华北克拉通乌拉山地区早前寒武纪岩浆作用和变质作用——锆石SHRIMP U-Pb定年及岩石地球化学研究

乌拉山地区位于大青山地区西侧,变泥砂质岩石大范围出露,并有一定数量变质岩浆侵入岩存在。本文对6个变质岩浆侵入岩进行了锆石SHRIMP U-Pb定年。片麻状闪长岩、片麻状英云闪长岩、片麻状花岗闪长岩和片麻状紫苏花岗岩等4个样品的锆石U-Pb数据点沿谐和线分散分布,n(~(207)Pb)/n(~(206)Pb)年龄从约2.5Ga到约1.8 Ga。变质辉长岩和眼球状石英二长岩锆石U-Pb数据点在谐和线上较集中分布,n(~(207)Pb)/n(~(206)Pb)年龄从约2.0Ga到约1.8 Ga。n(~(207)Pb)/n(~(206)Pb)年龄越小的锆石域通常显示越强烈的重结晶。结合已有研究和地球化学资料,可得出如下结论。(1)乌拉山地区存在新太古代晚期(约2.5 Ga)和古元古代中晚期(约2.0 Ga)岩浆侵入岩,后者形成于伸展构造环境。(2)乌拉山地区遭受新太古代晚期一古元古代早期和古元古代晚期两期构造热事件叠加改造。(3)乌拉山地区部分变泥砂质岩石形成于新太古代晚期,大青山地区原认为形成于古元古代早期的"大青山表壳岩"很可能也形成于新太古代晚期。(4)乌拉山地区和大青山具有类似或相同的早前寒武纪地质演化历史。     

双线偏振雷达资料在数值模式中的应用: 模拟器的构建

基于Rayleigh-Gans散射原理构造一个S波段双线偏振雷达模拟器。模拟器考虑了云冰、雪、雨和雹4种水凝物,以水凝物的混合比和数浓度以及水凝物粒子的轴比、相对介电常数、下落倾角为输入量,计算得到水平/垂直偏振反射率因子、差分反射率、比差分相位等偏振量。通过二维理想飑线模拟的试验结果表明,模拟器合理地再现了二维理想飑线系统成熟期的主要偏振特征:雹的反射率较高,差分反射率较低(又称Zdr洞);对流云区的Zdr柱;层云区的反射率和比差分相位的0℃层亮带特征;雨滴反射率与差分反射率因子的“雨线”统计特征。利用该模拟器建立了模式变量和偏振雷达观测的联系,有助于未来将偏振雷达观测资料应用于模式预报效果评估及对流尺度资料同化等方面的研究和应用。      

下扬子PTB界线深水相区粘土岩的火山成因研究及其对LPME的指示意义

全球,尤其是特提斯域二叠—三叠纪之交(PTB)剖面中普遍发育火山成因的粘土岩,对理解晚二叠世末生物大灭绝(LPME)的触发机制及相关基础地质问题具有重要意义。本文报道了在华南下扬子区新发现两条深水PTB剖面(皖南牛山和蔡村)的粘土岩工作,包括岩石学、矿物学和全岩地球化学等,填补了区域研究空白。研究结果发现,粘土岩主要由伊利石等粘土矿物,以及石英、岩浆锆石、长石等斑晶矿物组成。在地球化学上具有高K_2O、低Na_2O、相对富集大离子亲石元素(LILE)、相对亏损高场强元素(HFSE)等特征。据此,认为这些粘土岩为火山成因的钾质斑脱岩,其原岩可能为中酸性流纹英安岩,具有弧岩浆作用的源区背景。对比华南其他地区已发现的PTB界线粘土岩,发现它们成因类似,可能来源于古特提斯洋周缘陆陆碰撞,抑或是泛大洋俯冲潘吉亚大陆东缘(包括华南板块)所导致的长英质火山岩浆喷发,且具有多期多源性特点。PTB时期全球活跃的火山岩浆活动(包括镁铁质火山作用和华南地区火山灰所指征的长英质火山作用)可能是导致LPME的主要原因。     

城区内涝淹没模拟算法

针对城区内涝淹没范围和水深模拟问题,该文提出了一种基于约束Delaunay不规则三角网与三棱柱的城区内涝淹没模拟算法。该算法以沿地面三角形的顶点垂直向上引垂线形成的三棱柱为计算单元,通过"等体积"的方法,建立时间序列切片下的淹没水深和积水量的关系,据此实现淹没范围和水深模拟。以北京师范大学(简称"北师大")主校区为例,对单汇水区的水面高程上升模拟结果与实际观测值进行对比,基本吻合;并与传统栅格DEM的淹没效果进行了对比,表明该算法正确有效。     

