Towards a Method for Quantitative LA‐ICP‐MS Imaging of Multi‐Phase Assemblages: Mineral Identification and Analysis Correction Procedures

Here, we present an approach to laser ablation ICP‐MS mapping of multi‐phase assemblages that permits the use of different internal standard elements, concentration values and reference materials for each mineral. In this way, we obtain not only broad pictures of elemental distributions within samples but can also extract high accuracy concentration data for any user‐selected region. This is accomplished by assigning regions of an image to corresponding mineral phases on a pixel‐by‐pixel basis. In this way, accurate trace element concentrations can be determined for each mineral phase, despite potential variations in their ablation characteristics. We present an example where elemental maps are constructed from ablation of a gabbroic sample that includes the phases apatite, amphibole and plagioclase. This work represents an important first step towards development of a method to produce highly accurate LA‐ICP‐MS elemental maps of multi‐phase samples.     

Determination of U–Pb Ages for Young Zircons using Laser Ablation‐ICP‐Mass Spectrometry Coupled with an Ion Detection Attenuator Device

We have developed new analytical procedures to measure precise and accurate ²³⁸U–²⁰⁶Pb and ²³⁵U–²⁰⁷Pb ages for young (~ 1 Ma) zircons using laser ablation‐ICP‐mass spectrometry. For young zircons, both careful correction for the background counts and analysis of very small Pb/U ratios (i.e., ²⁰⁶Pb/²³⁸U < 0.00016 and ²⁰⁷Pb/²³⁵U < 0.0001 for 1 Ma zircons) are highly desired. For the correction of the background, the contribution of the background signal intensities for the analytes, especially for the residual signal intensities for ²⁰⁶Pb and ²⁰⁷Pb, was defined through laser ablation of synthesised zircons (ablation blank) containing negligible Pb. The measured signal intensities for ²⁰²Hg, ²⁰⁶Pb and ²⁰⁷Pb signals obtained by the ablation blank were slightly higher than those obtained by data acquisition without laser ablation (gas blank). For the wider dynamic range measurements on Pb/U ratios, an attenuator device for the ion detection system was employed to extend the capability to monitor high‐intensity signals (i.e., > 3 Mcps). Through the attenuator device, the ion currents were reduced to 1/450 of the signal intensity without the attenuator. Because the switching time for the attenuator was shorter than 1 ms, signal intensities for only specific isotopes could be reduced. With attenuation of the ²³⁸U signal, counting statistics on ²⁰⁶Pb and ²⁰⁷Pb isotopes could be improved and counting loss on the ²³⁸U signal could be minimised. To demonstrate the reliability of this new analytical technique, ²³⁸U–²⁰⁶Pb and ²³⁵U–²⁰⁷Pb ages for three young zircon samples (collected from Osaka Group Pink Volcanic Ash, Kirigamine and Bishop Tuff) were measured. The data presented here demonstrate clearly that the present technique could become a major analytical tool for in situ U–Pb age determination of young zircons (~ 1 Ma).     

Rapid Determination of Trace and Ultra Trace Level Elements in Diverse Silicate Rocks in Pressed Powder Pellet Targets by LA‐ICP‐MS using a Matrix‐Independent Protocol

A simple, single sample preparation involving pressed rock powder pellets was utilised to determine the trace and ultra trace abundances of petrogenetically important elements including high field‐strength elements and REEs by laser ablation‐ICP‐MS. One of the elements predetermined by XRF spectrometry served as an internal standard. The influence of sample preparation parameters (grain size, pellet compactness and amount of binding media) on analytical performance was also investigated, including sample homogeneity issues at the laser sampling scale. Line scanning with a high repetition frequency (20 Hz) and large beam diameter (200 μm) ensured ablation from a larger sample surface area, eliminating issues related to sample heterogeneity. A median grain size of about 10 μm for silicate rock powders was found to be sufficiently representative at this scale of laser sampling. Granitic rocks or samples containing resistant minerals such as zircon needed extra grinding to achieve grain sizes down to < 5 μm for better precision for elements that are concentrated in these phases. Using ¹³⁷Ba as an internal standard, reasonable accuracies within 15–20% for most of the high mass trace elements were achieved; in the case of low mass elements, it may deviate up to 40%. Precision of measurements rarely exceeded 15% RSD.     

