中国大陆科学钻探主孔自然放射性测井及其解释

为了认识江苏东海超高压变质带上地壳岩石自然放射性的垂向分布特征, 榴辉岩退变质程度对放射性元素浓度的影响, 以及放射性产热率对地温梯度的影响, 利用中国大陆科学钻探(CCSD) 主孔100~5000m自然放射性测井(自然伽马和自然伽马能谱) 资料统计了CCSD主孔各类岩石的自然放射性强度和铀、钍、钾元素的浓度, 计算出产热率曲线.自然伽马, 铀、钍、钾浓度和产热率从蛇纹岩到榴辉岩、角闪岩、副片麻岩、正片麻岩依次增大.随着榴辉岩退变质程度的增强, 其铀、钍、钾元素的浓度值逐渐增大.CCSD主孔自然放射性的垂向分布特征主要受岩性控制, 自然放射性随深度增加有增强趋势.产热率与自然伽马测井值之间有很好的线性关系, 在高放射性岩层的上部, 地温梯度会出现较强扰动和低值异常.      

Investigation of natural background radiation of sediments in Rameswaram Island,Tamil Nadu,India

The aim of the study is to assess the natural background radiation in and around Rameswaram Island. In this context, samples were collected to measure the gamma radiations of ²³⁸U, ²³²Th, and ⁴⁰K using NaI(Tl) detector-based gamma ray spectrometer. The average activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are noted to be well below the world average values. The calculated absorbed dose rate, radium equivalent activity, and hazard index values were below the prescribed limit. The grain size of the sediment was analyzed following Trefethen’s nomenclature, and its correlation with the natural background radioactivity was studied. The sample that contained clay show elevated activity of ⁴⁰K. The percentage of heavy minerals shows concomitant variation in natural radioactivity, especially in the activity of ²³⁸U and ²³²Th.     

青岛市地表天然放射性水平及其主控因素特征

通过对青岛市1500km^2范围内大密度土壤放射性核素（^238U、^232Th和^40K）和地表γ辐射测量,系统深入地研究了其放射性特征、分布规律及其影响因素。结果表明,青岛市土壤中核素^232Th和咏的放射性比活度偏高,而^238U偏低。地表γ辐射吸收剂量率（平均值91．87nGy·h^-1）略高于全国和世界平均值,研究发现地表93．14％的γ辐射来自地面放射性核素^238U、^232Th和^40K）的．γ辐射,其中^232Th和^40K的贡献占81．21％,是主要的贡献者。地质背景是影响地面γ辐射吸收剂量率的主要因素,燕山期各类花岗岩是导致青岛市区-王哥庄-带γ辐射吸收剂量率偏高的主要原因;同时环境因素（路面材料、地貌景观）对地表γ辐射吸收剂量率也存在一定影响。虽然研究区的γ辐射吸收剂量率较高,但其年有效剂量（0．56 mSv）远低于公众照射年剂量当量限值1.0 mSv,人居环境基本不受影响。     

Spectral gamma‐ray logs and palaeoclimate change? Permian–Triassic,Persian Gulf

Spectral gamma ray (SGR) logs are used as stratigraphic tools in correlation, sequence stratigraphy and most recently, in clastic successions as a proxy for changes in hinterland palaeoweathering. In this study we analyse the spectral gamma ray signal recorded in two boreholes that penetrated the carbonate and evaporate‐dominated Permian–Triassic boundary (PTB) in the South Pars Gasfield (offshore Iran, Persian Gulf) in an attempt to analyse palaeoenvironmental changes from the upper Permian (Upper Dalan Formation) and lower Triassic (Lower Kangan Formation). The results are compared to lithological changes, total organic carbon (TOC) contents and published stable isotope ( δ ¹⁸O, δ ¹³C) results. This work is the first to consider palaeoclimatic effects on SGR logs from a carbonate/evaporate succession. While Th/U ratios compare well to isotope data (and thus a change to less arid hinterland climates from the Late Permian to the Early Triassic), Th/K ratios do not, suggesting a control not related to hinterland weathering. Furthermore, elevated Th/U ratios in the Early Triassic could reflect a global drawdown in U, rather than a more humid episode in the sediment hinterlands, with coincident changes in TOC. Previous work that used spectral gamma ray data in siliciclastic successions as a palaeoclimate proxy may not apply in carbonate/evaporate sedimentary rocks. Copyright © 2014 John Wiley & Sons, Ltd.     

