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1.
Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California 总被引：2，自引：1，他引：1
Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks. 相似文献
2.
对安徽东至县铁炉地区开展了放射性污染调查工作,并提出了防治方案和治理措施。其方法是采用6台FD-3013γ辐射仪、1台FD-3022N道γ谱仪和1台FD-3017氡射气仪对该地区进行大比例尺地面γ辐射剂量率、地面γ能谱、水中氡浓度等测量。获得了该地区γ辐射剂量率为0．11～4.38μGy/h;铀质量活度为123-1 230Bq／kg,钍质量活度为21-411 Bq/kg,钾质量活度为264-528Bq／kg;水中铀活度浓度为4-12 300 Bq／L,水中氡活度浓度为2-155Bq／L;剥露的岩矿、矿渣中铀质量活度为1230-151 290 Bq／kg,钍质量活度为25-411 Bq／kg。该地区地面γ辐射剂量率、地层中铀、钍质量活度均高于安徽省平均值,而剥露的岩矿、矿渣中铀质量活度远大于地层中的铀质量活度,是该地区环境中最大的潜在污染源之一,并为此提出了4项治理措施。 相似文献
3.
大别山地面γ能谱资料的统计分析及其铀成矿信息 总被引：2，自引：2，他引：0
用GAD－6型4道γ能谱仪对大别造山带各地质体进行了地面γ能谱测定,获1324组eU,eTh,K含量数据。根据113组中子活化分析数据对能谱资料进行了质量检验。在计算能谱特征参数的基础上,将富铀钍地质体划分为铀源体、富铀体和含铀体,并探讨了其空间组合特征及其与铀成矿的关系。 相似文献
4.
S. I. Demidova M. A. Nazarov M. O. Anosova Yu. A. Kostitsyn Th. Ntaflos F. Brandstaetter 《Petrology》2014,22(1):1-16
Dhofar 1442 is one of the few lunar KREEP-rich meteorites, which contains KREEP norites and KREEP gabbronorite as well as low-Ti basalts and highly evolved granophyres. Zircon is a typical accessory mineral of KREEP rocks. U-Th-Pb dates of 12 zircon grains (four of them were in two lithic clasts, and the others were fragments in the meteorite matrix) indicate that the zircons belong to at least two groups of different age: “ancient” (～4.31 Ga) and “young” (～3.95 Ga), which correspond to two major pulses of KREEP magmatism in the source region of the Dhofar 1442 meteorite. The zircon of the “young” group was most probably related to the crater ejecta of the Mare Imbrium Basin. The rock fragments dated at approximately 3.95 Ga have the composition of KREEP gabbronorite. The parental rocks of the zircon of the “ancient” group in the Dhofar 1442 meteorite are uncertain and could be highly evolved granophyres. This hypothesis is supported by the high Th (100–300 ppm) and U (150–400 ppm) contents. These zircon fragments of the “ancient” group, higher than in the “young” group (<50 ppm Th and <70 ppm U) and are typical of zircon from lunar granitic rocks. The composition of the products of KREEP magmatism in the source region of the Dhofar 1442 meteorite could vary from predominantly granitic to KREEP gabbronoritic at 4.3–3.9 Ga. 相似文献
5.
6.
CE-1伽马能谱测量中4种月球岩石的能谱特征分析 总被引：1，自引：0，他引：1
从CE-1 γ能谱测量获得的数据出发,对原始数据进行处理,将原始谱线按每5°×5°网格内平均而获得月表上的γ能谱数据。选取了12条不同位置分别代表玄武岩、斜长岩、富镁岩和KREEP岩的能谱曲线进行分析,发现同一岩性的谱线具有相似性。通过对每种岩性选择的一条谱线进行分析可知,不同的岩性能谱曲线有一定的差别,表现为不同岩性在元素特征能谱峰的变化不同,玄武岩的能谱曲线特征峰主要的元素为Th、K、Si、Ca、C、Fe和Ti;斜长岩的能谱曲线特征峰主要元素为U、Ca、C、Mg、Al和Mn。KREEP岩的能谱曲线特征峰主要为K、Th、U、Si、Ca和Fe,而低C和Al;富镁岩能谱曲线表现为低U、Si、Ca和Cl而高K、Mg、Th和Fe含量特征。文中给出了能较好区分不同岩性的元素特征峰能量,可为月表γ能谱的定量分析奠定基础。 相似文献
7.
