Geochemical Mapping: With Special Emphasis on Analytical Requirements     

XIE Xuejing  CHENG Hangxin  LIU Dawen 《《地质学报》英文版》2008,82(2):451-462

More than 40 national and regional geochemical mapping projects in the world carried out from 1973 to 1988 do not conform to common standards. In particular they have many analytical deficiencies. In the period 1988 to 1992, the International Geochemical Mapping project （Project 259 of UNESCO＇s IGCP Program） prepared recommendations designed to standardize geochemical mapping methods. The analytical requirements are an essential component of the overall recommendations. They included the following： 71 elements should be analyzed in future mapping projects; the detection limits of trace and ultratrace elements must be lower than the corresponding crustal abundances; and the Chinese GSD and Canadian STSD standard sample series should be used for the correlation of global data. A proposal was also made to collect 5000 composite samples, at very low sampling densities to cover the whole Earth＇s land surface. In 1997 an IUGS Working Group on Global Geochemical Baselines was formed to continue the work which began with IGCP 259. From 1997 up to now, new progress has been made especially in China and FOREGS countries under the aegis of this working group, including the study of suitable sampling media, development of a multi-element analytical system, new proficiency test for selection of competent laboratories and role of wide-spaced mapping in mineral exploration. One of the major problems awaiting solution has been the inability of many laboratories to meet the IGCP recommendations to generate high quality geochemical maps. Fortunately several laboratories in China and Europe have demonstrated an ability to meet the requirements and they will be well placed to render technical assistance to other countries.  相似文献   

斜坡非饱和带低渗透岩石结构体风化前锋扩展过程   总被引：2，自引：0，他引：2  

徐则民 《地学前缘》2008,15(4):258-268

非饱和带低渗透岩石结构体风化前锋扩展是斜坡灾害孕育过程中的关键环节之一。到目前为止,化学风化领域的研究成果主要集中在高水-岩比的饱和环境下单矿物及矿物成分单一的碳酸盐岩的风化动力学方面,非饱和环境下的岩石风化研究还主要限于风化产物的特性描述方面。斜坡非饱和带低渗透岩石结构体风化前锋扩展是一种高度复杂的THMC过程。由于在溶解对象、溶解液及溶解过程的水动力-水化学环境等方面存在的显著差异,既有的地质材料风化动力学成果为探索这一复杂过程提供了理论储备,但还不能阐明其核心机理。斜坡非饱和带低渗透岩石结构体风化前锋的扩展过程研究不仅可以加深人们对斜坡灾害孕育的理解,为灾害预报-预警及其控制提供理论依据,同时可以促进岩石-岩体力学及浅表生水文地球化学等相关学科的交叉与发展。  相似文献   

邹平火山岩盆地铜矿地质成因地球物理特征探讨     

王聿军  ;汤立成 《山东地质》2008,(9):19-23

邹平铜矿处于齐河-广饶深大断裂带南部的邹平火山岩盆地中,形成于破火山口火山通道充填的石英正长闪长岩岩颈中央上部,包括伟晶岩型铜矿和细脉浸染状斑铜矿床两种类型。前者矿体较小,但品位高;后者品位较低,但规模中等。含矿石英正长闪长岩等密度小、磁性弱,故在火山岩系中呈现高背景重力场上的重力低和杂乱高磁场背景中的低负异常,即“重磁同低”,且高极化。重磁同低异常区和高极化率异常带,是本区寻找铜矿的有利部位。  相似文献   

箕状断陷湖盆缓坡带层序地层格架内成岩特征研究——以东营凹陷南部缓坡带沙河街组为例   总被引：1，自引：0，他引：1       下载免费PDF全文

董永志  田景春  张世平  谭先锋  孟万斌 《沉积与特提斯地质》2008,28(3):46-51

东营凹陷在沙河街组沉积期为北陡南缓的箕状断陷湖盆。通过钻井岩心、测井、薄片及扫描电镜分析,在断陷湖盆的南缓坡带古近系沙河街组中识别出了冲积扇、河流、三角洲和湖？白沉积体系,以及滨浅湖砂坝和缓坡远端浊积扇沉积相。建立了东营凹陷南部缓坡带层序地层格架及层序演化模式。在此基础上,详细研究了层序地层格架内的成岩作用特征。层序地层格架内主要成岩作用类型有压实作用、压溶作用、溶解作用等,成岩阶段为早成岩A、B期,晚成岩A、B期。层序地层格架内发育了碳酸盐胶结、石英次生加大、高岭石胶结和泥岩压实四种成岩相。  相似文献   

Mesozoic-Cenozoic tectonics and geodynamics of Altai, Tien Shan, and Northern Kazakhstan, from apatite fission-track data     

M.M. Buslov  D.A. Kokh  J. De Grave 《Russian Geology and Geophysics》2008,49(9):648-654

Apatite fission-track (AFT) thermochronological modeling as a diagnostic tool for periods of stability (peneplanation) and tectonic activity (orogeny) has been broadly used in tectonic studies of Central Asia in recent years. We discuss more than 100 AFT ages of samples from the Kyrgyz Tien Shan and Altai and compare them with AFT data from northern Kazakhstan. Geological, geomorphological, and AFT data indicate intense activity in the Late Cenozoic Eurasian continental interior. The impact from the India-Eurasia collision on the northern Tien Shan, Altai, and northern Kazakhstan regions showed up at 11, 5, and 3 Ma, respectively, as a result of stress propagation into the continent, with the ensuing reactivation and mountain growth. We hypothesize that a distant effect of the Late Cenozoic India-Eurasia collision was to rejuvenate Paleozoic fault zones and to deform the Mesozoic sedimentary cover north of the collision front as far as the West Siberian Plate. The reactivation facilitated formation of tectonic oil and gas traps. The activity in northern Central Asia under the effect of the Indian indentation into Eurasia appears to continue and may evolve to include uplift of southern West Siberian plate with uplift.  相似文献   