含金破碎蚀变带地面伽玛能谱特征——以吉林伊通新家地区为例

放射性方法是重要的地球物理勘查方法之一.本文以吉林省中部伊通新家地区为例,讨论了一定地质条件下含金破碎蚀变带的地面伽玛能谱特征和放射性异常组合型式,提供了放射性方法应用于金矿勘查的一个实例     

青岛市地表伽玛辐射特征及环境影响评价

对青岛市1 500 km 2范围内大密度土壤放射性核素和地表γ 辐射测量,系统深入研究了其放射性特征、分布规律及其影响因素。结果表明,青岛市土壤中核素232 Th 和40 K 的放射性比活度偏高,而238U 偏低。地表γ 辐射剂量率( 平均值91. 87 nGy /h) 略高于全国和世界平均值。研究发现,地表 93. 14%的γ 辐射来自地面放射性核素238U、232 Th 和40K 的γ 辐射,其中232 Th 和40K 的贡献占81. 21%,是主要的贡献者。地质背景决定地面γ 辐射剂量率值,燕山期各类花岗岩是导致青岛市区-王哥庄一带γ 辐射剂量率偏高的主要原因; 同时环境因素( 路面材料、地貌景观) 对其剂量率也存在一定影响。虽然研究区的γ 辐射剂量率较高,但其年有效剂量( 0. 56 mSv) 低于公众照射年剂量当量限值 ( 1. 0 mSv) ,人居环境基本不受影响。     

Radioactive occurrence in sediments of Cenozoic age near Bandha village,Jaisalmer district,Rajasthan

The radioactivity is dependent on the isotope and their concentration in the mineral such as potassium (K), uranium (U) and thorium (Th). In this paper the presence of a 3 to 5 m thick uranium and thorium bearing sediment of Cenozoic age is reported above Goru Formation of Jaisalmer basin. Gamma ray log response of Well-1 which falls under the study area has marked with very high GR (gamma ray) readings ranging from 350-1488 API coupled with high uranium and thorium content from spectral gamma ray log ranging from 92-178 ppm and 60-80 ppm respectively at the depth of 50 m from ground surface (-110m above MSL). Further studies are required to delineate the lateral thickness variation for mining purpose which may be a radioactive source.     

Characterisation of Memory Effects and Development of an Effective Wash Protocol for the Measurement of Petrogenetically Critical Trace Elements in Geological Samples by ICP-MS

High sensitivity and low detection limits would seem to make inductively coupled plasma-mass spectrometry (ICP-MS) an ideal analytical tool for determining low (sub-μg g^-1) concentrations of the rare earth elements (REE), Y, Zr, Nb, Hf, Ta, Sn, W, Mo, Th, and U in most mafic materials (e.g. Hall and Plant 1992). However, the generally "sticky" nature exhibited by most of the high field strength elements (HFSEs: Zr, Nb, Hf, Ta, Th and U) as well as Sn, W and Mo can result in spurious results due to memory effects transmitted between unknowns and calibration samples. This, in turn, can seriously compromise the sensitivity, accuracy, and precision of ICP-MS analyses for these elements in geological materials. Data resulting from analyses with poor accuracy and precision can lead to erroneous interpretation and misleading petrogenetic modelling. To resolve this problem, we propose an effective wash protocol for these critical trace elements.     

