月表构造与深部构造的关系

地球和月球很可能是通过大撞击形成的。在行星地质学中,研究月球的地质-构造现象,对了解月球、地球乃至太阳系的形成与演化历史都有很大帮助。月球的构造分为深部构造与月表构造,寻找它们在分布或成因上的关系,可以为月球甚至地月系的起源和演化历史提供重要参考。利用LROC的宽视角影像数据以及LOLA数据提取解译月表构造,结合深大断裂进行观察分析,并对月球的撞击盆地进行统计,最后以静海地区为例分析构造分布特征,发现月球的质量瘤盆地中具有环状分布的月岭,外侧具有近环状分布的深大断裂,自前酒海纪至酒海纪,具备上述特征的质量瘤盆地占总撞击盆地的比例突然有一个很大的提升,且静海地区西部具有该构造分布特征。推测该特征与撞击、月海沉降等有关,且在酒海纪与雨海纪期间月球有较多的月海玄武岩分布,由此判断静海西部存在质量瘤,发生过撞击与月海沉降。     

Social geography,spatial structure and social structure

This paper adopts a positivist approach to social geography, which is viewed as a study of the two-way relationship between spatial structure and social structure. This relationship is examined in cities in contemporary Britain and the United States. The concept of social structure is discussed in the first section. It is suggested, after Blau, that social structure may be delineated by parameters which demarcate the lines of differentiation among people, created in their social interaction. Area of residence may be considered such a parameter. Social structure comprises a complex configuration of these parameters. In general, coinciding parameters limit social mobility and lead to an atomised society. The processes by which social structure takes on spatial expression are discussed in the second section. The salience of various parameters of social structure in a spatial setting is assessed first. Behaviouralist, managerialist and structuralist approaches to residential differentiation are reviewed. It is argued that most insight will come from studies of the interaction between groups of households and the major institutions of the housing market in the context of characteristics of the housing supply. The impact of neighbourhood on social structure is examined in the third section. The role of propinquity in social interaction is discussed along with the role of neighbourhood as a status symbol. Individuals may change their position along structural parameters as a consequence of their residential location. Residential segregation is also a means, through its role in circumscribing contacts, by which the continuation of the stratification system is ensured in the next generation. In conclusion, it is noted that the isolation of racial minorities in the disadvantaged parts of the city poses a danger to social stability.     

Crystal structure of meteoritic schreibersites: determination of absolute structure

Minerals of the schreibersite–nickelphosphide series (Fe,Ni)₃P crystallize in the non-centrosymmetric space group . As a consequence, they can possess two different spatial arrangements of the constituting atoms within the unit cell, related by the inversion symmetry operation. Here, we present the crystal structure refinements from single crystal X-ray diffraction data for schreibersite grains from iron meteorites Acuña, Carlton, Hex River Mts. (three different crystals), Odessa (two different crystals), Sikhote Alin, and Toluca aiming for the determination of the absolute structure of the examined crystals. The crystals studied cover the composition range from ~58 mol% to ~80 mol% Fe₃P end-member. Unit-cell parameter a and volume of the unit cell V, as well as certain topological structural parameters tightly correlate with Fe₃P content. Unit-cell parameter c, on the other hand, does not show such strong correlation. Eight of the nine crystal structure refinements allowed unambiguous absolute structure assignment. The single crystal extracted from Toluca is, however, of poor quality and consequently the structure refinement did not provide as good results as the rest of the materials. Also, this crystal has only weak inversion distinguishing power to provide unequivocal absolute structure determination. Six of the eight unambiguous absolute structure determinations indicated inverted atomic arrangement compared to that reported in earlier structure refinements (here called standard). Only two grains, one taken from Odessa iron and the other from the Hex River Mts. meteorite, reveal the dominance of standard crystal structure setting.     

