用于GCM耦合的积雪模型的设计

文中描述一个一维的积雪分层模型,目的是要刻划雪盖随季节的变化,与其下冻土变动模型一起,构成完整的雪盖模型。为了保持一定精度,并能用于大气环模式（ＧＣＭ）研究,模型对积雪内部热量及质量输送过程的描述精细程度及计算时分层多少均有所考虑。模型中,改用内能代替温度作为预报量,克服了相变时直接预报温度时造成的计算误差,有效地预报了相变过程。对于积雪密度的变化,考虑了雪花形态的破坏而引起的密度变化及由于压实过程而引起的密度变化。并对各分层自重产生压实过程推导了相应的公式,在模型中对雪盖的光学特性、热力学特性及水流流动特性参数化方案设计也进行了分析。本简化模型的模拟结果与精细积雪模型的比较,具有几乎同等的精度,与俄罗斯的Ｙｅｒ－ｓｈｏｖ站实测数据相比,吻合十分理想。     

一种新的声速剖面结构参数化方法

在Munk模型和GDEM模型的基础上,提出了一种新的声速剖面结构参数化模型,即分层声速剖面模型(LSSPM).模型用含9个参数的四层分段函数分别描述混合层、主跃层、深海声道层和深海等温层的声速结构,形式简明、直观.数值实验结果表明,LSSPM模型对声速剖面的拟合可达到较高的精度,且对于中国周边的深海和浅海区域有较好的适...     

Melting and diffusion processes in closed-system migmatization

Estimated variations in mineral concentrations across leucosomes suggest that leucosomes are generated during anatexis by a diffusive exchange between the leucosome and the mesosome, and not by the migration of melt from the mesosome. However, the presence of melt is a precondition for the diffusive exchange to take place. Initially a crack is formed due to shear stress. The formation of a crack allows a diffusive exchange to take place through the melt, which causes melting of minerals situated near the crack. The diffusive exchange of material is less efficient in the mesosome where the melt is isolated at grain corners and edges. The microcline enrichment of some granitic leucosomes is thought to be due to the diffusive depletion of the mesosome caused by growth of alkali feldspar during the consolidation of the migmatite. In general, it seems unnecessary to invoke concentrations of water in the leucosome or the intrusion of external fluids or magmas for migmatite formation.     

Segregation of leucogranite microplutons during syn-anatectic deformation: an example from the Taylor Valley, Antarctica

A suite of migmatites in uppermost amphibolite facies schists of the Koettlitz Group exposed in the Taylor Valley, Antarctica, provides direct evidence of the behaviour of partially molten rock during syn-anatectic deformation. The geometry of the migmatites is directly related to their position relative to the hinge of a kilometre-scale antiform. Migmatitic rocks on the fold limbs are characterized by extensional shears and fractures, filled with leucosome material, that intersect the pervasive foliation and millimetre-thick stromatic leucosomes. Vein- and dyke-like leucosomes become more common and thicker from the limb to the hinge region of the antiform. Rocks characterized by high leucosome-to-rock ratios near the antiform hinge are xenolithic in appearance. Major parasitic folds within the hinge contain leucogranite 'microplutons' up to 50 m across beneath refractory 'cap-rock' layers.
Angular boudinage structures in schists surrounded by leucosomes indicate a relatively low yield strength in the leucosome, which is compatible with a molten rather than solid leucosome. Leucogranite-bearing extensional shears and fractures indicate that repeated extensional fracturing and shearing promoted by high fluid (melt) pressure is an important mechanism of melt segregation. Dilation in the hinges of developing folds aids the migration of melt into fold hinges and the development of 10–50-m-wide 'microplutons' of xenolith-rich leucogranite.
Lack of vapour-absent melting and consequent low melt-to-rock ratios allowed the Koettlitz Group to maintain its structural coherency on a kilometre scale. Consequently, leucosome 'microplutons' did not exceed 50 m in width, and therefore observed leucosomes have not contributed to the development of adjacent plutonic-scale granitoids.     

多次透射边界模拟成层介质中瞬态波动的精度分析

本文将对多次透射边界在瞬态波动模拟中的精度分析推广到介质中存在多个物理波速的情形，阐明了它模拟成层介质中瞬态波动的适用性，指出多次透射边界的误差随着透射阶数的增加而迅速减小，二阶透射边界已具有足够高的模拟精度。     

