IsoSpike: Improved Double‐Spike Inversion Software

The double‐spike approach for correction of instrumental mass bias in mass spectrometry data is well established. However, there is very little consistency within the scientific community in terms of double‐spike data reduction. Double‐spike solutions require computer calculation, using either geometric or algebraic approaches, and are often performed using spreadsheet calculations that vary from group to group and between isotope systems. Here, we present IsoSpike, a generalised computer procedure for the processing of double‐spike mass spectrometry data, built as an add‐on for the Iolite data‐reduction package ( www.iolite.org.au ). Use of this software permits visualisation of mass spectrometry data in a time window, and rigorous treatment and screening of data. Additionally, IsoSpike uses an integration‐by‐integration approach where the double‐spike calculations are performed on every integration within an analysis, providing straightforward quantification of uncertainties on double‐spike‐corrected isotope ratios. The advantages of this approach over traditional methods are discussed here. Platinum stable isotope data are presented as an example data set, although the procedure is applicable to any double‐spike system. IsoSpike is freely available from www.isospike.org .     

同位素双稀释剂技术的数值模拟与应用

近年来,非传统稳定同位素地球化学已成为新兴发展的研究领域,同位素双稀释剂技术是该领域的主流分析方法之一,但始终存在的困扰问题是如何进行同位素双稀释剂间以及稀释剂与样品间的最优混合。这两种混合比严重制约着同位素比值测试的准确度、精度和重现性。本文从同位素双稀释剂技术的数学原理出发,以Cr、Mo同位素为例,结合MonteCarlo误差模型,深入讨论和分析了两单稀释剂间比值(λ)及双稀释剂与自然样品间比值(p)的最优化数值模拟,得到了以双稀释剂~50(Cr)-~54(Cr)、~97(Mo)-~(100)Mo为例的λ、p值的最优取值范围。该数值模拟可适用于所有能够利用同位素双稀释剂技术的元素。在此基础上,就数值模拟结果如何应用于同位素双稀释剂的选择和组成标定也给予了详细说明,这为我国开展和使用同位素双稀释剂技术提供了基本思路和需要注意的关键问题,有助于推动同位素双稀释剂技术在我国地学界的广泛应用和发展。     

波阻抗反演方法在塔河碳酸盐岩储层预测中的应用

详细分析了约束稀疏脉冲反演、地震特征反演以及随机反演3种反演算法及其特点,针对塔河油田碳酸盐岩储层进行了反演试算对比.研究结果表明,约束稀疏脉冲反演结果与地震反射资料特征有较好的对应关系,但其反演结果分辨率不高.随机反演能客观地描述碳酸盐岩缝洞型储层非均质性极强的分布特征,克服了其他反演结果存在连续性、成层性的缺陷,但该方法难以求取准确的变差函数.3种反演结果中,地震特征反演结果与井史储层发育段的吻合率最高,说明地震特征反演在塔河奥陶系碳酸盐岩储层预测中仍然是一种较好的方法.     

地震检波器的横向灵敏度特性

地震检波器受到地面横向运动激励时的输入输出关系定义为检波器的横向灵敏度特性.本文对检波器线圈受到横向激励时产生的轴向振动进行了分析.可以看到,当悬挂线圈的弹簧片悬丝发生动力失稳时,检波器的横向灵敏度突然增大;在线圈横向振幅很小的情况下,失稳频率接近悬丝的横向固有频率.利用谱分析技术可以准确地从检波器噪声中检测出检波器的横向灵敏度和失稳频率,即检波器假频.     

Calcium Isotope Ratio (δ44/40Ca) Measurements of Ca‐Dominated Minerals and Rocks without Column Chemistry Using the Double‐Spike Technique and Thermal Ionisation Mass Spectrometry

In this study, to evaluate whether bias free Ca isotope ratios can be properly achieved by thermal ionisation mass spectrometry (TIMS) using the ⁴²Ca–⁴³Ca double‐spike technique without chemical purification, a series of comparable experiments (with or without column chemistry) were made on Ca‐dominated minerals and rocks. Minerals, including fluorite, calcite, titanite and apatite, displayed similar Ca isotope ratios with Δ^44/40Ca_{with‐without} ranging from ?0.02 to +0.07‰. For Ca‐rich rocks, we mainly focused on the carbonates since they are the main repositories of Ca at the surface of the Earth. Coral, stalagmite, carbonatite, dolomite, marble and limestone are studied here. Interestingly, δ^44/40Ca_{SRM 915a} of these minerals and rocks without chemical purification displayed little drift compared with that of rocks with chemical purification, with Δ^44/40Ca_{with‐without} merely spanning from ?0.04 to +0.04‰. This implies that Ca isotope ratios can be achieved without column chemistry, possibly due to a property of TIMS in which Ca ions are only ionised at a target temperature and with a specific activator without ionising other ions. Therefore, for Ca‐dominated minerals or rocks, we suggest that column chemistry is unnecessary if they are totally dissolved and mixed in proper proportion with the ⁴²Ca–⁴³Ca double spike for TIMS measurement.     

