翡翠原石的放射性水平研究

为了准确掌握翡翠原石的放射性水平,消除公众对珠宝玉石存在放射性的疑虑,本文选取了3种翡翠原石的10件样品,利用高纯锗型(HPGe)低本底多道γ能谱仪测量了样品中天然放射性核素²²⁶Ra、²³²Th和⁴⁰K的比活度值.结果表明,样品中有关核素的比活度值低于或仅略高于仪器检测限,样品的内照指数(I_Ra)和外照指数(I_γ)均远远低于国家对建筑材料中放射性核素的限量规定,说明翡翠原石的放射性水平很低,与环境的天然本底相当,不存在所谓的放射性危害.     

氡的多参数测量用于非铀矿地质问题

在非铀矿地质问题中,常存在着一种或几种氡的弱异常(如²²²Rn、²²⁰Rn等).在选用测氡方法来解决这类问题时,要求它具有高灵敏度、高测量精度和多测量参数的特点。选用静电α卡法、α杯法的多参数测量技术,在圈定岩脉边界、区分岩脉性质、找寻蓄水构造、确定油田范围的应用中取得了明显的效果,     

现代卫星测高重力异常分辨能力分析 及在海洋资源调查中应用

通过卫星测高重力数据与船载重力测量结果进行空间分辨率对比、海陆重力异常接图, 以及我国南黄海海域卫星测高重力对沉积盆地与隐伏构造解释的应用试验, 对现代国内外卫星测高重力数据获取与重力异常分辨能力进行了分析, 指出了现代卫星测高重力异常的精度达到4×10^-5m/s²左右, 可以满足1∶100万比例尺的海洋重力调查与辅助前期资源勘查的需要, 并对卫星测高重力技术的应用提出了建议。     

近仪物体对高精度重力测量的影响

近年来为满足地球动力学、大地测量学、地球物理学、计量学等方面的需要,绝对和相对的重力测量日益得到重视和发展。其观测精度已达到微伽(1μGal－10^-8m/s²)级,若要保证这样的精度,就必须顾及近仪物体的扰动或影响。本文将从一些实际资料说明这一情况,并从一些模型计算出发,不仅推导了有关公式,还重点讨论了它们的重力效应,以便得到消除或改正。     

土壤热释CO2测量法在碳硅泥岩型铀矿床上的试验效果

本文主要论述土壤热释CO₂测量法在碳硅泥岩型铀矿床上的试验效果,实测结果表明,该法是有效的.文章还对CO₂法找钻机制进行了初步探讨.有关取样技术、样品加工和分析测定方法也作了概述.最后认为土壤热释CO₂ 测量法可成为一种找铀的新方法.     

地面氡法测量技术在普查层间氧化带型砂岩铀矿中应用的可行性探讨

本文依据层间氧化带型砂岩铀矿床的成矿特点以及铀镭平衡变化的特征,根据²¹⁸Po测量技术在已发现的该类型铀矿床上普查找矿的试验结果,讨论了地面氡法测量技术作为寻找层间氧化带型砂岩铀矿床的普查手段的可行性问题。     

