Measurements of peroxyacetylnitrate in the marine boundary layer over the Atlantic

The atmospheric concentration of peroxyacetylnitrate (PAN) was measured during a cruise of the R.S. Polarstern from Bremerhaven (Germany) to Rio Grande do Sul (Brazil) in September/ October 1988. The measurements were made in-situ by a combination of electron capture gaschromatography with a cryogenic preconcentration step. The theoretical lower limit of detection (3) was 0.4 ppt. The mixing ratios of PAN varied by more than three orders of magnitude from 2000 ppt in the English Channel to less than 0.4 ppt south of the Azores (38° N). South of 35° N, PAN levels were below the detection limit, except at 30–31° S off the eastern coast of South America. Here, PAN mixing ratios of 10 to 100 ppt were detected in continentally influenced air masses. Detectable levels of PAN were mostly observed in air masses of continental or high northern origin. Changes in the wind directions were usually associated with substantial changes in the PAN mixing ratios.     

Theory of the local scale parameter method for EDM

The determination of a representative refractive index for the wave path is the main limitation of the attainable accuracy in electronic distance measurement. To overcome this limitation the length ratio method was initially proposed and later developed into the local scale parameter (LSP) method. In this paper, the mathematical model of the LSP method is derived for electro-optical distance measurement from first principles based on the physics of the atmospheric boundary layer. The model does not rely on standard atmospheres. It is shown that atmospheric temperatures and pressures must be observed at instrument stations but not at reflector stations. Appropriate LSP field procedures and the results of some field experiments are summarized. The method consistently produces accuracies of better than ±1 ppm. Use of the method is recommended for high precision (trilateration) networks, which need to be measured repeatedly and where absolute scale is not relevant.     

Clinometric records with two long water levels in Lohja,Finland, during the total solar eclipse in 1990

Two water tube clinometers are installed in a deep mine in Lohja, Finland. One, lying in an E-W direction, is 177 m long and the other, lying in a N-S direction, is 62 m long. These instruments are used for tidal records and research. Because the station was on the zone of totality of the 1990 solar eclipse, the instruments offered a suitable tool for investigating whether there was any shielding effect on the direction of the vertical. During the eclipse, the resolution of the instruments was increased to 0.00001 and 0.00004, respectively. p ]Recordings and data evaluation are discussed, and the results obtained show that no gravitational shielding was found at the level of the above accuracy.     

Thermobarometry, Geochronology and the Interpretation of P-T-t Data in the Britt Domain, Ontario Grenville Orogen, Canada

Textural evidence, thermobarometry, and geochronology were usedto constrain the pressure-temperature-time (P—T—t)history of the southern portion of the Britt domain in the CentralGneiss Belt, Ontario Grenville Province. Typical metapeliticassemblages are quartz+plagioclase+ biotite + garnet + kyanite alkali feldspar sillimanite rutile ilmenite staurolite gahnite muscovite. Metatonalitic assemblages have quartz+ plagioclase + garnet biotite + hornblende + rutile + ilmenite.Metagabbroic rocks contain plagioclase + garnet + clinopyroxene+ biotite + ilmenite hornblende rutile quartz. Notabletextural features include overgrowths of sillimanite on kyaniteand of spinel on staurolite. The spinel overgrowths can be modeledby the breakdown of staurolite via the reaction Fe-staurolite= hercynite +kyanite + quartz + H₂O. The decomposition of stauroliteto her-cynite has a steep dP/dT slope and constrains the lateprograde path of a staurolite metapelite. Garnet—Al₂SiO₅—plagioclase—quartz(GASP) barometry applied to metapelitic garnets that preservecalcium zoning reveals a pressure decrease from 11 to 6 kbat an assumed temperature of 700 C. Garnet—plagioclase—ilmenite—rutile—quartzand garnet—clinopyroxene—plagioclase—quartzbarometry is in good agreement with pressures obtained withthe GASP barometer. Geochronologic data from garnet, allanite,and monazite in metapelitic rocks give ages that fall into twogroups, 1–4 Ga and 1.1 Ga, suggesting the presence ofat least two metamorphic events in the area. It is most reasonableto assign the 1.4 Ga age to the high-pressure data and the 1.1Ga age to the lower-pressure data. Collectively the P—T—tdata indicate a complex and protracted history rather than asingle cycle of burial and uplift for this part of the GrenvilleProvince.     

