Characteristics of pegmatoidal granite exposed near Bayalan,Ajmer district,Rajasthan

The study involves the characterization of pegmatoidal granite, southeast of Beawar, Ajmer district, Rajasthan. Earlier researchers had described this granite as part of the BGC, basement to the Bhim Group of the Delhi Super Group rocks. However, the present study indicates that it is younger than the rocks of Bhim Group of South Delhi Fold Belt, into which it is intrusive. The intrusion is structurally controlled and the outcrop pattern is phacolithic. The granite had intruded post-D₂ deformation of the Delhi orogeny along the axial planes of D₂ folds. The intrusion has also resulted in the formation of a contact aureole about the calc gneisses.     

Geophysical investigation using resistivity and GPR methods: a case study of a lubricant oil waste disposal area in the city of Ribeirão Preto,São Paulo,Brazil

Geophysics has been shown to be effective in identifying areas contaminated by waste disposal, contributing to the greater efficiency of soundings programs and the installation of monitoring wells. In the study area, four trenches were constructed with a total volume of about 25,000 m³. They were almost totally filled with re-refined lubricating oil waste for approximately 25 years. No protection liners were used in the bottoms and laterals of the disposal trenches. The purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar (GPR) methods in characterizing the contamination of this lubricant oil waste disposal area in Ribeirão Preto, SP, situated on the geological domain of the basalt spills of the Serra Geral Formation and the sandstones of the Botucatu Formation. Geophysical results were shown in 2D profiles. The geophysical methods used enabled the identification of geophysical anomalies, which characterized the contamination produced by the trenches filled with lubricant oil waste. Conductive anomalies (smaller than 185 Ωm) immediately below the trenches suggest the action of bacteria in the hydrocarbons, as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature. It was also possible to define the geometry of the trenches, as evidenced by the GPR method. Direct sampling (chemical analysis of the soil and the water in the monitoring well) confirmed the contamination. In the soil analysis, low concentrations of several polycyclic aromatic hydrocarbons (PAHs) were found, mainly naphthalene and phenanthrene. In the water samples, an analysis verified contamination of the groundwater by lead (Pb). The geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area, and could be applied in the study of similar areas.     

Decompression and H<Subscript>2</Subscript>O exsolution driven crystallization and fractionation: development of a new model for low-pressure fractional crystallization in calc-alkaline magmatic systems

Magma ascent, decompression-induced H₂O exsolution and crystallization is now recognized as an important process in hydrous subduction zone magmas. During the course of such a process calculations suggest that the ascent rate of a degassing and crystallizing mafic magma will be greater than crystal settling velocities. Thus, any crystals formed as a consequence of volatile exsolution will remain suspended in the magma. If the magma erupts before the percentage of suspended crystals reaches the critical crystallinity value for mafic magma (~55 vol.%) it will produce the commonly observed crystal rich island arc basalt lava. If the magma reaches its critical crystallinity before it erupts then it will stall within the crust. Extension of compaction experiments on a 55 vol.% sand-Karo syrup suspension at different temperatures (and liquid viscosities) to the likely viscosities of interstitial andesitic to dacitic liquid within such a stalled magma suggest that small amounts (up to ~10%) can be expelled on a time scale of 1–10 years. The expelled liquid can create a new intermediate to silicic body of magma that is related to the original mafic magma via fractional crystallization. The short time scale for liquid expulsion indicate that decompression-induced H₂O exsolution and crystallization can be an important mechanism for fractional crystallization. Based on this assumption a general model of decompression-induced crystallization and fractionation is proposed that explains many of the compositional, mineralogical and textural features of Aleutian (and other andesites).     

Eutrophication,health risk assessment and spatial analysis of water quality in Gucheng Lake,China

The water characteristics of the Gucheng Lake, such as eutrophication, health and spatial distribution, were investigated. On the basis of the trophic state index (TSI) and entropy weight, a synthesized trophic state index (STSI) model was established to assess lake eutrophication condition through calculating STSI, choosing TP, TN, COD, BOD and NH₃-N as trophic variables. The STSI ranged from 50.58 to 62.44, which showed that the water has been between eutrophic and supereutrophic. A histogram was applied to health risk assessment which was analyzed from carcinogenic substances (Cr⁺⁶, As and Cd) and non-carcinogenic substances (hydroxybenzene, Pb, Hg, CN⁻ and NH₃), and the results showed that the former was much greater than the latter for effect. The total risk for each resident caused by all pollutants ranged from 5.18E-05 to 8.34E-05, which is far higher than the standard, recommended by Sweden Bureau of Environment Protection and Holland Ministry of Building and Environment Protection (1.0E-05). Cluster analysis was used to detect similarities and dissimilarities among the seven sampling sites and explain the observed clustering in terms of affected conditions. Twenty-one variables were used to divide seven sampling sites into three groups, namely, north lake, south lake and lake center.     