Australian crustal structure

There have been eight large-scale refraction experiments in Australia during the last fifteen years. P₁ velocities derived from these experiments are significantly higher in the Precambrian shield region than in eastern Australia. P_n-velocities are also higher beneath the shield, and appear to increase systematically from east to west across the continent. There is good evidence for an intermediate layer in all parts of Australia, with an average depth of about 20 km to the Conrad discontinuity. The crustal thickness has an average value of about 40 km, and the observed variations in thickness are apparently unrelated to topography in most cases.     

石英构造矿物学

石英属遍在性矿物，它在各种构造中常出现特殊的构造矿物学现象，这对于正确判断构造性质，构造几何学和构造动力学都有极好的效果。该文是作者多年科研成果和积累资料的总结。主要讨论了石英族矿物的变形，动态恢复重结晶，结构异常，化学变化和特征，识别标志，构造环境及标型意义。     

徐宿弧形构造对袁庄矿矿井构造的影响机制

以徐宿弧形构造西部外缘带中段闸河复式向斜北部的袁庄矿地质构造为主要研究对象,探讨了徐宿弧形构造对闸河向斜和袁庄矿矿井构造形成的影响机制,并分析了各级构造对煤层、瓦斯及岩浆岩的控制作用。研究表明:在徐宿弧形构造背景下,闸河向斜构造虽处于应力集中区,但因石炭-二叠纪地层软弱,故闸河向斜褶皱发育,逆冲断裂却很少,这与向斜两侧的逆冲断裂系形成鲜明对比;袁庄矿矿井构造秉承了闸河向斜构造特征,以褶皱为主要构造形式;煤层赋存、瓦斯含量及岩浆岩等开采地质条件的特征明显受各级构造形式的影响。研究认为,不同尺度下的各级构造有一定的相似性,但又有各自独有的特征,因此在多级次构造研究中,在考虑区域构造背景的同时还应重视次级构造自身条件的研究。      

既有建筑砌体结构、混凝土结构加层技术浅析

科学地利用建筑加层技术解决既有建筑物的扩容,并保证建筑物后续使用安全,同时,更好地实现既有建筑节能,已成为政府和相关企业关注和研究的焦点。既有建筑加层加固改造的同时建筑寿命也得到了延长,建筑寿命的延长是最大的节能。本文重点介绍既有建筑砌体结构、混凝土结构加层的选择原则、加层形式以及隔震托换技术在加层中的应用。     

Gas-solid molecular structure differences

Molecular geometries for a variety of classes of compounds are discussed. Where available, the structures of free molecules are compared with those in the crystal. Information inferred about intermolecular interactions are augmented with observations on structural consequences of dimerization and complex formation. Examples include substituted benzenes, sulfones, siloxane derivatives, metal halides, group four dihalides, tetrahaloaluminates, and donor-acceptor complexes.     

Magnetic structure of almandine

The magnetic structure of almandine has been investigated by electronic structure calculations in the local spin density approximation in order to arrive at a more detailed understanding of the magnetic structure and the exchange pathways. The calculations are based on experimentally determined geometrical data of the crystal structure at 100 K. The calculated quadrupole splittings, spin-allowed d–d transitions and magnetic moment for iron atoms are in reasonable agreement with the respective experimental values obtained by M?ssbauer and absorption spectroscopy, and magnetization measurements demonstrating the reliability of the calculations. The spin structure is derived from the calculated coupling constants for the possible exchange pathways. The competing superexchange pathways exist via oxygen bridges between directly neighboured iron ions and via edges of silicon tetrahedra and aluminium octahedra connecting more distant iron dodecahedra. Careful consideration revealed that almandine structure contains two identical interpenetrative sublattices of Fe dodecahedra connected via Al octahedra and Si tetrahedra. The calculations provide the information about ferromagnetic interaction between the iron spins within each sublattice, whereas the coupling between two magnetic sublattices is weakly antiferromagnetic via Al octahedra and Si tetrahedra. This antiferromagnetic interaction of two identical magnetic sublattices is in good agreement with the experiments and explains the M?ssbauer spectra of almandine below the Néel temperature. Since almandine belongs to most abundant crystallized silicates that are main constituents of the earth and main components of cosmic dust, these results have scientific importance of studying the universe.     

