海底热液羽流发展过程的数值模拟

 海底热液羽流系统对海洋底部热量与物质输运等科学问题的研究具有重要意义。本文采用数值模拟的方法研究在温度层结环境中二维轴对称热液羽流的发展过程,讨论热液羽流不同喷口条件对羽流发展过程的影响。计算结果表明,热液羽流的喷发过程分为2个阶段：上升过程中温度逐渐降低浮力减小,在背景层结的作用下达到稳定的上升高度;其后羽流顶部转向横向输运。喷口温度、喷口半径对热液羽流的上升高度和横向输运能力的影响正相关。     

A young source for the Hawaiian plume

Recycling of oceanic crust through subduction, mantle upwelling, and remelting in mantle plumes is a widely accepted mechanism to explain ocean island volcanism. The timescale of this recycling is important to our understanding of mantle circulation rates. Correlations of uranogenic lead isotopes in lavas from ocean islands such as Hawaii or Iceland, when interpreted as model isochrons, have yielded source differentiation ages between 1 and 2.5?billion years (Gyr). However, if such correlations are produced by mixing of unrelated mantle components they will have no direct age significance. Re-Os decay model ages take into account the mixing of sources with different histories, but they depend on the assumed initial Re/Os ratio of the subducted crust, which is poorly constrained because of the high mobility of rhenium during subduction. Here we report the first data on (87)Sr/(86)Sr ratios for 138 melt inclusions in olivine phenocrysts from lavas of Mauna Loa shield volcano, Hawaii, indicating enormous mantle source heterogeneity. We show that highly radiogenic strontium in severely rubidium-depleted melt inclusions matches the isotopic composition of 200-650-Myr-old sea water. We infer that such sea water must have contaminated the Mauna Loa source rock, before subduction, imparting a unique 'time stamp' on this source. Small amounts of seawater-derived strontium in plume sources may be common but can be identified clearly only in ultra-depleted melts originating from generally highly (incompatible-element) depleted source components. The presence of 200-650-Myr-old oceanic crust in the source of Hawaiian lavas implies a timescale of general mantle circulation with an average rate of about 2 (±1)?cm?yr(-1), much faster than previously thought.     

Shear heating as the origin of the plumes and heat flux on Enceladus

Enceladus, a small icy satellite of Saturn, has active plumes jetting from localized fractures ('tiger stripes') within an area of high heat flux near the south pole. The plume characteristics and local high heat flux have been ascribed either to the presence of liquid water within a few tens of metres of the surface, or the decomposition of clathrates. Neither model addresses how delivery of internal heat to the near-surface is sustained. Here we show that the most likely explanation for the heat and vapour production is shear heating by tidally driven lateral (strike-slip) fault motion with displacement of approximately 0.5 m over a tidal period. Vapour produced by this heating may escape as plumes through cracks reopened by the tidal stresses. The ice shell thickness needed to produce the observed heat flux is at least 5 km. The tidal displacements required imply a Love number of h2 > 0.01, suggesting that the ice shell is decoupled from the silicate interior by a subsurface ocean. We predict that the tiger-stripe regions with highest relative temperatures will be the lower-latitude branch of Damascus, Cairo around 60 degrees W longitude and Alexandria around 150 degrees W longitude.     

The auroral footprint of Enceladus on Saturn

Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede. Powerful field-aligned electron beams associated with the Io-Jupiter coupling, for example, create an auroral footprint in Jupiter's ionosphere. Auroral ultraviolet emission associated with Enceladus-Saturn coupling is anticipated to be just a few tenths of a kilorayleigh (ref. 12), about an order of magnitude dimmer than Io's footprint and below the observable threshold, consistent with its non-detection. Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon's footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters--and as such is probably indicative of variable plume activity.     

