Broad distribution of crystal-field environments for Nd<Superscript>3+</Superscript> in calcite

Calcite crystals were grown from solution with single-crystal dimensions up to 3 mm and doped up to 0.1 at% with Nd³⁺ ions. Phase purity was verified by powder X-ray diffraction. The concentration of Nd³⁺ was measured by energy-dispersive spectrometry and Rutherford backscattering spectrometry. Micro X-ray fluorescence mapping of the calcite grains indicates uniform Nd distribution in as-grown crystal grains. X-ray absorption fine structure suggests that Nd³⁺ is substituted for Ca²⁺ with local lattice distortion. Temperature-dependent near-infrared spectroscopy of Nd³⁺ impurities in calcite reveals large inhomogeneous linewidths and smooth line profiles that are characteristic of glassy hosts, though the samples are well crystallized.     

加强行业管理以产品质量占领测绘市场浅析

执行测绘法加强测绘行业管理,是规范测绘管理,提高测绘产品质量的前提。而以产品质量开创和巩固测绘市场是市场竞争的主要手段,质量是取信于用户的根本保障。     

盐湖沉积物的穆斯堡尔效应研究

对青海柴达木盆地察尔汗、昆特依盐湖以及新疆罗布泊盐湖一系列沉积物样品进行了穆斯堡尔效应的研究。对全部样品做了常温下的穆斯堡尔谱学测量,并对部分样品做了低温下的测量。从穆斯堡尔谱的解析结果可知,盐湖沉积物黏土矿中含二价铁的主要矿物是绿泥石,在察尔汗盐湖样品中有少量菱铁矿;三价铁存在于多种矿物和非晶态的氢氧化物中;某些样品中含有少量的赤铁矿,它在常温下即出现磁有序。不同盐湖的沉积物样品和同一盐湖不同深度样品的含铁矿物组成及相对含量不同,Fe2+/Fe3+的比值也不同。这些结果可以反映出盐湖沉积过程中地球化学和环境及气候的变化。     

贵州牛角塘镉锌矿床中发现原生硫镉矿

在贵州牛角塘镉锌矿床中既有次生硫镉矿的存在，也发现了原生硫镉矿。硫镉矿的产状如下：①呈包裹体形式产于硫化物中；②以不规则晶粒赋存于硫化物粒间：③形成硫镉矿．方铅矿细脉或硫镉矿微脉穿插硫化物；④分布在黄铁矿中方铅矿或闪锌矿周围；⑤被菱锌矿胶结并交代，形成硫镉矿残骸状角砾；⑥组成菱锌矿．硫镉矿疏松集合体或菱锌矿．硫镉矿细脉；⑦呈皮壳状或薄膜状分布在氧化矿石表面或裂隙面上。前五种形式产出的硫镉矿为原生硫镉矿，主要分布在原生矿石或弱氧化的矿石中。后两种产状的硫镉矿为次生硫镉矿，分布于氧化矿石晶洞中或矿石表面和裂隙面上。并从Cd、Zn地球化学特性、热力学和结晶化学性质探讨了原生硫镉矿形成机制。     

煤系地层中铁质矿物微观特征研究

通过对煤系地层中菱铁质鮞粒内部结构构造和黄铁矿、白铁矿微晶特征的研究，探讨了其生成的地球化学条件、形成机理，为地层对比、沉积地球化学条件的恢复等提供了依据。并对煤炭资源的勘探开发和利用具有实用意义。     

Prediction of Gibbs free energies of formation of minerals of the alunite supergroup

A method for the prediction of Gibbs free energies of formation for minerals belonging to the alunite family is proposed, based on an empirical parameter Δ_GO⁼ M^z+(c) characterizing the oxygen affinity of the cation M^z+. The Gibbs free energy of formation from constituent oxides is considered as the sum of the products of the molar fraction of an oxygen atom bound to any two cations, multiplied by the difference of oxygen affinity Δ_GO⁼ M^z+(c) between any two consecutive cations. The Δ_GO⁼ M^z+(c) value, using a weighing scheme involving the electronegativity of a cation in a specific site (12-fold coordination site, octahedral and tetrahedral) is assumed to be constant. It can be calculated by minimizing the difference between experimental Gibbs free energies (determined from solubility measurements) and calculated Gibbs free energies of formation from constituent oxides. Results indicate that this prediction method gives values within 0.5% of the experimentally measured values. The relationships between Δ_GO⁼ M^z+(alunite) corresponding to the electronegativity of a cation in either dodecahedral sites, octahedral sites or tetrahedral sites and known as Δ_GO⁼ M^z+(aq) were determined, thereby allowing the prediction of the electronegativity of rare earth metal ions and trivalent ions in dodecahedral sites and highly charged ions in tetrahedral sites. This allows the prediction of Gibbs free energies of formation of any minerals of the alunite supergroup (bearing various ions located in the dodecahedral and tetrahedral sites). Examples are given for hydronium jarosite and hindsalite, and the results appear excellent when compared to experimental values.     

