Computation of surface energies in an electrostatic point charge model: II. Application to zircon (ZrSiO4)

The attachment energies, the slice energies and the specific surface energies can be calculated in an electrostatic point charge model using the formula derived by Madelung for the potential introduced by an infinite row of equally spaced point charges. Power series are given for the Hankel function iH ₍₀₎ ⁽¹⁾ (iy) and (x)=d ln x!/dx. The logarithmic expression in the Madelung formula converges rapidly when applying a power series, which combines equally charged cations and anions. Besides the specific surface energy ( ^hkl), the slice energy (E _s ^hkl ) and the attachment energy (E _a ^hkl ) can be considered as special categories of surface energies as they depend on surface configurations as well. The specific surface energy is the energy per unit area of surface needed to split the crystal parallel to a face (hkl). The attachment energy (E _a) is the energy released per mole, when a new slice of thickness d _hkl crystallizes on an already existing crystal face (hkl). The growth rate of the crystal face (hkl) is a function of its attachment energy. The slice energy (E _s) is the energy released per mole, when a new slice d _hkl is formed from the vapour neglecting the influence of edge energies. The lattice energy (E _c) which is the energy released per mole of a crystal crystallizing from the vapour, is given by the following relation: E _c=E _a+E _s.     

Soft rock pillars

Summary Soft rock pillars can be designed by several methods available in the mining literature. All of these methods include the effect of shape, or geometry, on the average strength of specimens and pillars. All of the pillar design methods include some measurement of the strength of specimens of the pillar rock. The most common rock specimen strength property measured is the unconfined compressive strength. However, the average strength of triaxially confined rock specimens is much greater than the unconfined specimen strength, which can be more important to pillar strength. The estimation of the strength of a pillar is complicated by the decrease in rock specimen strength with increase in specimen size.Editor's note: In common with North American engineering practise, the paper uses English units throughout, where feasible conversions are included in the text. Where not, the following factors may be used: 1 inch=25.4 mm; 1 ft=0.3048 m; 1 lbf/in.^–2=6.895 kn/m^–2; 1Tonf.=8.896 kN.     

A non-glacial origin for the ordovician (middle caradocian) cosquer formation,veryarc'h,crozon peninsula,brittany, France

The presence of a dispersed clast fraction in strata near the base of the Cosquer Formation in west Brittany, does not support a glacial origin for this unit. The upper 25 to 30 m of the underlying Kermeur Formation consists of a prograding sequence of very fine to fine sandstones deposited in a mid to distal current swept shelf setting. This sequence shows signs of slope instability, as do the supposed ‘glacial strata’ which overlie it. The upper two thirds of the Cosquer Formation contain spectacular slump-breccias. Smaller clasts within the laminated mudrocks at the base of the formation are associated with thin graded and non-graded sandstone laminae. They show no evidence of active penetration into underlying laminae other than can be explained by compaction. Larger clasts are confined to thicker massive beds, or disrupted units with marked internal contorted lamination. This, along with the abundance of slump features within the sequence suggests lateral emplacement by sediment gravity flows in a distal shelf-slope setting. Surface textures of sand grains within the formation are related to rock disaggregation along fractures developed during post-depositional deformation and are not related to glacial processes. Distinctive mineralogically immature, poorly-sorted aggregate sediment pellets, which have been considered as positive proof of glaciation, are not present.     

冀东三屯营地区片麻岩的早太古宙全岩年龄

冀东三屯营地区麻粒岩相片麻岩由三组中酸性岩石组成。三组片麻岩Pb-Pb全岩等时线年龄为。三组片麻岩也各给自出了早太古宙年龄。岩石的这一年龄,是麻粒岩相变质过程中U和Th亏损之后发生均匀化的结果,因而表明麻粒岩相的变质作用结束于3563Ma之前。岩石在3563～2500Ma期间处于角闪岩相的环境。文中还给出了全岩Rb-Sr同位素的年龄成果,为2500～2800Ma。     

Lithofacies succession of maar crater deposits in the Eifel area (Germany)

ABSTRACT Maar craters often contain exceptionally preserved fossils and maar sediments may reflect detailed environmental changes. Volcanosedimentary processes in a Middle Eocene maar crater lake are illustrated by the deposits of Eckfeld Maar in the Tertiary Hocheifel Volcanic Field (Rhenish Massif, Germany). The maar origin of the basin is evident from a circular negative gravity anomaly which indicates a low-density funnel-shaped basin filling. From the facies analysis of an Eocene (Eckfeld) and a Pleistocene (Döttingen) maar we develop a lithozone classification for the interpretation of maar sediments: syn-/post-eruptive breccias are followed by a fining-upwards sequence of lacustrine mud with coarse layers and final swamp deposits. From the facies analysis and regional geological data we reconstruct the pre- to post-eruptive history of a maar crater prior to post-Eocene uplift. These observations can be used for the interpretation of Tertiary and Quaternary maar craters that are ideal fossil and sediment traps.     

