Apatite-hosted melt inclusions from the Panzhihua gabbroic-layered intrusion associated with a giant Fe–Ti oxide deposit in SW China: insights for magma unmixing within a crystal mush     

Kun?Wang  Christina?Yan?WangEmail author  Zhong-Yuan?RenEmail author 《Contributions to Mineralogy and Petrology》2018,173(7):59

The ～?2-km-thick Panzhihua gabbroic-layered intrusion in SW China is unusual because it hosts a giant Fe–Ti oxide deposit in its lower zone. The deposit consists of laterally extensive net-textured and massive Fe–Ti oxide ore layers, the thickest of which is ～?60 m. To examine the magmatic processes that resulted in the Fe enrichment of parental high-Ti basaltic magma and the formation of thick, Fe–Ti oxide ore layers, we carried out a detailed study of melt inclusions in apatite from a ～?500-m-thick profile of apatite-bearing leucogabbro in the middle zone of the intrusion. The apatite-hosted melt inclusions are light to dark brown in color and appear as polygonal, rounded, oval and negative crystal shapes, which range from ～?5 to ～?50 µm in width and from ～?5 to ～?100 µm in length. They have highly variable compositions and show a large and continuous range of SiO₂ and FeO_t with contrasting end-members; one end-member being Fe-rich and Si-poor (40.2 wt% FeO_t and 17.7 wt% SiO₂) and the other being Si-rich and Fe-poor (74.0 wt% SiO₂ and 1.20 wt% FeO_t). This range in composition may be attributed to entrapment of the melt inclusions over a range of temperature and may reflect the presence of µm-scale and immiscible Fe-rich and Si-rich components in different proportions. Simulating results for the motion of Si-rich droplets within a crystal mush indicate that Si-rich droplets would be separated from Fe-rich melt and migrate upward due to density differences in the interstitial liquid when the magma unmixed. Migration of the Si-rich, immiscible liquid component from the interstitial liquid caused the remaining Fe-rich melt in the lower part to react with plagioclase primocrysts (An_59–60), as evidenced by fine-grained lamellar intergrowth of An-rich plagioclase (An_79–84)?+?clinopyroxene in the oxide gabbro of the lower zone. Therefore, magma unmixing within a crystal mush, combined with gravitationally driven loss of the Si-rich component, resulted in the formation of Fe-rich, melagabbro and major Fe–Ti oxide ores in the lower part and Si-rich, leucogabbro in the upper part of the intrusion.  相似文献   

Fluid flow and pore pressure development throughout the evolution of a trough mouth fan,western Barents Sea     

Jaume Llopart  Roger Urgeles  Carl Fredrik Forsberg  Angelo Camerlenghi  Maarten Vanneste  Michele Rebesco  Renata Giulia Lucchi  Denise Christina Rüther  Hendrik Lantzsch 《Basin Research》2019,31(3):487-513

Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure.  相似文献   

Swedish coastal fisheries—From conflict mitigation to participatory management     

Karl Bruckmeier  Christina Höj Larsen 《Marine Policy》2008

Several research projects have studied Swedish coastal fishery to investigate the conflict between seals and fishery. In recent years, a strategy of participation by means of co-management has been unfolding. Realising that maintaining the coastal fishery requires societal support and knowledge integration, attempts have been made to introduce the principle of participatory management into the centralised Swedish fisheries management system. However, this co-management approach, presently implemented in six pilot projects, will take a long time to develop through a sustained process of experimentation and improvement.  相似文献   

An answer to an important controversy and the need for caution when using simple models to predict inelastic earthquake response of buildings with torsion     

Stavros A. Anagnostopoulos  Christina Alexopoulou  Kyriakos G. Stathopoulos 《地震工程与结构动力学》2010,39(5):521-540

This paper presents evidence that the extension of conclusions based on the widely used simplified, one story, eccentric systems of the shear‐beam type, to actual, nonsymmetric buildings and consequent assessments of the pertinent code provisions, can be quite erroneous, unless special care is taken to match the basic properties of the simplified models to those of the real buildings. The evidence comes from comparisons of results obtained using three variants of simplified models, with results from the inelastic dynamic response of three‐ and five‐story eccentric buildings computed with detailed MDOF systems, where the members are idealized with the well‐known plastic hinge model. In addition, a convincing answer is provided on a pertinent hanging controversy: For frame‐type buildings, designed in accordance with the dynamic provisions of modern codes (such as EC8 or IBC2000), which allow reduced shears at the stiff edge due to torsion, the frames at the flexible sides are the critical elements in terms of ductility demands. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Program HVRLV1—Interactive Determination of Horizontal Permeabilities within Uniform Soils from Field Tests Using Hvorslev's Formulae     

K. U. Weyer  W. C. Horwood-Brown 《Ground water》1982,20(3):289-297

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Non-linear inversion of scattered seismic surface waves     

Xander Campman  Christina Dwi Riyanti 《Geophysical Journal International》2007,171(3):1118-1125

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Dust in the Wind: Long Range Transport of Dust in the Atmosphere and Its Implications for Global Public and Ecosystem Health   总被引：4，自引：0，他引：4  

Dale W. Griffin  Christina A. Kellogg  Eugene A. Shinn 《Global Change & Human Health》2001,2(1):20-33