纳克级铅同位素分析中硅胶-高铼酸发射剂体系的建立

核取证分析中需要实施纳克级（ng）铅的同位素全谱分析,质谱测量中要求铅的电离效率较高（大于10^-3）。传统硅胶-磷酸技术多用于微克级（μg）铅分析,电离效率一般为10^-4~10^-3;尽管后来发展的硅胶-硼酸技术可以得到10^-3以上的发射效率,但是由于铅在电离过程中存在离子流反复升高-衰减的过程,导致离子流发射不稳定,质谱测量条件难以掌握。本文改进了传统的硅胶发射剂,建立了一种新型硅胶加载体系——硅胶-高铼酸体系。与硅胶-硼酸技术相比,采用硅胶-高铼酸体系可显著提高铅的发射效率并获得稳定的离子流。对于1 ng铅的同位素质谱全谱测量,²⁰⁴Pb/²⁰⁶Pb、²⁰⁷Pb/²⁰⁶Pb、²⁰⁸Pb/²⁰⁶Pb的相对标准偏差分别为0.4%、0.2%和0.1%,测试精度优于采用其他硅胶技术。通过实验比较了硅胶-高铼酸体系与多种传统硅胶发射剂体系对铅离子流的发射效果,优化了硅胶试剂用量为0.5~3.0 μL,采用“夹心饼干”的涂样顺序,对1~100 ng铅样品的发射效率达到6.0×10^-3~4.6×10^-2,比传统硅胶-磷酸体系的发射效率（10^-4~10^-3）高了近10倍,与硅胶-硼酸技术的发射效率相当（10^-3~10^-2）,但铅离子发射更为稳定。本文建立的硅胶-高铼酸体系在测量精度上可满足核取证研究中铅作为地域指示剂的需求。     

二连盆地苏尼特右旗地区HFU-39、40异常特征及找矿意义

为查明二连盆地苏尼特右旗地区HFU-39、HFU-40航放异常的铀成矿情况,本文在分析异常区区域地质资料基础上,采用地质剖面测量、地面伽玛总量测量、伽玛能谱剖面测量、土壤氡剖面测量及岩石化探取样分析综合方法,对HFU-39、HFU-40两个异常进行查证及评价。查证结果显示异常呈团块状展布,地面伽玛能谱测量铀含量最高达w（U）=135×10^-6,岩石化学分析铀含量最高达w（U）=256×10^-6,该区域氡异常突出;综合异常查证结果和对二连盆地泥岩型铀矿化的形成环境分析,指出了该区的下一步铀找矿方向。     

我国海洋地质分析测试技术

21世纪是海洋开发和利用的新世纪,随着国家对海洋地质调查工作的日益重视,海洋地质分析测试技术迎来了快速发展时期。本文对我国海洋地质分析测试技术的最新进展进行了简要评述:为满足海洋区域调查、海岸带地质调查的需要,建立了以大型分析仪器为主的多元素同时分析海洋地质样品的快速高效分析方法体系;针对新能源天然气水合物样品,开展了异常识别测试技术和应用测试技术研究,建立了用离子色谱法快速测定孔隙水中阴离子Cl^-、Br^-、SO₄^2-和阳离子Na⁺、NH₄⁺、K⁺、Ca²⁺、Mg²⁺ 的方法,开发出了以声学、电阻、时域反射(Time Domain Reflectometry, 简称为TDR)三种探测技术为主的适用于天然气水合物模拟实验的探测新技术;对于海洋沉积物中有机污染物样品,采用复合固相萃取净化柱,对海洋沉积物萃取液样品进行净化分离,依次选用正己烷和正己烷－二氯甲烷混合液淋洗固相萃取净化柱,可有效保留基体杂质,实现了海洋环境地质调查中基质复杂沉积物样品的同时净化、分离与测试,可显著提高实验效率;同时在大洋矿产样品分析技术、海洋地质标准物质研制、船载与原位化学探测技术等方面也取得了重要进展。本文还提出在海洋调查和监测的应用中,船载及原位测试技术将愈趋重要,加强海洋化学传感器的性能和检测集成化技术是今后的一个重要发展方向。     

云南程海富营养化过程的碳氧稳定同位素示踪

近500年来程海生物成因碳酸盐δ¹⁸O和δ¹³C及其有机质δ¹³C同位素记录了程海湖泊环境由贫营养到中富营养的演化过程.碳酸盐δ¹⁸O记录显示,大约1690年程海成为封闭湖泊后,当时湖泊贫营养环境并没有发生变化,但造成了湖泊水体交换周期加长,碳酸盐δ¹³C、有机质δ¹³C及其色素含量、碳酸盐含量变化指示湖泊生产力开始增高.1911～1942年碳酸盐δ¹⁸O和δ¹³C及有机质δ¹³C突然显著偏负,表明湖泊生物种群结构发生转变,湖泊初级生产力迅速增加,湖泊由贫营养向中营养转化.湖泊沉积物色素含量及碳酸盐含量变化也记录了这一湖泊环境的转换过程.约1986年以来,随着藻类养殖业及其农业耕作方式的转变,程海水环境渐渐转变成目前的中富营养化状态.     

