Rare Earth Element Determination in Olivine by Laser Ablation‐Quadrupole‐ICP‐MS: An Analytical Strategy and Applications          下载免费PDF全文

Clare V. Stead  Emma L. Tomlinson  Balz S. Kamber  Michael G. Babechuk  Cora A. McKenna 《Geostandards and Geoanalytical Research》2017,41(2):197-212

Olivine offers huge, largely untapped, potential for improving our understanding of magmatic and metasomatic processes. In particular, a wealth of information is contained in rare earth element (REE) mass fractions, which are well studied in other minerals. However, REE data for olivine are scarce, reflecting the difficulty associated with determining mass fractions in the low ng g^?1 range and with controlling the effects of LREE contamination. We report an analytical procedure for measuring REEs in olivine using laser ablation quadrupole‐ICP‐MS that achieved limits of determination (LOD) at sub‐ng g^?1 levels and biases of ~ 5–10%. Empirical partition coefficients (D values) calculated using the new olivine compositions agree with experimental values, indicating that the measured REEs are structurally bound in the olivine crystal lattice, rather than residing in micro‐inclusions. We conducted an initial survey of REE contents of olivine from mantle, metamorphic, magmatic and meteorite samples. REE mass fractions vary from 0.1 to double‐digit ng g^?1 levels. Heavy REEs vary from low mass fractions in meteoritic samples, through variably enriched peridotitic olivine to high mass fractions in magmatic olivines, with fayalitic olivines showing the highest levels. The variable enrichment in HREEs demonstrates that olivine REE patterns have petrological utility.  相似文献   

Hafnium Isotope Characteristics of Palaeoarchaean Zircon OG1/OGC from the Owens Gully Diorite,Pilbara Craton,Western Australia          下载免费PDF全文

Anthony I. S. Kemp  Jeffrey D. Vervoort  Katarina E. Bjorkman  Linda M. Iaccheri 《Geostandards and Geoanalytical Research》2017,41(4):659-673

We report Hf isotope data for 3467 Ma igneous zircons from the Owens Gully Diorite of the Pilbara Craton. These zircons, designated OG1 or OGC, have simple, well‐defined U‐Pb age systematics. Measurements obtained by single crystal dissolution yield a moderate range in ¹⁷⁶Hf/¹⁷⁷Hf (mean 0.280633 ± 34) and ¹⁷⁶Lu/¹⁷⁷Hf (mean 0.00119) that translate into initial (3467 Ma) ¹⁷⁶Hf/¹⁷⁷Hf values that are equivalent within measurement uncertainty (mean 0.280554 ± 7, ε_Hf = +0.6 ± 0.2, 2s). Laser ablation analysis yielded clustered initial ¹⁷⁶Hf/¹⁷⁷Hf ratios (mean 0.280560 ± 20, 2s) indistinguishable from those obtained by solution analysis. The antiquity and moderately high ¹⁷⁶Lu/¹⁷⁷Hf of these zircons result in significant corrections for radiogenic ingrowth of ¹⁷⁶Hf (to 6 ε_Hf units). Depth profiling by concurrent Pb‐Hf isotope determination reveals trends to lower ²⁰⁷Pb/²⁰⁶Pb in several crystals, although these are not accompanied by shifts in ¹⁷⁶Hf/¹⁷⁷Hf. We conclude that zircons from the Owens Gully Diorite are homogeneous for Hf isotopes at the scale of sampling and within the uncertainty limits of the measurement techniques employed. Zircon OG1/OGC would appear to be an ideal quality monitor for laser ablation Hf isotope determination in ancient zircons, and for laser ablation techniques where Hf isotope and age information are determined concurrently or simultaneously.  相似文献   

