The influence of cosmic-ray production on extinct nuclide systems   总被引：1，自引：0，他引：1  

Ingo Leya  Rainer Wieler 《Geochimica et cosmochimica acta》2003,67(3):529-541

Variations in the atomic abundances of ⁵³Cr, ⁹²Zr, ⁹⁸Ru, ⁹⁹Ru, and ¹⁸²W in meteorites and lunar samples relative to terrestrial values may imply the early decay of radioactive ⁵³Mn, ⁹²Nb, ⁹⁸Tc, ⁹⁹Tc and ¹⁸²Hf, respectively. From this one can deduce nucleosynthetic sites and early solar system timescales. Because these effects are very small, production and consumption of the respective isotopes by cosmic-ray interactions is a concern. It has recently been demonstrated that ¹⁸²W production by neutron capture reactions on ¹⁸¹Ta is crucial for most lunar samples (Leya et al., 2000a). In this study the neutron fluence of each sample was estimated from its nominal cosmic-ray exposure age as deduced from noble gas data. This approach overestimates the true cosmogenic isotopic shift for samples that might have been irradiated very close to the regolith surface. Here we therefore combine our model calculations with the neutron dose proxies ¹⁵⁷Gd/¹⁵⁸Gd and ¹⁴⁹Sm/¹⁵⁰Sm. This allows us to accurately correct the measured W isotopic data for cosmic-ray induced shifts without the explicit knowledge of the exposure age or the shielding depth of the sample simply by measuring ¹⁵⁷Gd/¹⁵⁸Gd and/or ¹⁴⁹Sm/¹⁵⁰Sm in an aliquot. In addition we present new model results for the GCR-induced effects on ⁵³Mn-⁵³Cr, ⁹²Nb-⁹²Zr and ⁹⁸Tc-⁹⁹Tc-⁹⁸Ru-⁹⁹Ru. For each of these systems, except Tc-Ru, a proper cosmic-ray dose proxy is given, permitting the accurate correction of measured isotopic ratios for cosmogenic contributions.  相似文献   

Erratum to dähn et al. (2003), “Structural evidence for the sorption of Ni(II) atoms on the edges of montmorillonite clay minerals. A polarized X-ray absorption fine structure study”: geochimica et cosmochimica actavol. 67(1), 1-15     

Rainer Dähn 《Geochimica et cosmochimica acta》2003,67(12):2299

  相似文献   

Li abundances in eclogite minerals: a clue to a crustal or mantle origin?     

Alan B. Woodland  Hans-Michael Seitz  Rainer Altherr  Horst Marschall  Bettina Olker  Thomas Ludwig 《Contributions to Mineralogy and Petrology》2002,144(1):128-130

  相似文献   

A receiver function perspective of the Dharwar craton (India) crustal structure   总被引：1，自引：0，他引：1  

Dipankar Sarkar  M. Ravi Kumar  Joachim Saul  Rainer Kind  P. S. Raju  R. K. Chadha  A. K. Shukla 《Geophysical Journal International》2003,154(1):205-211

  相似文献   

Possible Effects of Altered Growth Behaviour of Norway Spruce (Picea abies) on Carbon Accounting     

Rainer Joosten  Andreas Schulte 《Climatic change》2002,55(1-2):115-129

Implementing the Kyoto Protocol necessitates precise and practical inventory methods for estimating the carbon reservoir in forests. An analysis of the German state North Rhine-Westphalia forest inventory data showed enormous deviations from the yield tables of Wiedemann (1936, 1942). Specifically the ratio of height/diameter at breast height was up to 30% lower than in the yield tables, which indicated wider annual rings and a lower basic density. Such differences most likely pose consequences for the calculation of the amount of carbon in these forests. In this study the aboveground green weight, moisture and the carbon content of fifteen 46-year old Norway spruces (Picea abies) were measured, and two approaches for calculating the aboveground carbon content of trees were discussed: the common methodology of applying expansion and conversion factors as well as using optimized regression equations. The average expansion factor deviated approximately 1.2% from the yield tables of Grundner and Schwappach (1906). The wood density was 368 kg/m³ and within the European scope of 320–420 kg/m³ (Bosshard, 1984; Hakkila, 1989; Knigge and Schulz, 1966; Trendelenburg and Mayer-Wegelin, 1955). The woody carbon content was found to be 50.42%, which corresponded well with reference values of 50.3% (Bosshard, 1984) and 51.4% (Knigge and Schulz, 1966). However, the average percentage of crown material carbon content was 0.75% higher than in the tree boles. This study demonstrated that the most reliable methodology for calculating aboveground tree carbon was a power regression function, which calculated the growing stock volume, converting it directly into tree carbon content. The results deviated by less than 1.3% (R² = 0.99) from the measured tree carbon. Using volume expansion factors and factors of basic density and carbon percentage, as in Burschel et al. (1993), the calculated results diverged –3.7% from the measured outcome. The adapted form according to Fang et al. (2001) deviated –1.2% (R² = 0.63) and the form following Brown and Schroeder (1999) about –2.5% (R² = 0.61) from the measured carbon of the sample trees. However, coefficients of variation from 12% and 13% for the presented algorithm illustrated that in reality the calculated carbon of single trees could diverge considerably from the model results.  相似文献   

