西秦岭天水市元龙地区新元古代花岗质片麻岩锆石LA-ICP-MSU-Pb定年及其地质意义

西秦岭元龙花岗质片麻岩位于天水市伯阳—元龙之间的渭河断裂北侧。花岗质片麻岩中锆石Th/U比值较高,阴极发光图像显示锆石内部发育振荡环带,具岩浆成因特点。LA-ICP-MS的锆石U-Pb同位素206Pb/238U加权平均年龄为(924.2±2.7)Ma(MSWD=0.67),表明花岗岩岩体形成于新元古代,反映晋宁期西秦岭北缘曾存在一次俯冲碰撞事件,与Rodinia超大陆的汇聚事件一致。     

基于MO和ArcSDE的城镇地籍建库工具箱开发与应用

城镇地籍数据建库是一项系统性、工程性和技术性相结合的工作。为了高效地、高质 量地、高水平地完成测绘数据的交换处理、权属数据的录入和图属一致控制,开发并 应用一套城镇地籍建库工具集具有极其重要的意义。本文基于MO和ArcSDE设计并 开发了企业级的建库工具箱,集中了各个环节的工具,为北京市城镇地籍建库提供了 有力支持。     

A New Genus of Fossil Cycads Yixianophyllum gen. nov. from the Late Jurassic Yixian Formation, Western Liaoning, China

A new genus of fossil Cycads, Yixianophyllum gen. nov., is reported here. The specimens were collected from the southern hill of Jinjiagou village, Toudaohezi Town, Yixian County, western Liaoning Province, China. The fossil plant-beating bed belongs to the lower part, the Zhuanchengzi bed, of the Upper Jurassic Yixian Formation （Yixianian）. The new genus in leaf shape, venation and epidermal structure shows a transitional form between Mesozoic Cycads （Ctenis, Nilssonia） and modem Cycads （Stangeria and Encephalartos）. Since the features of these specimens differ from any known genera of Cycads, a new generic name Yixianophyllum is proposed for these leaves. Typical species, Yixianophyllum jinjiagouense gen. et sp. nov. is described here. A supposed evolutionary tendency of Cycadean leaf-forms with Taeniopteris-type is discussed.     

Geophysical monitoring and evaluation of coastal plain aquifers

We use time domain electromagnetic (TDEM) soundings to monitor ground water conditions beneath the coastal plain in eastern North Carolina. The TDEM method measures the earth's response to an induced electromagnetic field. The resulting signal is converted, through a complex inversion process, to apparent resistivity values, which can be directly correlated to borehole resistivity logs. TDEM soundings are used to map the interface between fresh and salt water within coastal aquifers, and estimate depth to basement when siting new monitoring wells. Focused TDEM surveys have identified areas of salt water encroachment caused by high volumes of discharge from local supply wells. Electromagnetic sounding, when used in tandem with the state's network of monitoring wells, is an accurate and inexpensive tool for evaluating fresh water/salt water relationships on both local and regional scales within coastal plain aquifers.     

冀北隆化早前寒武纪高级变质区内的晚古生代片麻状花岗闪长岩--锆石SHRIMP U-Pb年龄及其构造意义

本文报道了冀北隆化早前寒武纪高级变质区中片麻状花岗闪长岩的SHRIMP U-Ph锆石年龄为311±2Ma(95％置信度)。锆石为典型的岩浆结晶锆石,少量继承锆石年龄平均为 1809±21 Ma(95％置信度),与华北克拉通的形成年龄接近,可能与本区早元古代末华北克拉通的最后拼合有关。冀北隆化早前寒武纪高级变质区中晚古生代片麻状花岗闪长岩的确定说明:内蒙古隆起(即“内蒙地轴”)实际为晚古生代-早中生代期间构造变形及剥露的结果。这一发现对于认识燕山构造带的早期演化历史有重要意义。     

浅谈盆地热历史及烃源岩热演化研究在中国油气资源战略选区调查评价中的意义

目前国家开展了全国油气资源战略选区调查与评价专项10个项目,包括陆上新区,海域,老油气区的新领域、新层系、新类型,长期久攻不克的地区、盆地和地表、地形条件复杂的地区。这些地区总体来讲油气工作程度较低。在油气调查评价中,特别是初期,烃源岩的评价是第一位的,而烃源岩热演化研究是烃源岩评价的重要内容之一。同时盆地内烃源岩热演化史的差异对盆地内的油气分布具有重要影响;热历史又从另一个侧面反映了盆地的成因及发展过程,对于指导油气勘探具有重要意义。     

用边长变化结果计算地应变及块体划分

在均匀应变的假设下，给出了由边长变化求解地应变的新方法，通过统计检验相邻三角形的最大主应变，可判别相邻测点是否位于同一个均匀应变体上，采用弹性位错理论设计的模拟算例表明，该方法能成功地将位于断层两侧的测量点分辨开。     

Failure to Precipitate Dolomite at 25 °C fromDilute Solution Despite 1000-Fold Oversaturation after32 Years

Dolomite failed to precipitate despite more than1000-fold oversaturation (IAP approximately10-13.8) from dilute solution (ionic strength =0.025) at 25 °C after 32 years.     

Cubic anomalies in the Wilkinson Microwave Anisotropy Probe

We perform a frequentist analysis of the bispectrum of the Wilkinson Microwave Anisotropy Probe first-year data. We find clear signal domination up to  ℓ≈ 200  , with overall consistency with Gaussianity, except for the following features. There is a flat patch (i.e. a low χ² region) in the same-ℓ components of the bispectrum spanning the range  ℓ= 32–62  ; this may be interpreted as ruling out Gaussianity at the 99.6 per cent confidence level. There is also an asymmetry between the north and south inter-ℓ bispectrum components at the 99 per cent confidence level. The preferred asymmetry axis correlates well with the  (ℓ, b ) = (57, 10)  direction quoted in the literature for asymmetries in the power spectrum and three-point correlation function. However, our analysis of the quadrupole (its bispectrum and principal axes) fails to make contact with previously claimed anomalies.