Geological,fluid inclusion and stable isotope studies of Mo mineralization,Galway Granite,Ireland

Mo mineralization within the Galway Granite at Mace Head and Murvey, Connemara, western Ireland, has many features of classic porphyry Mo deposits including a chemically evolved I-type granite host, associated K- and Si-rich alteration, quartz vein(Mace Head) and granite-hosted (Murvey) molybdenite, chalcopyrite, pyrite and magnetite mineralization and a gangue assemblage which includes quartz, muscovite and K-feldspar. Most fluid inclusions in quartz veins homogenize in the range 100–350°C and have a salinity of 1–13 eq. wt.% NaCl. They display Th-salinity covariation consistent with a hypothesis of dilution of magmatic water by influx of meteoric water. CO₂-bearing inclusions in an intensely mineralized vein at Mace Head provide an estimated minimum trapping temperature and pressure for the mineralizing fluid of 355°C and 1.2 kb and are interpreted to represent a H₂O-CO₂ fluid, weakly enriched in Mo, produced in a magma chamber by decompression-activated unmixing from a dense Mo-bearing NaCl-H₂O-CO₂ fluid. ³⁴S values of most sulphides range from c. 0 at Murvey to 3–4 at Mace Head and are consistent with a magmatic origin. Most quartz vein samples have ¹⁸O of 9–10.3 and were precipitated from a hydrothermal fluid with ¹⁸O of 4.6–6.7. Some have ¹⁸O of 6–7 and reflect introduction of meteoric water along vein margins. Quartz-muscovite oxygen isotope geothermometry combined with fluid inclusion data indicate precipitation of mineralized veins in the temperature range 360–450°C and between 1 and 2 kb. Whole rock granite samples display a clear ¹⁸O-D trend towards the composition of Connemara meteoric waters. The mineralization is interpreted as having been produced by highlyfractionated granite magma; meteoric water interaction postdates the main mineralizing event. The differences between the Mace Head and Murvey mineralizations reflect trapping of migrating mineralizing fluid in structural traps at Mace Head and precipitation of mineralization in the granite itself at Murvey.     

Electron optical and X-ray powder diffraction study of synthetic and natural potassic cordierites

The microstructural and X-ray diffraction characteristics of natural K-bearing cordierites in buchites (Blaue Kuppe, Germany), and paralavas (Bokaro, India) are compared to those of three suites of synthetic, K-bearing Mg-cordierite, studied after annealing glasses of the requisite compositions for durations between 5 min and 255 days at 1,290° C and 1 bar. In analogy to pure Mg-cordierite, hexagonal high-cordierite initially crystallizes from the glass and subsequently transforms to orthorhombic low-cordierite. After annealing for 30–60 min, the crystals develop tweed-structure. With prolonged annealing, the pattern coarsens and develops into lamellar twinning. Higher K-contents favour earlier development of tweed-contrast. Distortion indices obtained by X-ray powder diffraction show a sharp initial increase of with annealing time, followed by a levelling off after approximately 10 h. Higher K-contents delay this initial increase, and decrease drastically the maximum distortion index that can be attained. The contrasting observations with respect to increasing K-content are due to the different levels of information yielded by TEM and X-ray diffraction. Analyses of electron diffraction patterns indicate that the metric state of individual crystals in any single sample annealed for more than one hour is highly heterogeneous, while no compositional differences could be detected. Hexagonal and variously distored crystals coexist. Thus intermediate structural states of cordierite in the classical sense are shown to exist, although intermediate distortion indices obtained by routine X-ray powder diffraction are largely due to a summation effect over such structurally heterogeneous populations. Although distinct differences in microstructure between the synthetic and the natural Fe²⁺-bearing cordierites exist, the Bokaro samples most closely resemble the early (1–10 h) tweed-structure of the synthetic products, whereas the Blaue Kuppe samples are comparable to a more mature (1–3 days) stage. It is thus concluded that the cordierite-bearing Bokaro paralavas cooled considerably faster than the Blaue Kuppe buchites.     

