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Secondary‐volatiles linked metallic iron in eucrites: The dual‐origin metals of Camel Donga 
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下载免费PDF全文 Paul H. Warren Junko Isa Mitsuru Ebihara Akira Yamaguchi Bastian Baecker 《Meteoritics & planetary science》2017,52(4):737-761
The unique occurrence of abundant (~1 vol%) near‐pure‐Fe metal in the Camel Donga eucrite is more complicated than previously believed. In addition to that component of groundmass metal, scattered within the meteorite are discrete nodules of much higher kamacite abundance. We have studied the petrology and composition of two of these nodules in the form of samples we call CD2 and CD3. The nodules are ovoids 11 (CD2) to 15 (CD3) mm across, with metal, or inferred preweathering metal, abundances of 12–17 vol% (CD2 is unfortunately quite weathered). The CD3 nodule also includes at its center a 5 mm ovoid clumping (6 vol%) of F‐apatite. Both nodules are fine‐grained, so the high Fe metal and apatite contents are clearly not flukes of inadequate sampling. The metals within the nodules are distinctly Ni‐rich (0.3–0.6 wt%) compared to the pure‐Fe (Ni generally 0.01 wt%) groundmass metals. Bulk analyses of three pieces of the CD2 nodule show that trace siderophile elements Ir, Os, and Co are commensurately enriched; Au is enriched to a lesser degree. The siderophile evidence shows the nodules did not form by in situ reduction of pyroxene FeO. Moreover, the nodules do not show features such as silica‐phase enrichment or pyroxene with reduced FeO (as constrained by FeO/MgO and especially FeO/MnO) predicted by the in situ reduction model. The oxide minerals, even in groundmass samples well away from the nodules, also show little evidence of reduction. Although the nodule boundaries are generally sharp, groundmass‐metal Ni content is anti‐correlated with distance from the CD3 nodule. We infer that the nodules represent materials that originated within impactors into the Camel Donga portion of the eucrite crust, but probably were profoundly altered during later metamorphism/metasomatism. Origin of the pure‐Fe groundmass metal remains enigmatic. In situ reduction probably played an important role, and association in the same meteorite of the Fe‐nodules is probably significant. But the fluid during alteration was probably not (as previously modeled) purely S and O, of simple heat‐driven internal derivation. We conjecture a two‐stage metasomatism, as fluids passed through Camel Donga after impact heating of volatile‐rich chondritic masses (survivors of gentle accretionary impacts) within the nearby crust. First, reduction to form troilite may have been triggered by fluids rich in S2 and CO (derived from the protonodules?), and then in a distinct later stage, fluids were (comparatively) H2O‐rich, and thus reacted with troilite to form pure‐Fe metal along with H2S and SO2. The early eucrite crust was in places a dynamic fluid‐bearing environment that hosted complex chemical processes, including some that engendered significant diversity among metal+sulfide alterations. 相似文献
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Willis Gwenzi Erik J. Veneklaas Timothy M. Bleby Isa A.M. Yunusa Christoph Hinz 《水文研究》2012,26(21):3281-3292
Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design and management of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deep drainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporal trends of plant water potential (ψp), stomatal conductance (gs), and transpiration in a 4‐year‐old evergreen woody vegetation growing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7 mm day?1 in winter, when rainfall was frequent, but declined to 0.2 mm day?1 in the dry summer, when the plants were quite stressed. In winter, the mean ψp was ?0.6 MPa at predawn and ?1.5 MPa at midday, which were much higher than the corresponding summer values of ?2.0 MPa and ?4.8 MPa, respectively. The gs was also higher in winter (72.1–95.0 mmol m?2 s?1) than in summer (<30 mmol m?2 s?1), and negatively correlated with ψp (p < 0.05, r2 = 0.71–0.75), indicating strong stomatal control of transpiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22% of the annual rainfall (673 mm), compared with 77% to 99% for woody vegetation in Western Australia. The low annual transpiration was attributed to the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial root system constrained by high subsoil pH. Amending the substrate with fine‐textured materials should improve water storage of the substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the early stages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties, vegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Abdul-Lateef Balogun Abdul-Nasir Matori Adekunle Isa Hamid-Mosaku Dano Umar Lawal Imtiaz Ahmed Chandio 《Marine Georesources & Geotechnology》2017,35(7):961-969
