br Calibration and correction methods of

Calibration and correction methods of trp channels contents
Calibration and correction methods of the isotopic ratios After the true signal intensity of the measured isotopes is obtained by interference correction, the mass fractionation of isotopic ratios should be corrected by rigorous correction methods. Up to now, there are two widely used approaches to normalize mass fractionation in LA-ICP-MS, which namely internal and external standard calibration method (Albarède et al., 2004; Meija et al., 2012; Yang, 2009). Here the terms internal and external are used synonymously with simultaneous and sequential analysis of the sample and reference material (Meija et al., 2012). In the following sections, we describe them in detail (Table 3).
Uncertainty assessment For the measurement of both elemental compositions and the isotopic ratios, it is necessary to assess the quality of results by an uncertainty, which is generally expressed at the level of 2σ (data point) or 95% confidence (population). So the uncertainty of a data is no less significant than the data point itself and it is essential to proper assessment of the uncertainty (Ludwig, 2003). In general, the less the datum needs reducing or correcting the fewer the uncertainties that will need propagating and the lower the overall uncertainty (Horstwood, 2008). Contributions to the final analytical uncertainty must be assessed: Uncertainties should be propagated using the following Equation (11):where is the final uncertainty; are the various uncertainty components related to the calibration methods; is the coverage factor ( is commonly chosen to be 2, which means that uncertainty corresponds to a level of confidence of approximately 95%) (Jochum et al., 2012a).
Examples for data reduction of isotopic analyses
Data reduction software: ICPMSDataCal Data reduction software ICPMSDataCal was written in the Visual Basic programming language and works on the Microsoft Excel. This software integrates all the above calculation and correction methods for LA-ICP-MS and LA-MC-ICP-MS analyses of element contents and isotopic ratios. It gives users a unique analytical environment, based on the interactive selection of background and sample intervals from the time-resolved signals provided by (MC)-ICP-MS. It provides real-time and on-line data reduction for the LA-(MC)-ICP-MS analyses, and features linked graphics and analysis tables, greatly improving both productivity and the flexibility of analysis. At present, data analyzed by (MC)-ICP-MS of Agilent, Thermo X and Neptune, Elan, Varian, and Nu Plasma and AttoM can be directly used without additional adjustment. In order to guide the users through the data reduction software, a detailed manual (Guide book for ICPMSDataCal) includes the specific operations of different applications (e.g., U–Pb dating of zircon, trace element analyses of mineral and melt/fluid inclusion, and isotope analyses of Li, Sr, Nd, Hf, Os, Pb). In addition, the software is upgrading and modifying based on the different requirements. The functions and features of ICPMSDataCal mainly include:
Conclusion and outlook
Acknowledgment Charlotte M. Allen and two anonymous reviewers are thanked for the detailed comments that helped us to improve the manuscript. Tong Xirun, Zhu Lvyun and Xu Lei are thanked to provide the knowledge of Sr, Os and Nd data reduction analysis. This work was funded by the National Natural Science Foundation of China (41125013, 41525012), 111 plans of Ministry of Education (B07039), the MOST Special Funds of the State Key Laboratory of Geological Processes and Mineral Resources (MSFGPMR04).
Introduction Due to the extremely limited availability of pristine rock samples from the deep interior of the Earth, the mineralogical model for the upper mantle is usually built by comparing the elastic data of geochemically plausible minerals to the observed seismic velocity data (Weidner and Ito, 1987; Li and Liebermann, 2007; Irifune et al., 2008). Ringwoodite (Rw), with a conventionally-accepted composition of approximately (Mg0.89Fe0.11)2SiO4, is commonly regarded as the most abundant mineral in the lower part of the mantle transition zone (MTZ) by the geological scientific community (Irifune and Ringwood, 1987; Ita and Stixrude, 1992). Since a complete series of Rw solid solutions exists between Mg2SiO4 and Fe2SiO4, compositionally characterized by the parameter XFe = Fe/(Fe + Mg) (in molar units), the correlation between the elastic properties, used in the sound velocity calculation, and composition of the Rw might be important indicator to the compositional and mineralogical model of the MTZ. Many efforts, both experimental and theoretical, have thus been made to constrain the elastic features of the ringwoodites with different compositions, and significant advances have been achieved in the last half century or so (e.g., Mao et al., 1969; Sato, 1977; Weidner et al., 1984; Zerr et al., 1993; Kiefer et al., 1997; Sinogeikin et al., 1998; Nishihara et al., 2004; Higo et al., 2006; Li et al., 2006; Matsui et al., 2006; Liu et al., 2008a; Nunez Valdez et al., 2012).