Using numerical modelling to evaluate tsunami hazard near the Kuril Island

A sequence of computer experiments is used to study questions concerning the tsunami problem as a quantitative estimate of tsunami danger, detailed geographical tsunami classification, determination of the parameters of critical tsunami waves, and the conditions of their development. We call a wave critical, if its impact on the coast is most hazardous.Using the Middle Kuril Island as an example, we present the results of a computer experiment which includes determining the wavefields on the shelf and estimating the effects connected with the deep-water Bussol and Diana Straits.Numerical simulation of tsunami waves of different sources permits the assessment of the extent of tsunami danger in different areas of the coastal zone of Simushir Island, depending on the location of the focus zone and their geometry.The major singularities of the wavefield arise in the zones of the deep-water straits. The distribution of the amplification factors is determined by both the global parameters of the wavefields and the local properties of individual harbours. The results obtained for a particular harbour in the northern part of Simushir Island, formed the basis for the quantitative estimate of tsunami danger for this area.     

Fluid-rock interaction in the Mo-bearing Nebelstein greisen complex,Bohemian Massif (Austria)

Summary In the Nebelstein area, molybdenite-bearing greisens occur together with peraluminous leucogranites. In the compositional change of the granites to the greisens, there is an almost complete loss of Na, combined with a decrease in Ca, Mg, Sr, and Ti concentrations. The progressive alteration is reflected by lower homogenization temperatures and increasing salinity in aqueous fluid inclusions. The fluid regime prior to greisenization was water-dominated with low salt contents, while the early stage of the greisen development was characterized by a mixed fluid containing carbon dioxide and water. This was succeeded by a moderate saline aqueous fluid which caused the mineralization by exchange of metal ions for Na⁺(Ca²⁺, K⁺). A negative correlation between salt content in fluid inclusions and Na₂O concentrations in the bulk rocks supports this model. Mass balance calculations for this interaction yield a minimum fluid-rock ratio of approximately 2 : I. Greisenization took place at a minimum pressure of 180 MPa (1.8 kb) and in a temperature range between 200 and < 400 °C.

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Fluid-Gestein-Wechselwirkung in dem Molybdänit führenden Greisenkomplex Nebelstein, Böhmische Masse (Österreich)

Zusammenfassung Die Molybdänglanz führenden Greisengesteine des Nebelsteins sind an peraluminöse Granite gebunden. Bei der Alteration der Granite ist für den Übergang Biotitgranit zu Greisen eine weitestgehende Verarmung an Na zu beobachten, gleichzeitig nehmen auch die Gehalte an Ca, Mg, Sr und Ti ab. Die fortschreitende Greisenbildung dokumentiert sich in den wäßrigen Flüssigkeitseinschlüssen durch steigende Salinität bei sinkenden Homogenisierungstemperaturen. Die fluide Phase war vor der Greisenbildung H₂O dominiert und niedrig salinar. Der Beginn der Alterationsprozesse ist durch CO₂ und H₂O hältige Fluide gekennzeichnet. Danach folgt ein Anstieg der Salinität, der auf den Austausch von Metallchloridlösungen gegen Na⁺, K^- und Ca^2- zurückgeführt wird. Dies läßt sich durch eine negative Korrelation der Salinität in den Flüssigkeitseinschlüssen mit dem Na-Gehalt der Gesteine belegen. Daraus wurde die Volumsbeziehung der den Granit durchströmenden fluiden Phase relativ zum Gestein mit mindestens 2 : 1 abgeleitet. Die Mineralisation fand bei einem Minimaldruck von 1,8 kb in einem Temperaturbereich von 200 - < 400 °C statt.

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This paper was presented at the IGCP 291 Project Symposium Metamorphic Fluids and Mineral Deposits, ETH Zürich, March21–23,1991.     

Water-rock interaction in a zone of lateral flow: A natural example from the active geothermal field and gold-mineralized zone of Beppu (Kyushu Island,Japan)

Summary Beppu is a water-dominated active geothermal system in Kyushu (Japan). Gold mineralization exists in places within altered Pleistocene volcanites in the southernmost part of this field. A shallow 300 m well was drilled in an alluvial fan deposit made up of unsorted volcanic clasts of andesite and dacite. Water and core samples were collected and a temperature log was carried out. In the depth range of 150-230 m and at temperatures of 126-148° C the main authigenic minerals are quartz, calcite, K-feldspar, mixed layers illite/smectite, stilbite and pyrite. The chemical data of the waters indicate that mixing occurs between shallow bicarbonate waters and deep Na-Cl geothermal waters in the outflow zone. The authigenic mineral assemblages found in the well are analogous to those found in the epithermal gold deposits of southern Kyushu. Au concentration data for the hydrothermal springs of Beppu (0.53 g/kg) indicate that the fluids found in the borehole at 148° C could theoretically deposit gold. It is reasonable to hypothesise that a process of mixing between deep Na-Cl fluids and shallow Ca-HCO₃-SO₄ fluids were responsible for massive silicate deposition, accompanied in places by Au mineralizations.