238U, 232Th profiling and U-series isotope analysis of fossil teeth by laser ablation-ICPMS

U and Th concentration profiles in fossil hominid and faunal teeth have been measured by laser ablation ICPMS. These profiles record diverse modes of U and Th uptake, particularly within enamel, that can be broadly related to the state of sample preservation. Observed U profiles are in general inconsistent with existing diffusion–adsorption models developed for U-uptake in bone and teeth. Where the models appear applicable, calculated diffusion rates are several orders of magnitude smaller than previous estimates. Laser ablation ICPMS offers a means of rapidly characterizing U and Th distributions in the enamel and dentine components of teeth as a precursor to ESR and U-series dating. In particular, it should allow the identification of teeth (and also bone) samples that have simple U-uptake histories and are amenable to precise dating by time-consuming and expensive Th–U and Pa–U TIMS techniques. We also demonstrated the use of laser ablation ICPMS to measure U-series isotopes in dentine and enamel samples with relatively high U concentrations (>20 ppm). These results, obtained using a quadrupole ICPMS, illustrate significant promise for in situ U-series isotope analysis, particularly when combined with the greater sensitivity and multi-collection capabilities of new sector ICPMS instrumentation. The latter may permit precise isotope ratio measurements on samples containing only a few ppm of U.     

X射线荧光光谱法同时测定土壤样品中的36种组分的探讨

采用粉末压片法制样,使用新型X射线荧光光谱仪,对土壤样品中的C、N、S、Cl、Na、Mg、Al、Si、K、Ca、Fe、As、Ba、Br、Ce、Co、Cr、Cu、Ga、Hf、La、Mn、Nb、Ni、P、Pb、Rb、Sc、Sr、Th、Ti、U、V、Y、Zn、Zr等36种组分的直接同时测试进行了探讨测试。研究了测试中各种分析条件及存在问题。结果表明,方法的检出限、精密度和准确度大多数满足多目标地球化学调查样品分析质量的要求,标准物质的测定值与其标准值相吻合,适合土壤样品中多组分的同时直接测定。     

平面型高纯锗低能γ谱仪测定铀矿样中^235U,^238U,^226Ra及^232Th含量

本文对选用低能γ射线测定铀矿中的~(235)U、~(238)U、~(226)Ra、~(232)Th含量进行了讨论,提出了一种对样品进行自吸收校正的简单准确方法,对铀矿样中的~(235)U、~(238)U、或~(235)U/~(238)U比值测定获得了较高的分析精度和准确度。     

Aspects of U-Th fractionation in Tertiary limestones and calcretes of Dhofar,southern Oman

This paper presents findings from a comprehensive geochemical and geophysical re-examination of known radiogenic anomalies in Tertiary limestones and (sub-)recent calcretes of southwestern Dhofar in the Sultanate of Oman. U-Th-enrichments seem to be associated with deep-rooted fault systems that cross-cut C_org-rich shales at depths of some 800–1000?m, which generally show elevated gamma-ray levels in southern Oman and act as the initial geochemical trap. Metals and radiogenic elements, such as K (max?1945?ppm), U (max?44?ppm), and Th (max?26?ppm) mobilised from these rocks and emplaced higher up in the faults must have constituted radiogenic lineaments at and near the surface (observed in a different but difficult to access location). However, successive weathering partially obscured such anomalies through further re-mobilisation/-mineralisation processes within the calcretes that also enriched Sr and V. In these carbonates, uranium correlates positively with Sr but not very well with V, while thorium shows moderate positive correlations with Sr and V. Both U and Th are also not present (i.e., below the detection limits of a few ppm) in a second sample group that represents background conditions. Being much more immobile than U, Th remained closer to the original western fault positions of the examined site (outlined by magnetics and VLF-EM during the surveys), while uranium moved down-dip over the plateau and through underlying sub-horizontal strata towards the eastern fault system. Here, supergene Sr-enriched calcite preferentially incorporated U, thus reflecting the observed U-Th fractionation.     