黑龙江饶河枕状玄武岩地质、地球化学特征及其构造属性

为了确定饶河玄武岩的构造属性,在野外地质观察的基础上,对玄武岩进行岩石学研究和地球化学分析。玄武岩具有典型的枕状构造、淬冷边、中空骸晶和鬣刺结构等特征,反映其形成于海底喷发环境。化学分析样品具有高TiO_2、MgO和低Al_2O_3、CaO、P_2O_5、K_2O等特征,富集大离子亲石元素(Rb、Sr和Ba),微量元素蛛网图呈向上隆起形态,稀土元素配分曲线为右倾型(∑LREE/∑HREE为5.8~6.5),无δEu异常(0.92~0.97),表明样品具有洋岛玄武岩特征。主量和微量元素构造环境判别图指示了样品形成于洋岛或板内环境。样品与亚速尔型和夏威夷型洋岛玄武岩地球化学特征对比,表现出明显的夏威夷型洋岛玄武岩特征。岩石源区分析揭示出岩浆具有地幔热柱起源,并有先期交代地幔熔体的混入,岩浆源区还受壳幔循环的影响。研究表明,饶河枕状玄武岩为夏威夷型洋岛玄武岩,形成于洋壳消减阶段的洋中脊轴外板内喷发环境,为饶河地区存在成熟的洋盆提供直接证据。结合区域研究成果,认为饶河地区经历了古太平洋板块的扩张、洋中脊轴外板内地幔柱上涌、洋壳俯冲消减以及向佳木斯地块仰冲增生的构造演化过程。     

敦密断裂带白垩纪两期重要的变形事件

本文报道了敦密断裂带糜棱岩中黑云母~(40)Ar/~(39)Ar定年结果和大规模走滑-逆冲断裂的几何学、运动学特征及其形成时代,以便揭示断裂带两期变形事件的构造属性。黑龙江省密山市花岗质糜棱岩中黑云母~(40)Ar/~(39)Ar加权平均年龄为132.2±1.2Ma,它是敦密断裂带经历伸展事件的冷却年龄,也是东北亚大陆边缘在早白垩世Hauterivian期-Albian期发生强烈区域伸展作用的产物。密山市至辽宁省清原县系列大型走滑-逆冲断层和断层相关褶皱揭示出在晚白垩世晚期-末期发生右旋走滑-逆冲事件,该事件规模大,影响范围广,导致整个断裂带遭受到强烈改造,形成对冲式断裂系统。将研究区走滑-逆冲断裂与山东省郯庐断裂带中段挤压构造对比,认为郯庐断裂带北段和中段在晚白垩世末期都发生了强烈的走滑-逆冲事件,它们具有相同的构造特征和构造属性。     

Numerical Investigation of Submarine Hydrodynamics and Flow Field in Steady Turn

This paper presents numerical simulations of viscous flow past a submarine model in steady turn by solving the Reynolds-Averaged Navier?Stokes Equations (RANSE) for incompressible, steady flows. The rotating coordinate system was adopted to deal with the rotation problem. The Coriolis force and centrifugal force due to the computation in a body-fixed rotating frame of reference were treated explicitly and added to momentum equations as source terms. Furthermore, velocities of entrances were coded to give the correct magnitude and direction needed. Two turbulence closure models (TCMs), the RNG model with wall functions and curvature correction and the Shear Stress Transport (SST) model without the use of wall functions, but with curvature correction and low-Re correction were introduced, respectively. Take DARPA SUBOFF model as the test case, a series of drift angle varying between 0° and 16° at a Reynolds number of 6.53×106 undergoing rotating arm test simulations were conducted. The computed forces and moment as a function of drift angle during the steady turn are mostly in close agreement with available experimental data. Though the difference between the pressure coefficients around the hull form was observed, they always show the same trend. It was demonstrated that using sufficiently fine grids and advanced turbulence models will lead to accurate prediction of the flow field as well as the forces and moments on the hull.     

An integrative study of larval organogenesis of American shad <Emphasis Type="Italic">Alosa sapidissima</Emphasis> in histological aspects

We describe organogenesis at a histological level in American shad (Alosa sapidissima) larvae from 0 until 45 days after hatching (DAH). Larval development was divided into four stages based on the feeding mode, external morphological features, and structural changes in the organs: stage 1 (0–2 DAH), stage 2 (3–5 DAH), stage 3 (6–26 DAH) and stage 4 (27–45 DAH). At early stage 2 (3 DAH), American shad larvae developed the initial digestive and absorptive tissues, including the mouth and anal opening, buccopharyngeal cavity, oesophagus, incipient stomach, anterior and posterior intestine, differentiated hepatocytes, and exocrine pancreas. The digestive and absorptive capacity developed further in stages 2 to 3, at which time the pharyngeal teeth, taste buds, gut mucosa folds, differentiated stomach, and gastric glands could be observed. Four defined compartments were discernible in the heart at 4 DAH. From 3 to 13 DAH, the excretory systems started to develop, accompanied by urinary bladder opening, the appearance and development of primordial pronephros, and the proliferation and convolution of renal tubules. Primordial gills were detected at 2 DAH, the pseudobranch was visible at 6 DAH, and the filaments and lamellae proliferated rapidly during stage 3. The primordial swim bladder was first observed at 2 DAH and started to inflate at 9 DAH; from then on, it expanded constantly. The spleen was first observed at 8 DAH and the thymus was evident at 12 DAH. From stage 4 onwards, most organs essentially manifested an increase in size, number, and complexity of tissue structure.     

Charophytes from the Upper Cretaceous to probably Paleocene Jiaozhou Formation in the Jiaolai Basin (Eastern China)

正Objective The Cretaceous–Paleogene boundary(K–Pg boundary)marks the beginning of the Cenozoic,and is one of the most important geological boundaries.Charophytes are usually very abundant in the non-marine strata near the K–Pg boundary,and the change in the charophyte flora can help to recognize the K–Pg boundary.The position of K–