Research on the middle-of-receiver-spread assumption of the MASW method

The multichannel analysis of surface wave (MASW) method has been effectively used to determine near-surface shear- (S-) wave velocity. Estimating the S-wave velocity profile from Rayleigh-wave measurements is straightforward. A three-step process is required to obtain S-wave velocity profiles: acquisition of a multiple number of multichannel records along a linear survey line by use of the roll-along mode, extraction of dispersion curves of Rayleigh waves, and inversion of dispersion curves for an S-wave velocity profile for each shot gather. A pseudo-2D S-wave velocity section can be generated by aligning 1D S-wave velocity models. In this process, it is very important to understand where the inverted 1D S-wave velocity profile should be located: the midpoint of each spread (a middle-of-receiver-spread assumption) or somewhere between the source and the last receiver. In other words, the extracted dispersion curve is determined by the geophysical structure within the geophone spread or strongly affected by the source geophysical structure. In this paper, dispersion curves of synthetic datasets and a real-world example are calculated by fixing the receiver spread and changing the source location. Results demonstrate that the dispersion curves are mainly determined by structures within a receiver spread.     

太阳微波尖峰辐射的高时间、高频率分辨率偏振观测

利用北京天文台 ２．６—３．８ ＧＨｚ频谱仪的观测资料,找到 １１个微波尖峰辐射事件．尖峰一般具有数十毫秒的寿命,数百个ｓｆｕ的流量密度和数十至数百ＭＨｚ的带宽,这与以前的报道类似．尖峰的偏振度各式各样,有的尖峰还有数千ＭＨｚ／ｓ的频率漂移．某些尖峰在二个偏振态之间有８毫秒的时间延迟（最大延迟可达１６毫秒）．另外,还发现了尖峰的偏振度随频率剧烈变化的偏振反转现象．     

铅同位素"双稀释剂"同位素定年法计算方法研究

铅同位素研究已广泛应用于模式定年、成矿物质来源示踪和化探找矿评价等许多领域。铅同位素“双稀释剂”同位素定年法是当前应用较广的一种铅同位素定年方法。双同位素稀释法的目的在于校正质量鉴别效应,提高测定精度。由于实验条件和分析技术的改善和提高,使铅同位素“双稀释剂”测定精度和准确度大大提高,从而铅同位素“双稀释剂”同位素定年法也将得到更为广泛的应用。本主要是研究该法的计算,分析样品中元素量的计算,并结合几种岩石年龄方法(Pb-Pb等时线法、不一致线模式计算法、三阶段模式计算等)的计算,归纳总结出计算样品中元素量和岩石形成年龄的方法。     

灰岩裸露区检波器三自由度耦合系统理论的研究

中国南方海相碳酸盐岩沉积盆地的分布幅员辽阔,地下油气等资源极为丰富,但是由于大面积坚硬灰岩的出露,给检波器完好耦合带来了很大困难,从而降低了地震采集资料的品质,严重制约了该地区未来的油气勘探.目前野外检波器耦合试验缺乏较为合适的理论指导,带有较大的盲目性.为此,本文考虑到检波器与灰岩耦合时增加了耦合介质（石膏、泥饼等）的实际情况,提出了检波器-灰岩三自由度耦合系统的理论,研究了耦合介质、尾锥和阻尼等耦合因素对检波器-灰岩耦合系统传输函数的影响规律.发现检波器-灰岩耦合系统是具有三个谐振频率的谐振系统,通过增加耦合介质的弹性模量、减小耦合介质的底面积和高度、选用介质密度较小的尾锥、减小尾锥的高度、增加尾锥的底面积等,可以提高耦合谐振频率.通过适当增加耦合系统的阻尼,可以减小耦合系统的窄频带“带通滤波”的影响.最后,通过振动台实验初步验证了检波器-灰岩三自由度耦合系统理论模型.     

Analysis of spike emission data at 2545/2645 MHz in the peak year of the 22nd solar cycle

We briefly discuss the observed features including the high flux density, short duration, narrow emission band, fast frequency drift, quasi-periodic oscillation and fast variation of polarized components, of 51 spike emission events observed at 2545/2645 MHz in the solar activity peak year, 1991 January–December, and carry out correlation analysis between these events and optical flares, magnetic field intensity and configuration of flare regions, and sunspot evolution types of active regions. In view of the fact that the observed and statistical characteristics of the spike emissions are very different from those of known types of solar radio burst and known solar radio components, we think that the spike emission in the peak years is probably a new type of radio burst excited by electron cyclotron maser instability under wave-particle resonance, or a new solar radio component.