Neutron activation analysis of the rare earth elements in rocks from the earth's upper mantle and deep crust

Three techniques for analyzing rare earth elements (REE) in geological materials are described, i.e. instrumental neutron activation analysis (INAA), neutron activation analysis with pre-irradiation chemical REE separation (PCS-NAA) and radiochemical neutron activation analysis (RNAA). The knowledge of REE concentrations in eclogites, peridotites and minerals from the earth's lower crust and upper mantle is very useful in constraining their petrogenetic history.     

The non-destructive determination of REE in fossilized bone using synchrotron radiation induced K-line X-ray microfluorescence analysis

The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner provided the concentrations of individual REE are above 10 μg/g.     

The non-destructive determination of REE in fossilized bone using synchrotron radiation induced K-line X-ray microfluorescence analysis

The sensitivity and applicability of the synchrotron radiation induced X-ray microfluorescence (μ-SRXRF) spectrometer at the Hamburg synchrotron laboratory Hasylab for the determination of the distribution of trace concentrations of rare-earth elements (REE) in fossilized bone are discussed and critically compared to those of other trace analytical methods such as instrumental neutron activation analysis (INAA) and LAMP-ICPMS (laser ablation microprobe inductively-coupled plasma mass spectrometry). Measurements were carried out on two bone samples from contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania). Results indicate that the microdistribution of the REE in these biological materials is not homogeneous and that the relative abundance of these elements can provide information on the palaeoenvironment during the fossilization process. The heterogeneous distribution of the REE can be determined in a quantitative and completely non-destructive manner provided the concentrations of individual REE are above 10 μg/g. Received: 18 January 1998 / Revised: 6 October 1998 / Accepted: 10 October 1998     

Trace Rare-Earth Element analysis of briny groundwaters

Rare-Earth Element (REE) concentrations in briny groundwaters are very low, and range from ppb to ppt levels. REE can be measured at these low levels using prechemistry to concentrate the REE, postchemistry as an REE group separation following neutron activation, and reactivation for chemical yields. The brine solutions appear to be stable with respect to trace elements (such as the REE) over the four years of sample storage. The brine REE patterns are highly fractionated from light REE to heavy REE, including a negative Eu anomaly. The REE patterns appear to be characteristic of each formation and its source region.     

Trace element partitioning between phenocrysts of plagioclase,pyroxenes and magnetite and the host pyroclastic matrix

Up to 26 trace elements were determined in 9 different samples of plagioclase, orthopyroxene, clinopyroxene and magnetite and the host pyroclastic matrix material using instrumental neutron activation analysis. Mineral to whole-rock partition coefficients were reported and interrelationships between chemical composition and crystal structure of the minerals were discussed, especially in the case of REE in plagioclase.     

Determination of rare earth elements in international geochemical reference materials

Instrumental neutron activation analysis of eight geochemical standard materials has been carried-out and the concentration values of nine rare-earth elements (REE) (La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu) have been determined. Discussion of some problems in the determination of those elements is presented and the results obtained are compared with literature values. In general, good agreement with available data was obtained but discrepancies with concentration values for a number of elements in some of these standards are discussed.     

Elemental characterization of the new Czech meteorite ‘Morávka’ by neutron and photon activation analysis

Forty two major, minor and some trace elements were determined by activation analysis in the new Czech Morávka H5 chondrite, which fell on May 6, 2000 in the vicinity of Morávka, north-east Moravia. The elements Na, Mg, Al, Si, Cl, Ca, Ti, V, Mn, Co, Ni, and Cu were determined by means of instrumental short-time neutron activation analysis (INAA), whereas another group of elements, namely Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Sb, La, Sm, Ir, Au and Hg were assayed using long-time INAA. Most of the rare earth elements (REE) were determined by radiochemical neutron activation analysis (RNAA) using precipitation of their oxalates, whilst for the determination of Rb and Cs an RNAA procedure based on selective sorption of the elements on ammonium phosphomolybdenate was employed. Mg, Ca, Ti, Mn, Ni, Sr, Y and Zr were determined by instrumental photon neutron activation analysis (IPAA) using the irradiation with 20 MeV bremsstrahlung from a microtron. For quality control, the U.S. Geological Survey (USGS) reference rocks basalt BCR-1 and diabase W-1 were analyzed. Moreover, the self-verification principle in activation analysis was employed to increase the credibility of the obtained results.     