层状介质中断层位错引起的重力异常及其数值模拟

修正了文献［１］给出的两个公式和计算机程序中的个别错误，并根据文献［１］利用层状介质中的位错理论及其与相应重力变化的关系［２，５］，通过数值模拟方法研究了矩形位错面在不同尺度、倾向、埋深和位错的情况下有不同取向、量值的重力异常变化。此外，还对唐山地震、共和地震的重力资料作了几个测点的计算以探索地震物理前兆场空间和强度分布的复杂性。结果表明，断层错动引起的重力变化在空间、强度上的分布是十分复杂的。它是位错地表形变和地下层界面形变效应共同作用的产物，既可以是正异常，也可以是负异常。位错源的几何条件、埋深条件、位错方向和量值等对重力的空间、强度分布和范围有较强的影响。这就说明对于地震与重力异常的关系不能一概而论，要考虑一次地震特定条件的影响。本研究也为我们理解其它地震前兆物理场的复杂性提供了有益的启示     

Mantle–crust interactions during Variscan subduction in the Eastern Alps (Nonsberg–Ulten zone): geochronology and new petrological constraints

We have analyzed the Sm–Nd and Rb–Sr whole-rock and mineral isotope systematics of garnet peridotites and associated eclogites and migmatitic gneisses from the Nonsberg–Ulten zone of the Eastern Alps. The garnet peridotites include coarse-grained varieties, characterized by well-preserved to slightly modified mantle geochemical signatures, and finer-grained varieties enriched in amphibole and LILE. Hydration of some of the most strongly deformed, fine-grained peridotites by crustal fluids caused isotopic disequilibrium between the peridotite minerals, preventing accurate age determinations. The coarse-grained peridotites, the eclogites and the country migmatitic gneisses yield garnet–whole-rock and garnet–clinopyroxene Sm–Nd ages that indicate for all rock types an isotopic homogenization event at ca. 330 Ma. The similar ages suggest that all rock types shared a common history since the incorporation of the peridotites in the crust, and constrain the garnet-facies metamorphism of the peridotites, as well as partial melting of the crust, to an episode of crustal subduction at the end of the Variscan orogenic cycle.     

Layered convection with an interface at a depth of 1000 km: stability and generation of slab-like downwellings

We investigate the stability of hypothetical layered convection in the mantle and the mechanisms how the downwelling structures originating in the lower layer are generated. The stability is studied by means of numerical simulations of the double-diffusive convection in a 2D spherical model with radially dependent viscosity. We demonstrate that the stability of the layering strongly depends not only on the density contrast between the layers but also on the heating mode and the viscosity profile. In the case of the classical Boussinesq model with an internally heated lower layer, the density contrast of about 4% between the compositionally different materials is needed for the layered flow to be maintained. The inclusion of the adiabatic heating/cooling in the model reduces the temperature contrast between the two layers and, thus, enhances the stability of the layering. In this case, a density contrast of 2-3% is sufficient to preserve the layered convection on a time scale of billions of years. The generation of the downwelling structures in the lower layer occurs via mechanical or thermal coupling scenarios. If the viscosity dependent on depth and average temperature at each depth is considered, the low viscosity zone develops at a boundary between the two convecting layers which suppresses mechanical coupling. Then the downwelling structures originating in the lower layer develop beneath upper layer subductions, thus resembling continuous slab-like structures observed by seismic tomography.     

Melt-producing and melt-consuming reactions in the Achankovil cordierite gneisses, South India

Migmatitic cordierite gneisses within the Achankovil Zone (AZ) of southern Pan‐African India record melt‐producing and subsequent melt‐consuming mineral reactions. Early mineral assemblages Bt‐Sil‐Qtz and Bt‐Sil‐Spl, deduced from inclusion textures in garnet prophyroblasts, break down via successive dehydration melting reactions to high‐T phase assemblages (e.g. Grt‐Crd‐Liq, Opx‐Liq, Spl‐Crd‐Liq). Later back reactions between the restite and the in situ crystallizing melt resulted in thin cordierite coronas separating garnet from the leucosome, and partial resorption of garnet to Opx‐Crd or Crd‐Bt‐Qtz symplectites. Leucosomes generally display a moderate (low‐strain gneisses) to strong (high‐strain gneisses) depletion of alkali feldspar attributed to mineral‐melt back reactions partly controlled by the degree of melt segregation. Using a KFMASH partial petrogenetic grid that includes a melt phase, and qualitative pseudosections for microdomains of high and low Al/Si ratios, the successive phase assemblages and reaction textures are interpreted in terms of a clockwise P–T path culminating at about 6–7 kbar and 900–950 °C. This P–T path is consistent with, but more detailed than published results, which suggests that taking a melt phase into account is not only a valid, but also a useful approach. Comparing P–T data and lithological and isotopic data for the AZ with adjacent East Gondwana fragments, suggests the presence of a coherent metasedimentary unit exposed from southern Madagascar via South India (AZ) and Sri Lanka (Wanni Complex) to the Lützow–Holm Bay in Eastern Antarctica.