Genetic types of diamond mineralization

The paper describes the proposed models of diamond formation both in meteorites and in kimberlite and lamproite bodies, metamorphic complexes and explosive-ring structures (“astroblemes”). The diamond distribution in meteorites (chondrites, iron meteorites and ureilites) is restricted to taenite-kamasite phase. The diamond generation here is tied up with the first stage of evolution of the planets. This stage is characterized by high pressure of hydrogen, leading to the formation of the planet envelope. The second stage of planet evolution began with the progressive impoverishment of their atmospheres in hydrogen due to its predominant emission into the space and to progressive development of oxidative conditions. The model appears to have proved the relict nature of diamond mineralization in meteorites. Diamond and other high-pressure minerals (its “satellites”) were crystallized without any exception in the early intratelluric stages of peridotite and eclogite-pyroxenite magma evolution just before the magma intrusion into the higher levels of the mantle and crust where diamond is not thermodynamically stable. The ultramafic intrusive bodies (bearing rich relict diamonds) in the base of a platform appear to be the substrata for the formation of kimberlite-lamproite magma chambers as a result of magmatic replacement. The model explains the polyfacial nature of diamondiferous eclogites, pyroxenites and peridotites and discusses the process of inheritance of their diamond mineralization by kimberlites and lamproites. Diamond productivity of metamorphic complexes is originated by the inheritance of their diamonds from the above-mentioned primary diamondiferous rocks. Large diamondiferous explosive-ring structures were formed by high-energy endogenic explosions of fluid which came from the Earth’s core. This high energy differs endogenic impactogenesis from explosive volcanism. It proceeds at very high temperature to create diaplectic glasses (monomineral pseudomorphs) —the product of isochoric melting, at the pressure high enough for the stable formation of very high-density minerals (coesite, stishovite, diamond, lonsdaleit, and chaoite). The research project was financially supported by the Russian Foundation of Fundamental Sciences (93-05-8566, 96-05-64307, and 96-05-00026c0) and China National Natural Science Foundation (No.49794041, No.49611121831).     

恩施球粒陨石热历史及原始氩特征

H_s型恩施球粒陨石K-Ar年龄为4503±91Ma,~(40)Ar-~(39)Ar坪年龄为4518±8Ma,总气体年龄为4515±23Ma,等时线年龄为4505±16Ma,年龄的一致性表明该陨石未经受过明显的热扰动,它是我国首次发现的Ar保存年龄高达45亿年以上的陨石。陨石形成早期有过短期的快速冷却。陨石母体在4.66±0.04Ma时破裂。恩施球粒陨石原始捕获(~(40)Ar/~(36)Ar)_t为0.89±0.44,推测4.5Ga前太阳风中~(40)Ar/~(36)Ar近于l。     

中国大陆与香港及周围地区的地震目录完全性分析

地震活动性中心Ｇｕｔｅｎｂｅｒｇ－Ｒｉｃｈｔｅｒ关系（ｌｏｇＮ＝ａ－ｂＭ）在确定地震发生率时起着重要作用，实际分析中存在的对Ｇ－Ｒ关系的偏离主要是由于地震目录的不完全性引起：即在低震级端因地震的监测能力有限，在高震级端因大震的稀少导致的统计涨落。     

复杂地形上湍流扩散的数值模拟

本文采用准静力大气热力——动力学方程组和平流扩散方程的数值解方法,模拟了汾河河谷地区的流场、温度场和浓度场。所得结果和1984年春该地区进行的一次SF_6示踪试验资料做了对比。计算浓度场采用了三种方法:一般网格的数值模式、套网格数值模式和正态模式。和实测值的比较表明,套网格模式给出较好的计算结果,并且不需要增加过多的计算时间。     

山西省代县高凡水系沉积物金异常及验证效果

高凡Au异常受控于Nw向和NE向断裂构造交汇部位的特征,打破了前人局限于燕山期中酸性斑岩体内外接触带找Au—Ag矿的常规,为晋东北构造蚀变岩型Au—Ag矿的寻找提供了先例。另外,各种地球化学参数表明,高凡矿区Ag矿远景比Au矿更大。     

清原树基沟英云闪长岩40Ar/39Ar年龄谱

清原太古代花岗-绿岩地体位于华北断块北缘,辽宁地块铁岭-靖宇古隆起中部,分布面积约8,000平方公里,花岗岩与绿岩出露面积比为2.5:1。绿岩地层自下而上分为石棚子组、红透山组和南天门组。石棚子组与红透山组整合接触,南天门组不整合于红透山组之上。     

