南极乔治王岛阿德默勒尔蒂湾火山活动时空演化

在乔治王岛中部的阿德默勒尔蒂湾 ,凯勒半岛、于尔曼山嘴和埃内坎角是第三纪火山岩集中分布区。野外地质调查和同位素年代学研究表明 ,凯勒半岛发生了三期火山喷发 (三个火山喷发旋回 ) ,同时伴随着火山活动中心的不断北移 ;在第二期火山喷发之后 ,火口塌陷 ,形成破火山 ,之后在半岛北部又发生火山喷发 ,并向东迁移到于尔曼山嘴。因此凯勒半岛是一复活破火山 ,火山活动具有随时间迁移的特性。埃内坎角火山活动虽与上述两地区大致同时 ,但化学成分上不存在明显演化关系 ,应属另一相对独立的火山活动中心     

Simulation of Stress Distribution around Tunnels and Interaction between Tunnels Using an Elasto–plastic Model

This article presents a computer simulation of stress distribution around tunnels and interaction between tunnels using an elasto-plastic model. A finite element method using ANSYS software has been used for the analyses of one and two tunnels at different overburden depths with different separating distances between the tunnels. The results of numerical analyses indicate that stress distribution and stress concentration around the tunnels vary with the overburden depths. It is found that the coefficients of stress concentration for elasto-plastic medium are smaller than those for elastic one by 1.9%. Furthermore, the interaction between the two tunnels rapidly decreases with the increase of separation distance between them. In addition, for quantitatively describing the interaction between the two tunnels, a critical separation distance is introduced. The critical separation distances between the two tunnels at different overburden depths are 8 m, 12 m, and 14 m respectively. This fact is very important and essential for the design of mining tunnels and to ensure safety in tunnel engineering.     

Thermodynamic properties of wadsleyite with anharmonic effect

The thermodynamic properties of crystals can be routinely calculated by density functional theory calculations combining with quasi-harmonic approximation.Based on the method developed recently by Wu and Wentzcovitch(Phys Rev B 79:104304, 2009) and Wu(Phys Rev B 81:172301, 2010), we are able to further ab initio include anharmonic effect on thermodynamic properties of crystals by one additional canonical ensemble with numbers of particle, volume and temperature fixed(NVT) molecular dynamic simulations. Our study indicates that phonon–phonon interaction causes the renormalized phonon frequencies of wadsleyite decrease with temperature. This is consistent with the Raman experimental observation. The anharmonic free energy of wadsleyite is negative and its heat capacity at constant pressure can exceed the Dulong–Petit limit at high temperature. The anharmonicity still significantly affects thermodynamic properties of wadsleyite at pressure and temperature conditions correspond to the transition zone.     

A Review on the Global Stratotype Section and Point of the Permian-Triassic Boundary

1 Introduction The Global Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary (PTB) has been ratified by IUGS in 2001 (Yin et al., 2001). It is defined at the base of the Hindeodus parvus horizon, i.e. the base of Bed 27c of Meishan Section D, Changxing County, Zhejiang Province, South China. The PTB is important because it is not only an erathem boundary but also a great turning point of geological history symbolized by profound global changes and the strongest …     

Neoproterozoic Molar-tooth Structure and Constraint of Depositional Facies and Environment in the North China Platform in Jiangsu, Anhui and Liaoning, Eastern China

Molar tooth structure （MTS） represented by complex ptygmatical shapes is widely distributed in the Proterozoic of the world. MTS filled by fine, equant sparry calcite （or dolomite） displays an abrupt contact with hosting rocks, which are mainly composed of carbonaceous micrites and fine-grained carbonates with local silts and stormdominated deposits with graded, cross or wave beddings, numerous erosional surfaces and truncated and fills or guttered bases. Occurrence of MTS suggests a result of the constraint of sedimentary facies, and the storm-base in ramp settings is the maximum depth for the formation of MTS. Vertical succession of MTS-bearing carbonates shows a deposition stacked by high-frequency shallow subtidal and peritidal cycles. An individual cyclic MTS-bearing sequence is characterized by thinning, shallowing and dynamic decreasing-upward, and peritidal caps of purple red iron and organic carbonaceous sediments with more complicated shapes of MTS are common on the top of individual MTS-bearing sequences.     