Recommended Values of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu Concentrations in Reference Material IAEA-315 (Marine Sediment) Estimated by Thermal Ionisation Mass Spectrometry, Inductively Coupled Plasma-Mass Spectrometry and Alpha Spectrometry     

Taeko Shinonaga  Helmuth Aigner  Dilani Klose  Peter Spinder  Heinz Fröschl  David Donohue 《Geostandards and Geoanalytical Research》2008,32(1):93-101

The recommended concentrations of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu in reference material IAEA‐315 (marine sediment) were estimated by three analytical methods: isotope dilution thermal ionisation mass spectrometry (TIMS), isotope dilution inductively coupled plasma‐mass spectrometry (ICP‐MS) and alpha spectrometry. The determination of ²³⁹Pu and ²⁴⁰Pu (^239+240Pu by alpha spectrometry) was carried out with samples from randomly selected bottles using each method. Plutonium‐238 was also measured by alpha spectrometry. A plutonium‐242 reference material was used as a spike for the quantitative analysis. The influence of ²⁴²Pu in the samples was therefore calculated; however, this contribution was less than the range of uncertainty and did not influence the final results. The obtained data were statistically analysed using variance component analysis and paired comparison. The combined standard uncertainties from “method/measurement”, “bottle” and “sub‐sample” were in the order of 3 to 6%. The main contributions to the uncertainty were from the material heterogeneity and from systematic differences between methods. Based on this study with twenty‐seven analyses using 10–14 g sample mass, concentrations of (38 ± 3) Bq kg^?1, (28 ± 3) Bq kg^?1 and (66 ± 4) Bq kg^?1 are proposed as recommended values for ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu, respectively, and (9.5 ± 0.4) Bq kg^?1 for ²³⁸Pu as an information value in reference material IAEA‐315. In mass concentration units, these amount to (16.4 ± 1.2) ng kg^?1, (3.3 ± 0.4) ng kg^?1 and (0.015 ± 0.003) ng kg^?1 for ²³⁹Pu, ²⁴⁰Pu and ²³⁸Pu, respectively. The certified reference materials NIST 4350B and NIST 4354 were also analysed by TIMS for quality assurance of the method used in this study.  相似文献   

塔里木盆地塔中低凸起地层水化学特征对不整合的响应          下载免费PDF全文

曾溅辉  吴琼  钱诗友  孔旭  马中良 《古地理学报》2008,10(5)

对塔中低凸起地层水化学特征与不整合之间关系的研究结果表明,地层水化学特征对不整合具有很好的响应。在遭受强烈抬升和剥蚀、之间形成不整合的奥陶系和志留系,以及紧靠不整合面附近的石炭系CⅢ油组,其地层水具有矿化度、Cl-含量、K Na 含量和r(Cl-Na)/rMg值相对较小,而HCO3-含量、rNa/rCl值和rSO42-×100/rCl值相对较大的特点,反映出地质历史时期大气降水的影响。在志留系与石炭系之间以及志留系与奥陶系之间的不整合面附近,地层水的矿化度、r(Cl-Na)/rMg值和B3 含量变小,而rNa/rCl值和rSO24-×100/rCl值变大,具有典型的遭受大气淋滤的地层水化学基本特征。  相似文献   

Springs of Great Britain     

J. B. W. Day 《Environmental Geology》1996,27(2):77-78

Predictably, in a country such as Britain, with its preponderance of consolidated, sedimentary, mainly fissure-flow aquifers, there is a very large number of springs, many of which are, or have been, used for public supply. Migratory springs are a feature of the British (Ur. Cretaceous) Chalk, the most important British aquifer. The Chalk's low specific yield and high capillary moisture retention together give rise to very considerable fluctuations (more than 33 m in some areas) of the unconfined water table. Along the gentle dip slopes of the Chalk (North and South Downs of southern and southeastern England) springs may migrate laterally for several miles, giving rise to seasonal streams locally known as bournes or lavants. However, springs such as at Duncton, West Sussex, at the base of the much steeper scarp slopes of the Chalk, form point sources, the flows from which tend to be relatively steady; such springs commonly supply and are the original reason for the existence of many of the small towns and villages which nestle along the bases of the chalk scarps of Sussex and Kent.Where the Chalk forms coastal cliffs, a number of springs break out at the base of the cliff between high and low tide levels; there are major chalk coastal springs, for instance, at St. Margaret's Bay (Kent) and at Arish Mells, east of Lulworth Cove, Dorset. Such springs are not used for direct supply (their salinity is usually too high) but are indicators of the presence of local reserves of groundwater for possible future development.  相似文献   

Comparison of two methods for seismic hazard assessment in a low-seismicity area     

Th. De Crook  J. J. Egozcue 《Natural Hazards》1992,6(1):39-49

The EGO method, developed by Egozcue et al. and the SRAMSC method, originally developed by Cornell and later programmed by McGuire, to assess the seismic hazard, are compared for the low seismicity area Belgium, The Netherlands, and NW Germany. Using the same input data, the results of the EGO method without the majority criterion and the SRAMSC method with upper bound XII agree very well. The influence of the zoning is investigated for the EGO method. It is not necessary to define the zones for the EGO method so strictly as for the SRAMSC method, but too wide zones can give bad results.  相似文献   

浅变质岩区地层特征及地层单位探讨   总被引：2，自引：0，他引：2  

袁鄂荣 《地球科学》1990,15(2):137-144,T001

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