Barium Isotopic Compositions of Geological Reference Materials

The interest in variations of barium (Ba) stable isotope amount ratios in low and high temperature environments has increased over the past several years. Characterisation of Ba isotope ratios of widely available reference materials is now required to validate analytical procedures and to allow comparison of data obtained by different laboratories. We present new Ba isotope amount ratio data for twelve geological reference materials with silicate (AGV‐1, G‐2, BHVO‐1, QLO‐1, BIR‐1, JG‐1a, JB‐1a, JR‐1 and JA‐1), carbonate (IAEA‐CO‐9) and sulfate matrices (IAEA‐SO‐5 and IAEA‐SO‐6) relative to NIST SRM 3104a. In addition, two artificially fractionated in‐house reference materials BaBe12 and BaBe27 (δ^137/134Ba = ?1.161 ± 0.049‰ and ?0.616 ± 0.050‰, respectively) are used as quality control solutions for the negative δ‐range. Accuracy of our data was assessed by interlaboratory comparison between the University of Bern and the United States Geological Survey (USGS). Data were measured by MC‐ICP‐MS (Bern) and TIMS (USGS) using two different double spikes for mass bias correction (¹³⁰Ba–¹³⁵Ba and ¹³²Ba–¹³⁶Ba, respectively). MC‐ICP‐MS measurements were further tested for isobaric and non‐spectral matrix effects by a number of common matrix elements. The results are in excellent agreement and suggest data accuracy.     

Calcium Isotopic Fractionation and Compositions of Geochemical Reference Materials

High‐precision calcium isotopic compositions of a set of geological reference materials from the IAG (OU‐6), ANRT (UB‐N), MPI‐DING, USGS and GSJ, relative to NIST SRM 915a, are reported here. Measurements were performed by thermal ionisation mass spectrometry (Triton instrument) using a ⁴²Ca–⁴³Ca double spike. δ^44/40Ca values of selected reference materials, mainly felsic rocks, are reported for the first time. Felsic rock values of δ^44/40Ca ranged from 0.13‰ to 1.17‰, probably implying Ca isotopic fractionation could occur during magma evolution. δ^44/40Ca values of ultramafic rocks, ranging from 0.74‰ to 1.51‰, were positively correlated with MgO and negatively with CaO contents, possibly owing to Ca isotopic fractionation during partial melting. δ^44/40Ca of intermediate‐mafic rocks were around 0.78‰ and displayed limited variation, suggesting Ca isotopic fractionation is insignificant during magma evolution processes. As expected, δ^44/40Ca of sedimentary and metamorphic rocks varied widely due to complex geological processes.     

约束稀疏脉冲反演在大庆茂兴地区泉四段储层研究中的应用

笔者从约束稀疏脉冲反演技术的基本原理入手,重点说明稀疏脉冲反演在大庆茂兴地区泉四段储层的应用,其基本步骤和方法,如子波估算、初始模型建立和Lambda取值等,为约束稀疏脉冲反演技术的合理应用提供参考。     

镉稳定同位素研究进展

Cd具有挥发性和亲硫性,在海洋环境中Cd为微量营养元素,而在生态环境及农业土壤环境中Cd为有毒元素。因此,镉同位素被应用于海洋科学、地球科学、环境科学及农业科学研究,并展现出巨大的应用潜力。本文总结了近年来富含有机质的环境样品、植物样品和生物样品的消解方法,以及Cd分离纯化及双稀释剂校正方法的研究进展。采用微波、高压灰化和高氯酸消解等样品前处理方法均可消除有机质对镉同位素测定的影响;基于AG MP-1（M）树脂-盐酸淋洗体系可有效分离基体及干扰元素,不会导致镉同位素分馏;111Cd-113Cd同位素双稀释剂校正体系的测试精度高,可达0.1εCd/amu。同时,本文阐述了镉同位素在海洋科学、地球科学、环境科学及农业科学领域研究的最新进展和认识。镉同位素已成功应用于构建海洋生物地球化学Cd循环体系、反演古海洋环境及初级生产力变化,硫化物矿床成矿流体演化、成矿物质来源示踪及不同成因矿床类型判别研究,环境体系Cd污染源的源区判别、农田面源Cd来源及其运移、循环及储存机制研究。本文提出需要进一步开展镉同位素分馏机制及分馏模型的研究,构建Cd稳定同位素地球化学体系。     

涡流地震检波器的特性及测试方法的研究

本文介绍了涡流地震检波器的工作原理、结构及其频率响应特性——涡流检波器的输出特性在固有频率之上是按外界激励频率的平方递增。高频灵敏度随着激励频率的增加而增高有助于弥补高频信号通过地层传播时的急剧衰减,从而提高了地震勘探的分辨率。在固有频率之下,则加强了低频滤波作用。 本文还以对单自由度线性振动系统的动态分析为基础,研究了利用实验幅频特性曲线来求该系统的固有频率和阻尼系数的方法,推导出必要的计算公式。最后举出一个应用实例,并检验了这种方法的可信度。     

A new gnetalean macrofossil from the Early Cretaceous and its evolutionary significance

Modern gnetophytes consist of three families, i.e. the Ephedraceae, the Gnetaceae, and the Welwitschiaceae, which show diversified morphology. The basal group Ephedraceae possesses an extremely reduced female cone with only the uppermost pair/whorl being fertile, while both the Gnetaceae and the Welwitschiaceae bear female cones/spikes with multiple whorls of fertile bracts. Here, we describe a new ephedroid macrofossil, Liaoningia decussata Yang et Lin, gen. et sp. nov., from the Lower Cretaceous Yixian Formation of western Liaoning in China. This species has typical ephedroid morphology, e.g. the dichasial branching shoot system, swollen nodes, internodes having many fine longitudinal striations, and decussate phyllotaxy, lengthy linear leaves possessing two parallel veins, and female cones consisting of paired bracts. This new genus is similar to the Ephedraceae in its vegetative organs, but differs from the latter by the female spikes with multiple pairs of fertile bracts. In this respect Liaoningia is similar to both the Gnetaceae and the Welwitschiaceae, but distinctly differs from the latter two genera in its vegetative organs. As a result, our new genus shows intermediate morphology between the Ephedaceae and the other two families of the gnetophytes, and is probably a missing link in the evolutionary process from the Ephedraceae to the clade including the Gnetaceae and the Welwitschiaceae.     