东营凹陷咸化湖相纹层状烃源岩初次生排烃流体特征

以东营凹陷古近系咸化湖相成熟页岩内顺层纤维状脉体(Beef)为研究对象,基于脉体岩相学、流体包裹体等方面分析,结合显微荧光光谱和激光拉曼光谱等技术手段,在证明Beef为初次生排烃产物的基础上,确定东营凹陷早期烃类流体特征。结果表明:成脉矿物均为铁方解石,整体上为一期成岩产物,脉体生长过程中伴随的烃类流体成熟度总体较低且含有大量沥青质,烃类流体整体上具有较高的芳烃(质量分数平均为38.8%)、非烃(质量分数平均为6.8%)含量及较高的API度(平均为32.9);基于图解特征参数计算得出平均等效R o为0.59%;Beef是东营凹陷成熟页岩内有机质初次生烃导致流体异常高压产生顺层微裂缝的重要标志,由于咸化湖相烃源岩在低熟阶段具有较高的降解率,因此超压压裂顺层微裂缝排烃是早期数量可观的低熟油气排出烃源岩的一种重要方式,且在水平运移过程中伴随有明显的轻重组分分馏效应。     

层状砂岩油藏提高水驱油效率的对策分析

通过对砂体几何形态、沉积韵律、连通特性等特征的研究,以及对上述诸特征起主控因素即沉积环境的具体分析,就不同沉积环境下所形成砂体的注水开发特征进行了详细论述,并提出了相应的压裂、酸化等开发工艺措施,为改善开发方案,提高采收率提供了理论依据     

Io as a source of the jovian dust streams

Streams of dust emerging from the direction of Jupiter were discovered in 1992 during the flyby of the Ulysses spacecraft, but their precise origin within the jovian system remained unclear. Further data collected by the Galileo spacecraft, which has been orbiting Jupiter since December 1995, identified the possible sources of dust as Jupiter's main ring, its gossamer ring, comet Shoemaker-Levy 9 (ref. 8) and Io. All but Jupiter's gossamer ring and Io have since been ruled out. Here we find that the dominant source of the jovian dust streams is Io, on the basis of periodicities in the dust impact signal. Io's volcanoes, rather than impact ejecta, are the dust sources.     

异常高压变形介质油藏的开发动态特征研究--以尕斯库勒油田E3油藏为例

目的 通过研究异常高压变形介质油藏的开发动态特征，探讨该类油藏的开发模式。方法以尕斯库勒油田E3异常高压变形介质油藏为例，应用变形介质渗流理论，结合渗透率地层条件下模拟试验及典型井组生产动态数据分析，研究异常高压下变形介质油藏开发特征及合理开发模式。结果异常高压变形介质油藏表现出不同于常规油藏的开发动态特征，在开发过程中随着地层压力的下降，介质弹塑性形变，渗透率大幅度下降，不同结构的岩石发生不同程度的弹塑性形变；当关井恢复压力时油藏渗透率有所恢复，但随地层压力的进一步下降，介质发生不可逆形变，渗透率将逐渐下降，从而使油井产能降低；变形介质油藏具有特殊的弹塑性驱动渗流指示曲线特征，油井产量随压差增加到一定极限后，再增加压差产量随之下降。结论变形介质油藏的开发应尽可能在原始地层压力下开采，在合理生产压差下开发。     

Seismological constraints on a possible plume root at the core-mantle boundary

Recent seismological discoveries have indicated that the Earth's core-mantle boundary is far more complex than a simple boundary between the molten outer core and the silicate mantle. Instead, its structural complexities probably rival those of the Earth's crust. Some regions of the lowermost mantle have been observed to have seismic wave speed reductions of at least 10 per cent, which appear not to be global in extent. Here we present robust evidence for an 8.5-km-thick and approximately 50-km-wide pocket of dense, partially molten material at the core-mantle boundary east of Australia. Array analyses of an anomalous precursor to the reflected seismic wave ScP reveal compressional and shear-wave velocity reductions of 8 and 25 per cent, respectively, and a 10 per cent increase in density of the partially molten aggregate. Seismological data are incompatible with a basal layer composed of pure melt, and thus require a mechanism to prevent downward percolation of dense melt within the layer. This may be possible by trapping of melt by cumulus crystal growth following melt drainage from an anomalously hot overlying region of the lowermost mantle. This magmatic evolution and the resulting cumulate structure seem to be associated with overlying thermal instabilities, and thus may mark a root zone of an upwelling plume.     