矿物中4He同位素提取和含量测定研究

(U-Th)/He定年是一种有效的低温热年代学定年技术,现已被广泛应用于地质研究的各个领域,而矿物中4He同位素的有效提取和含量准确测定是该技术的关键。磷灰石和锆石是(U-Th)/He定年最常用的矿物,其4He提取条件及铀钍含量测定方法都较为成熟;而其他矿物(如磁铁矿、橄榄石、针铁矿、石榴子石等)的研究则相对较少。文章介绍了当前国内外(U-Th)/He研究中采用的4He同位素提取方法———真空炉加热法和激光加热法,激光加热法因具有低4He背景值和耗时短的优点而成为主要的提取方法。以磷灰石样品测试为例,介绍了成都地质矿产研究所建立的采用激光加热法和四极杆质谱提取4He同位素及其含量测量过程、含量计算和校正方法。指出未来(U-Th)/He测试技术除继续改进现有分析方法外,应加强对更多不同矿物的测试研究。     

Predicting discharge coefficient of compound broad-crested weir by using genetic programming (GP) and artificial neural network (ANN) techniques

Compound broad-crested weir is a typical hydraulic structure that provides flow control and measurements at different flow depths. Compound broad-crested weir mainly consists of two sections; first, relatively small inner rectangular section for measuring low flows, and a wide rectangular section at higher flow depths. In this paper, series of laboratory experiments was performed to investigate the potential effects of length of crest in flow direction, and step height of broad-crested weir of rectangular compound cross-section on the discharge coefficient. For this purpose, 15 different physical models of broad-crested weirs with rectangular compound cross-sections were tested for a wide range of discharge values. The results of examination for computing discharge coefficient were yielded by using multiple regression equations based on the dimensional analysis. Then, the results obtained were also compared with genetic programming (GP) and artificial neural network (ANN) techniques to investigate the applicability, ability, and accuracy of these procedures. Comparison of results from the GP and ANN procedures clearly indicates that the ANN technique is less efficient in comparison with the GP algorithm, for the determination of discharge coefficient. To examine the accuracy of the results yielded from the GP and ANN procedures, two performance indicators (determination coefficient (R ²) and root mean square error (RMSE)) were used. The comparison test of results clearly shows that the implementation of GP technique sound satisfactory regarding the performance indicators (R ²?=?0.952 and RMSE?=?0.065) with less deviation from the numerical values.     

微波消解-电感耦合等离子体质谱法测定煤中的硼

煤中硼的准确测定对于研究成煤的沉积环境具有重要意义。微波消解-电感耦合等离子体质谱(ICP-MS)可以有效地测定煤中的大部分微量元素,但由于硼易挥发等特殊的物理化学性质,致使硼的测定过程较为繁琐,测试结果不够准确。本文对微波消解ICP-MS测定煤中硼含量的分析方法进行了改进。样品中加入磷酸、硝酸和氢氟酸,用微波消解仪消解完全,置于电热板加热赶酸完毕后用硝酸提取。硼的卤化物易挥发,磷酸的加入使硼与磷酸结合生成难挥发的稳定络合物,起到了固硼的作用。ICP-MS测定中采用铍作为内标,通过在线加入的方式有效地补偿了基体效应产生的影响;用稀氨水冲洗进样系统,很好地降低了硼的记忆效应;选择高分辨率模式来测定,避免了12C和40Ar4+等质谱峰的干扰。方法的仪器检出限(0.22ng/mL)和方法检出限(0.34 ng/mL)较低,方法精密度(RSD)小于0.6%,灵敏度高,且测定标准样品的准确度良好。该方法简单快速,适用于批量分析煤样中硼的含量。     