川西呷村黑矿型多金属矿床热液体系稀土元素组成特征

本文首次测定了呷村黑矿矿石中流体包裹体的ＲＥＥ组成,计算了与含矿流纹岩系熔体平衡的岩浆热液ＲＥＥ含量。主成矿期流体具有轻稀土富集、Ｅｕ明显正异常的特点,但岩浆热液却具有明显的Ｅｕ负异常特征,结合热液体系氧同位素及稀土元素交换反应模拟,表明岩浆热液不是直接的成矿热液。蚀变围岩具显著的Ｅｕ正异常,其它稀土元素出现亏损。蚀变反应水／岩比值较大,蚀变岩中的ＲＥＥ组成反映了成矿热液ＲＥＥ的特点,且ＲＥＥ亏损     

辽宁四道沟热液金矿床中石英的稀土元素的特征及意义

本文用ＩＣＰ－ＭＳ测定了辽宁四道沟金矿矿脉中石英及其中流体包裹体中的稀土元素含量,发现石英的稀土元素配分模式类似于其中流体包裹体的稀土元素配分模式,推断石英中的稀土元素主要赋存于注流体包裹体中,流体包裹体中的稀土元素了石英的稀土元素配分模式,原生包裹中的流体是和石英同源的,其稀土元素指示的是石英形成过程中流体的信息。而次生包裹体中的流体是石英形成后的流体活动产物,其稀土元素指示的是后期流体活动的信     

感耦等离子体发射光谱法测定原油中痕量铁镍铜钒

系统地试验了用感耦等离子体发射光谱同时测定原油中痕量元素Ｆｅ、Ｎｉ、Ｃｕ和Ｖ的多种前处理方法,制定出Ｈ２ＳＯ４、ＨＮＯ３分步炭化,５００℃灰化,ＨＣｌ＋ＨＮＯ３（ＶＨＣｌ∶ＶＨＮＯ３＝１∶１）溶解灰分的最佳分解方案。该方法的检出限为１．０～６．０μｇ／Ｌ,精密度好,ＲＳＤ（ｎ＝４）＜４．６％,加标回收率为９６．２％～１１１％。方法已应用于大庆、苏北、惠州等原油样品的分析。     

基于Delaunay三角剖分的ICP算法研究与实现

针对ICP迭代点云配准算法,利用MATLAB中封装的三角剖分函数,迅速搜索迭代过程中的最近点,简化ICP配准算法的实现,并设计一种模拟实验的方法验证算法的有效性。实验表明,利用基于三角剖分的ICP迭代算法可以达到较好的配准精度。     

基于特征点法向量的点云配准算法

在传统的迭代最近点算法（ICP）中,需要两片点云具有良好的初始位置,否则在配准时容易陷入局部最优。针对该问题,本文提出了一种基于特征点提取与配对的粗配准方法,以调整两片点云重叠部分的初始位置。首先,利用SIFT算法提取两片点云公共部分的特征点;其次,根据特征点法向量之间的欧氏距离将两片点云的特征点两两配对;然后,利用法向量的夹角对特征点对进行提纯;最后,通过单位四元数法,求解出旋转及平移矩阵,完成粗配准。试验表明,本文基于特征点法向量的粗配准方法可为精配准提供良好的初始位置,在一定程度上避免配准时陷入局部最优的现象。     

融合反射强度图像的地铁隧道点云自动配准

针对地铁隧道点云数据特征点少、在大视角点云数据间配准拼接时出现精度差、效率低等问题,本文以提高配准效率及精度作为出发点,以目前主流的ICP算法为基础,首先将激光点云按中心投影方式生成反射强度图像并以此作为配准源,采用规则格网分割提取匹配,建立均匀分布的同名点;然后利用反射强度图像上的同名点与点云之间的一一对应关系,完成视角点云间的初配准;最后在初次配准的基础上,采用KD树改进算法进行点云数据的精细配准。试验结果表明,本文在实现点云数据自动配准的同时,提高了地铁隧道点云数据的配准效率及精度。     

8410型直读光谱仪中开关电源工作原理及维修

在维修和改造8410型电感耦合等离子体直读光谱仪过程中,经常需要对ICP高频发生器中的开关电源进行维修和调整。简述开关电源基本原理,介绍-145V开关电源稳压过程及故障维修。