Effects of defect and pressure on the thermal expansivity of Fe x O

Pressure–volume–temperature measurements have been carried out using synchrotron X-ray diffraction for wüstite at static pressures of 1.9, 2.6, and 5.4 GPa. Our results revealed that the composition change of wüstite and, hence, rearrangements of defect structures are primarily caused by the magnetite (Fe₃O₄) exsolution at temperatures of 523–723 K. Based on the isobaric volume–temperature data collected during cooling, the contribution of compositional variations to the unit-cell volumes of wüstite in the ranges of 300–673 K and 723–1073 K is negligibly small, within the experimental uncertainties. These observations suggest that the measured volume changes in the range of 300–673 K and 723–1,073 K can be attributed to the metal–oxygen bond expansion. Owing to the magnetite exsolution, thermal expansion data are obtained in each experiment at 1.9, 2.6, and 5.4 GPa for wüstite of two different compositions, Fe_0.987O and Fe_0.942O. At all three pressures, Fe_0.942O shows a thermal expansion that is about 30% larger than Fe_0.987O. Such findings represent the first experimental evidence of a substantial effect of nonstoichiometry on thermal expansivity, and based on previous thermodynamic calculations of the defect formation and interaction, this effect is likely associated with the distinct defects arrangements in iron-rich and more iron-deficient wüstite. This study also presents thermal equations of state for wüstite of two different compositions. Such volume-related properties at high temperatures are experimentally difficult to obtain in wüstite but important for thermodynamic studies in the binary Fe–O system.     

Assessment of geomorphic hazards in connection with permafrost occurrence in the Zugspitze area (Bavarian Alps, Germany)

In the Zugspitze area (Bavarian Alps, Germany), permafrost conditions are present in limestone bedrock and in regolith. Distribution is strongly dependent on topography in the east–west oriented mountain crest with steep north- and south-facing slopes. Numerous structures mainly for tourist purposes (cable car and recreation buildings, ski-lift masts, rack-railway tunnel, tunnel with supply facilities) are situated in the area, and several of them are placed on ground with permafrost. Results from a temperature measurement programme and distribution modelling show that for some of these constructions, the effects of permafrost degradation have to be considered in terms of stability of the foundations.The permafrost limit is close to the summit crest, and therefore, stability evaluations for the constructions in this area have to bear in mind the possible warming or even melting of ice within the bedrock crevasses caused by climate warming. Stability of the foundations as well as stability of rock walls in this area will probably be affected by a shifting of the permafrost limit. Constructions in the Zugspitzplatt area are already affected by the melting ground ice, and stabilizing measures have to be evaluated for several foundations where subsidence is likely to occur.Besides the local results, the study provides for the first time data on permafrost distribution in the northern Alpine margin based on standard methods of BTS measurements and numerical modelling.     

小波变换在前兆观测资料分析中的应用

由于数字化前兆具有高精度特点，因此，如何分离数字化前兆中的高频与低频信息，以及如何识别地震前兆的趋势异常与短期异常，是数字化前兆资料分析应用中的一个重要问题。本文给出了小波变换应用于正常的数字化前兆资料高频与低频信息的分离方法，并实际应用于地震前兆观测资料的处理，结合实例给出了地震前兆的趋势异常与短期异常的识别思路，从而为数字化前兆的趋势异常与短期异常的识别提供了一种新的有效方法。     

Closure of the Fe-S-Si liquid miscibility gap at high pressure

A high pressure investigation of melting relationships in the Fe-S-Si system has been conducted in a multi-anvil apparatus from 10 to 27 GPa and up to 2343 K. At 1 atm, the Fe-S-Si ternary system exhibits a vast miscibility gap [Raghavan, V., 1988. Phase diagrams of ternary iron alloys. Part 2: Ternary systems containing iron and sulphur. Indian Institute of Metals, Calcutta]. Quenched samples from experiments conducted at 10 and 12 GPa show an emulsion of immiscible liquids (an Fe-S melt and an Fe-Si melt). The liquid miscibility gap persists to at least 2343 K at 10 GPa. At 15 GPa, only one liquid is quenched, with a fine homogeneous dendritic texture. The results provide a mechanism to incorporate both S and Si as the light elements into the Earth’s core during a moderately high-pressure differentiation, consistent with geochemical models predicting up to 15 wt.% of light elements in the Earth’s core with 2-5 wt.% S and 7-10 wt.% Si. In contrast, for small planets such as Mars and Ganymede, differentiation took place within the pressure range of the miscibility gap. The composition of these cores is likely to be S-rich but Si-poor.     

高含水量软土地基水泥土桩成桩质量试验研究

针对淮盐高速公路淮安段高含水量软土地基的工程地质特性，依据设计文件进行水泥土搅拌桩成桩质量的现场试验研究，提出采用增强剂(石膏)和减水剂(木钙)作为水泥土搅拌桩的外加剂，以保证水泥土桩的成桩质量。提出了保证成桩质量的控制管理措施。     

A visualization system for mineral elasticity

The authors have developed an efficient visualization system to gain insight into large collections of mineral elasticity data produced by an increasing number of both theoretical calculations and experiments. The system allows us to visualize multivariate elastic moduli (i.e., elastic constant tensors) and their variation with composition, pressure and temperature. Moreover, it supports visualization of elastic wave propagation in an anisotropic medium by rendering the wave velocity data, which are calculated as a function of propagation direction in a three-dimensional space. This paper describes the design, implementation and application of the visualization scheme we have developed for mineral elasticity. In particular, our scheme exploits a combination of parallel coordinates, star plot, scatter plot and polygon-surface rendering techniques, which are implemented using OpenGL, GLUI and C++. The result is a highly portable and flexible interactive visualization system. For illustration, the elastic properties of several important oxide and silicate minerals are successfully visualized as a function of pressure and temperature.Reviewed by: D. Yuen, G. Erlebacher     

Isotopic evidence of middle proterozoic magmatism from bombay high field: Implications to crustal evolution of western offshore of India

Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67 Ma with an initial⁸⁷Sr/⁸⁶Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43 Ma and 1465 ± 43 Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42 Ma and 1425 ± 40 Ma with an overall mean age of 1438 ± 19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield.     

无连接挡板高填方路堤薄壁挡土墙土压力模型试验研究

提出了一种新型的互锚薄壁挡土墙,该挡土墙是在传统加筋土墙的基础上发展起来的。以钢筋为拉筋,两侧的挡土墙面板通过拉筋对称连接互锚。通过模型试验测试了该结构挡土墙面板后土压力的分布规律。挡土面板后土压力并不是呈线性分布,也没有表现中间大、两端小的三角形分布或曲线,即在挡土墙的墙底和墙顶土压力接近于0、在挡土墙的中间土压力最大的分布规律,而是在距离挡土墙顶部1/3h以上(h为墙高),挡土墙面板后的土压力分布完全呈线性分布,与朗肯主动土压力理论相似;但是在距离挡土墙顶部1/3h以下位置,挡土墙面板后的土压力随着挡土墙高度的延伸,土压力基本保持不变,近似呈现一条竖线段。结果表明这种挡土墙的承栽能力得到明显加强。     

Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ₀ = 3.888 g/cm³ and a bulk modulus of K₀ = 229 ± 9 GPa for K^′₀ = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K^′₀ = 4, then the value of K₀ = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.     

用高密度电法精确圈定硅灰石矿

利用高密度电法勘查岩溶、破碎带的过程中,提出物探相对高、低的灵活应用,并结合地质成因、控矿构造,得出由直接找矿变为间接找矿的新思路。