双道氢化物原子荧光法同时测定地球化学样品中的微量砷和锑

已有大量研究工作表明砷是各种类型金矿床的极有效的探途元素,它也是许多热液多金属矿床的通用指示元素。锑作为指示元素做的工作比砷少,但是根据已有资料,它也是锑矿床、金矿床及多金属矿床的指示元素。我国最近发表的《苗龙金矿的发现》一文中很好地说明了砷及锑对找金矿的指示作用。     

Germanium isotope measurements of high-temperature geothermal fluids using double-spike hydride generation MC-ICP-MS

We present a double-spike isotope dilution MC-ICP-MS technique for the determination of germanium (Ge) isotope fractionation. Using this technique we determined Ge isotope compositions of geothermal spring fluids, a Columbia River Basalt sample, and an in-house diatom standard. Our technique uses a ⁷³Ge/⁷⁰Ge double spike in combination with hydride generation for Ge extraction from the sample matrix. Fractionation is determined on the ⁷⁴Ge/⁷²Ge mass ratio. The double spike allows us to effectively correct analytical isotope fractionation. Our external standard reproducibility is 0.4‰ (2 SD) over the course of several months. The minimum quantity of Ge needed for isotope analysis is approximately 2 ng. Consistent with previous work on geothermal fluids, Ge in the geothermal spring samples presented here is enriched over Si as compared to low temperature weathering signatures. This observation is typically interpreted as Ge exclusion during silicate mineral precipitation (e.g., quartz). Our isotope results indicate that the analyzed high temperature fluids fractionate Ge isotopes with a range in δ⁷⁴Ge between −0.4‰ and −1.4‰ relative to a Columbia River basalt. We cautiously interpret the observed fractionation as preferential removal of heavy Ge isotopes out of solution during cooling of the hydrothermal fluid and subsequent precipitation of quartz.     

Ferric iron content of mineral inclusions in diamonds from George Creek, Colorado determined using Mössbauer spectroscopy

The Mössbauer milliprobe allows the determination of Fe³⁺/ΣFe in samples as small as 50?μm. For the first time this technique is applied to a suite of diamonds of eclogitic paragenesis, where three garnet and five clinopyroxene inclusions in diamonds from George Creek, Colorado have been analysed. For garnet Fe³⁺/ΣFe ranges from 0–7%, while values for clinopyroxene range from 8–14%. These results are consistent with the low oxygen fugacity conditions implied by the presence of the inclusions in diamond.     

Accurate and Precise Elemental Abundance of Zinc in Reference Materials by an Isotope Dilution Mass Spectrometry TIMS Technique

A thermal ionisation mass spectrometric technique enabled the abundance of Zn in geological and biological reference materials and water samples to be measured by double spiking isotope dilution mass spectrometry enriched in the ⁶⁷Zn and ⁷⁰Zn isotopes. In the past, thermal ionisation mass spectrometry proved to be difficult for low-level zinc isotopic measurements. The size of Zn samples used for isotopic determination, in particular the biological RMs, represents an important breakthrough. These results represent the most accurate and precise concentrations measured for Zn in these samples. The maximum fractional uncertainty was that for TILL-3 (2%), while the minimum fractional uncertainty was 0.7% for both BCR-1 and W-2. The inhomogeneity of Zn in HISS-1 was revealed while other reference materials appeared homogeneous at the 95% confidence uncertainty. The certified concentration of Zn in HISS-1 and IMEP-19 by their producers are 28% and 3.8% higher than the values measured in this work. These are the first Zn concentration measurements in these materials by the isotope dilution-TIMS technique, except for BCR-1, NIES N^o 9 and IMEP-19. Reducing the blank enabled accurate measurement in water at the ng g^-1 level demonstrating the applicability of the technique for low-level Zn samples.     