Sodic Pyroxene and Sodic Amphibole as Potential Reference Materials for In Situ Lithium Isotope Determinations by SIMS     

Michael A.W. Marks  Roberta L. Rudnick  Thomas Ludwig  Horst Marschall  Thomas Zack  Ralf Halama  William F. McDonough  Detlef Rost  Thomas Wenzel  Edward P. Vicenzi  Ivan P. Savov  Rainer Altherr  Gregor Markl 《Geostandards and Geoanalytical Research》2008,32(3):295-310

Two large pegmatitic crystals of sodic pyroxene (aegirine) and sodic amphibole (arfvedsonite) from the agpaitic igneous Ilímaussaq Complex, south Greenland were found to be suitable as reference materials for in situ Li isotope determinations. Lithium concentrations determined by SIMS and micro‐drilled material analysed by MC‐ICP‐MS generally agreed within analytical uncertainty. The arfvedsonite crystal was homogeneous with [Li] = 639 ± 51 μg g^?1 (2s, n = 69, MC‐ICP‐MS and SIMS results). The aegirine crystal shows strongly developed sector zoning, which is a common feature of aegirines. Using qualitative element mapping techniques (EPMA), the homogeneous core of the crystal was easily distinguished from the outermost sectors of the crystals. The core had a mean [Li] of 47.6 ± 3.6 μg g^?1 (2s, n = 33) as determined by SIMS. The seven micro‐drilled regions measured by solution MC‐ICP‐MS returned slightly lower concentrations (41–46 μg g^?1), but still overlap with the SIMS data within uncertainty. Based on MC‐ICP‐MS and SIMS analyses, the variation in δ⁷Li was about 1‰ in each of the two crystals, which is smaller than that in widely used glass reference materials, making these two samples suitable to serve as reference materials. There was, however, a significant offset between the results of MC‐ICP‐MS and SIMS. The latter deviated from the MC‐ICP‐MS results by ?6.0 ± 1.9‰ (2s) for the amphibole and by ?3.9 ± 1.9‰ (2s) for the aegirine. This indicates the presence of a significant matrix effect in SIMS determinations of Li isotopes for amphibole and pyroxene relative to the basalt glasses used for calibration. Based on the MC‐ICP‐MS results, mean δ⁷Li values of +0.7 ± 1.2‰ (2s, n = 10) for the arfvedsonite crystal and of ?3.7 ± 1.2‰ (2s, n = 7) for the core of the aegirine crystal were calculated. Adopting these values, SIMS users can correct for the specific IMF (instrumental mass fractionation) of the ion probe used. We propose that these two crystals serve as reference materials for in situ Li isotope determinations by SIMS and pieces of these two crystals are available from the first author upon request.  相似文献   

Alpine metamorphism of organic matter in metasedimentary rocks from Mt. Medvednica (Croatia)     

Katalin Judik  Gerd Rantitsch  Thomas M. Rainer  Péter Árkai  Bruno Tomljenović 《Swiss Journal of Geoscience》2008,101(3):605-616

  相似文献   

Fluid flow and rock alteration along the Glarus thrust     

Jean-Pierre Hürzeler  Rainer Abart 《Swiss Journal of Geoscience》2008,101(2):251-268

  相似文献   

The enhanced element enrichment in the supercritical states of granite–pegmatite systems     

Rainer Thomas  Paul Davidson  Karen Appel 《Acta Geochimica》2019,(3):335-349

In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical melt or fluid is a silicate phase in which volatiles; principally H_2O are completely miscible in all proportions at magmatic temperatures and pressures. This phase evolves from felsic melts and changes into hydrothermal fluids, and its unique properties are particularly important in sequestering and concentrating low abundance elements, such as metals. In our past research, we have focused on processes observed at upper crustal levels, however extensive work by us and other researchers have demonstrated that supercritical melt/fluids should be abundant in melting zones at deep-crustal levels too. We propose that these fluids may provide a connecting link between lower and upper crustal magmas,and a highly efficient transport mechanism for usually melt incompatible elements. In this paper, we explore the unique features of this fluid which allow the partitioning of variouselements and compounds, potentially up to extreme levels,and may explain various features both of mineralization and the magmas that produced them.  相似文献   

东印度洋近20 ka以来的生物硅记录及其古生产力意义     

徐勇航  王亮  赖志坤  徐晓辉  王凤  刘升发  石学法  TROA Rainer Arief  ZURAIDA Rin  TRIARSO Eko  HENDRIZAN Marfasran 《海洋学报(英文版)》2019,38(1):78-84

通过对东印度洋钻孔CJ01-185的生物硅来探讨东印度洋古生产力的变化和古气候演化的响应。CJ01-185钻孔的生物硅含量在末次冰期最低,为0.86%;而到了全新世晚期生物硅含量达到1.89%。全新世晚期生物硅的堆积速率明显大于末次冰期。随着全新世海平面的快速上升,巽他海峡贯通,来自爪哇海的陆源物质输入到东印度洋,导致全新世的生物硅含量和生物硅的堆积速率增加。研究表明：巽他海峡贯通前,研究区的古生产力主要受东南季风变化和上升流的活动影响;而巽他海峡贯通后,古生产力很明显受到陆源物质输入的控制,东南季风变化和上升流的影响较弱。  相似文献