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Wasser-Gesteins-Wechselwirkung in einer Zone lateraler Fließbewegung: ein natürliches Beispiel aus der aktiven Geothermal-Golderz-Zone von Beppu (Kyushu, Japan)

Zusammenfassung Beppu ist ein geothermales System auf der Insel Kyushu, Japan, in der Wasser die dominante Rolle spielt. Goldvererzungen treten stellenweise in umgewandelten pleistozänen Vulkaniten im südlichsten Teil des Gebietes auf. Ein 300 m tiefes Bohrloch wurde in einem alluvialen Sedimentations-Fächer, der aus unsortierten vulkanischen Klasten, aus Andesit und Dazit besteht, niedergebracht. Wasserproben und Kernproben wurden genommen und die Temperaturen im Bohrloch systematisch gemessen. In Tiefen von 150–230 m und bei Temperaturen von 126–148°C sind die wichtigsten autigen gebildeten Minerale Quarz, Calcit, K-Feldspat, Illit/Smectit, Stilbit und Pyrit. Der Chemismus der Wässer zeigt, daß eine Mischung zwischen seichten Bikarbonat-Wässern und aus der Tiefe stammenden Na-Cl geothermalen Wässern erfolgt. Die autigenen Mineralassoziationen in diesem. Bohrloch sind vergleichbar mit denen in epithermalen Goldlagerstätten des südlichen Kyushu. Auf der Basis von existierenden Goldkonzentrationsdaten für die hydrothermalen Quellen auf Beppu (0.53 g/kg) läßt sich zeigen, daß die Fluide, die in dem Bohrloch bei 148 angetroffen wurden, theoretisch Gold absetzen könnten. Daher läßt sich die Theorie vertreten, daß Mischungsvorgänge zwischen einem aus der Tiefe stammenden Na-Cl Fluid und einem oberflächennahen Ca-HCO₃-SO₄ Wasser für die massive Silikatausscheidung verantwortlich waren, die stellenweise von Goldmineralisation begleitet wurden.

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Contribution No 4. Foreign Visiting Scientist Section, Beppu Geophysical Research Laboratory, Kyoto University.

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This paper was presented at the IGCP 291 Project Symposium Metamorphic Fluids and Mineral Deposits, ETH Zurich, March 21–23, 1991.     

Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels

Reports of the 13C content of marine particulate organic carbon are compiled and on the basis of GEOSECS data and temperatures, concentrations, and isotopic compositions of dissolved CO2 in the waters in which the related phytoplankton grew are estimated. In this way, the fractionation of carbon isotopes during photosynthetic fixation of CO2 is found to be significantly correlated with concentrations of dissolved CO2. Because ancient carbon isotopic fractionations have been determined from analyses of sedimentary porphyrins [Popp et al., 1989], the relationship between isotopic fractionation and concentrations of dissolved CO2 developed here can be employed to estimate concentrations of CO2 dissolved in ancient oceans and, in turn, partial pressures of CO2 in ancient atmospheres. The calculations take into account the temperature dependence of chemical and isotopic equilibria in the dissolved-inorganic-carbon system and of air-sea equilibria. Paleoenvironmental temperatures for each sample are estimated from reconstructions of paleogeography, latitudinal temperature gradients, and secular changes in low-latitude sea surface temperature. It is estimated that atmospheric partial pressures of CO2 were over 1000 micro atm 160 - 100 Ma ago, then declined to values near 300 micro atm during the next 100 Ma. Analysis of a high-resolution record of carbon isotopic fractionation at the Cenomanian-Turonian boundary suggests that the partial pressure of CO2 in the atmosphere was drawn down from values near 840 micro atm to values near 700 micro atm during the anoxic event.