Provenance studies of obsidian artifacts: Trace elements analysis and data reduction

Iron and trace elements, such as rare-earth elements, scandium, rubidium, cesium, tantalum, thorium and uranium were determined by instrumental neutron activation analysis in geological samples of obsidian rocks from the Mediterranean Area and in obsidian artifacts found in some prehistorical human settlements in Italy. REE patterns and discriminant analysis allow a firm identification of the source material of artifacts, thus confirming and implementing fission track data of the same artifacts and rocks on the origin of the obsidian rock used to mould the artifacts.     

Trace elements in Turkish tobacco determined by instrumental neutron activation analysis

The concentration of 20 trace elements in nine different brands of Turkish cigarette tobacco and in a brand of pipe tobacco and in tobacco ash has been determined by instrumental neutron activation analysis. The percent transference of elements into smoke has been estimated from the amounts remaining in the ash.     

Rare-earth elements in recent calcareous benthic organisms

Fresh and aged samples of foraminifera and red algae from two different climatic areas (the Great Barrier Reefs of Australia and the northwestern Mediterranean Sea) were analyzed by non-destructive thermal and epithermal neutron activation for some traces and rare-earth elements (REE). Mechanisms were tentatively proposed to explain the measured distributional differences: iron scavenging effect, microbial intervention at given stages of very early diagenesis, feeding behaviour of organisms... REE and traces follow increases of iron content during biodiagenesis; this process does not apparently originate discrimination in the distributional pattern of REE. Eu negative and Ce positive anomalies were recorded in both types of organisms; these anomalies were explained by bioprocesses.     

Radiochemical neutron-activation analysis of uncertified ultra-trace rare earth elements in two biological certified reference materials

Radiochemical neutron activation analysis (RNAA) has been used for the determination of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu) in two Chinese certified reference materials (CRM), GBW 08503 (wheat powder) and GBW 09101 (human hair). These determinations are important for possible certification of the above mentioned ultra-trace elements, so far not certified. A simple one-step (REE)F3 precipitation was used. Chemical yields were determined for all relevant elements by means of tracer experiments. The two CRM were also analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to compare the merits and draw-backs of these two major trace analytical techniques for these particular elements. RNAA was proven to be a reliable technique for ultra-trace analysis, especially in the certification of some ultra-trace elements.     

Instrumental neutron activation analysis of carbonatites from Homa Mountain, Kenya

Twenty eight (major and trace) elements including eight rare earth elements (REEs) in African carbonatite samples were determined by instrumental neutron activation analysis. The geochemical behavior of trace elements was studied in relation to the order of carbonatite intrusion from C1 to C4 through C2 and C3 at Homa Mountain, Kenya. The enrichment of Mn, Fe, Sr, Ba, Th, U and REE is found in the sixteen carbonatites examined in this study. The general increase in the concentrations of Na, Sc, Mn, Sb, Ba, Th, U and REE occurs from C1 to C4 through C2 and C2c, but C3 carbonatite shows a different pattern. The C3 carbonatite is extraordinarily enriched in Mn, Fe and Ba and is highly enriched in Cr, As, Sb and Th. The chondrite-normalized REE distribution pattern of the C3 carbonatite is not rich in the light REE. Strong fractionation between light and heavy REEs is found in the carbonatites, and moderate fractionation in the two alkalic igneous rock samples. In order to evaluate partitioning of REEs into carbonate, oxide and other mineral fractions, a selective chemical leaching technique on carbonatites was applied and is discussed in this study. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physical fractionation of trace and rare earth elements in the sediments of Lake Nasser

The distribution of major, trace and rare earth elements in bulk, different particle sized and strongly magnetic fractions of Lake Nasser sediments has been investigated. The elements were determined using neutron activation analysis. Statistical data processing indicates good correlation between Th, La and Ce, suggesting that accessory minerals such as monazite may play a role in controlling rare earth elements (REE) in the lake sediments. The highly significant relationship between Al and light-REE accounts for the capability of clay minerals to host these elements. In addition, principle components analysis reflects that there are only four factors which could explain about 90% of the total variance in the lake sediments. The results show also that Al, Th and REE have low contents in the sediment magnetic fraction relative to the corresponding values in the bulk sediments, whereas Fe, Mn, Ti, Co, Cr, Hf, V and Zn have higher concentrations in the same fraction than the corresponding values in the bulk sediments. This may be attributed to their incorporation in Fe-Mn minerals.     