Rare Earth Elements in Coal-Bearing Deposits: Distribution Features and Geochemical Significance 总被引：1，自引：0，他引：1
The examination of Lower Cretaceous coals and clayey fractions of terrigenous host rocks of the Zyryanka Basin has revealed a generally negative type of the relative REE distribution (with a predominance of LREE over HREE) and a similar behavior of Th and U. Analogous characteristics are typical for metamorphic and igneous rocks of intermediate composition dominating in the provenance. In terms of the concentration and distribution of REE, Th, and U coal-bearing terrigenous rocks of the Zyryanka Basin are close to Phanerozoic clays and silty sandstones of the Russian Platform, while coals of the Zyryanka Basin are similar to metal-free coals of various basins (Kizel, Pennsylvanian, and others). Average REE and Th contents in the studied coals are five times lower than those in host terrigenous rocks. The coals differ from these rocks by relatively elevated HREE concentrations largely due to adsorption mechanism of the HREE accumulation. Data obtained on the REE, Th, and U distribution in coals and clayey fractions of host rocks are of fundamental significance for the comparitive analysis of the behavior of these elements in metal-bearing coals of various basins. 相似文献
8.
航空伽玛能谱测量所提供的钾、铀和钍含量等放射性参数之间通常存在着显着的相关性,从而掩盖了一些有用信息。应用主分量分析方法可以从相关性强的多个观测变量中提取出少数几个互不相关的新变量,因此能克服上述不足之处。在CDM盆地中部地区应用主分量分析方法对航空伽码能谱数据解释的结果表明,该方法可用来协助进行岩性和构造填图,识别有利于铀矿和钾盐沉积的环境,可以建立铀和钾盐矿床的成矿模式,进行铀和钾盐成矿远景的预测。可见,在航空伽玛能谱测量中它很可能成为一种新的有潜力的解释技术。 相似文献
9.
A.O. Volynets M.M. Pevzner M.L. Tolstykh A.D. Babansky 《Russian Geology and Geophysics》2018,59(12):1577-1591
Based on the geochemical characteristics of the Miocene-Quaternary volcanic rocks of the Sredinny Range of Kamchatka, we divide it into northern and southern provinces; the latter comprises the “eastern”, “western”, and “central” flanks. We present new data on the composition of Neogene-Quaternary volcanic rocks in the southern part of the Sredinny Range of Kamchatka: Khangar and Icha volcanic massifs and Mt. Yurtinaya on the “western” flank, Bystrinsky and Kozyrevsky Ridges on the “eastern” flank, and Anaunsky Dol and Uksichan massif located in between. We show systematic differences in the composition of rocks from the “western” and “eastern” flanks. During the Neogene, a typical island-arc volcanism took place within the “eastern” flank. Quaternary volcanic rocks of this area have both island-arc and within-plate geochemical features. We propose to call rocks of this type hybrid rocks. Within the “western” flank, hybrid volcanism has been manifested since the Neogene, while typical island-arc rocks are not found. Magma generation processes on the “western” flank of the Sredinny Ridge are influenced by an enriched mantle source; the effect of fluid is less pronounced here as compared to the rocks of the “eastern” flank, where it is clearly traced. 相似文献
10.
伽马能谱测量在陆地伽马空气吸收剂量率评价中的应用 总被引：2，自引：2，他引：2
2002～200年,国内首次采用就地伽马能谱测量方法在广东珠海市进行了面积性测量,并用该方法定量解释求得的钾、铀、钍含量用Beck公式估算了地表1 m高处的吸收剂量率,同时用塑料闪烁体X-γ吸收剂量率仪在相同测点做了比对测量.2种方法对比结果(514个测点)显示很好的一致性,珠海市区实测吸收剂量率和伽马能谱估算吸收剂量率平均值分别为(145.07±26.5) nGy/h和(162.10±1.51) nGy/h,计算结果与实测结果的相对误差为11.74%. 相似文献
11.
应用美国S101图像处理系统,对山东水道—冯家幅能谱(U、K、Th、Tc)数据作了图像处理.能谱比值合成图像反映了原图件未显示的线性、环形构适、蚀变带等,其中一些环形构造与MSS图像上反映的环形构造一致.依据地质图件,应用能谱图像,详细划分岩性,圈定了构造、岩体和蚀变带,取得了满意的地质解译效果. 相似文献
12.
A radiometric survey on a sector of the Lipari volcanic island particularly affected by argillification due to hydrothermal processes was carried out. Preliminarily, on the basis of a wide set of field measurements over unaltered outcrops U and K distribution maps were obtained. The concentration of these radioelements increases with the degree of magma differentiation; the U and K content shows maxima (13.4 ppm and 3.7% on average, respectively) in the felsic materials, belonging to the youngest volcanic cycles, and minima (2.7 ppm and 2.0%) in the mafic rocks of the oldest cycles. The Th/U ratio insignificantly varies with magma differentiation and it equals 3.2. Laboratory measurements on volcanic products from altered zones were then used to identify radiometric anomalies related to hydrothermal processes. On the average, argillized rocks have radioactivity approximately five times lower than that measured in the unaltered volcanics. The Th/U ratio against U is rather uniform, whereas Th/K ratio is of the order of 3.6 in less altered rocks K > 0.2%) and it ranges from 7 to 11 in kaolin deposits having the largest depletion in potassium. 相似文献
13.
