Stable isotopes of carbon dioxide in soil gas over massive sulfide mineralization at Crandon, Wisconsin     

Charles N. Alpers  David L. Dettman  Kyger C. Lohmann  Dragan Brabec 《Journal of Geochemical Exploration》1990,38(1-2)

Stable isotope ratios of oxygen and carbon were determined for CO₂ in soil gas in the vicinity of the massive sulfide deposit at Crandon, Wisconsin with the objective of determining the source of anomalously high CO₂ concentrations detected previously by McCarthy et al. (1986). Values of δ¹³C in soil gas CO₂ from depths between 0.5 and 1.0 m were found to range from −12.68‰ to −20.03‰ (PDB). Organic carbon from the uppermost meter of soil has δ¹³C between −24.1 and −25.8‰ (PDB), indicating derivation from plant species with the C₃ (Calvin) type of photosynthetic pathway. Microbial decomposition of the organic carbon and root respiration from C₃ and C₄ (Hatch-Slack) plants, together with atmospheric CO₂ are the likely sources of carbon in soil gas CO₂. Values of δ¹⁸O in soil-gas CO₂ range from 32 to 38‰ (SMOW). These δ¹⁸O values are intermediate between that calculated for CO₂ gas in isotopic equilibrium with local groundwaters and that for atmospheric CO₂. The δ¹⁸O data indicate that atmospheric CO₂ has been incorporated by mixing or diffusion. Any CO₂ generated by microbial oxidation of organic matter has equilibrated its oxygen isotopes with the local groundwaters.The isotopic composition of soil-gas CO₂ taken from directly above the massive sulfide deposit was not distinguishable from that of background samples taken 1 to 2 km away. No enrichment of the δ¹³C value of soil-gas CO₂ was observed, contrary to what would be expected if the anomalous CO₂ were derived from the dissolution of Proterozoic marine limestone country rock or of Paleozoic limestone clasts in glacial till. Therefore, it is inferred that root respiration and decay of C₃ plant material were responsible for most CO₂ generation both in the vicinity of the massive sulfide and in the “background” area, on the occasion of our sampling. Interpretation of our data is complicated by the effects of rainfall, which significantly reduced the magnitude of the CO₂ anomaly. Therefore, we cannot rule out the possible mechanism of carbonate dissolution driven by pyrite oxidation, as proposed by Lovell et al. (1983) and McCarthy et al. (1986). Further work is needed on seasonal and daily variations of CO₂ concentrations and stable isotope ratios in various hydrogeologic and ecologic settings so that more effective sampling strategies can be developed for mineral exploration using soil gases.  相似文献   

Stability of the glacial thermohaline circulation and its dependence on the background hydrological cycle     

V.?RomanovaEmail author  M.?Prange  G.?Lohmann 《Climate Dynamics》2004,22(5):527-538

Different reconstructions of glacial sea-surface temperatures (SST) are used to force a hybrid coupled atmosphere–ocean model. The resulting glacial states differ in global salinity and temperature distributions, and consequently in the strength of the thermohaline circulation. Stability analysis of the Atlantic Ocean circulation, by means of freshwater-flux hysteresis maps, reveals mono-stability for each glacial background state, which appears to be a robust feature of the glacial ocean. We show that this behaviour is directly linked to the hydrological cycle. A monotonic relation between the freshwater input necessary for reaching the off-mode and the hydrological budget in the Atlantic catchment area, accounts for the sensitivity of the oceans circulation. The most sensitive part of the hydrological balance appears to be in the tropical and subtropical regions suggesting that the Achilles heel of the global conveyor belt circulation is not restricted to the northern North Atlantic where convection occurs.  相似文献   

Die verteilung der Lichtschwachen Sterne im Offenen Sternhaufen NGC 2477     

Werner Lohmann 《Astrophysics and Space Science》1973,24(2):531-533

The relative frequency of the fainter stars increases from the centre of the cluster to the boundary.  相似文献   

Die masse von M33     

Werner Lohmann 《Astrophysics and Space Science》1974,29(1):61-62

According to the Bottlinger law the mass of M33 is determined with (1.29±0.23)×10¹⁰ M from measurements of the velocities of the neutral hydrogen by Warneret al. (1973).

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Mitteilungen Serie A.  相似文献   

Der offene Sternhaufen M6 (NGC 6405)     

Werner Lohmann 《Astrophysics and Space Science》1976,45(1):27-29

The open star cluster M6 (NGC 6405) is investigated by strip counts on reproductions of the chart of Vleeming (1974). The results are collected in Part 3.

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Mitteilungen Serie A.  相似文献   

Paläozoische Vereisungen in Bolivien     

Dr. Hans Hinrich Lohmann 《International Journal of Earth Sciences》1964,54(1):161-165

Zusammenfassung Im mittleren Silur ist das Zapla-Eis vom Pampeanischen Massiv und vom Altiplano-Massiv nach Nordosten geflossen. Die Gondwana-Vereisung lä\t sich in Bolivien nur im Karbon feststellen, sie wird von der unterpermischen marinen Copacabana-Gruppe überdeckt. Das Gondwana-Eis in Bolivien ist anscheinend nicht vom Brasilianischen Schild, sondern aus Nordwest-Argentinien abzuleiten.

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Resumen Durante el SilÚrico Médio el glaciár de Zapla se movía hacia el Noreste, partiendo del Macizo Pampeano y del Macizo Altiplánico. — Tilitas del Gondwana fuerón observadas en Bolivia sólamente en el Carbonífero; superpuésto se encuentran los sedimentos calcáreos marinos del grupo Copacabana de edad Pérmica inferior. La glaciación del Gondwana en Bolivia probablemente no se deriva del Escudo Brasileño, mas bien de la región de La Rioja en el Noroeste Argentino

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Der staatlichen bolivianischen Erdölgesellschaft Y. P. F. B. danke ich für die Ermöglichung dieser Studien in den Jahren 1961 bis 1963, au\erdem vielen Kollegen für anregende Diskussionen.  相似文献   

Über den Aufbau von 11 offenen Sternhaufen     

W. Lohmann 《Astronomische Nachrichten》1972,294(3):105-111

The strip functions, circular velocity functions and various characteristic parameters of NGC 659, 1027, 1245, 1502, 1528, 1907, 2420, 6830, 6866, 7062 and IC 1848 are derived. From these functions the relative density distribution in the “mean” cluster defined by the 11 clusters is determined. The corresponding generalized SCHUSTER model is found (n = 3.04). The stars of the mean cluster are somewhat more concentrated to the centre than in the model.  相似文献   

ROSAT PSPC observations of the Orion Trapezium area II. Source variability and revised source list     

P. Lohmann  H.J. Wendker 《Astronomische Nachrichten》2000,321(2):81-100

A deep ROSAT PSPC image centred on the Orion Trapezium has been reduceda second time using an improved version of the PSF to fit the data. The outer rim of the field of view was also included. The new catalogue contains 316 X‐ray sources which are easily identified with pre‐main sequence stars of the Ori OB1 Ic and Id association. All 316 sources were tested for variability. No variations were found inside the single exposures of about 45 minutes length each. Between the 4 exposures spaced over 5 days about 1/3 of the sources show signs of activities of various forms. As above 25% of these have somewhat regular lights curves (monotonically rising or falling or hill‐shaped) we infer that at least some outbursts with time scales longer than a day are present and that past searches for X‐ray flares of pre‐main sequence stars were biased towards shorter time scales.  相似文献