Pollution of agricultural crops with lanthanides,thorium and uranium studied by instrumental and radiochemical neutron activation analysis

The lanthanide elements, Th and U were measured in soils and agricultural crops collected in an area polluted by emissions from a phosphate fertilizer plant. Concentrations of the above elements in the soil and crop samples were determined by instrumental neutron activation analysis (INAA). Selected crop samples were also analyzed using radiochemical neutron activation analysis (RNAA) based on alkaline-oxidative fusion of the irradiated samples followed by precipitation of REE oxalates. Elevated levels of lanthanides, Th and U were found in some samples, especially in wheat chaff and parsley.     

用草酸钙共沉淀法分离富集骨中稀土元素

采用草酸钾作沉淀剂 ,在 pH2时将骨中钙部分沉淀 ,通过草酸钙载体共沉淀富集骨中稀土元素。用分光光度法、同位素示踪法和中子活化法检验模拟样品中稀土元素富集效果。结果显示 ,当每 g钙的沉淀量为48mg时 ,微克量和纳克量的稀土元素共沉淀率达到90 %以上。方法简单、可靠 ,且避免了钙、磷和钠等宏量元素的干扰 ,可对0.5～5g骨样中的稀土元素进行有效的分离富集。     

Precise determination of rare earth elements in rocks by neutron activation analysis

A pre-irradiation group separation method has been developed for the neutron activation analysis of rare earth elements (REE) and Ba in silicate rocks. REE and Ba were quantitatively separated from other elements by cation exchange column method. The chemical yield of each separation was monitored with Pr added to the sample powder before decomposition. The accuracy and precision were tested by repeated analyses of JB-1 and one analysis of BCR-1. In addition, it was found that REE distribution in a granitic rock powder was inhomogeneous and therefore special care must be taken for the sampling of granitic rock powders.     

Radiochemical neutron activation analysis of rare earth elements in peridotitic rocks

The understanding of the geochemistry of basalt petrogenesis and the nature of the upper mantle requires the examination of such rocks as peridotites which in many cases are thought to represent upper mantle material. The mineralogical composition of peridotitic rocks in such that they accommodate large proportions of such trace elements as the transition elements but very small amounts of the rare earths and hygromagmaphile elements. The last two groups are often able to provide a large amount of information leading to petrogenetic models. Owing to the extremely low concentrations of the REE in peridotitic rocks it is necessary to separate them from other elements which will interfere with their precise determination. We have used a radiochemical neutron activation analytical method which is adapted from various published methods. It involves a post-irradiation sample fusion, two separate ion-exchange chromatographic stages and finally a fluoride precipitation. The RNAA procedure is capable of providing very precise REE data for perioditic samples and we have used it for the analysis of such rocks from several geodynamic environments.     

Multielemental analysis of soil samples by fast-neutron activation

Neutron activation analysis (NAA) have been used for the determination of major, minor, and trace elements in 20 soil samples from 5 crop fields of the Crop Research Centre, Pantnagar, India. Fast neutron activation analysis (FNAA) and cyclic neutron activation analysis (CNAA) have been used to determine the concentrations of various elements. The results for minor and trace elements are compared with the level of abundances of world soils. The present study provides the basic data of elemental concentrations in soil samples of 5 major crop fields located in one of the leading agricultural universities of India for future measurements with the objectives of efficient use of fertilizers and pesticides in accordance with the high yield.     

Investigations of the separation of Np,Pa, U,Th and ree in geological samples

In the first part some methods of the radiochemical neutron activation analysis of U, Th and REE trace amounts in geological samples have been studied. They are: (i) cation exchange and extraction, and (ii) extraction chromatography. The behaviour of U and Th was also observed and conclusions were made regarding the applicability of the methods for the rocks which are rich in U and Th but depleted of REE. The method is recommen ded for the selective separation of U and Th. The second part represents an effective separation method for the determination of all REE and Th contents in monazites.     

土壤-植物体系稀土元素的分异现象

用仪器中子活化分析测定了从同一地点采集的9种不同植物根和叶中8个稀土元素（La,Ce,Nd,Sm,Eu,Tb,Yb和Lu)的含量，研究了稀土元素在植物根、叶及相应母土中的分布特征。结果表明，同一植物的根、叶和母土中稀土分布模式均有较大差异。生长在同一地点不同植物根中稀土分布模式非常相似，而叶中分布规模差别较明显。说明根对单一稀土元素的吸收主要取决于这个元素在土壤中有效态的含量，而在稀土从根到叶的运输和积累过程中出现的分异则由植物自身的结构特征决定。