山东金伯利岩蒙山矿(mathiasite)研究的新进展──上地幔含大阳离子Cr、Ti、Fe氧化物矿物研究之三

本文回顾了国内外金伯利岩及其它地幔岩中发现的K、Ba、Ca、REE的Ti-Cr－Fe－Mg氧化物矿物的研究现状，包括沂蒙矿系列、蒙山矿系列及柱红石系列。在此基础上概括性地总结了笔者近一、二年对山东蒙阴金伯利岩中蒙山矿矿物所进行的微区矿物学方向研究取得的最新进展，包括：①揭示了K、Ba、Ca、REE等半径较大的元素在蒙山矿中的不均匀分布特点；②首次在金伯利岩中发现了蒙山矿系列矿物的Ca端元——Ca蒙山矿及K－Ba－Ca三个端元蒙山矿在同一矿物颗粒中的共存现象；③进行了高分辨透射电镜工作，拍摄了晶格条纹象，从而完善了蒙山矿的晶体结构资料；④确定了蒙山矿后期熔融交代形成的多种矿物相。这些研究成果，证实了地幔交代作用的存在和复杂性，应引起矿物岩石学界的充分重视。     

水杨基萤光酮—Triton X—100析相光度法测定岩矿中的钛

研究了水杨基萤光酮(SAF)-Triton X-100体系中痕量Ti(N)的显色-析相反应。试验表明,在适量的抗坏血酸及Triton X-00存在下,控制介质酸度为pH2左右,Ti(N)-SAF配合物的最大吸收峰为532.2nm,摩尔吸光系数为1.60×10~5L·mol~(-1)·cm~(-1),0～600ng/ml Ti(Ⅳ)服从比尔定律。方法用样少,操作简便,无需特殊仪器,灵敏度高,选择性较好,能用于低钼试样中Ti的测定。     

矿物热力学数据的获取

简介矿物热力学数据获取方法发展现状,重点评述量热法和相平衡法的近期发展状况。     

First-order asymptotic theory of the polar phase shift of Rayleigh waves

The precision of measurement of surface-wave phase velocities at very long periods has reached a point where the exact, rather than asymptotic, form of the spherical harmonics must be considered in order to compute theoretical phase velocities or phase delays. The zeroth-order (i.e. constant) polar phase shift afterBrune et al. (1961) applies only between stations antipodal to each other. Everywhere else a correction for incomplete polar phase shift must be applied even if the waves do not cross a pole between the stations. The correction can exceed one percent of the total phase delay and thus be of the same order as the expected regional anomalies. It depends on the epicentral distance on the signal period and on the focal mechanism; the latter dependence can make the practical application cumbersome. We derive first-order asymptotic formulae for the correction of local phase velocities and total phase travel times of Rayleigh waves.Contribution No. 247 of the Institute of Geophysics, Swiss Federal Institute of Technology, Zürich.     

TDR detection of nonaqueous phase liquids in sandy soils using the eigendecomposition method

In this study, the presence of nonaqueous phase liquids (NAPL) in sandy soils are detected using a TDR probe system and the eigendecomposition method of analysis. As a demonstration, five NAPLs with different physicochemical properties (acetone, benzene, heptane, trichloroethylene, and xylene; Table 1) were used. Samples were prepared in such a way that the soil pore fluid has different contents of deionized water and NAPLs. For each experiment, a pulse signal with known characteristics was used and reflected signals were captured by an oscilloscope and analyzed using the eigendecomposition method. Autoregressive modeling and singular value decomposition were used to calculate the eigenvalues. The most significant eigenvalues were identified based on their power spectrum. The relative eigenvalue of the first mode (Eow), which is a measure of the power carried by the signal, was calculated and correlated to NAPL type and content, and octanol water partition coefficient (log Kow). The results indicated that for the same NAPL content, as log Kow increases, Eow decreases due to increase of hydrophobicity. For the same log Kow, as the organic content in soil pore fluid increases, Eow increases due to decrease of dielectric properties of the pore fluids.     

Site-specific multipath characteristics of global IGS and CORS GPS sites

The site-specific multipath characteristics of 217 Global Positioning System (GPS) sites worldwide were analyzed using the variability of the post-fit phase residuals. Because the GPS satellite constellation returns to the same configuration in a sidereal day (23 h 56 min 4 s), the multipath repeats on that period. However, daily GPS position estimates are usually based on the solar day. When several days of GPS data are processed, this steady change in the orientation of the satellite constellation with respect to the station manifests itself in the form of patterns in the post-fit phase residuals which shift by 3 min 56 s per day. It was found that the mean root mean square of the time-shifted post-fit phase residuals is highly dependent on the GPS antenna type. The conclusions derived from the analysis of the time-shifted post-fit residuals were verified by performing a cross-correlation of the post-fit residuals across many days for selected sites.     

Complex Site Effects in Thessaloniki (Greece): II. 2D SH Modelling and Engineering Insights

This paper presents results of numerical modelling of site response for Thessaloniki, obtained with two different 2D methods; a finite difference and a finite element method. Ground motion across a 2D model of the subsoil of the city has been simulated for vertically incident SH waves. The predominance of locally generated surface waves is very clear in the synthetic seismograms of a weak event and of stronger ones. These results are then compared with the observations in time domain and frequency domain. The role of the soil formations with high attenuation in the lateral propagation and the effect of the differential motion close to the lateral variations are also pinpointed. The stronger events were finally used to compute strong ground motion in order to reveal and to discuss practical engineering aspects such as peak ground acceleration value, the most familiar indicator in seismic norms, the soil to rock spectral coefficients for the period bandwidth of interest, and the aggravation factor in terms of 2D to 1D response spectra as a useful ruler to account for complex site effects.     

High-pressure Partial Melting of Mafic Lithologies in the Mantle

We review experimental phase equilibria associated with partialmelting of mafic lithologies (pyroxenites) at high pressuresto reveal systematic relationships between bulk compositionsof pyroxenite and their melting relations. An important aspectof pyroxenite phase equilibria is the existence of the garnet–pyroxenethermal divide, defined by the enstatite–Ca-Tschermakspyroxene–diopside plane in CaO–MgO–Al₂O₃–SiO₂projections. This divide appears at pressures above 2 GPa inthe natural system where garnet and pyroxenes are the principalresidual phases in pyroxenites. Bulk compositions that resideon either side of the divide have distinct phase assemblagesfrom subsolidus to liquidus and produce distinct types of partialmelt ranging from strongly nepheline-normative to quartz-normativecompositions. Solidus and liquidus locations are little affectedby the location of natural pyroxenite compositions relativeto the thermal divide and are instead controlled chiefly bybulk alkali contents and Mg-numbers. Changes in phase volumesof residual minerals also influence partial melt compositions.If olivine is absent during partial melting, expansion of thephase volume of garnet relative to clinopyroxene with increasingpressure produces liquids with high Ca/Al and low MgO comparedwith garnet peridotite-derived partial melts. KEY WORDS: experimental petrology; mantle heterogeneity; partial melting; phase equilibrium; pyroxenite