中东T油田灰岩储层自然伽马能谱测井的应用

中东地区T油田主力含油储层受高放射性物质影响,导致利用常规自然伽马测井资料无法合理求取泥质含量。同时,由于岩芯分析资料较少,确定各主力含油储层的黏土类型就显得比较困难。针对这些问题,笔者基于自然伽马能谱测井中铀、钍、钾与地层中黏土矿物的密切关系,利用无铀伽马测井资料对泥质含量进行了合理计算,参考斯仑贝谢理论交会图版,利用钍与钾交会图法确定了黏土类型,通过制作钍与铀比值的直方图对沉积环境进行了研究,取得了较好的应用效果,为油田后期的开发提供了更加可靠的资料支持。     

伽玛能谱测量比值参数的地质学意义及其在寻找隐伏金矿床上的应用

用伽玛能谱测量找金,主要是通过研究铀、钍和钾3种元素在土壤和岩石中的分配、分布与金矿成矿地质条件及金矿近矿围岩蚀变的关系,总结出作为间接找金的伽玛能谱标志,用来进行同类地质条件地区的找金预测.通过对伽玛能谱测量的物理学和地质学阐述,解释了能谱比值参数的地质意义、总结了在团山子地区预测隐伏金矿体的复合参数特征,并通过矿点外围的钻探得到了很好的验证.     

Well log data analysis for lithology and fluid identification in Krishna-Godavari Basin,India

Well log analysis provides the information on petrophysical properties of reservoir rock and its fluid content. The present study depicts interpretation of well log responses such as gamma ray, resistivity, density and neutron logs from six wells, namely W-1, W-2, W-9, W-12, W-13 and W-14 under the study area of Krishna-Godavari (K-G) basin. The logs have been used primarily for identification of lithology and hydrocarbon-bearing zones. The gamma ray log trend indicates deposition of cleaning upward sediment. Coarsening upward, clayey-silty-sandy bodies have been evidenced from the gamma ray log. Gas-bearing zones are characterised by low gamma ray, high deep resistivity and crossover between neutron and density logs. Total 14 numbers of hydrocarbon-bearing zones are identified from wells W-9, W-12, W-13 and W-14 using conventional log analysis. Crossplotting techniques are adopted for identification of lithology and fluid type using log responses. Crossplots, namely P-impedance vs. S-impedance, P-impedance vs. ratio of P-wave and S-wave velocities (Vp/Vs) and lambda-mu-rho (LMR), have been analysed to discriminate between lithology and fluid types. Vp/Vs vs. P-impedance crossplot is able to detect gas sand, brine sand and shale whereas P-impedance vs. S-impedance crossplot detects shale and sand trends only. LMR technique, i.e. λρ vs. μρ crossplot is able to discriminate gas sand, brine sand, carbonate and shale. The LMR crossplot improves the detectability and sensitivity of fluid types and carbonate lithology over other crossplotting techniques. Petrophysical parameters like volume of shale, effective porosity and water saturation in the hydrocarbon-bearing zones in these wells range from 5 to 37%, from 11 to 36 and from 10 to 50% respectively. The estimated petrophysical parameters and lithology are validated with limited core samples and cutting samples from five wells under the study area.     

X射线荧光光谱法同时测定土壤样品中碳氮等多元素

报道了采用粉末压片制样-X射线荧光光谱法测定土壤样品中C、N、S、Cl、Br、Hf、Mo、Sn、Se、Na、Mg、Al、Si、P、K、Ca、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、As、Rb、Sr、Y、Zr、Nb、Ba、La、Ce、U、Th、Pb等38种元素的分析方法。着重研究了C和N的分析条件、存在问题和注意事项。所拟方法的检出限，精密度和准确度大多数满足覆盖区多目标地球化学调查样品分析质量的要求。     

随钻脉冲中子-伽马密度测井响应数值模拟

随钻过程中采用D-T可控中子源和2个NaI晶体探测器系统,记录两个探测器的非弹性散射和俘获伽马射线,采用俘获伽马计数比值进行含氢指数校正后,建立非弹性散射伽马计数比和地层密度的响应关系,从而实现脉冲中子-伽马密度测井.利用蒙特卡罗方法模拟地层条件下非弹性散射和俘获伽马分布,得到非弹伽马计数与地层密度和含氢指数都有关,但近、远探测器俘获伽马计数比反映含氢指数灵敏度高,利用其对含氢指数校正后就可以得到非弹伽马计数与地层密度的关系;通过二元回归方法得出地层密度校正后的响应公式,校正后视密度和真密度值相差很小.研究结果表明,在随钻过程中利用脉冲中子伽马测井方法可以确定地层密度.      

