北京西山晚中生代火山岩U-Pb锆石年代学及地球化学研究   总被引：15，自引：0，他引：15  

袁洪林  柳小明  刘勇胜  高山  凌文黎 《中国科学D辑》2005,35(9):821-836

对北京西山髫髻山组和东岭台组火山岩锆石U-Pb SHRIMP和LA-ICP-MS定年及地球化学的研究结果表明, 髫髻山组上部火山岩时代为137.1±4.5 Ma(2σ), 东岭台组中部火山岩时代为130~134 Ma. 前者略老于后者, 但两者时代相差<5 Ma, 证明两组火山岩的喷发是在很短的时间内完成的. 北京西山地区髫髻山组火山岩的年龄与承德盆地髫髻山组火山岩的年龄明显不同, 表明髫髻山组火山岩年龄可能存在明显区域变化. 北京西山髫髻山组中存在典型的埃达克岩(SiO₂含量约为56%, Na₂O = 3.99~6.17, Na₂O/K₂O = 2.2~3.1, Sr = (680~1074)×10^-6, Y = (13.2~16.3)×10^-6, Yb = (1.13~1.52)×10^-6, Sr/Y = 43~66 ), 高镁埃达克岩和高镁安山岩(Mg# = 54~55). 髫髻山组埃达克岩及与其共生的其它中酸性火山岩均具有典型的Nb-Ta负异常和Pb正异常等大陆地壳特征, 表明它们是陆壳岩石部分熔融的产物. 上述结果表明, 北京西山地区髫髻山组埃达克岩代表了中生代曾存在于华北克拉通的加厚榴辉岩下地壳与岩石圈地幔一同拆沉至软流圈中, 榴辉岩随后发生部分熔融, 熔体上升过程中与地幔橄榄岩发生相互作用的产物. 髫髻山组火山岩的年龄制约了拆沉作用至少延续至137 Ma. 东岭台组火山岩为Mg#正常的流纹岩和英安岩, 表明它们没有与地幔发生反应, 它们可能代表了拆沉作用导致的软流圈地幔物质上涌造成的深部地壳物质重熔的产物.  相似文献   

用希腊历史地震目录对VAN方法做统计评估     

Acev.  RL 钱家栋 《世界地震译丛》1997,(2):73-77

采用一种新的统计检验方法对ＶＡＮ方法在１９８７￣１９８９年间预报成功率和随机采样地震目录获得的成功率之间进行了对比（成功率是把成功预报的次数与所发出的预报总次数的比值）。与以往的检验不同，这次检验所采样的分布是从１９６０￣１９８５年间的历史地震空间和震级的分布所得出的。ＶＡＮ方法预报成功率以延时２２天为计达６７．９％，而在ＮＥＩＣ人武部目录上随机极样中仅为３７．２％，可达到上述指标（６７．９％），  相似文献   

高精度波前追踪旅行时计算     

Coul.  RL 李占顺 《国外石油地质》1995,(2):55-64

常规初至计算的射线追踪算法的不足之处是：（１）不能保证在多条路径中找到旅行时最小的路径。（２）存在盲区，而且难以找出含有折射或绕射能量的最短旅行时路径。而波前追踪算法可避免这些问题，它的基础是在顶点和沿着边缘带有节点的变速三角网格组成的地层模型其节点位于初至波前（传播方向和到达时间）轨迹聚集的地方。此算法是波前（节点处采样）通过整个模型从震源向外传播，它们是局部传播的绕射波、直达波或沿固有最小时间  相似文献   

辽东清原地区太古代岩石Rb—Sr年代   总被引：3，自引：0，他引：3  

孙荣圭 Arms.  RL 《地球化学》1989,(1):84-91

清原地区太古界岩石和矿物的Rb-Sr研究给出五个等时线年龄:2924±325Ma(城子疃组麻粒岩),2625±376Ma(通什村组麻粒相岩石),2359±81Ma(线金厂紫苏花岗岩),2366±48Ma(斗虎屯附近混合岩中的包体角闪岩),1639±49Ma(城子疃组麻粒岩的分离矿物)。根据等时线和模式年龄推断:城子疃组和通什村组的火成原岩年龄分别为2900—2800Ma和2600Ma;紫苏花岗岩侵位和麻粒岩相变质作用几乎同时发生于2600Ma前;2360Ma前发生广泛的混合岩化;1640Ma前有后期变质作用叠加。  相似文献   

Characterizing aquatic sediment-oil aggregates using in situ instruments     

Sterling MC  Bonner JS  Ernest AN  Page CA  Autenrieth RL 《Marine pollution bulletin》2004,48(5-6):533-542