Electronic structure of spinel

The fundamental band gap between conduction and valence bands in aluminate spinels has been found to be at least 8·1 eV; the optical reflectivity peak at this energy possibly represents the lowest-energy exciton. In crystals with non-stoichiometric Al/Mg ratios, the intensity of this first reflection peak appears to decrease with increasing Al/Mg ratio; however, the peak energies themselves are essentially independent of stoichiometry. It seems likely that spinel and olivine in spinel-structure will have electronic transport behavior similar to that of olivine in its normal structure.     

Crustal structure of Antarctica

Seismic refraction profiles completed in the past twenty years reveal that the top of the basement complex generally lies near sea level in East Antarctica but typically 2 or 3 km below sea level in West Antarctica. Throughout much of East Antarctica the thickness of the layer overlying the basement complex is less than half a kilometer, although a Phanerozoic sequence more than 1 km thick probably underlies the ice at the South Pole. Throughout central West Antarctica, on the other hand, a section one to several kilometers thick generally overlies the basement complex. The observed sedimentary section is no more than one half kilometer thick on either side of the Transantarctic Mountains. Rocks with high seismic velocities typical of the lower continental crust occur within a few kilometers of the surface on both sides of the Transantarctic Mountains. This occurrence lends support to the hypothesis of an abrupt increase in crustal thickness between West and East Antarctica.

In 1969, deep seismic soundings were carried out by the 14th Soviet Antarctic Expedition near the coast of Queen Maud Land. The crustal thickness was found to be about 40 km near the mountains, decreasing to about 30 km near the coast. In the top 15 km of the crust there is a gradual downward increase in P-wave velocity from 6.0 to 6.3 km/sec. The average velocity through the crust is 6.4 km/sec and the measured velocity below the M-discontinuity is 7.9 km/sec.

At the southwestern margin of the Ronne Ice Shelf, near-vertical reflections from the M-discontinuity have been recorded. A mean P-wave velocity of 6 km/sec in the crust was measured, leading to an estimated depth to M of 24 km below sea level.

Seismic surface wave dispersion studies indicate a mean crustal thickness of about 30 km in West Antarctica and about 40 km in East Antarctica. The dispersion data also show that group velocities across East Antarctica are much closer to those along average continental paths than to those across the Canadian shield. The results thus support other indications that central East Antarctica is not a simple crystalline shield.

P′P′-reflections beneath the continent support the existence of a low-velocity channel for P-waves, but show no significant difference in deep structure between Antarctica and other continents.     

Crystal structure of daqingshanite

Daqinshanite, a new mineral recently discovered in China, is a kind of strontium-rare earth-bearing phosphate-carbonate. The ideal formula is: (Sr, Ca, Ba), RF(PO₄)(CO₃)₃. The mineral belongs to the trigonal system. The intensity data were collected with a single-crystal four-circle diffractometer. The lattice parameters are given as:a=10.058(±0.002) Å;c=9.225(±0.003) Å. Space group=R3m,Z=3. The crystal structure was solved by Patterson and electron density synthesis methods. The least-squares refinement led to a final conventional factorR=0.079. Crystal structural analysis shows that daqingshanite is of calcite-type structure and the ordered model of cations is similar to that of huntite (Mg₃Ca(CO₃)₄).     

Crustal structure in Alaska

Knowledge of the crustal structure is still fragmentary, despite the stimulus to geophysical work provided by the earthquake of March 28, 1964 (GMT), the underground nuclear explosion LONGSHOT, and the June 1967 series of earthquakes in the Fairbanks area. The most reliable information about struc ture has come from a combination of seismic explosion-refraction profiles, gravity surveys, and magnetic surveys. This report is a summary of recent investigations, but the results are not adequate to permit unambiguous generalizations about crustal structure.     