U and Th zonation in Fish Canyon Tuff zircons: Implications for a zircon (U-Th)/He standard

The inability to accurately determine the distribution of U and Th in zircon crystals analysed using (U-Th)/He is a major source of error, and limits the confidence in subsequent data interpretation. The Fish Canyon Tuff (FCT) zircon standard shows (U-Th)/He age reproducibility in excess of ±10%. We have tested the extent to which this is due to U and Th zonation using a combination of cathodoluminescence and ion probe analysis of a population of FCT zircons. Primarily we find that FCT zircons exhibit extreme U and Th zonation, and the population has large inter-crystalline variability. Furthermore, the net cathodoluminescence intensity from the FCT zircons is negatively correlated with U and Th concentration, allowing cathodoluminescence emission to be used as a proxy for U and Th zonation. This correlation was exploited to constrain the U and Th zonation within the crystal population, and to show that the poor age reproducibility of the FCT zircons is consistent with the observed zonation.     

引绰济辽工程文得根引水隧洞放射性调查评价

对长约70 km引水工程洞线上进行的地面伽马能谱测量、陆地伽马剂量率测量、土壤氡浓度测量、岩石表面氡析出率测量以及钻孔岩芯样品的放射性元素U、Ra、Th、K含量分析的综合放射性地质调查,并对获得的测量数据进行分析研究。结果表明,测区引水沿线地质体放射性核素当量含量平均值为：U 1.56×10-6,Th 14.12×10-6,K 2.16×10-2;钻孔岩芯放射性元素分析含量平均值为：U 32.34 Bq/kg,Ra 35.68 Bq/kg,Th 35.29 Bq/kg,K 865.65 Bq/kg。陆地伽马剂量率为90.42 nGy/h;土壤氡浓度平均值为4 272.1 Bq/m3;岩石表面析出率平均值为4.01×10-2 Bq/m2·s。根据测量结果,利用内照射和外照射辐射剂量计算了对施工人员造成的辐照剂量为0.759 mSv,低于国家对公众的剂量限值1 mSv/a,表明引水工程输水隧洞的施工在安全辐射范围内。     

Uranium series disequilibrium in young lacustrine sediments from an arid environment at Henkries,Republic of South Africa

Uranium adsorbed on to carbonaceous material and clays, and in minerals (boltwoodite, carnotite, zippeite), is present in a lacustrine deposit from an arid environment of southern Africa. Granites in the area, which may contain up to 50 ppm U₃O₈, are believed to be the original source for the U mineralization. The U is concentrated selectively in certain strata which are characterized by high diatomaceous earth and carbonaceous contents, high moisture contents, low densities, and considerable porosity.Activities of the ²³⁸U series nuclides (²³⁸U, ²³⁴U, ²³⁰Th and ²²⁶Ra) were determined by alpha spectrometry and indicate: (1) the deposit is geologically young; and (2) disequilibrium among nuclides in the U series is prevalent at present. Because of this disequilibrium between U and its daughter products, there is no correlation between U₃O₈ determined by chemical analysis and that inferred from radiometric methods based on gamma ray spectrometry (eU₃O₈); in some cases chemical U₃O₈ is higher than eU₃O₈ inferred from gamma ray spectrometry whereas in other cases the reverse is true. In order to evaluate the deposit, all drill core, and trench and pit samples were analysed by X-ray fluorescence. At this time, movement of U and its daughter elements appears to be an active process, particularly in those layers which are porous and have a high moisture content. Paleoclimatic studies have shown that alternating pluvial and arid periods existed in the last 40 000 yr in southern Africa. These would result in fluctuations in the water table sufficient to cause selective relative migrations of ²³⁸U series nuclides thus accounting for at least some of the observed disequilibrium.