地球化学样品中铀的激光荧光法测定     

张桂英  董亚妮  李力争 《陕西地质》2003,21(2):107-110

采用四酸分解样品，盐酸浸取分取溶液，激光荧光法测定地球化学样品中的铀。应用内滤效应校正法和标准物质校正法，消除铁元素干扰而引起结果偏低的系统误差问题，取得了满意的效果，铀的检出限为0．44μg／g；实际测定的精密度RSD≤5．51％。  相似文献   

Laser microprobe sulphur isotope analysis of arsenopyrite: experimental calibration and application to the Boliden Au–Cu–As massive sulphide deposit     

Thomas Wagner  Adrian J. Boyce  Erik Jonsson  Anthony E. Fallick 《Ore Geology Reviews》2004,25(3-4):311-325

Metamorphic remobilization of arsenopyrite-rich ores is a globally important process which can lead to significant concentrations of gold. In order to understand this and related processes, relations of sulphur isotopes can give a number of important clues. To resolve such relations in detail, we have successfully calibrated and applied a laser combustion system for in situ analysis of sulphur isotopic compositions of arsenopyrite. Experimental calibration of the laser fractionation factor (+0.4‰) was obtained by using compositionally and isotopically homogeneous natural samples from ore deposits at Boliden (Sweden) and Freiberg (Germany); subsequent to detailed microscopic study, the S isotope ratios of these samples were measured by conventional and laser combustion techniques.The present application to different types of arsenopyrite in the Palaeoproterozoic metamorphosed VHMS ores of the Boliden Au–Cu–As deposit, Skellefte district, northern Sweden, shows that the sulphur isotope composition of arsenopyrite is essentially unmodified during medium-grade metamorphic recrystallization and remobilization. Here, massive arsenopyrite ore is crosscut by later veins that carry a complex quartz–sulphosalt–sulphide assemblage. The latter ore type is markedly Au-rich compared to the host ore, and thus of significant economic interest. We find that both ore types exhibit very similar sulphur isotope compositions, ca. +2‰ to +3‰ (V-CDT), which is similar to most massive sulphide deposits in the Skellefte district. Thus, the crosscutting Au-rich vein ore has inherited the sulphur isotope composition from sulphur liberated by metamorphic reactions affecting the massive ore, and most likely also inherited the Au through this mechanism. The latter finding clearly has important implications both for the general discussion on, and the prospecting for, similar high-grade Au ores in this world-class mining region.  相似文献   

隐藏在苏鲁地体斜长角闪岩锆石中超高压变质作用的信息   总被引：2，自引：0，他引：2       下载免费PDF全文

刘福来  张泽明  许志琴  杨经绥  S．Maruyama 《地球学报》2003,24(5):409-414

运用激光拉曼和阴极发光技术，配备电子探针测试，发现苏鲁地体地表露头和中国大陆科学钻探工程预先导孔CCSD-PP1和CCSD-PP2斜长角闪岩锆石中均保存以柯石英为代表的典型超高压矿物组合：柯石英 石榴石 绿辉石 金红石；柯石英 石榴石 绿辉石；柯石英 石榴石 绿辉石 多硅白云母 金红石 磷灰石；柯石英 绿辉石 金红石；柯石英 菱镁矿。该类矿物包体组合与苏鲁地体超高压榴辉岩的峰期矿物组合十分相似，表明斜长角闪岩可能是由超高压变质的榴辉岩在构造抬升过程中退变质而成。  相似文献   

Study of a wide-angle laser ranging system for relative positioning of ground-based benchmarks with millimeter accuracy     

O. Bock  M. Kasser  C. Thom  J. Pelon 《Journal of Geodesy》1998,72(7-8):442-459

A wide-angle airborne laser ranging system (WA-ALRS) is developed at the Institut Géographique National (IGN), France, with the aim of providing a new geodesy technique devoted to large (100 km²) networks with a high density (1 km⁻²) of benchmarks. The main objective is to achieve a 1-mm accuracy in relative vertical coordinates from aircraft measurements lasting a few hours. This paper reviews the methodology and analyzes the first experimental data achieved from a specific ground-based experiment. The accuracy in relative coordinate estimates is studied with the help of numerical simulations. It is shown that strong accuracy limitations arise with a small laser beam divergence combined with short range measurements when relatively few simultaneous range data are produced. The accuracy is of a few cm in transverse coordinates and a few mm in radial coordinates. The results from ground-based experimental data are fairly compatible with these predictions. The use of a model for systematic errors in the vehicle trajectory is shown to be necessary to achieve such a high accuracy. This work yields the first complete validation of modelization and methodology of this technique. An accuracy better than 1 mm and a few mm in vertical and horizontal coordinates, respectively, is predicted for aircraft experiments. Received: 19 June 1997 / Accepted: 17 February 1998  相似文献   

一个改进的陆面过程模式及其模拟试验研究第二部分:陆面过程模式与区域气候模式的耦合模拟试验   总被引：20，自引：6，他引：14  

丁一汇  张晶  赵宗慈 《气象学报》1998,56(4):385-400

在第一部分提出的陆面过程模式与区域气候模式ＲｅｇＣＭ实现耦合的基础上,利用这一耦合模式（简称ＣＲｅｇＣＭ）对中国中东部地区１９９１年５～７月江淮大暴雨时期的强降水气候特征进行了模拟,并与ＮＣＡＲ的区域气候模式ＲｅｇＣＭ２（此处称ＮＲｅｇＣＭ）在同样初、边值条件和同样物理过程选项下的模拟结果进行了对比分析。分析结果表明,模式ＣＲｅｇＣＭ具有较强的模拟性能和模拟能力,基本上成功地模拟了这次极端的降水气候事件。在某些方面,如地面气温和与陆面过程有关要素的模拟上,ＣＲｅｇＣＭ的模拟结果要比ＮＲｅｇＣＭ的结果更合理。  相似文献   