下地幔矿物研究及其进展

文中综述了20世纪90年代以来对下地幔矿物高温高压研究的进展,详细评论了下地幔温压下(Mg,Fe)SiO3钙钛矿的稳定性、(Mg, Fe)SiO3 钙钛矿和(Mg, Fe)O镁方铁矿的高压状态方程和热弹性及高压熔化、核幔边界温压下铁和硅酸盐的化学反应等几个热点问题;探讨了下地幔的矿物学组成,对下地幔的地震波速异常给出了可能的矿物学解释;介绍了国内同领域的研究工作;展望了下地幔矿物研究的发展方向。     

A simple relationship between isothermal bulk modulus and thermal pressure for geophysical minerals

The variations in isothermal bulk modulus with an increase in temperature are found to be related linearly with the change in thermal pressure for geophysical minerals, such as MgO, CaO, Al₂O₃, MgAl₂O₄ and Mg₂SiO₄. Analysis of the relationship yields a value of the Anderson–Gruneisen parameter for each mineral in close agreement with known values. An important finding of the present study is the derivation of an isobaric equation of state representing the relationship between volume and temperature at ambient pressure. This equation for isobaric volume expansion looks like the Birch equation for isothermal compression. The calculated values of volume expansion for the minerals at high temperatures present close agreement with the available experimental data. The formulation developed in the present study has also been used to predict the volumes at simultaneously elevated temperatures and pressures for CaSiO₃ perovskite and NaCl minerals, in good agreement with the experimental values.     

Relation between semen quality and rangeland diets of mixed-breed male goats

The impact of range plant toxins on the reproductive performance of female cattle is economically important to the livestock industry. Nevertheless, there is little information on the significance of toxicosis from range plants on semen quality in domestic ruminants. A total of 18 adult mixed-breed bucks under range conditions were used to evaluate the effect of diet composition (microhistological analysis of fecal samples) on some semen characteristics, and blood and fecal components in April and August. Forages in the buck diets were grouped into 2 classes: low or high levels of each plant in the buck diets. Bucks with higher proportion of Acacia greggii, Flourensia cernua and Lindleya mespiloides in their diets yielded 23–50% less (p<0.05) semen than bucks with low proportion of these shrubs in their diet. Sperm motility was reduced by 3–8 percent units (p<0.05) by high levels of five rangeland shrubs in the buck diets. Bucks consuming high levels of Acacia greggii showed significantly lower percentages of normal sperm (92±10 vs. 96±3; p<0.05) than bucks with low intake of this forage. High proportions of Rhus virens and Solanum elaeagnifolium in the buck diet increased the percentage of normal sperm (5 units, p<0.05) when compared to bucks with low utilization of these forages. Increased intake of Acacia greggii, Dalea bicolor, Opuntia rastrera, Larrea tridentata and Cowania plicata reduced percentage of live sperm by 5 units (p<0.05). Blood metabolites analysis showed that increased levels of Acacia greggii and Parthenium incanum were related to better nutritional status of bucks. Zn (−), Cu (−) and glucose (+) were significant predictors of semen volume (r²=0.30). Cu (−) and cholesterol (−) accounted for 37% of the variation in percentage of normal sperms. Forty-four percent of the variation in secondary abnormalities was accounted by Zn (+) and cholesterol (+), whereas fecal N, serum total proteins and creatinine positively affected percentage of live sperms (r²=0.37). These results indicate that semen quality and metabolic profiles of grazing bucks were sensitive to the ingestion of some Chihuahuan desert forages.     

Placer formation in gravel-bedded rivers: A review

The literature on placer formation processes within fluvial systems is widespread and ranges between detailed laboratory studies of the hydrodynamic segregation processes through to the intuitive interpretation of the distribution of minerals within geological sections. However, there are few, if any, comprehensive reviews of the literature. Surprisingly, given the economic importance of placers, the theoretical framework relating to the hydrodynamics of physical grain sorting is not well developed and there are relatively few detailed laboratory hydraulic investigations to inform theory. In this wide-ranging review, the history of the development of principles of placer formation is explored as far as possible in a non-technical fashion. A consideration is given to the hydrodynamics of physical grain sorting above lower-stage and upper-stage bedforms and the typical internal sedimentary structures associated with placer concentrations are detailed. Finally, examples of the depositional environment of diamond, tin and gold placers are considered.