Crystal structure of xinganite

Xinganite is a new REE-Be-rich silicate discovered in China. Its ideal formula is: (Y, Ce)Be SiO₄ OH. The mineral is of monoclinic system. The intensity data were collected with a single-crystal four-circle diffractometer. The lattice parameters are: a=4.7681 (± 0.00263) Å,b=7.7657 (± 0.00686) Å, c=9.9301 (± 0.00639) Å; α =90°, β=90.171° (±0.0053°), γ=90° space group p2¹/c;,Z=4. The crystal structure has been determined by direct methods and electron density synthesis methods. The least squares refinement gave a final discrepancy indexR=0.086. The crystal structural analysis shows that xinganite is of datolite-type structure.     

Iron local structure in tektites and impact glasses by extended X-ray absorption fine structure and high-resolution X-ray absorption near-edge structure spectroscopy

The local structure of iron in three tektites has been studied by means of Fe K-edge extended X-ray absorption fine structure (EXAFS) and high-resolution X-ray absorption near-edge structure (XANES) spectroscopy in order to provide quantitative data on <Fe-O> distance and Fe coordination number. The samples studied are a moldavite and two australasian tektites. Fe model compounds with known Fe oxidation state and coordination number were used as standards in order to extract structural information from the XANES pre-edge peak. EXAFS-derived grand mean <Fe-O> distances and Fe coordination numbers for the three tektite samples are constant within the estimated error (<Fe-O > =2.00 Å ± 0.02 Å, CN = 4.0 ± 0.4). In contrast to other data from the literature on Fe-bearing silicate glasses, the tektites spectra could not be fitted with a single Fe-O distance, but rather were fit with two independent distances (2 × 1.92 Å and 2 × 2.08 Å). High-resolution XANES spectra of the three tektites display a pre-edge peak whose intensity is intermediate between those of staurolite and grandidierite, thus suggesting a mean coordination number intermediate between 4 and 5. Combining the EXAFS and XANES data for Fe, we infer the mean coordination number to be close to 4.5.Comparison of the tektites XANES spectra with those of a suite of different impact glasses clearly shows that tektites display a relatively narrow range of Fe oxidation state and coordination numbers, whereas impact glasses data span a much wider range of Fe oxidation states (from divalent to trivalent) and coordination numbers (from tetra-coordinated to esa-coordinated). These data suggest that the tektite production process is very similar for all the known strewn fields, whereas impact glasses can experience a wide variety of different temperature-pressure-oxygen fugacity conditions, leading to different Fe local structure in the resulting glasses. These data could be of aid in discriminating between tektite-like impact glasses and impact glasses sensu strictu.     

Geologic structure of Lesser Khingan and its position in structure of Far East

The Lesser Khingan has been variously assigned to, 1) a zone of Mesozoic folding at the western margin of the East Asian Mesozoic-Cenozoic folded belt; 2) the Mongol-Okhotsk folded belt. 3) the marginal zone of the northeast side of the Chinese platform as altered by very late folding, hi order to establish its tectonic affinity, the geologic and especially tectonic history is considered from Proterozoic rime to the present. Tectonic maps give details of structures within Proterozoic. Mesozoic, and Cenozoic sadimentary and associated igneous rock complexes. Major anticlinoria and synclinoria are discussed and the role of ancient deep faults is noted. From a consideration of the several stages in the history of the Lesser Khingan it is concluded that its geosynclinal. development within the southern (Paleozoic) branch of the Mongol-Okhotsk belt has been completed by the end of Paleozoic time, This means that the area has no direct affinity with the younger East Asia geosynclinal belt. However, it seems logical that the lesser Khingan should have exerted a dynamic action on the adjacent young platform to the west, as shown by extensive dislocation of Mesozoic strata in its eastern structures.—W.D. Lowry