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41.
在69~100 GPa冲击压力(估算温度为2600~4300 K)范围内进行了初始样品为(Mg0.92,Fe0.08)SiO3顽火辉石和MgO+SiO2的冲击压缩回收实验.对回收样品进行的X射线衍射(XRD)分析结果表明:两发顽火辉石回收样品的主相均是单链状结构硅酸盐,而非钙钛矿结构;另外,回收样品中均未观察到氧化物SiO2和(Mg0.92,Fe0.08)O的XRD特征谱线;两发MgO+SiO2回收样品中均观察到SiO2和镁橄榄石(Mg2SiO4)而没有氧化物MgO.实验结果表明:在冲击压缩过程中样品处于钙钛矿结构,在冲击卸载过程中样品发生了由钙钛矿结构向单链状结构的逆转相变;在实验的温压范围内,不可能发生由(Mg0.92,Fe0.08)SiO3向SiO2和(Mg0.92,Fe0.08)O的化学分解相变,顽火辉石的高压相--钙钛矿结构是稳定的.高压加载或卸载过程引起的晶格畸变导致回收样品和原始样品的谱线差异,而高压加载导致钙钛矿型(Mg0.92,Fe0.08)SiO3晶格畸变的可能性更大. 相似文献
42.
Klaus Peter Jochum Ulrike Weis Brigitte Stoll Dmitry Kuzmin Qichao Yang Ingrid Raczek Dorrit E. Jacob Andreas Stracke Karin Birbaum Daniel A. Frick Detlef Günther Jacinta Enzweiler 《Geostandards and Geoanalytical Research》2011,35(4):397-429
We present new reference values for the NIST SRM 610–617 glasses following ISO guidelines and the International Association of Geoanalysts’ protocol. Uncertainties at the 95% confidence level (CL) have been determined for bulk‐ and micro‐analytical purposes. In contrast to former compilation procedures, this approach delivers data that consider present‐day requirements of data quality. New analytical data and the nearly complete data set of the GeoReM database were used for this study. Data quality was checked by the application of the Horwitz function and by a careful investigation of analytical procedures. We have determined quantitatively possible element inhomogeneities using different test portion masses of 1, 0.1 and 0.02 μg. Although avoiding the rim region of the glass wafers, we found moderate inhomogeneities of several chalcophile/siderophile elements and gross inhomogeneities of Ni, Se, Pd and Pt at small test portion masses. The extent of inhomogeneity was included in the determination of uncertainties. While the new reference values agree with the NIST certified values with the one exception of Mn in SRM 610, they typically differ by as much as 10% from the Pearce et al. (1997) values in current use. In a few cases (P, S, Cl, Ta, Re) the discrepancies are even higher. 相似文献
43.
Stephen C. Kuehn Duane G. Froese Franklin F. Foit Jr. Peter Rotheisler 《Quaternary Research》2009,71(2):201-47
The Glacier Peak tephra beds are among the most widespread and arguably some of the most important late Pleistocene chronostratigraphic markers in western North America. These beds represent a series of closely-spaced Plinian and sub-Plinian eruptions from Glacier Peak, Washington. The two most widespread beds, Glacier Peak ‘G’ and ‘B’, are reliably distinguished by their glass major and trace element abundances. These beds are also more broadly distributed than previously considered, covering at least 550,000 and 260,000 km2, respectively. A third bed, the Irvine bed, known only from southern Alberta, is similar in its major-element composition to the Glacier Peak G bed, but it shows considerable differences in trace element concentrations. The Irvine bed is likely considerably older than the G and B tephras and probably records an additional Plinian eruption, perhaps also from Glacier Peak but from a different magma than G through B. A review of the published radiocarbon ages, new ages in this study, and consideration in a Bayesian framework suggest that the widespread G and B beds are several hundred years older than widely assumed. Our revised age is about 11,600 14C yr BP or a calibrated age (at 2 sigma) of 13,710-13,410 cal yr BP. 相似文献
44.
不可见金的赋存状态研究 总被引:10,自引:0,他引:10
电子探针、扫描电镜和溶矿试验研究证明,在某地“卡林型”金矿中,黄铁矿是最主要的载金矿物。黄铁矿由先期形成的含Au和As很低的自形晶核心和后期形成的含Au和As很高的环边组成,其中Au和As呈正消长关系。因此,根据As的分布情况即可研究和认识Au的分布规律。研究结果为改善矿石的氧化焙烧、氯化处理和氰化浸出工艺设计提供了科学依据。 相似文献
45.
46.
U-Th-Pb副矿物的原地原位测年微束分析方法比较与微区晶体化学研究 总被引:5,自引:2,他引:5
系统地对比分析了各种微束分析技术在原地原位测年中的优势和局限性,并对近年发展的微区原位化学测年技术(EPMA)和质子激发X射线微探针分析技术(μ-PIXE)进行了探讨.阐明了矿物微区晶体化学研究的各种方法及其对实现精确原地原位测年的重要性.介绍了北大别黄土岭麻粒岩锆石测定点的晶体化学特征,应用激光剥蚀微探针-感应耦合等离子体质谱(LAM-ICPMS)技术对其进行了锆石的U-Pb表面年龄的测定,结果表明该岩石的麻粒岩相变质发生在2.050 Ga前,锆石来源为多源区. 相似文献
47.