A. I. Malov 《Lithology and Mineral Resources》2013,48(3):254-265
Using the Severnaya Dvina Basin as an example, it is shown that information on the distribution of natural U isotopes in aquifers can be applied for practical estimation of the duration of interaction between groundwater and host rocks (age of groundwater). The proposed calculation method includes preliminary determination of the generalized calculated parameter (probability of the transfer of 234U excess to water) based on geological benchmarks, hydrodynamic calculations, and paleohydrogeological reconstructions. It is assumed that this probability is constant for aquifers composed of homogeneous rocks with certain lithological composition and oxidizing conditions for U. The obtained correlations are valid for a model, where water entering the aquifer lacks U. If it contains such U, the “transport” time, which is equivalent to the timing of respective concentrations and isotopic ratios in the aquifer unit, is determined and estimates of the “water-rock” interaction in the aquifer unit are corrected. 相似文献
14.
ZHAO Yingjun LIU Dechang Beijing Research Institute of Uranium Geology Beijing 《《地质学报》英文版》2000,74(2):381-383
This paper introduces how to use remote sensing images including Landsat (MSS and TM) andairborne radioactivity images to identify the type of rocks in the areas covered by vegetation. The relationship between light spectrum (Landsat MSS and TM) and energy spectrum (U, Th and K) is discussed on the basis of correlation analysis, and it is proven that there are correlations between the Landsat MSS or TM data and the U, Th and K. data. By using the fusion technique, new images were generated, which contain both the light spectrum and the energy spectrum information.Taking the Lucong basin as the study area, the present paper demonstrates the successful identification of various types of rocks using the fusion technique. Different types of rocks are represented by different colours on the new light-energy spectrum images, so that volcanic rocks of the Jurassic and Cretaceous periods can be discriminated. Another example, in the Lingquan basin in Northeast China, not only the different types of rocks are su 相似文献
15.
以柴达木盆地北缘的鱼卡煤田为例,对含煤地层中的各种岩性的测井响应特征进行分析,认为该区的地球物理特征属＂简单易区别＂型,即煤岩层的物性差异较大,物性条件较好,不同岩性在伽马-伽马、自然伽马、电阻率等测井曲线上的特征明显,根据曲线的变化幅度、峰值高低等曲线特征,可有效进行煤岩层划分与对比。根据实际测井解释成果,对侏罗系上统红水沟组、采石岭组、侏罗系中-下统大煤沟组的页岩段、上含煤段及下含煤段等标志层段的测井曲线组合特征进行了描述。 相似文献
16.
形成于印支期的大别造山带和周缘中生代盆地构成了一级源汇系统,其中位于造山带北缘的合肥盆地中生代地层发育,且以盆地南缘出露最好,这为盆山源汇系统研究提供了理想的沉积记录。笔者从合肥盆地南缘采集了10个砂岩样品和1个砾岩样品,进行锆石U/Pb (LA-ICP-MS)定年分析,获得了742个有效年龄(置信度不小于85%),范围为113±3. 6-2983 Ma。这些碎屑锆石年龄谱可以被分为5个年龄段:113-137 Ma,峰值131 Ma; 184-273 Ma,峰值226 Ma; 274-517. 3 Ma,具有2个峰值280 Ma和474 Ma; 532-856. 6 Ma,具有3个峰值572 Ma、649 Ma和772 Ma; 1786-2600 Ma,具有2个峰值2035 Ma和2506 Ma。同时,总结了物源区大别造山带不同单元锆石U-Pb年龄特征。根据锆石U/Pb年龄和Th/U值,发现这5个年龄段比较准确地记录了物源区地质体,分别是早白垩世的岩浆岩、大别山高压—超高压变质岩、北淮阳的浅变质岩、北大别的正片麻岩和卢镇关群变质岩。根据锆石最小年龄,修正了合肥盆地南缘中生代地层格架,为源汇系统研究确立了时间框架。合肥盆地南缘中生代沉积可以分为4个演化阶段:晚三叠世瑞替期—早侏罗世辛涅缪斯期、中—晚侏罗世、早白垩世早期和早白垩世晚期,并据此确定了每个阶段主要物源区特征及其时空变化。碎屑锆石U/Pb年龄和Th/U值限定了大别造山带仅存在三叠纪的超高压变质作用,且超高压变质岩折返到地表的最早时间是晚三叠世瑞替期,大别造山带大陆岛弧发育的时间是新元古代。上述研究结果不仅为恢复大别造山带构造古地理做出了新的贡献,而且更为盆山源汇系统研究提供了一个实例。 相似文献
17.
