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11.
Ryohei Suzuki Jun-Ichiro Ishibashi Miwako Nakaseama Uta Konno Urumu Tsunogai Kaul Gena Hitoshi Chiba 《Resource Geology》2008,58(3):267-288
The Yonaguni Knoll IV hydrothermal vent field (24°51′N, 122°42′E) is located at water depths of 1370–1385 m near the western edge of the southern Okinawa Trough. During the YK03–05 and YK04–05 expeditions using the submersible Shinkai 6500, both hydrothermal precipitates (sulfide/sulfate/carbonate) and high temperature fluids (Tmax = 328°C) presently venting from chimney‐mound structures were extensively sampled. The collected venting fluids had a wide range of chemistry (Cl concentration 376–635 mmol kg?1), which is considered as evidence for sub‐seafloor phase separation. While the Cl‐enriched smoky black fluids were venting from two adjacent chimney‐mound structures in the hydrothermal center, the clear transparent fluids sometimes containing CO2 droplet were found in the peripheral area of the field. This distribution pattern could be explained by migration of the vapor‐rich hydrothermal fluid within a porous sediment layer after the sub‐seafloor phase separation. The collected hydrothermal precipitates demonstrated a diverse range of mineralization, which can be classified into five groups: (i) anhydrite‐rich chimneys, immature precipitates including sulfide disseminations in anhydrite; (ii) massive Zn‐Pb‐Cu sulfides, consisting of sphalerite, wurtzite, galena, chalcopyrite, pyrite, and marcasite; (iii) Ba‐As chimneys, composed of barite with sulfide disseminations, sometimes associated with realgar and orpiment overgrowth; (iv) Mn‐rich chimneys, consisting of carbonates (calcite and magnesite) and sulfides (sphalerite, galena, chalcopyrite, alabandite, and minor amount of tennantite and enargite); and (v) pavement, silicified sediment including abundant native sulfur or barite. Sulfide/sulfate mineralization (groups i–iii) was found in the chimney–mound structure associated with vapor‐loss (Cl‐enriched) fluid venting. In contrast, the sulfide/carbonate mineralization (group iv) was specifically found in the chimneys where vapor‐rich (Cl‐depleted) fluid venting is expected, and the pavement (group v) was associated with diffusive venting from the seafloor sediment. This correspondence strongly suggests that the subseafloor phase separation plays an important role in the diverse range of mineralization in the Yonaguni IV field. The observed sulfide mineral assemblage was consistent with the sulfur fugacity calculated from the FeS content in sphalerite/wurtzite and the fluid temperature for each site, which suggests that the shift of the sulfur fugacity due to participation of volatile species during phase separation is an important factor to induce diverse mineralization. In contrast, carbonate mineralization is attributed to the significant mixing of vapor‐rich hydrothermal fluid and seawater. A submarine hydrothermal system within a back‐arc basin in the continental margin may be considered as developed in a geologic setting favorable to a diverse range of mineralization, where relatively shallow water depth induces sub‐seafloor phase separation of hydrothermal fluid, and sediment accumulation could enhance migration of the vapor‐rich hydrothermal fluid. 相似文献
12.
The study of young star cluster (YSC) systems, preferentially in starburst and merging galaxies, has seen great interest in the recent past, as it provides important input to models of star formation. However, even some basic properties (such as the luminosity function; LF) of YSC systems are still being debated. Here, we study the photometric properties of the YSC system in the nearest major merger system, the Antennae galaxies. We find evidence for the existence of a statistically significant turnover in the LF. 相似文献
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Uta Fritze-von Alvensleben Peter Weilbacher Jens Bicker 《Astrophysics and Space Science》2003,284(2):893-896
To account for the range of stellar metallicities in local galaxies and for the increasing importance of low metallicities
at higher redshift we present chemically consistent models for the spectral and chemical evolution of galaxies over cosmological
timescales. We discuss advantages, limitations and future prospects of our approach.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
Danielle Alloin Carme Gallart Emmanuel Fleurence Emanuela Pompei Daniel Raimann Uta Fritze- Von Alvensleben Sukyoung Yi 《Astrophysics and Space Science》2002,281(1-2):109-113
The goal of this project is to analyze the integrated-light spectrum of a region in the LMC bar, for which HST images are
already available yielding color-magnitude diagrams reaching the oldest main-sequence turnoff. Then, we can derive the star
formation history in this field through evolutionary/population synthesis of the integrated light from 330 to 990 nm by a
variety of independent methods and compare the results with the - in principle - more reliable results derived from the analysis
of the color-magnitude diagram (CMD). This confrontation is the key ‘truth-test’ needed for the understanding of the abilities
and the limitations of the evolutionary/population synthesis methods that must be applied of necessity to unresolved nearby
and far-away galaxies. We report here on the observational part of the project.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
17.