牙形石SHRIMP微区原位氧同位素分析方法 总被引:7,自引:0,他引:7
氧同位素温度计已被用于古温度变化研究多年。生物化石磷酸盐中的氧同位素组成对古气候环境变化响应灵敏,牙形石在古生代到中生代的古海洋地层中广泛存在,并具有较为重要的地层学意义,是研究古温度变化的最佳样品之一。SHRIMP具备高分辨、高灵敏、高精度和微量及原位微区分析的特点,可以进行20μm范围内的原位(in-situ)同位素分析。本文介绍了作者利用SHRIMP IIe-MC建立的牙形石微区原位氧同位素分析方法,这是国内关于该方法的首次报导。本文对磷灰石标准样Durango进行了测定,连续七昼夜获得的253次测定结果,平均值为δ18 Oapatite=9.78‰±0.29‰,与该标准参考值δ18 Oapatite=9.81‰±0.25‰(Williams,未刊资料)一致。作者并以二叠系—三叠系界线上下海水温度变化研究为示范,对采自西藏文布当桑二叠系—三叠系剖面上的49个层位中的237件牙形石样品进行了914个氧同位素分析,为研究二叠系—三叠系界线上发生的生物灭绝事件前后的海水温度变化提供了可靠详实的数据。 相似文献
48.
Ludmila A. Pavlova Ludmila Ph. Paradina Olga Yu. Belozerova 《Geostandards and Geoanalytical Research》2001,25(2-3):333-344
In this paper we report the results of electron probe X-ray microanalysis (EPMA) that was used to study environmental materials. The mode of preparation and certification of reference samples based on a basaltic glass matrix for environmental applications of EPMA is described. These samples were prepared containing scandium, strontium and barium (from 0.03 up to 7% m/m) and an evaluation was made of homogeneity, their stability to local heating, followed by analysis by independent methods for certification of composition. Matrix correction procedures for the EPMA technique have been developed for particles having a size commensurable with the volume of X-ray generation. An analytical equation for the size factor is proposed and two techniques for selecting optimum conditions for the analysis of environmental samples by EPMA are reported. These procedures provided satisfactory results when utilized in analysing sediments recovered from snow, coal fly ash and the bones of animals and fish, results from which can be used as indicators for evaluating the pollution level of the lower atmosphere, surface and ground water, as well as revealing pollution mechanisms. 相似文献
49.
Qi‐Chao Yang Klaus Peter Jochum Brigitte Stoll Ulrike Weis Dmitry Kuzmin Michael Wiedenbeck Heike Traub Meinrat O. Andreae 《Geostandards and Geoanalytical Research》2012,36(3):301-313
To test whether the silicate reference glasses BAM‐S005‐A and BAM‐S005‐B from BAM (The Federal Institute for Materials Research and Testing, Germany) are suitable materials for microanalysis, we investigated the homogeneity of these reference glasses using the microanalytical techniques EPMA, LA‐ICP‐MS and SIMS. Our study indicated that all major and most trace elements are homogeneously distributed at micrometre sampling scale in both types of glass. However, some trace elements (e.g., Cs, Cl, Cr, Mo and Ni) seem to be inhomogeneously distributed. We also determined the composition of BAM‐S005‐A and BAM‐S005‐B. The EPMA data of major elements confirmed the information values specified by the certificate. With the exception of Sr, Ba, Ce and Pb, our trace element data by LA‐ICP‐MS were also in agreement with the certified values within the stated uncertainty limits. The reasons for the discrepancy in these four elements are still unclear. In addition, we report new data for twenty‐two further trace elements, for which the concentrations were not certified. Based on our investigation, we suggest that both of these materials are suitable for many microanalytical applications. 相似文献
50.
Hafnium Isotope Characteristics of Palaeoarchaean Zircon OG1/OGC from the Owens Gully Diorite,Pilbara Craton,Western Australia 下载免费PDF全文
Anthony I. S. Kemp Jeffrey D. Vervoort Katarina E. Bjorkman Linda M. Iaccheri 《Geostandards and Geoanalytical Research》2017,41(4):659-673
We report Hf isotope data for 3467 Ma igneous zircons from the Owens Gully Diorite of the Pilbara Craton. These zircons, designated OG1 or OGC, have simple, well‐defined U‐Pb age systematics. Measurements obtained by single crystal dissolution yield a moderate range in 176Hf/177Hf (mean 0.280633 ± 34) and 176Lu/177Hf (mean 0.00119) that translate into initial (3467 Ma) 176Hf/177Hf values that are equivalent within measurement uncertainty (mean 0.280554 ± 7, εHf = +0.6 ± 0.2, 2s). Laser ablation analysis yielded clustered initial 176Hf/177Hf ratios (mean 0.280560 ± 20, 2s) indistinguishable from those obtained by solution analysis. The antiquity and moderately high 176Lu/177Hf of these zircons result in significant corrections for radiogenic ingrowth of 176Hf (to 6 εHf units). Depth profiling by concurrent Pb‐Hf isotope determination reveals trends to lower 207Pb/206Pb in several crystals, although these are not accompanied by shifts in 176Hf/177Hf. We conclude that zircons from the Owens Gully Diorite are homogeneous for Hf isotopes at the scale of sampling and within the uncertainty limits of the measurement techniques employed. Zircon OG1/OGC would appear to be an ideal quality monitor for laser ablation Hf isotope determination in ancient zircons, and for laser ablation techniques where Hf isotope and age information are determined concurrently or simultaneously. 相似文献