GRACE监测青藏高原及邻区陆地水储量变化结果的可变性     

相龙伟  汪汉胜  贾路路 《大地测量与地球动力学》2017,37(3):311-318

结合4种不同的去相关滤波和2种平滑滤波,利用5组GRACE数据反演了青藏高原及邻区陆地水储量变化趋势,研究了结果的可变性。结果表明,采用S&W（P2M8）变宽度滑动窗口去条带效果较好,其结果中的湖水、冰川信号与卫星测高观测的信号位置具有较好的一致性。高斯滤波的异常幅值与扇形滤波相差10%~30%,平滑处理后异常幅值减少,观测分辨率降低,部分湖和冰川信号甚至消失。CSR/GFZ/JPL重力场模型反演的结果相近,但CSR去条带效果最好;JPL质量模型MAS/MAS_S的结果也相近,但在高原西部有较大差异。重力场模型与质量模型的结果相差很大。在利用GRACE卫星监测本地区陆地水储量变化时,推荐使用S&W（P2M8）去条带滤波器、CSR重力场模型数据。  相似文献   

基于球体几何关系的球标靶特征提取算法     

权力奥  杨荣华  潘蕾西兰  方西南  万震 《大地测量与地球动力学》2017,37(8):860-863

利用“球面上任意3点确定的平面与球的相交曲线为圆,该截面圆心与球心的连线(球截面圆心法线)垂直于圆平面”的几何关系,提出一种基于球体几何关系的球标靶特征提取算法。通过对球标靶点云构建多组截面圆,对截面圆设定约束条件,构造球心到球截面圆心法线距离平方和的目标函数,以此目标函数最小为条件求解球标靶的球心坐标。通过实验比较本文方法、最小二乘方法、整体最小二乘方法、加权整体最小二乘方法和稳健加权整体最小二乘方法对球标靶的处理效果,结果表明本文方法具有较高的准确性和稳健性。  相似文献   

三维激光扫描变形可监测性指标的确定     

曾政祥  陈西江 《大地测量与地球动力学》2017,37(5):516-520

将三维激光扫描技术应用到变形监测中,对三维激光扫描测距、测角、光斑及配准误差进行分析,给出点云误差椭球模型。利用得到的误差椭球半轴长度和点位误差极限值的关系,推导点云变形可监测性指标。最终通过模拟的滑坡实验,验证了该变形可监测性指标的可行性。  相似文献   

Towards a protocol for laser scanning of rock surfaces     

Martin Schaefer  Robert Inkpen 《地球表面变化过程与地形》2010,35(4):147-423

The precision of height measurements derived from laser scanning a weathered rock surface was analysed. Different registration methods for comparing surfaces to deduce weathering were assessed and the most precise was found to be the method that used registration shapes as control, located in different planes relative to the scanned surface. In addition, the different sources of error in scanning precision were assessed by varying factors such as scan distance, lens configuration, scan angle and the nature of the topography being scanned. From this analysis it was possible to suggest what the optimal scanning conditions were for this particular experimental set‐up. The procedures outlined for assessing errors in the precision of height measurements are transferable to other scanning studies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

应用激光扫描技术进行岩体结构面的半自动统计研究   总被引：4，自引：0，他引：4       下载免费PDF全文

刘昌军  高立东  丁留谦  孙东亚 《水文地质工程地质》2011,38(2):52-57

以力丘河某边坡裸露岩体结构面的快速统计为例,提出了利用三维激光测量方法进行岩体结构面的半自动快速统计方法。详细介绍了三维激光扫描仪和高精度GPS的联合测量方法,激光点云数据的坐标转换和边坡表面三角网重构方法。在此基础上,研究了采用三维激光点云数据和三角网数据进行岩体结构面平面方程的半自动拟合方法、岩体结构面法向量和产状的关系等。利用得到的岩体结构面产状快速绘制岩体结构面密度图、玫瑰图、极点图和赤平投影图,得到了该边坡裂隙结构面分布规律和几何信息等。和传统方法相比,该方法具有快速测量和远距离测量的优点,且减少了攀爬高陡岩坡的危险。  相似文献   

Source of error and uncertainty in sheet erosion rates estimated from dendrogeomorphology          下载免费PDF全文

José M. Bodoque  Juan A. Ballesteros‐Cánovas  Ana Lucía  Andrés Díez‐Herrero  José F. Martín‐Duque 《地球表面变化过程与地形》2015,40(9):1146-1157