High precision measurements of Mg/Ca and Sr/Ca ratios in carbonates by cold plasma inductively coupled plasma quadrupole mass spectrometry

We present a new high precision analytical method for the determination of Mg/Ca and Sr/Ca ratios in carbonates using an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) with a 650-W cold plasma technique and a desolvation introduction system. Signal intensities are detected in pulse-counting mode and Mg/Ca and Sr/Ca ratios are calculated directly from intensity ratios of ²⁴Mg/⁴³Ca and ⁸⁶Sr/⁴³Ca using external matrix-matched standards for every 4–5 samples to correct for instrumental mass discrimination and low-frequency ratio drift. Significant matrix effect of Ca content on Mg/Ca determination (− 0.018 Mg/Ca (mmol/mol)/[Ca] (ppm)), can be overcome by diluting [Ca] to 6–8 ppm in the sample solution or using an empirical correction. The Sr/Ca ratio affects the Mg/Ca determination, with a factor of − 0.32% Mg/Ca per mmol/mol. This is mainly caused by the influence of doubly charged ⁸⁶Sr, which biases the intensity measurement of the ⁴³Ca⁺ ion beam. This effect results in a trivial offset of less than 0.1% on Mg/Ca measurements for Quaternary foraminiferal and coral samples. The internal precision of our method ranges from 0.1 to 0.2%. Replicate measurements made on standards and samples show long-term external uncertainties (2σ) of Mg/Ca = 0.84% and Sr/Ca = 0.49%. The minimum sample size requirement is only 3.5 μg of carbonate. The application of this newly developed technique on the planktonic foraminifera Globigerinoides ruber from a core recovered in the southern South China Sea yields a glacial–interglacial difference in sea surface temperature (SST) of 3 °C. Three-year coral Sr/Ca data suggest that the seasonal SST ranged from 22.6–23.8 °C in winter to 26.9–27.9 °C in summer in Nanwan, south Taiwan, during 2000–2002. The coral-Sr/Ca inferred SSTs in 2002 match well with instrumental records, which demonstrates the validity of this ICP-QMS method.     

Determination of groundwater availability in shallow arid region aquifers utilizing GIS technology: a case study in Hada Al-Sham, Western Saudi Arabia

A simple, physically based method is developed in this paper to assist in the allocation of areas with high groundwater potential and for the determination of maximum allowed pumping rate to ensure proper groundwater management. This method utilizes the aquifer physical properties as well as GIS technology to accomplish this purpose. The design of this method was considered to be applicable in areas with little data, such as in most arid regions. This technique was applied to a catchment in an arid environment where qualitative as well as quantitative analyses of the results were undertaken. Locations of available groundwater and rates of maximum allowable pumping were compared with observations and experiments in the field and a good agreement was found. It was concluded that the best groundwater location was in the alluvial area, which represents only 16% of the total aquifer, which is a typical case in arid region catchments. The rate of maximum pumping was estimated to be 65 m³/h. However, to benefit 55% of the area, the maximum pumping rate should only be 40 m³/h with an average rate throughout the area (55%) of about 24 m³/h.This revised version was published online in December 2004 with corrections to the category.     

广东高凤金矿形成时代的Rb-Sr、40Ar-39Ar年龄测定

用含金石英脉流体包裹体Rb-Sr和⁴⁰Ar-³⁹Ar方法测定了广东高凤金矿的形成时代为印支期(215×10⁶a)。两种方法的结果在误差范围内完全一致，两种测定方法相互验证，结果准确可靠。研究表明含金石英脉流体包裹体Rb-Sr和⁴⁰Ar-³⁹Ar年代方法对于解决石英脉型金矿的成矿时代具有很好的应用前景。