Movement of soil particles in atmospheres is a normal planetary process. Images of Martian dust devils (wind-spouts) and dust storms captured by NASA's Pathfinder have demonstrated the significant role that storm activity plays in creating the red atmospheric haze of Mars. On Earth, desert soils moving in the atmosphere are responsible for the orange hues in brilliant sunrises and sunsets. In severe dust storm events, millions of tons of soil may be moved across great expanses of land and ocean. An emerging scientific interest in the process of soil transport in the Earth's atmosphere is in the field of public and ecosystem health. This article will address the benefits and the potential hazards associated with exposure to particle fallout as clouds of desert dust traverse the globe. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Enhanced data and methods for improving open and free global population grids: putting ‘leaving no one behind’ into practice     

Sergio Freire  Marcello Schiavina  Aneta J. Florczyk  Kytt MacManus  Martino Pesaresi  Christina Corbane 《International Journal of Digital Earth》2020,13(1):61-77

ABSTRACT

Data on global population distribution are a strategic resource currently in high demand in an age of new Development Agendas that call for universal inclusiveness of people. However, quality, detail, and age of census data varies significantly by country and suffers from shortcomings that propagate to derived population grids and their applications. In this work, the improved capabilities of recent remote sensing-derived global settlement data to detect and mitigate major discrepancies with census data is explored. Open layers mapping built-up presence were used to revise census units deemed as ‘unpopulated’ and to harmonize population distribution along coastlines. Automated procedures to detect and mitigate these anomalies, while minimizing changes to census geometry, preserving the regional distribution of population, and the overall counts were developed, tested, and applied. The two procedures employed for the detection of deficiencies in global census data obtained high rates of true positives, after verification and validation. Results also show that the targeted anomalies were significantly mitigated and are encouraging for further uses of free and open geospatial data derived from remote sensing in complementing and improving conventional sources of fundamental population statistics.  相似文献   

Restoration of submerged vegetation in shallow eutrophic lakes – A guideline and state of the art in Germany     

Sabine Hilt  Elisabeth M. Gross  Michael Hupfer  Harald Morscheid  Jens Mhlmann  Arnulf Melzer  Jens Poltz  Stefan Sandrock  Eva-Maria Scharf  Susanne Schneider  Klaus van de Weyer 《Limnologica》2006,36(3):155-171

One of the most serious problems caused by eutrophication of shallow lakes is the disappearance of submerged macrophytes and the switch to a turbid, phytoplankton-dominated state. The reduction of external nutrient loads often does not result in a change back to the macrophyte-dominated state because stabilising mechanisms that cause resilience may delay a response. Additional internal lake restoration measures may therefore be needed to decrease the concentration of total phosphorus and increase water clarity. The re-establishment of submerged macrophytes required for a long-term stability of clear water conditions, however, may still fail, or mass developments of tall-growing species may cause nuisance for recreational use. Both cases are often not taken into account when restoration measures are planned in Germany, and existing schemes to reduce eutrophication consider the topic inadequately. Here we develop a step-by-step guideline to assess the chances of submerged macrophyte re-establishment in shallow lakes. We reviewed and rated the existing literature and case studies with special regard on (1) the impact of different internal lake restoration methods on the development of submerged macrophytes, (2) methods for the assessment of natural re-establishment, (3) requirements and methods for artificial support of submerged macrophyte development and (4) management options of macrophyte species diversity and abundance in Germany. This guideline is intended to help lake managers aiming to restore shallow lakes in Germany to critically asses and predict the potential development of submerged vegetation, taking into account the complex factors and interrelations that determine their occurrence, abundance and diversity.  相似文献   

Stable Cu and Zn isotope ratios as tracers of sources and transport of Cu and Zn in contaminated soil   总被引：7，自引：0，他引：7  

Moritz Bigalke  Stefan Weyer  Jozef Kobza 《Geochimica et cosmochimica acta》2010,74(23):6801-6813

Copper and Zn metals are produced in large quantities for different applications. During Cu production, large amounts of Cu and Zn can be released to the environment. Therefore, the surroundings of Cu smelters are frequently metal-polluted. We determined Cu and Zn concentrations and Cu and Zn stable isotope ratios (δ⁶⁵Cu, δ⁶⁶Zn) in three soils at distances of 1.1, 3.8, and 5.3 km from a Slovak Cu smelter and in smelter wastes (slag, sludge, ash) to trace sources and transport of Cu and Zn in soils. Stable isotope ratios were measured by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) in total digests. Soils were heavily contaminated with concentrations up to 8087 μg g⁻¹ Cu and 2084 μg g⁻¹ Zn in the organic horizons. The δ⁶⁵Cu values varied little (−0.12‰ to 0.36‰) in soils and most wastes and therefore no source identification was possible. In soils, Cu became isotopically lighter with increasing depth down to 0.4 m, likely because of equilibrium reactions between dissolved and adsorbed Cu species during transport of smelter-derived Cu through the soil. The δ⁶⁶Zn_IRMM values were isotopically lighter in ash (−0.41‰) and organic horizons (−0.85‰ to −0.47‰) than in bedrock (−0.28‰) and slag (0.18‰) likely mainly because of kinetic fractionation during evaporation and thus allowed for separation of smelter-Zn from native Zn in soil. In particular in the organic horizons large variations in δ⁶⁶Zn values occur, probably caused by biogeochemical fractionation in the soil-plant system. In the mineral horizons, Zn isotopes showed only minor shifts to heavier δ⁶⁶Zn values with depth mainly because of the mixing of smelter-derived Zn and native Zn in the soils. In contrast to Cu, Zn isotope fractionation between dissolved and adsorbed species was probably only a minor driver in producing the observed variations in δ⁶⁶Zn values. Our results demonstrate that metal stable isotope ratios may serve as tracer of sources, vertical dislocation, and biogeochemical behavior in contaminated soil.  相似文献