New data on the Albian-Cenomanian radiolarians from the Karai Formation (South India)

Radiolarians from the lower part of the Karai Formation (upper Albian-middle Cenomanian) are studied in detail for the first time. Among over 50 radiolarian species identified in the formation, there are Acaeniotyle amplissima (Foreman), Savaryella novalensis (Squinabol), S. quadra (Foreman), Vitorfus campbelli Pessagno, Archaeodictyomitra montisserei (Squinabol), Holocryptocanium barbui Dumitrica, Pseudoeucyrtis sp. cf. Ps. spinosa (Squinabol), Stichomitra communis Squinabol, Tubilustrionella transmontanum (O’Dogherty), and others. The discovered radiolarians are divided into the Halesium triacanthum-Orbiculiforma nevadaenis (late Albian-early Cenomanian), Crucella latum-Cryptamphorella micropora (late Albian?-early Cenomanian), and Becus sp. B-Godia concava (terminal Albian-middle Cenomanian) assemblages. In general, the Albian-Cenomanian radiolarians of South India are comparatively less diverse than the concurrent assemblages of the Mediterranean region and California. In taxonomic composition and morphological peculiarities, they are comparable with the Aptian-Albian radiolarians of Western Australia (Ellis, 1993). Consequently it can be postulated that sea basins of South India were situated during the Albian-Cenomanian in the temperate latitudes of the Southern Hemisphere.     

基于短波红外技术的西藏多龙矿集区铁格隆南矿床荣那矿段及其外围蚀变填图-勘查模型构建

采用短波红外技术测量西藏多龙矿集区铁格隆南矿区地表岩石样本,发现蚀变矿物主要有绢云母和绿泥石,并在地表形成了一套从绢英岩化带-青磐岩化带的具有斑岩特点的蚀变矿物组合特征。通过测量地下ZK0804,ZK1604,ZK2404,ZK3204四个钻孔岩心的短波红外特征,发现钻孔岩心中存在大量明矾石、高岭石、地开石和绢云母,在东西向展布的过程中,绢云母数量及厚度明显增大,有继续向下延伸的趋势,说明矿体向深部逐渐从富含明矾石、地开石、高岭石的高硫、低温类型的矿物组合向绢英岩化带转变,并构成了规律的蚀变分带系统。根据地表、地下岩（矿）石的短波红外光谱特征及蚀变矿物分布趋势,构建了基于短波红外勘查技术的多龙矿集区斑岩-高硫浅成低温热液型铜（金）矿床找矿勘查模型,总结了从钾化带-绢英岩化带-泥化带-高级泥化带（明矾石-地开石-高岭石组合）-青磐岩化带的一套完整蚀变矿物组合及光谱特征。     

流土和管涌破坏机理研究

首先针对渗流破坏的机理进行研究,区别在堤防工程中常用的流土和管涌的概念,从现有的大量土的渗流破坏的实验资料,结合理论分析,从微观的角度去阐述渗流破坏的形成机理,提出了在级配连续性土和级配不连续性土中进行管涌型土和流土型土判别的标准.然后从定量的角度去推导出各种渗流破坏类型的判别公式以及临界抗渗坡降计算公式.     

Melanterite and szomolnokite as weathering products of pyrite from the Bazhenovo Formation

Weathering of pyrite in the core recovered from black shales of the Bazhenovo Formation (Upper Jurassic-Lower Cretaceous) in the West Siberian marine basin promoted the successive formation of melanterite (FeSO₄ · 7H₂O) and szomolnokite (FeSO₄ · H₂O). Szomolnokite was detected in West Siberia for the first time.     

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.     

Fault-line uplifts in the Northeastern Pacific

The nearly latitudinal giant fracture zones in the northeastern Pacific Ocean are accompanied by narrow fault-line uplifts making up tectonic couples that strike for thousands of kilometers. They are especially distinctly expressed in the gravity map of the World Ocean [7]. As is shown in the paper, a compensation mechanism of deep mass displacement operates in the uplift-deepwater trench system. The uplifts have similar asymmetric structures, which reflects the long-term unidirectional effect of the deep geodynamic stress. In my opinion, the system of the fault-line uplifts began to form at the Cretaceous-Cenozoic boundary.     

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).