Peter Anders Uta Fritze-von Alvensleben Richard de Grijs 《Astrophysics and Space Science》2003,284(2):937-940
The observational properties of globular cluster systems (GCSs) are vital tools to investigate the violent star formation
histories of their host galaxies. This violence is thought to have been triggered by galaxy interactions or mergers. The most
basic properties of a GCS are its luminosity function (number of clusters per luminosity bin) and color distributions. A large
number of observed GCS show bimodal color distributions, which can be translated into a bimodality in either metallicity and/or
age. An additional uncertainty comes into play when one considers extinction. These effects can be disentangled either by
obtaining spectroscopic data for the clusters or by imaging observations in at least four passbands. This allows us then to
discriminate between various formation scenarios of GCSs, e.g. the merger scenario by Ashman and Zepf, and the multi-phase
collapse model by Forbes et al. Young and metal-rich star cluster populations are seen to form in interacting and merging
galaxies. We analyse multiwavelength broad-band observations of these young cluster systems provided by the ASTROVIRTEL project.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Lukas P. Loose Jens Lange Aaron Budde Barbara Herbstritt Nicola Fohrer Uta Ulrich 《水文研究》2024,38(1):e15058
The protection of the globally widespread lentic small water bodies (LSWB) must be based on detailed knowledge about their hydrological connectivity and water balance. The study aimed to identify and quantify water balance components as well as surface-groundwater interaction of two LSWB in a characteristic lowland region with a combination of different methods. This includes the collection of hydrological data and the use of bromide and water stable isotopes (δ2H and δ18O) as tracers. With their help, mixing models were established, and daily water balances were assessed. The results show a strong bidirectional interaction of both LSWB systems with shallow groundwater. Bromide and stable isotope tracers allowed for the identification of the most relevant in- and outflow sources and pathways. Thereby, isotope data revealed isotopic enrichment typical for open-water bodies and only minor precipitation inputs mainly relevant at the end of the dry season. Water balance calculations suggested accentuated seasonal dynamics that were strongly influenced by shallow groundwater, which represented large inputs into both LSWB. By that, different phases could be identified, with high inflow rates in winter and spring and decreasing fluxes in summer. In one LSWB, a drainage system was found to have a major impact next to the shallow groundwater interaction. The findings of this research provide detailed insights into the influence and importance of shallow groundwater for LSWB in lowland regions. This impacts the diffuse input of agricultural pollutants into these ecologically important landscape features. 相似文献
19.
Uta Hohn 《GeoJournal》1994,34(2):213-230
In 1943, the British Ministry of Economic Warfare (MEW) issued the Bomber's Baedeker. A Guide to the Economic Importance of German Towns and Cities, followed by a second extended edition in 1944. Both editions have now been analysed completely for the first time. Based on information taken from the second edition, the analysis on the macro-level allows statements about the spatial distribution of the most important war-economic targets of the German Reich within the borders of 1937, as seen from the British point of view, just as about the distribution of target priorities within the town hierarchy, classified by population size, and on the micro-level about the information density provided for any single town. The final picture to emerge of the destruction of German towns at the end of the war reveals that quite a number were bombed which the MEW had not recommended for attack. This was due to the economically orientated target selection of the MEW being eclipsed and intermingled with the aims of those who promised to decide the war by demoralising the German population through general dehousing as well as by bombardments in support of ground forces advancing into the German hinterland at the end of the war. 相似文献
20.
Uta Koedel 《Environmental Earth Sciences》2018,77(18):649
The NovCare 2017 International Conference (Novel Methods for Subsurface Characterization and Monitoring: From Theory to Practice) took place in June 2017 and was the fifth conference in a series that has proven to be an excellent forum for exchanging ideas and experiences related to the challenges of subsurface characterization and monitoring. Some of the presented work is included in this Thematic issue NovCare 2017. 相似文献