Oxygen isotope ratios of phenocrysts from alkali basalts of the Pannonian basin: Evidence for an O-isotopically homogeneous upper mantle beneath a subduction-influenced area   总被引：1，自引：0，他引：1  

G  bor Dobosi  Hilary Downes  David Mattey  Antal Embey-Isztin 《Lithos》1998,42(3-4):213-223

Oxygen isotope compositions of olivine and pyroxene phenocrysts and pyroxene and amphibole megacrysts from Neogene alkali basalts of the Pannonian basin (0.5–11 Ma) have been determined by laser fluorination. Measured δ¹⁸O values in olivine and clinopyroxene phenocrysts show rather restricted variations from 5.00 to 5.20‰ and from 5.07 to 5.34%., respectively, with cpx-ol fractionations Δ¹⁸O(cpx-ol) ranging from + 0.04 to + 0.29‰. These δ¹⁸O values are significantly lower than those of the corresponding whole rocks, suggesting that low temperature alteration has increased the ¹⁸O/¹⁶O ratios of the groundmass of host rocks, even in fresh looking samples, whereas their phenocrysts have retained original oxygen isotope compositions. The uniform oxygen isotope ratio in the phenocrysts suggests that the mantle source of the alkali basalts was also homogeneous with respect to its oxygen isotope composition, which is in contrast to the relatively wide variation of Sr, Nd and Pb isotope ratios in the source. Variations in radiogenic isotope compositions in the basalts have been explained by the interaction of subduction-related fluids with the mantle source of the basalts. If this is the case, then the fluids which caused significant changes in the Sr and Pb isotope ratios of the mantle source clearly did not noticeably modify its oxygen isotope composition. These data support the opinion that the upper mantle is more homogeneous with respect to its oxygen isotope composition than it was previously considered.  相似文献   

一个具有高分辨率海洋分量的海气耦合模式   总被引：1，自引：0，他引：1       下载免费PDF全文

张韬郭裕福  吴国雄 《应用气象学报》2002,13(6):688-695

发展了中国科学院大气物理研究所（IAP）大气科学与地球流体力学数值模拟国家重点实验室(LASG)全球海-陆-气耦合系统模式的一个新版本（GOALS-5），其中海洋分量是基于30层高分辨率的海洋环流模式。对该耦合模式成功地进行了30年的积分，基本上克服了气候飘移。与GOALS较早的几个版本模拟的SST相比，北半球夏季中高纬地区的误差显著改善，可能主要是由于采用了GM90的等密度混合方案使经向热输送增强的结果。对赤道中东太平洋冷暖事件有较好的模拟能力，并且对SST变率的模拟在位置和强度上比旧版本有明显改善。  相似文献   

Investigation of tidal effects in lunar laser ranging     

J. Müller  V. Tesmer 《Journal of Geodesy》2002,76(4):232-237

 The analysis of lunar laser ranging (LLR) data enables the determination of many parameters of the Earth–Moon system, such as lunar gravity coefficients, reflector and station coordinates which contribute to the realisation of the International Terrestrial Reference Frame 2000 (ITRF 2000), Earth orientation parameters [EOPs, which contribute to the global EOP solutions at the International Earth Rotation Service (IERS)] or quantities which parameterise relativistic effects in the solar system. The big advantage of LLR is the long time span of lunar observations (1970–2000). The accuracy of the normal points nowadays is about 1 cm.  The capability of LLR to determine tidal parameters is investigated. In principle, it could be assumed that LLR would contribute greatly to the investigation of tidal effects, because the Moon is the most important tide-generating body. In this respect some special topics such as treatment of the permanent tide and the effect of atmospheric loading are addressed and results for the tidal parameters h ₂ and l ₂ as well as values for the eight main tides are given. Received: 14 August 2000 / Accepted: 15 October 2001  相似文献   

海洋测量船激光码头标校的论证与试验     

陈一飞 《测绘学院学报》1990,(1)

本文简要介绍激光码头标校方案,采用电子全站仪的极坐标法测定激光束首尾两点的坐标,来解算惯性导航平面倾角(θ、ψ)和航向角κ。文中对DIOR 3002测距仪无反光镜合作时的测距精度、电子全站仪的定点精度、电子全站仪之间同步测量、数据自动传输等作了详细的试验,得出了适合于激光码头标校最佳测量条件,为激光码头标校部分代替船坞标校提供了论证基础。  相似文献   

Shear dispersion in a fracture with porous walls     

《Advances in water resources》2014

We present an analytical expression for the shear dispersion during solute transport in a coupled fracture–matrix system. The dispersion coefficient is obtained in a fracture with porous walls by taking into account an accurate boundary condition at the interface between the matrix and fracture, and the results were compared with those in a non-coupled system. The analysis presented identifies three regimes: diffusion-dominated, transition, and advection-dominated. The results showed that it is important to consider the exchange of solute between the fracture and matrix in development of the shear dispersion coefficient for the transition and advection-dominated regimes. The new dispersion coefficient is obtained by imposing the continuity of concentrations and mass fluxes along the porous walls. The resulting equivalent transport equation revealed that the effective velocity in a fracture increases while the dispersion coefficient decreases due to mass transfer between the matrix and fracture. A larger effective advection term leads to greater storage of mass in the matrix as compared with the classical double-porosity model with a non-coupled dispersion coefficient. The findings of this study can be used for modeling of tracer tests as well as fate, transport, and remediation of groundwater contaminants in fractured rocks.  相似文献