Sami Hamed Abd El Nabi 《Arabian Journal of Geosciences》2013,6(4):1249-1261
The radiometric responses of the Gebel (G., which means mountain in Arabic) Meatiq area display the overall high radiation of the high grade metamorphic Um Ba’anib granite gneiss, metasediments, as well as Arieki adamellite rocks. Whereas, the low grade metamorphic ophiolitic nappes country reveal the lowest radiometric response. The eU, eTh, and K contents tend to increase with the youthfulness of the plutons with a maximum amounts in the more alkali varieties, e.g., Arieki adamellite (580 Ma), then the high grade metamorphic rocks of the younger Meatiqian orogeny (626?±?2 Ma). Also, these rocks reveal that the major radiometric anomaly with exposure rates ≈139 nGy/h, more than double of the global terrestrial values. While, the low grade metamorphic ophiolitic rocks reveal the lowest average exposure rates ≈46.8 nGy/h. The areas of high gamma ray values of F-parameter of Efimov (K × U/Th), ternary composite map, K map, K/eTh, and K/eU ratios maps are related to K enrichment conditions during formation (diagenesis) or deformation of the high grade metamorphic rocks and the Arieki adamellite intrusion. From the geochemical point of view, these areas are associated with rocks that are characterized by high-K calc-alkaline, calc-alkaline affinity, and enriched in REE. 相似文献
18.
张广才岭帽儿山组双峰式火山岩成因: 年代学与地球化学证据 总被引：19，自引：0，他引：19
对张广才岭中生代帽儿山组火山岩进行了锆石LA-ICP-MS U-Pb 年代学和岩石地球化学研究,确定其时代及形成的构造背景。研究区内两个代表性火山岩中的锆石均呈自形-半自形晶,显示出典型的岩浆生长环带或条痕状吸收,结合其高的Th /U 比值( 0. 40 ～ 2. 08) ,暗示其岩浆成因。测年结果表明,研究区内所讨论的火山岩为早侏罗世( 179 ～ 184 Ma) 岩浆喷发的产物,而非前人认为的晚侏罗世; 此外,帽儿山组火山岩具双峰式组合的特点,粗面岩与粗面安山岩以富碱、高钾、高度富集大离子亲石元素和轻稀土元素为特征,而流纹岩显示A 型流纹岩特点。小兴安岭-张广才岭早侏罗世双峰式火成岩的存在,揭示该区早侏罗世处于一种强烈的伸展环境。结合区域该时期火成岩的空间展布特征,帽儿山组双峰式火山岩的形成应与太平洋板块向欧亚大陆下的俯冲作用相联系,形成于类似弧后盆地的伸展环境。 相似文献
19.
在总结松辽盆地北部三肇凹陷扶余油层和杨大城子油层地质特征的基础上,设计了烃源岩之下岩性油藏实验模型;通过物理模拟实验,再现了烃源岩之下岩性油藏的形成过程,对油气运移的受力状态进行分析,探讨了烃源岩之下岩性圈闭中油气聚集成藏的机制.实验结果及实例表明,该类油藏的形成须满足两个地质条件,即上覆优质烃源岩具有足够超压和有断裂沟通烃源岩与下伏砂体,超压是油气向下运移的动力,断裂则是其主要运移通道,这对寻找烃源岩之下岩性油藏具有重要的指导意义. 相似文献
20.
V. A. Kamzolkin A. V. Latyshev Yu. P. Vidyapin M. L. Somin A. I. Smul’skaya S. D. Ivanov 《Geotectonics》2018,52(3):331-345
The paper presents new data on the composition, age, and relationships (with host and overlying deposits) of intrusive rocks in the basement of the Fore Range zone (Greater Caucasus), in the Malaya Laba River Basin. The evolutionary features of intrusive units located within the Blyb metamorphic complex are described. It is shown for the first time that the lower levels of this complex are, in a structural sense, outcrops of the Late Vendian basement. The basement is composed of the Balkan Formation and a massif of quartz metadiorites that intrudes it; for the rocks of this massif, ages ranging from 549 ± 7.4 to 574.1 ± 6.7 Ma are obtained for three U–Pb datings by the SHRIMP-II method. The Herzyinan magmatic event is represented by a group of granodiorite intrusions penetrating the Blyb complex on a series of faults extending along its boundary with the Main Range zone. The obtained estimate for the U–Pb age of one of the intrusions (319 ± 3.8 Ma) corresponds to the end of the Serpukhovian stage of the Early Carboniferous. 相似文献