Microstructure characteristics and forming environment of late Quaternary Period loess in the Loess Plateau of China

Since the late Quaternary Period, the rapid rising of the northeastern Qinghai-Tibetan Plateau has greatly changed the East Asian climate and formed different regional monsoon climates. Various microstructures of the loess in northern China have formed under a variety of climatic conditions. The scanning electron microscope (SEM) and energy spectrum analysis are used in this paper to study the relationship between the indexes of loess microstructures and the forming climates, and the indexes include the diameter of sand grains, Ca/Fe value and the characteristic shapes of the loess from SEM microstructures pictures. In terms of their respective climatic circumstances, the major microstructures of regional loess may be classified into nine categories according to their forms and particle sizes, such as loess formed in near-sand source, loess of granule sand dropping, and loess formed in hot and rainy places, i.e. with the loess SEM pictures, climates of about 15 ka b.p. in different places may be evaluated. In conclusion, the clear and distinguishable loess microstructures and their indexes in the Loess Plateau of China can also deduce the evolution of climate, such as warm or cold and wet or dry, and even sandstorm activities when the loess is deposited.     

不同模式模拟的降水稳定同位素效应的比较和评估

利用引入水稳定同位素循环的ECHAM4、GISS E、HadCM3、MUGCM以及iAWBM的模拟数据,分析了全球降水中稳定同位素效应的空间分布特征,对不同模式的模拟结果之间以及模拟结果与GNIP（Global Network of Isotopes in Precipitation）的实际监测结果之间进行了比较,旨在对稳定同位素大气环流模式的模拟有效性进行评价,改善对水循环中水稳定同位素效应的理解和认识。结果显示,5个模式均很好地再现了全球降水中平均δ18O和平均δ18O季节差的空间分布特征,降水中稳定同位素的温度效应、降水量效应的分布特点以及全球大气水线GMWL（Global Meteoric Water Line）均被很好地模拟出。比较而言,ECHAM4模拟的降水中的平均δ18O以及δ18O平均季节差的空间分布与GNIP的实际分布最接近,拟合水平也最高;ECHAM4、GISS E、MUGCM和iAWBM再现全球温度效应空间分布的能力较强,拟合水平大致相当;由iAWBM模拟的降水量效应空间分布与实际分布之间的相关性最强,5个模式模拟的与实测的δ18O/P相关系数符号相同的站点数大致位于同一水平;GISS E和iAWBM模拟的全球大气水线与实测的GMWL最接近。     

Efficient Modeling of Gravity Fields Caused by Sources with Arbitrary Geometry and Arbitrary Density Distribution

We present a brief review of gravity forward algorithms in Cartesian coordinate system, including both space-domain and Fourier-domain approaches, after which we introduce a truly general and efficient algorithm, namely the convolution-type Gauss fast Fourier transform (Conv-Gauss-FFT) algorithm, for 2D and 3D modeling of gravity potential and its derivatives due to sources with arbitrary geometry and arbitrary density distribution which are defined either by discrete or by continuous functions. The Conv-Gauss-FFT algorithm is based on the combined use of a hybrid rectangle-Gaussian grid and the fast Fourier transform (FFT) algorithm. Since the gravity forward problem in Cartesian coordinate system can be expressed as continuous convolution-type integrals, we first approximate the continuous convolution by a weighted sum of a series of shifted discrete convolutions, and then each shifted discrete convolution, which is essentially a Toeplitz system, is calculated efficiently and accurately by combining circulant embedding with the FFT algorithm. Synthetic and real model tests show that the Conv-Gauss-FFT algorithm can obtain high-precision forward results very efficiently for almost any practical model, and it works especially well for complex 3D models when gravity fields on large 3D regular grids are needed.     

Geomorphological site classification for the Fujian province

Geomorphological classification of the Fujian province was done based on remote-sensing imaging, digital elevation maps, and slope gradient data acquired by ArcGIS 9.2. The engineering geological units in the Fujian province were divided into five types by the geomorphologic shape and genesis. The relationship among geomorphological type, engineering geological unit, and site category was determined using engineering geological data and site category data. Then, after making a preliminary site classification adjusted by drill hole data, the site was classified into four types: I₀, I₁, II, and III according to site classification standards of equivalent shear-wave velocity and overburden thickness. The results showed that the site categories in the Fujian province mainly consist of type II, which accounts for 85.26 % of the land area. The percentage of I₀ was the smallest, which accounts for only 2.44 % of the total area.