塔里木盆地巴什托普构造带志留系、奥陶系油气藏预测

巴什托普构造带已经发现了石炭系的生物碎屑灰岩油藏,其烃源岩为寒武系—奥陶系海相碳酸盐岩层。推测油气运移必经之路上的志留系圈闭和奥陶系圈闭中可能存在油气藏。对巴什托普构造带石炭系以下志留系和奥陶系的分析表明,志留系下砂岩段与其上覆的红色泥岩段可以构成一个有利的储盖组合,下奥陶统石灰岩段有可能形成石灰岩岩溶并与其上覆志留系巨厚的暗色泥岩段组成一套储盖组合。在巴什托普构造带,在与油源沟通良好、构造圈闭有利的位置上,应该可以形成工业性油气藏。     

Effect of boundary element details on the seismic deformation capacity of structural walls

The objective of this study is to investigate the effect of boundary element details of structural walls on their deformation capacities. Structural walls considered in this study have different sectional shapes and/or transverse reinforcement content at the boundaries of the walls (called boundary element details hereafter). Four full‐scale wall specimens (3000mm (h_w)×1500mm (l_w)×200mm (T)) were fabricated and tested. Three specimens are rectangular in section and the other specimen has a barbell‐shaped cross‐section (a wall with boundary columns). The rectangular wall specimens are reinforced according to the common practice used for reinforced concrete residence buildings in Korea and Chile. In this study, the primary variable for these rectangular specimens is the content of transverse reinforcement to confine the boundary elements of a wall. The barbell‐shaped specimen was designed in compliance with ACI 318‐95. The response of the barbell‐shaped specimen is compared with those of other rectangular specimens. The effective aspect ratio of the specimens is set to two in this study. Based on the experimental results, it is found that the deformation capacities of walls, which are represented by displacement ductility, drift ratio and energy dissipation capacities, are affected by the boundary element details. Copyright © 2002 John Wiley & Sons, Ltd.     

Determination of ductility factor considering different hysteretic models

In current seismic design procedures, base shear is calculated by the elastic strength demand divided by the strength reduction factor. This factor is well known as the response modification factor, R, which accounts for ductility, overstrength, redundancy, and damping of a structural system. In this study, the R factor accounting for ductility is called the ‘ductility factor’, R_μ. The R_μ factor is defined as the ratio of elastic strength demand imposed on the SDOF system to inelastic strength demand for a given ductility ratio. The R_μ factor allows a system to behave inelastically within the target ductility ratio during the design level earthquake ground motion. The objective of this study is to determine the ductility factor considering different hysteretic models. It usually requires large computational efforts to determine the R_μ factor. In order to reduce the computational efforts, the R_μ factor is prepared as a functional form in this study. For this purpose, statistical studies are carried out using forty different earthquake ground motions recorded at a stiff soil site. The R_μ factor is assumed to be a function of the characteristic parameters of each hysteretic model, target ductility ratio and structural period. The effects of each hysteretic model to the R_μ factor are also discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Influence of environmental disturbances and reproductive strategy on genetic diversity and differentiation of Zostera marina populations on the southern coast of Korea

The genetic diversity and differentiation of four Zostera marina populations along the southern coast of Korea were estimated using random amplified polymorphic DNA (RAPD) markers to determine the effects of natural and anthropogenic stresses and reproductive strategy on within‐population genetic diversity. The mean number of alleles and gene diversities, indicating population genetic diversity, was highest in the Z. marina population that was exposed to repeated environmental disturbances, and lowest in the most undisturbed population. The higher genetic diversity in the disturbed population was associated with a higher contribution of sexual reproduction to population persistence. This suggests that both the level of disturbances and the reproductive strategy for population persistence contributed significantly to population genetic diversity at the study sites. According to the analysis of molecular variance (AMOVA), 76% genetic variation was attributable to differences among individuals within populations. The observed genetic differentiation (F_ST = 0.241) among Z. marina populations at the study sites appeared to result from reduced meadow size, increased genetic drift, and a high incidence of asexual reproduction. Increased population genetic diversity can enhance resistance and resilience to environmental disturbances; thus, this investigation of seagrass population genetics provides valuable new insights for the conservation, management, and restoration of seagrass habitats.