The effects of emulsified crude oil and salinity (15, 30 per thousand ) on the steady state aggregate volume distributions and fractal dimensions were determined for a range of mean velocity gradients, (G(m) =5-50 s(-1)). Aggregation was performed in a 40-L cylindrical tank with a 4-blade paddle mixer. Three-dimensional fractal dimensions (D3) and volume distributions were determined using a procedure integrating data from an electrozone and an in situ light scattering instrument. Two-dimensional fractal dimensions (D2) and derived volume distributions were determined using a recently developed submersible flow cytometer equipped with a digital camera and image analysis software. For latex beads or emulsified crude oil systems, the above listed instruments yielded consistent size distributions and fractal dimensions (D2=1.92 +/- 0.16, D3=2.94 +/- 0.12). Mean volume aggregate diameters determined using the FlowCAM were consistently larger that those determined using the LISST-100 or Coulter Multisizer due to aggregate orientations during measurements. With increasing G(m) values, all colloidal aggregates showed increasing D3 values due to reduced aggregate length. Because of the compactness of all the aggregates (D3 >2), D2 values remained constant at 2. Neither salinity nor sediment type significantly affected D2 values calculated for sediment-crude oil aggregates. However, clay-oil aggregates showed higher D3 values than clay aggregates. This suggests that colloidal oil and mixing shear are the more dominant factors influencing aggregate morphology in nearshore waters. Overall, the data suggests that the analysis methods provide consistent size distribution results. However, because of the shear and salinity of coastal waters, resulting aggregates are too compact to estimate their D3 values using image analysis alone.  相似文献   

Science, policy and the management of sewage materials. The New York City experience     

Swanson RL  Bortman ML  O'Connor TP  Stanford HM 《Marine pollution bulletin》2004,49(9-10):679-687

Development of national policy on sewage sludge management is a classic example of incremental policy formulation [Fiorino, D.J. 1995. Making Environmental Policy. University of California Press. Berkeley, CA. p. 269]. Consequently, policy has developed piecemeal, and results are, in some ways, different than intended. Land application of sewage sludge has not been a panacea. Many of the same types of policy are now being raised about it. We demonstrate this by examining the management of sewage materials by New York City from near the turn of the 20th century, when ocean dumping was viewed as a means to alleviate some of the gross pollution in New York Harbor, to when ocean dumping was banned, and thence to the present when sludge is applied to land as "biosolids." Lessons learned during this long, sometimes contentious history can be applied to present situations--specifically not understanding the long-term consequences of land-based reuse and disposal technologies.  相似文献   

Reflectance spectroscopy of ferric sulfate-bearing montmorillonites as Mars soil analog materials     

Bishop JL  Pieters CM  Burns RG  Edwards JO  Mancinelli RL  Fröschl H 《Icarus》1995,117(1):101-119

Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, M?ssbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature M?ssbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. M?ssbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites.  相似文献   

Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization     

Mautner MN  Leonard RL  Deamer DW 《Planetary and Space Science》1995,43(1-2):139-147

Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350 degrees C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 x 10(-3) N m-1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120 degrees C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of microorganisms to metabolize extraterrestrial organics.  相似文献   

1300 micron continuum and C18O line mapping of giant molecular cloud cores. II. W3, NGC 2264, NGC 6334I, RHO Ophiuchi and S140     

Schwartz PR  Snell RL  Schloerb FP 《The Astrophysical journal》1989,336(1):519-525

In this paper we present nearly simultaneous 1300 microns continuum and J = 2-1 C18O maps of the cores of five molecular clouds, W3, NGC 2264, NGC 6334I, rho Oph, and S140. The purpose of this experiment was to compare these two column density tracers. We find that dust continuum and C18O emission are equally effective tracers of column density in molecular cloud cores and give a good indication of cloud structure. When the maps are analyzed in terms of the quantity q = Q/[a rho RX(C18O)], we find that q does not vary by much more than an order of magnitude either within objects or from object to object, implying that nominal dust parameters of absorption efficiency, radius, and gas-to-dust ratio and CO abundance are on average correct in a variety of sources. We did detect source-to-source variations in q. This variation could be either in the dust-to-CO number density ratio or in grain parameters. These variations are not well correlated with total source luminosity, average or typical temperature, or total column density. The best example of this variation appears to be rho Oph where q is about a factor of 7 lower than is typically found. Our approach is analogous to the study of the A nu to CO ratio and is probably equivalent to extending this study to large A nu if the same grains are responsible for both optical opacity and far-infrared to millimeter-wave emission. There is no fundamental reason to expect A nu/NCO or q to be constant and, in fact, we have found that it is not constant in even a small source sample.  相似文献   

黄河三角洲滨海区沉积物的分异特征与规律   总被引：7，自引：0，他引：7  

陈小英  陈沈良  刘勇胜 《沉积学报》2006,24(5):714-721

根据2000年79月黄河三角洲滨海区表层沉积物的分析结果,运用F lem ing的三角图式对沉积环境进行划分,并在此基础上结合沉积物结构、地形和水动力条件,探讨了沉积物的分布规律及其作用机制。结果表明:研究区域可划分为废弃三角洲滨海区、现行河口区和莱州湾滨海区三个沉积环境。对于废弃三角洲沉积区,在早期废弃的湾湾沟海区风浪作用为主,沉积物普遍较粗,抗冲能力较强;废弃不久的飞雁滩海区在波流联合作用下,沉积物粒径由岸向海变细,大致在-5-6m水深处存在一明显的界限,该水深以浅砂含量较高;而该水深以深以粉砂和粘土为主,砂含量较低。现行河口区,由于沙嘴前方强潮流带的作用,沉积物粒径由岸向海表现为粗—细—粗的演变趋势。在莱州湾海区,由于潮流场的影响,以广利河河口为界,以北粒径较细,而以南则较粗。   相似文献