于桥水库水源地富营养化的调查及分析评价

通过选用综合营养状态指数法对于桥水库水质监测的原始数据进行营养状况综合评价。结果表明：于桥水库水质已呈中富营养化状态,有向富营养化发展的潜在趋势。最后,结合于桥水库的实际情况,提出几点消减于桥水库水源地的营养盐水平的建议,防止水源地富营养化的发展。     

Fruit bats as a natural reservoir of zoonotic viruses

The outbreak of a cluster of three zoonotic diseases in Australasian region has caused devastating loss of hu-man life and economy between 1994 and 1999. Thepathogens of these diseases are newly discovered viruses and have caused a worldwide regard. The result of epide-miological research indicates that the outbreak is related to the natural history of the viruses that caused these dis-eases and fruit bats are the natural reservoir of theseagents. The appearance of atypical pneumonia referred …     

Association of the jets of Enceladus with the warmest regions on its south-polar fractures

Jets of material have been seen emanating from the south-polar terrain of Saturn's satellite Enceladus. Observations have shown that this region is anomalously warm, with the hottest measured temperatures coinciding with the four 'tiger stripe' fractures, named Alexandria, Cairo, Baghdad and Damascus, that straddle the region. Here we use Cassini images taken from a variety of viewing directions over two years to triangulate the source locations for the most prominent jets, and compare these with the infrared hotspot locations and the predictions from a recent model of tidally induced shear heating within the fractures. We find that the jets emanate from the four tiger stripes, with the strongest sources on Baghdad and Damascus. All the jets from each fracture seem to lie in the same nearly vertical plane. There is a strong spatial coincidence between our geographical sources and the locations of increased temperature revealed by the infrared experiment. Comparison with the shear heating model shows broad agreement; the exception is the prediction that Baghdad is the least active lineament, whereas we find it to be the most active. We predict that several new hotspots remain to be discovered by future thermal observations.     

Eruptions arising from tidally controlled periodic openings of rifts on Enceladus

In 2005, plumes were detected near the south polar region of Enceladus, a small icy satellite of Saturn. Observations of the south pole revealed large rifts in the crust, informally called 'tiger stripes', which exhibit higher temperatures than the surrounding terrain and are probably sources of the observed eruptions. Models of the ultimate interior source for the eruptions are under consideration. Other models of an expanding plume require eruptions from discrete sources, as well as less voluminous eruptions from a more extended source, to match the observations. No physical mechanism that matches the observations has been identified to control these eruptions. Here we report a mechanism in which temporal variations in tidal stress open and close the tiger-stripe rifts, governing the timing of eruptions. During each orbit, every portion of each tiger stripe rift spends about half the time in tension, which allows the rift to open, exposing volatiles, and allowing eruptions. In a complementary process, periodic shear stress along the rifts also generates heat along their lengths, which has the capacity to enhance eruptions. Plume activity is expected to vary periodically, affecting the injection of material into Saturn's E ring and its formation, evolution and structure. Moreover, the stresses controlling eruptions imply that Enceladus' icy shell behaves as a thin elastic layer, perhaps only a few tens of kilometres thick.     

A simple plume model induced by stack effect in a vertical shaft

After comparing the mechanism of tilted plume under stack effect with that of spill plume,the tilted plume model induced by stack effect in a vertical shaft is developed simply based on the theoretical results and a series of full-scale tests. It is shown that the two sides of plume are symmetrical and have an accordant regulation that the plume radius has a linear relation to the height z. The profile of fire plume under stack effect is similar to the windblown flame in wind tunnel,and the range of flame deflection angle is about from 50 to 60 degree.     

层状岩质边坡失稳的燕尾突变模型

根据层状岩质边坡含软弱夹层失稳的特点,建立了边坡地质力学模型,应用非线性科学理论中的突变理论建立了完善的边坡失稳燕尾突变模型。研究得出内外环境参数的变化改变系统控制变量的取值。边坡势函数形式发生变化,边坡在演化过程中可能处于稳定状态,也可能处于失稳状态,其稳定性取决于边坡岩体的内在和外界因素。计算了边坡处于失稳状态下系统所释放出的能量。研究结果加深了对滑坡成因的认识,论证了应用突变理论研究边坡失稳现象的可行性。