed extinctions varies considerably, becoming zero or even negative. The most striking feature, however, is the different course of the extinction for the two wave lengths as a function of the number or size of the droplets.The size of the fog droplets in the counter was deduced from the extinction measurements for these two wave lengths and by collecting the falling droplets on coated slides. The radius of the droplets obtained by the optical method varies from 1.81 to 3.19 when the extinction decreases from 86 to 56%. The radius of the droplets as deduced from gelatine coated slides dyed with Naphtol Green B increases from 1.44 at 67.4% extinction (42 400 nuclei/cm³) to 6.30 at 15.6% (858 nuclei/cm³).

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Zusammenfassung Der Einflus der isothermalen Destillation, des Einschrumpfens der Tröpfchen durch Verdunstung ohne Wiederkondensation des freiwerdenden Wasserdampfes, des Zusammenfliessens und Absetzens der Nebeltröpfchen auf die Extinktion, welche im Nebel des photo-elektrischen Kernzählers stattfinden und die in den ersten Sekunden nach seiner Bildung eine kleine zusätzliche Extinktion (im folgenden Kriechen genannt) erzeugen können, wurde numerisch geprüft. Der entsprechende Beitrag jedes einzelnen der oben genannten Prozesse zum Gesamtbetrag des beobachteten Kriechens wurde abgeschätzt. Es wurde gefunden, dass isothermale Destillation zusätzliche Extinktions-Beträge (bis zu 1.70%) erzeugen kann, welche jene durch Verdunstung oder Zusammenfliessen der Tröpfchen verursachten, beträchtlich übersteigen. Die Resultate dieser Berechnungen erklären das Auftreten des Kriechens bei Konzentrationen grösser als ca. 25 000 Kerne per cm³ in Nebelrohren von 3.85 cm Luftsäulen-Durchmesser.Dass das Verschwinden des Kriechens in Nebelrohren mit einem Durchmesser von 2.5 cm und weniger dem beschleunigten Wärmefluss von den Wänden des engen Nebelrohres zuzuschreiben ist, wurde früher durch eine entsprechende Verengung des Lichtbündels, welches zur Durchleuchtung des Nebels verwendet wird, bewiesen. Um dem Einwand zu begegnen, dass bei so starker Verkleinerung des Querschnittes des Lichtbündels, wie sie benützt wurde, schon die Feinstruktur des Nebels eine Rolle spielt, wurde diesmal die Verlängerung der Laufzeit der Wärme von den Wänden durch Erweiterung des Nebelrohres auf 8 cm Durchmesser erzielt, während der Durchmesser des Lichtbündels mit 2.8 cm — wie im «Standard photo-elektrischen Kernzähler 1946» — unverändert belassen wurde. Entsprechend den Erwartungen wurde bei jeder einzelnen Messung bis zu Lesungen von 53% Kriechen festgestellt. Typische Beispiele der Bewegung des Galvanometer-Zeigers und photographische Aufzeichnungen der Extinktion während der Nebelbildung in einem solchen weiten Nebelrohr werden für Lesungen zsischen ca. 10 und 76% gegeben und ihre Eigentümlichkeiten besprochen.Die Extinktion für Konzentrationen zwischen 175 000 und 20 000 Kernen per cm³ wurde auch mit einem roten und blauen Interferenz-Filter gemessen und die Resultate den für diese zwei Wellenlängen berechneten Extinktionen gegenübergestellt. Es wurde festgestellt, dass bei der gleichen Kernzahl die Extinktion für rotes Licht im allgemeinen grösser ist als jene für blaues; die Differenz zwischen den beobachteten Extinktionen schwankt beträchtlich, wird null oder sogar negativ. Am auffallendsten ist jedoch der verschiedene Verlauf der Extinktion für die zwei Wellenlängen als Funktion der Zahl oder Grösse der Tröpfchen.Die Grösse der Nebeltröpfchen im Nebelrohr des photo-elektrischen Kernzählers wurde aus den Extinktions-Messungen in diesen zwei Wellenlängen und durch Auffangen der fallenden Tröpfchen auf Mikroskop-Objektträgern und Deckgläsern, welche mit gefärbter Gelatine überzogen waren, bestimmt. Der Radius der Tröpfchen, welcher mittels der optischen Methode ermittelt wurde, liegt zwischen 1.81 und 3.19 , wenn die Extinktion von 86 auf 56% abnimmt.Der Tröpfchenradius, wie er aus den Flecken auf den Mikroskopgläschen, deren Gelatineüberzug mit Naphtol Grün B eingefärbt war, bestimmt wurde, wächst von 1.44 bei 67.4% Extinktion (42 400 Kerne per cm³) auf 6.30 bei 15.6% (858 Kerne per cm³).

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The research reported in this article has been sponsored and supported in part by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, United States Air Force, under Contract AF 61(052)-26, through the European Office, ARDC in Brussels.     

Ing. Dr Ladislav J. Lukeš

Ohne Zusammenfassung     

High-resolution garnet chronometry and the rates of metamorphic processes

Garnets in an amphibolite-facies metasediment from Sulitjelma, North Norway yield precise and concordant SmNd, UPb and RbSr ages that relate directly to the pressure (P) and temperature (T) conditions of mineral growth. Differential mineral reaction between graphitic and non-graphitic layers within this sample preserves a record of theP-T and time (t) history experienced during Barrovian regional metamorphism. Garnets in graphitic layers grew during prograde metamorphism at462 ± 16°C and5.2 ± 0.5 kbar under conditions of lowaH₂O, and yield indistinguishable¹⁴⁷Sm¹⁴³Nd and²³⁸U²⁰⁶Pb ages of434.1 ± 1.2 Ma and433.9 ± 1.0 Ma, respectively. In contrast, garnet growth in adjacent graphite-free layers did not occur untilP-T conditions of540 ± 18°C and8.0 ± 1.0 kbar were attained, with continued growth in response to minor heating and decompression with final matrix equilibration at544 ± 16°C and7.0 ± 1.0 kbar. The inclusion-free garnet rims in this assemblage record indistinguishable¹⁴⁷Sm¹⁴³Nd and²³⁸U²⁰⁶Pb ages of424.6 ± 1.2 Ma and423.4± 1.7 Ma, respectively. These results provide precise estimates for average heating and burial rates during prograde metamorphism of 8.6_−4.4^+7.5°C Ma⁻¹ and 0.8_−0.5^+0.9 km Ma⁻¹, respectively. Rb and Sr exchange between coexisting silicates in the graphite-free assemblage continued for some 37 Ma after the “peak” of metamorphism, and require an average cooling rate of about 4.0°C Ma⁻¹ during uplift. These results illustrate a clear relationship between reaction history and the timing of mineral growth and provide definitive constraints on the rates of thermal and tectonic processes accompanying regional metamorphism.