Dendrogeomorphology has been used since the 1960s to estimate sheet erosion rates. To date, most efforts have focused on accurately determining the first year of root exposure. However, an adequate methodological approach that takes into consideration the microtopography of the ground surface when estimating sheet erosion rates using dendrogeomorphology has not been proposed. In this study, terrestrial laser scanning (TLS) was used for the first time to examine how changes in microtopography determine the level of certainty in estimates. To this end, highly accurate TLS‐based digital elevation models representing exposed roots and their immediate vicinity were analysed using geographic information system tools. The results indicate that erosion rates calculated using the standard dendrogeomorphic method have been underestimated by up to 29% because the method does not take into account changes to the microtopography caused by the axial and radial pressure of the roots. Another source of uncertainty, which we estimate to be 50%, was also found and is the result of changes in the ground surface microtopography caused by variations in soil roughness. These findings do not invalidate the usefulness of dendrogeomorphology for assessing soil erosion, although they do show the need for correct characterization of the microtopography to guarantee reliability. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Investigating the geomorphological potential of freely available and accessible structure‐from‐motion photogrammetry using a smartphone          下载免费PDF全文

Natan Micheletti  Jim H. Chandler  Stuart N. Lane 《地球表面变化过程与地形》2015,40(4):473-486

We test the acquisition of high‐resolution topographic and terrain data using hand‐held smartphone technology, where the acquired images can be processed using technology freely available to the research community. This is achieved by evaluating the quality of digital terrain models (DTM) of a river bank and an Alpine alluvial fan generated with a fully automated, free‐to‐use, structure‐from‐motion package and a smartphone integrated camera (5 megapixels) with terrestrial laser scanning (TLS) data used to provide a benchmark. To evaluate this approach a 16.2‐megapixel digital camera and an established, commercial, close‐range and semi‐automated software are also employed, and the product of the four combinations of the two types of cameras and software are compared. Results for the river bank survey demonstrate that centimetre‐precision DTMs can be achieved at close range (10 m or less), using a smartphone camera and a fully automated package. Results improve to sub‐centimetre precision with either higher‐resolution images or by applying specific post‐processing techniques to the smartphone DTMs. Application to an entire Alpine alluvial fan system shows the degradation of precision scales linearly with image scale, but that (i) the expected level of precision remains and (ii) difficulties in separating vegetation and sediment cover within the results are similar to those typically found when using other photo‐based techniques and laser scanning systems. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A review of terrestrial radar interferometry for measuring surface change in the geosciences          下载免费PDF全文

Rafael Caduff  Fritz Schlunegger  Andrew Kos  Andreas Wiesmann 《地球表面变化过程与地形》2015,40(2):208-228

This paper presents a review of the current state of the art in the use of terrestrial radar interferometry for the detection of surface changes related to mass movement. Different hardware‐types and acquisition concepts are described, which use either real or synthetic aperture for radar image formation. We present approaches for data processing procedures, paying special attention to the separation of high resolution displacement information from atmospheric phase variations. Recent case studies are used to illustrate applications in terrestrial radar interferometry for change detection. Applications range from detection and quantification of very slow moving (millimeters to centimeters per year) displacements in rock walls from repeat monitoring, to rapid processes resulting in fast displacements (~50 m/yr) acquired during single measurement campaigns with durations of only a few hours. Fast and episodic acting processes such as rockfall and snow avalanches can be assessed qualitatively in the spatial domain by mapping decorrelation caused by those processes. A concluding guide to best practice outlines the necessary preconditions that have to be fulfilled for successful application of the technique, as well as in areas characterized by rapid decorrelation. Empirical data from a Ku‐band sensor show the range of temporal decorrelation of different surfaces after more than two years for rock‐surfaces and after a few seconds to minutes in vegetated areas during windy conditions. The examples show that the displacement field can be measured for landslides in dense grassland, ice surfaces on flowing glaciers and snowpack creep. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献