Thermodynamics of mixing in diopside–jadeite,CaMgSi<Subscript>2</Subscript>O<Subscript>6</Subscript>–NaAlSi<Subscript>2</Subscript>O<Subscript>6</Subscript>, solid solution from static lattice energy calculations

Static lattice energy calculations (SLEC), based on empirical interatomic potentials, have been performed for a set of 800 different structures in a 2 × 2 × 4 supercell of C2/c diopside with compositions between diopside and jadeite, and with different states of order of the exchangeable Na/Ca and Mg/Al cations. Excess static energies of these structures have been cluster expanded in a basis set of 37 pair-interaction parameters. These parameters have been used to constrain Monte Carlo simulations of temperature-dependent properties in the range of 273–2,023 K and to calculate a temperature–composition phase diagram. The simulations predict the order–disorder transition in omphacite at 1,150 ± 20°C in good agreement with the experimental data of Carpenter (Mineral Petrol 78:433–440, 1981). The stronger ordering of Mg/Al within the M1 site than of Ca/Na in the M2 site is attributed to the shorter M1–M1 nearest-neighbor distance, and, consequently, the stronger ordering force. The comparison of the simulated relationship between the order parameters corresponding to M1 and M2 sites with the X-ray refinement data on natural omphacites (Boffa Ballaran et al. in Am Mineral 83:419–433, 1998) suggests that the cation ordering becomes kinetically ineffective at about 600°C.     

大别造山带毛屋超镁铁岩的铂族元素研究

采用镍锍火试金法结合ICP-MS分析了毛屋斜方辉石岩和石榴二辉岩样品中的Ir、Ru、Rh、Pt和Pd的含量,结果显示其铂族元素(PGE)的含量随岩石类型无规律性的变化,原始地幔标准化后的铂族元素分布模式呈负斜率,Pd、Ir发生了分异。毛屋超镁铁岩铂族元素特征的形成受岩石中铂族元素的存在相制约,PPGE富集在富Cu硫化物,而IPGE以类似残留相、不熔的单硫化物固熔体形式存在,其中地壳混染也起了一定的作用;同时,成岩过程中流体的存在造成了Pt和Pd的活化。因此,单硫化物固熔体和流体的共同作用形成了毛屋超镁铁岩类似残留地幔岩的铂族元素分布特征。     

基于解析方法计算频散层状介质的探地雷达响应

考虑频散介质的电磁波传播,采用Cole-Cole公式建立频散模型。只考虑介质的介电常数随外加电磁场频率的变化,采用高密度采样滤波算法,模拟层状介质的雷达响应,从中可以看出频散介质对雷达波的衰减影响。     

一种微地形探测回波信号处理的新算法

针对钴结壳具体赋存环境和开采技术要求,作者提出了利用Morlet小波信号包络和高斯函数曲线及能量相关性算法对拟设计的微地形探测方法接收到的超声回波信号进行分析与计算。由实验初步验证,利用该算法计算出来的被测对象位置精度及误差稳定性均高于传统的超声波单波束多探头探测方法。     

GPS数据采样率对定轨误差的影响

通过对星载GPS接收机测量数据的仿真，生成了5组不同采样率的GPS接收机测量模拟数据。采用了相应的力学模型和测量模型，对GPS模拟数据进行精密定轨处理后，在不同GPS采样率情况下，得到了飞行器的GPS定轨误差结果。     

广西固体矿产钻探工程技术与管理现状及其对策

从钻探设备、工艺技术、生产管理与人员素质等方面，简要分析了广西地矿局固体矿产钻探工程施工技术与管理现状，指出当前存在的突出问题以及解决这些问题的一些建议与对策。     

On the resurfacing of Ganymede by liquid-water volcanism

A long-popular model for producing Ganymede's bright terrain involves flooding of low-lying graben with liquid water, slush, or warm, soft ice. The model suffers from major problems, however, including the absence of obvious near-surface heat sources, the negative buoyancy of liquid water, and the lack of a mechanism for confining the flows to graben floors. We present new models for cryovolcanic resurfacing to overcome these difficulties. Tidal heating within an ancient Laplace-like orbital resonance (Showman and Malhotra 1997, Icarus 127, 93; Showman et al., 1997, Icarus 129, 367) provides a plausible heat source and could allow partial melting to occur as shallow as 5-10 km depth. Our favored mechanism for delivering this water to the surface invokes the fact that topography—such as a global set of graben—causes subsurface pressure gradients that can pump water or slush upward onto the floors of topographic lows (graben) despite the negative buoyancy of the liquid. These eruptions can occur only within the topographic lows; furthermore, as the low areas become full, the pressure gradients disappear and the resurfacing ceases. This provides an explanation for the observed straight dark-bright terrain boundaries: water cannot overflow the graben, so resurfacing rarely embays craters or other rough topography. Pure liquid water can be pumped to the surface from only 5-10 km depth, but macroscopic bodies of slush ascending within fractures can reach the surface from much greater depths due to the smaller negative buoyancy of slush. A challenge for these models is the short predicted gravitational relaxation timescale of topographic features at high heat flows; the resurfacing must occur before the graben topography disappears. We also evaluate alternate resurfacing mechanisms, such as pumping of liquid water to the surface by thermal expansion stresses and buoyant rise of water through a silicate-contaminated crust that is denser than liquid water, and conclude that they are unlikely to explain Ganymede's bright terrain.