Extreme Enrichment of Tellurium in Deep-Sea Sediments

Tellurium is a sort of scattered rare element on the earth. Its concentration is very low in earth＇s crust, only 1.0 ng/g. However, it has extremely high abundance in Co-rich crusts, marine polymetallic nodules, deep-sea sediments and aerolites. To find out the origin of tellurium enrichment in deep-sea sediments, we analyzed and compared tellurium concentrations and helium isotope compositions in the magnetic parts and those in the bulk parts of deep-sea sediments. The result indicates that the helium content, 3He/4He ratio and tellurium concentration are obviously higher in the magnetic parts than those in the bulk parts. The 3He abundance varies synchronously with the tellurium concentration. 3He and Te have a distinct positive correlation with each other. It is the first time that the paper brings forward that the extreme enrichment of tellurium in deep-sea sediments, like helium isotope anomalies, probably results from the input of interplanetary dust particles （IDPs）. Similarly, the extreme enrichment of tellurium in marine polymetallic nodules and Co-rich crusts is possibly related to IDPs.     

Organic Geochemistry of the Early Jurassic Oil Shale from the Shuanghu Area in Northern Tibet and the Early Toarcian Oceanic Anoxic Event

This paper presents new geological and geochemical data from the Shuanghu area in northern Tibet, which recorded the Early Toarcian Oceanic Anoxic Event. The stratigraphic succession in the Shuanghu area consists mostly of grey to dark-colored alternating oil shales, marls and mudstones. Ammonite beds are found at the top of the Shuanghu oil shale section, which are principally of early Toarcian age, roughly within the Harplocearasfalciferrum Zone. Therefore,the oil shale strata at Shuanghu can be correlated with early Toarcian black shales distributing extensively in the European epicontinental seas that contain the records of an Oceanic Anoxic Event. Sedimentary organic matter of laminated shale anomalously rich in organic carbon across the Shuanghu area is characterized by high organic carbon contents, ranging from 1.8% to 26.1%. The carbon isotope curve displays the δ^13C values of the kerogen (δ^13Ckerogen) fluctuating from -26.22 to -23.53‰ PDB with a positive excursion close to 2.17‰, which, albeit significantly smaller, may also have been associated with other Early Toarcian Oceanic Anoxic Events (OAEs) in Europe. The organic atomic C/N ratios range between 6 and 43, and the curve of C/N ratios is consistent with that of the δ^13Ckerogen values. The biological assemblage,characterized by scarcity of benthic organisms and bloom of calcareous nannofossils (coccoliths), reveals high biological productivity in the surface water and an unfavorable environment for the benthic fauna in the bottom water during the Oceanic Anoxic Event. On the basis of organic geochemistry and characteristics of the biological assemblage, this study suggests that the carbon-isotope excursion is caused by the changes of sea level and productivity, and that the black shale deposition, especially oil shales, is related to the bloom and high productivity of coccoliths.     

Evidences for Incipient Hydrothermal Event(s) in the Central Indian Basin: A Review

1 IntroductionMetalliferous sediments and mounds occur in all majortectonic settings in the oceans (e.g., the Galapagos Rift,East Pacific Rise (EPR), Bauer Deep and Central Basin ofthe Pacific; Heath and Dymond, 1977). Further, massivesulphide deposits and high-temperature vents have beenreported along the mid-ocean ridges (MOR). In the IndianOcean, an inactive hydrothermal field and a hydrothermalplume site have been discovered along the Central IndianRidge (CIR). The SONNE Hydro…     

基于多尺度边缘约束的重力场信号的向下延拓

利用多尺度边缘检测理论,研究改善重力场信号向下延拓稳定性的新方法,简要介绍了小波多尺度边缘检测的基本原理,以EGM96重力场模型为例分析了地球重力场的多尺边缘。提出了基于多尺度边缘约束的向下延拓方法,并给出了模拟算例。计算结果表明,利用多尺度边缘约束改善向下延拓的稳定性是可行的,在观测值信噪比较差的情况下该方法的效果尤为明显。     

基于树形结构的地震数据库系统设计方法

地震观测数据的大量增长给数据管理提出了新的要求. 本文将树形结构引入到数据库设计中, 提出了基于树形结构设计关系数据库的方法. 该方法简单、 直观、 易于数据的组织, 可以简化数据库的设计过程. 在ldquo;长江三峡工程诱发地震监测系统地震监测总站数据库rdquo;设计中应用了该方法, 并取得了良好的效果.