Metamorphic and deformational imprint of Cambrian–Lower Ordovician rifting in the Ossa-Morena Zone (Iberian Massif, Spain)

The high-temperature metamorphism recorded in the Valuengo and Monesterio areas constitutes a rare occurrence in the Ossa-Morena Zone of Southwest Iberia, where low-grade metamorphism dominates. The metamorphism of the Valuengo area has been previously considered either Cadomian or Variscan in age, whereas that of Monesterio has been interpreted as a Cadomian imprint. However, these areas share important metamorphic and structural features that point towards a common tectonometamorphic evolution. The metamorphism of the Valuengo and Monesterio areas affects Late Proterozoic and Early Cambrian rocks, and is syn-kinematic with a top-to-the-north mylonitic foliation, which was subsequently deformed by early Variscan folds and thrusts. The U–Pb zircon age (480±7 Ma) we have obtained for an undeformed granite of the Valuengo area is consistent with our geological observations constraining the age of the metamorphism. We propose that this high-temperature metamorphic imprint along a NW–SE ductile extensional shear zone is related to the crustal extension that occurred in the Ossa-Morena Zone during the Cambro-Ordovician rifting. In the same way, the tectonothermal effect of the preorogenic rifting stage may have been wrongly attributed to orogenic processes in other regions as well as in this one.     

生物标志化合物与相关的全球变化

在各种地质体中广泛分布的生物标志化合物在全球变化研究中有着广泛应用,特别是在海洋和湖泊沉积物中,研究工作已涉及到古植被、古温度、古降水量、古大气CO2浓度和古季风等的恢复.文章介绍利用气相色谱仪、气相色谱-质谱联用仪、气相色谱-热转换-同位素比质谱仪分析了一个长40cm泥炭岩芯(约222年)的生物标志化合物的分布及其单体氢同位素.结果显示,不管是生物标志化合物的分布,还是其单体稳定同位素特征都记载了气候(温度)的变化.正构脂肪酸的碳优势指数(CPI值)、正构烷烃C23/C31比值、正构烷烃C23的δD值与温度有很好的对应关系.     

Assessment of noise exposure and associated health risk in school environment

Noise exposure has become one of the most important factors in determining the quality of life in indoor environments. This paper assesses and analyzes noise exposure levels at school and preschool classrooms with different indoor environments. The sound level [A-weighting equivalent steady sound level L _Aeq (dBA)] was measured using a CEL-63× digital sound level meter. The noise level measurements were performed inside two preschools at three classrooms (an activity room, classroom KG1 and classroom KG2) and three schools at different classrooms, starting from grade 1 to grade 12. The logarithmic average noise levels (L _{Aeq avg}) and the 8-h average noise exposure level (L _{EX, 8-h}) were estimated for each classroom. Furthermore, health risk issues associated with the exposure to high noise levels were investigated using a questionnaire and an interview with more than 250 teachers at the preschools and the schools. Then, the results were analyzed using different statistical tools and were compared with the World Health Organization, Occupational Health and Safety and National Institute for Occupational Safety and Health standards. Also, the results were compared with those from different countries worldwide. The study results show that the 8-h average noise exposure level exceeded the allowable limits in some schools, which indicates that students and teachers can face a serious health effects from noise exposure. The comparisons show that the values of noise levels in Kuwait are higher than those in different countries. The maximum value of noise levels was found in secondary schools. The health problems found during the survey are potentially associated with issues related to hearing, voice, headache and the physiological function of teachers.     

Community‐Derived Standards for LA‐ICP‐MS U‐(Th‐)Pb Geochronology – Uncertainty Propagation,Age Interpretation and Data Reporting

The LA‐ICP‐MS U‐(Th‐)Pb geochronology international community has defined new standards for the determination of U‐(Th‐)Pb ages. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. Only data with uncertainties relating to random error should be used in weighted mean calculations of population ages; uncertainty components for systematic errors are propagated after this stage, preventing their erroneous reduction. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences. New reference values for commonly used zircon, monazite and titanite reference materials are defined (based on ID‐TIMS) after removing corrections for common lead and the effects of excess ²³⁰Th. These values more accurately reflect the material sampled during the determination of calibration factors by LA‐ICP‐MS analysis. Recommendations are made to graphically represent data only with uncertainty ellipses at 2s and to submit or cite validation data with sample data when submitting data for publication. New data‐reporting standards are defined to help improve the peer‐review process. With these improvements, LA‐ICP‐MS U‐(Th‐)Pb data can be considered more robust, accurate, better documented and quantified, directly contributing to their improved scientific interpretation.