Pressure State in Deep Crust and Formation Depth of UHP Metamorphic Rocks

INTRODUCTIONSincethediscoveryofeclogiteswithcoesiteanddia mondinclusionsrelatedtothecontinent continentcollision orogenyenvironment,theultrahigh pressuremetamorphism(UHPM )intheDabie Suluhasarousedgreatinterestinmanygeologists (Liouetal .,1994 ;Xuetal.,1992 ) .Experimentalstudieshaveprovedthatsuchmineralsasdia mond ,coesiteandomphaciteoccurredat 2 - 5GPa (andatthecorrespondingtemperatures) (Stevenetal.,1982 ;MirwaldandMasonne ,1980 ) .However,itdoesnotmeanthatthemetamorphicrockscanbe…     

Time-Frequency Variations of Plio-Pleistocene Foraminiferal Isotopes： A Case Study from Southern South China Sea

The continuous wavelet transform (CWT) analysis reveals the instantaneous variability of the foraminiferal δ18O and δ13C of Site 1143 for the past 5 Ma at the eccentricity, obliquity and precession bands. The cross CWT analysis further demonstrates nonstationary phases of the benthic -δ18O relative to ETP at the three primary Milankovitch bands in the last 5 Ma. The instantaneous phases between benthic -δ18O and δ13C at the precession band display a prominent 128 ka period, probably the cyclicity of the nonstationary climate close to the eccentricity. To explain these nonstationary phases, it is desirable to introduce a nonlinear response model to the global climate system, in which the output has a prominent cycle around 100 ka to match the 128 ka cycle of the instantaneous phase of the δ13C and -δ18O on the precession band.     

Late Quaternary downcutting rates of the Qianyou River from U/Th speleothem dates, Qinling mountains, China

Dating deposits in caves formed by rivers may yield insight into rates and processes of bedrock incision. Three cave passages at different levels have developed in the walls of the Qianyou River valley in the Qinling mountains, south of the city of Xian, China. Twelve speleothem samples near the position of palaeowater tables in three cave passages are dated by the ²³⁰Th dating method. The results show that the river cut down at the rate of 0.23 ± 0.02 mm/yr from 358,000 ± 38,000 to 247,000 ± 28,000 yr ago, 0.19 ± 0.03 mm/yr from 247,000 ± 28,000 to 118,000 ± 19,000 yr ago, and 0.51 ± 0.08 mm/yr from 118,000 ± 19,000 yr ago until today. These fall very close to the glacial-interglacial transition following marine oxygen isotope stages 10, 8, and 6, respectively. The increase in downcutting rates during the interglacial period is consistent with warm, wet weather, increasing rates of erosion. This may lead us toward an underlying mechanism for modulating incision that is not in a direct response to the presence of headwater glaciers.     

Acidification and Trace Metals of Lakes in Taiwan

One hundred and eighty lakes, ponds and reservoirs in Taiwan, and the offshore islands have been investigated since 1985. Effects such as warming/cooling, mixing, photosynthesis and respiration on pH have been identified. These effects were found to be less profound than those resulting from the geology. Since there is little rain or lake water pH data available prior to 1970, it was necessary to use proxy data in order to ascertain the history of lake acidification. In this study, we present data based on diatoms in a sediment core collected from a lake in the remote subalpine region of southern Taiwan. The acidity of this lake water was found to have increased since 1900. We measured the concentrations of 55 chemical species in lake water samples. In addition, concentrations of 26 chemical species were obtained from sediments. Conductivity, alkalinity (HCO₃ ^?), most other major and minor chemical species, as well as the non sea-salt SO₄/Na ratio in lake water clearly decrease with elevation. Distribution of pH is similar, although the trend is less clear. Distribution of trace metals, however, shows a different trend as anthropogenic pollution, diagenetic reduction and lake acidification are at play.     

从等值线图形获取DAT和GRD格式的数据文件

在盆地模拟研究工作中，需要处理大量的地质数据和地质图件，一方面，随时需要把各种数据变为可视的图形；另一方面，还时常需要从图形中得到研究中所必需的数据，例如，由构造图得到研究区域的深度数据文件。本文介绍一种从等值线图形获取DAT格式和网格化GRD格式的数据文件的方法。     

金坛市开发区的数字影像测图

为完善数字化测图功能，通过全数字摄影测量系统(VirtuoZo)的数字影像测图模块(IGS)在金坛市开发区1：500测区中的应用，总结提高测图精度和速度的体会。     

基于J2EE的分布式WebGIS研究

在对比分析传统的WebGIS各种实现模式优缺点的基础上，探讨了利用企业级J2EE技术实现分布式WebGIS的解决方案，使WebGIS更好地满足企业级应用的需要。     

起伏地形下我国太阳直接辐射空间制图

建立了起伏地形下太阳直接辐射分布式计算模型 ;成功地解决了起伏地形中地形相互遮蔽对太阳直接辐射影响的难题 ;采用数据集群技术 ,探讨了不同数据集情况下太阳直接辐射计算模式的时空有效性 ;以 1km× 1km分辨率的DEM数据作为地形的综合反映 ,完成了我国 1km× 1km分辨率各月气候平均太阳直接辐射空间分布制图     

矢量地形图拓扑等问题的研究与实践

对矢量地图生产过程中常见的图形拓扑、数据冗余问题进行分析和研究；在此基础上结合生产实践，提出了相应的解决办法。研制了基于AutoCAD2000平台的相关程序。