Proper pipeline route selection is an integral component of a typical oil exploration and transportation project. Improperly selected routes could have severe consequences including pipe failures, oil spillage, and environmental disasters. Consequently, technologies like geographic information systems (GIS) are increasingly being used to facilitate the oil pipeline route selection procedure—especially for onshore routing projects. Surprisingly, not much has been documented on the application of GIS to offshore pipeline routing. With recent discoveries on the merits of offshore oil exploration, it is necessary to extend the analytical capabilities of GIS to the unique offshore domain. However, concerns have been raised regarding the limitations of GIS in accurately prioritizing diverse selection criteria in typical multi-criteria decision-making (MCDM) problems like route selection. Consequently, this paper addresses the offshore/subsea pipeline routing constraint using a hybrid decision support system (DSS), which integrates a GIS and fuzzy logic-based approximate reasoning (AR) models for optimal performance. The resultant spatial decision support system (SDSS) was successfully applied to a case study in Malaysia. The AR algorithm calculated the significance level of the multiple criteria using various fuzzy linguistic variables and membership functions. The aggregated priority ranking from different pipeline routing experts showed that the overall influence of the environmental criteria (61.4%) significantly exceeded that of other equally important criteria in the study area. These rankings were inputted into the SDSS to simulate various probable routes. Final results accurately highlighted an optimal route, which places a premium on the protection of environmental features in the subsea study area—in alignment with the preferences of majority of the experts. 相似文献
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Olumuyiwa T. Akinsanpe Adekunle A. Adepelumi Uzochukwu K. Benjamin Dele E. Falebita 《中国海洋大学学报(英文版)》2017,16(6):1027-1034
Comprehensive qualitative and semi-quantitative seismic analysis was carried out on 3-dimensional seismic data acquired in the deepwater compressional and shale diapiric zone of the Niger Delta Basin using an advanced seismic imaging tool. The main aim of this work is to obtain an understanding of the forming mechanism of the gas hydrate system, and the fluid migration paths associated with this part of the basin. The results showed the presence of pockmarks on the seafloor and bottom simulating reflectors (BSRs) in the field, indicating the active fluid flux and existence of gas hydrate system in the area. In the area of approximately 195 km2 occupying nearly 24% of the entire study field, three major zones with continuous or discontinuous BSRs of 3 to 7 km in length which are in the northeastern, southern and eastern part of the field respectively were delineated. The BSR is interpreted to be the transition between the free gas zone and the gas hydrate zone. The geologic structures including faults (strike-slip and normal faults), chimneys and diapirs were deduced to be the main conduits for gas migration. It is concluded that the biogenic gases generated in the basin were possibly transported via faults and chimneys by advection processes and subsequently accumulated under low temperature and high pressure conditions in the free gas zone below the BSR forming gas hydrate. A plausible explanation for the presence of the ubiquitous pockmarks of different diameters and sizes in the area is the transportation of the excessive gas to the seafloor through these mapped geologic structures. 相似文献
6.
Isioye Olalekan Adekunle Combrinck Ludwig Botai Joel 《Theoretical and Applied Climatology》2018,132(3-4):1099-1116
Theoretical and Applied Climatology - This study presents an in-depth analysis to comprehend the spatial and temporal variability of zenith tropospheric delay (ZTD) over Nigeria during the period... 相似文献
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This study investigated morphological variation and biomass accumulation that occurred in Sida acuta and Chromolaena odorata plants grown in lead polluted soil under organic fertilizer amendment. The study was carried out in the screen house at the Biological Gardens of the Obafemi Awolowo University, Ile-Ife, Osun State. The experiment was a factorial combination of one heavy metal (Pb) at five levels of concentration (0, 200, 400, 800 and 1,000 mg/kg) in a completely randomized design, and were replicated three times for each of the two plants and two levels (0 g/kg and 9.4 g/kg) of organic fertilizer (OBD-Plus). Each pot was filled with 5 kg of air-dried and sieved soil and placed on a plastic tray for the collection of excess water. Two weeks after planting, seedlings of uniform height were transplanted from the nursery to experimental pots at the rate of one seedling per pot and grown for 10 weeks. The growth parameters of the plants were biomonitored for 7 weeks. After 10 weeks of treatment, the plants were harvested and dried to calculate the biomass accumulation. The two plant species performed better under fertilizer application than without it. For each of the plant species the growth parameters decreased as the levels of Pb concentration increased. Furthermore, the plants' biomass decreased significantly (p<0.05) as the levels of Pb concentration increased. The organic fertilizer helped to improve the plants' performance in lead-polluted soil. 相似文献
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Thamer Khazaal Al-Ameri Nagham Mohammed Al-Jubouri Murtadha J. Isa Rami Eidan Al-Azzawi 《Arabian Journal of Geosciences》2013,6(10):3725-3735