双稀释剂法在非传统稳定同位素测定中的应用——以钼同位素为例

仪器的质量分馏校正是提高同位素分析数据精度的关键。"同位素双稀释剂"的测定方法可实现严格的仪器质量分馏校正。文章以Mo同位素为例,详细介绍了同位素双稀释剂法的原理、计算方法以及应用多接收器等离子体质谱仪(MC-ICP-MS)进行Mo同位素组成高精度分析的方法。双稀释剂和标准样品的100Mo/97Mo使用Pd溶液的104Pd/102Pd标定,其他Mo同位素比值通过100Mo/97Mo标定。对100Mo/95Mo、98Mo/95Mo和97Mo/95Mo三组Mo同位素比值建立3个非线性方程,组成一个非线性方程组,在认为仪器质量分馏和自然分馏都符合指数法则的前提下,通过Taylor公式将非线性方程组转换成线性方程组,使用牛顿迭代法计算出样品的Mo同位素组成。在使用MC-ICP-MS分析过程中,每组数据采集20个数据点,最终的δ100Mo/95Mo、δ98Mo/95Mo和δ97Mo/95Mo是这20组数据得到的20组δ100Mo/95Mo、δ98Mo/95Mo和δ97Mo/95Mo的平均值。     

太阳活动区上空两个微波超快速吸收现象的观测与分析

1987年5月19日世界05h50m17-05k50m25s和1986年6月29日世界时07h38m50s-07h38m58s两个罕见的微波超快速吸收现象分别出现在太阳活动区NOAA／USAF4808和5060上空的3.67GHz和4.00GHz大气层中.当云南天文台高时间分辨率射电望远镜观测到这种吸收现象时,在2.84GHz和1.42GHz大气层中出现的是尖峰辐射,两次超快速吸收现象的显著观测特征是：（1）吸收期的持续时间为20—25ms;（2）吸收的流量范围在17-215s．f.u．;（3）超快速吸收形态与快速吸收形态基本相似;（4）超快速吸收现象均叠加在秒级爆发上,秒级爆发分别为44NS和46C型;（5）相伴随的Ha耀斑分别为SF级和3B级．     

Mass‐Independent and Mass‐Dependent Ca Isotopic Compositions of Thirteen Geological Reference Materials Measured by Thermal Ionisation Mass Spectrometry

We report mass‐independent and mass‐dependent Ca isotopic compositions for thirteen geological reference materials, including carbonates (NIST SRM 915a and 915b), Atlantic seawater as well as ten rock reference materials ranging from peridotite to sandstone, using traditional ε and δ values relative to NIST SRM 915a, respectively. Isotope ratio determinations were conducted by independent unspiked and ⁴³Ca‐⁴⁸Ca double‐spiked measurements using a customised Triton Plus TIMS. The mean of twelve measurement results gave ε^40/44Ca values within ± 1.1, except for GSP‐2 that had ε^40/44Ca = 4.04 ± 0.15 (2SE). Significant radiogenic ⁴⁰Ca enrichment was evident in some high K/Ca samples. At an uncertainty level of ± 0.6, all reference materials had the same ε^43/44Ca and ε^48/44Ca values. We suggest the use of δ^44/42Ca to report mass‐dependent Ca isotopic compositions. The precision under intermediate measurement conditions for δ^44/42Ca over eight months in our laboratory was ± 0.03‰ (with n ≥ 8 repeat measurements). Measured igneous reference materials gave δ^44/42Ca values ranging from 0.27‰ to 0.54‰. Significant Ca isotope fractionation may occur during magmatic and metasomatism processes. Studied reference materials with higher (Dy_n/Yb_n) tend to have lower δ^44/42Ca, implying a potential role of garnet in producing magmas with low δ^44/42Ca. Sandstone GBW07106 had a δ^44/42Ca value of 0.22‰, lower than all igneous rocks studied so far.     

Pb-Isotope Analyses of USGS Reference Materials

Conventional corrections for thermal ionisation mass spectrometer (TIMS) induced Pb-isotopic fractionation often result in a loss of accuracy because the commonly employed pure Pb reference materials (NIST SRM 981, 982) frequently exhibit markedly different fractionation behaviour to real geological samples. As a result, these SRMs are inappropriate for comparison and/or correction of inter-operator/ laboratory biases. A matrix-matched reference material would be preferable but, as yet, no systematic study has approached this problem. Here we present high quality Pb-isotope ratio determinations, obtained using a double spike procedure, for six USGS reference materials in an attempt to address this deficiency. Our data suggest that most of these rocks could be used as isotopic reference materials comparable, in terms of uncertainty, to the NIST SRMs. However, significant differences in isotopic composition exist between first (e.g. BCR-1) and second (e.g. BCR-2) generation samples. The cause of these differences remains unclear but has significant implications for their use as trace element reference materials.