Organic geochemical analysis and palynological studies of the organic matters of subsurface Jurassic and Lower Cretaceous Formations for two wells in Ajeel oil field, north Iraq showed evidences for hydrocarbon generation potential especially for the most prolific source rocks Chia Gara and Sargelu Formations. These analyses include age assessment of Upper Jurassic (Tithonian) to Lower Cretaceous (Berriasian) age and Middle Jurassic (Bathonian–Tithonian) age for Chia Gara and Sargelu Formations, respectively, based on assemblages of mainly dinoflagellate cyst constituents. Rock-Eval pyrolysis have indicated high total organic carbon (TOC) content of up to 18.5 wt%, kerogen type II with hydrogen index of up to 415 mg HC/g TOC, petroleum potential of 0.70–55.56 kg hydrocarbon from each ton of rocks and mature organic matter of maximum temperature reached (Tmax) range between 430 and 440 °C for Chia Gara Formation, while Sargelu Formation are of TOC up to 16 wt% TOC, Kerogen type II with hydrogen index of 386 mg HC/g TOC, petroleum potential of 1.0–50.90 kg hydrocarbon from each ton of rocks, and mature organic matter of Tmax range between 430 and 450 °C. Qualitative studies are done in this study by textural microscopy used in assessing amorphous organic matter for palynofacies type belonging to kerogen type A which contain brazinophyte algae, Tasmanites, and foraminifera test linings, as well as the dinoflagellate cysts and spores, deposited in dysoxic–anoxic environment for Chia Gara Formation and similar organic constituents deposited in distal suboxic–anoxic environment for Sargelu Formation. The palynomorphs are of dark orange and light brown, on the spore species Cyathidites australis, that indicate mature organic matters with thermal alteration index of 2.7–3.0 for the Chia Gara Formation and 2.9–3.1 for the Sargelu Formation by Staplin's scale. These characters have rated the succession as a source rock for very high efficiency for generation and expulsion of oil with ordinate gas that charged mainly oil fields of Baghdad, Dyala (B?aquba), and Salahuddin (Tikrit) Governorates. Oil charge the Cretaceous-Tertiary total petroleum system (TPS) are mainly from Chia Gara Formation, because most oil from Sargelu Formation was prevented passing to this TPS by the regional seal Gotnia Formation. This case study of mainly Chia Gara oil source is confirmed by gas chromatography–mass spectrometry analysis for oil from reservoirs lying stratigraphically above the Chia Gara Formation in Ajeel and Hamrine oil fields, while oil toward the north with no Gotnia seal could be of mainly Sargelu Formation source. 相似文献
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Isa Asudeh 《Earth and Planetary Science Letters》1982,61(1):136-142
In active tectonic areas like Iran, where the coverage of seismograph stations is inadequate but earthquakes occur frequently, uppermost mantle body wave velocities are conventionally determined by using a single station and an array of earthquake sources. This method fails when earthquakes are mislocated or source areas have varied structures. An extension of the traditional surface wave two-station method is developed for body waves and shown to be independent of mislocation errors. It thus gives accurate estimates of body wave velocities along two station paths with greatly reduced errors.Uppermost mantle P wave (Pn) velocities are determined along several paths in Iran using this method and show zones of low-velocity corresponding to zones of high attenuation and Quaternary volcanic activity in the country. A remarkably high Pn velocity of 8.30 km/s is found for the Zagros area of western Iran more typical of shield like structures than that of tectonic areas. 相似文献
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In this study, the statistical characterization of sea conditions in the East China Sea(ECS) is investigated by analyzing a significant wave height and wind speed data at a 6-hour interval for 30 years(1980–2009), which was simulated and computed using the WAVEWATCH Ⅲ(WW3) model. The monthly variations of these parameters showed that the significant wave height and wind speed have minimum values of 0.73 m and 5.15 ms~(-1) and 1.73 m and 8.24 ms~(-1) in the month of May and December, respectively. The annual, seasonal, and monthly mean sea state characterizations showed that the slight sea generally prevailed in the ECS and had nearly the highest occurrence in all seasons and months. Additionally, the moderate sea prevailed in the winter months of December and January, while the smooth(wavelets) sea prevailed in May. Furthermore, the spatial variation of sea states showed that the calm and smooth sea had the largest occurrences in the northern ECS. The slight sea occurred mostly(above 30%) in parts of the ECS and the surrounding locations, while higher occurrences of the rough and very rough seas were distributed in waters between the southwest ECS and the northeast South China Sea(SCS). The occurrences of the phenomenal sea conditions are insignificant and are distributed in the northwest Pacific and its upper region, which includes the Southern Kyushu-Palau Ridge and Ryukyu Trench. 相似文献