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Optimization Of Combined With Conditions Of LA-ICP-MS And Its Application In The Zircon U-Pb Dating

Posted on:2011-04-07Degree:MasterType:Thesis
Country:ChinaCandidate:F C LiFull Text:PDF
GTID:2120360308959231Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
At present, the conventional device used to link sample chamber of laser ablation and ICP-MS is through a plastic tube whose diameter is about 3mm. The device is used to directly send the aerosol mixed by the laser ablation sample and carrier gas to the torch of ICP-MS. Then ICP-MS detects the exact content of various elements (isotopes) in the sample. Pulse frequency of currently used 193 um laser ablation is usually 10Hz and the ICP-MS signal acquisition rate is fast, so the RSD (relative standard deviation) of the sample analysis is large, usually close to 10%.The key of influencing data accuracy of sample analysis is whether the sample can be uniformly delivered from the laser sample chamber to the torch of ICP-MS. In view of this, I designed to add an external container between LA and ICP-MS in this study. By doing so, the accumulation of appropriate volume of aerosol ablated by LA can be sent to ICP-MS. In this way, the pattern of aerosol delivered to ICP-MS is approximately continuous.The study made spherical and cylindrical glass mixed sample containers of different volume for systematic on-line experiment at the laser plasma mass spectrometer laboratory of China University of Geosciences (Beijing). According to the testing results of standard samples (NIST 610) which were getting from loading non-mixed sample containers and will-mixed sample containers in New Mave193 um laser and Agilent 7500a quadrupole plasma mass spectrometer, such as RSD and cps (signal intensity count) values of light, medium and heavy representative elements and the morphology of plasma mass spectrum, I made a system analysis and evaluated advantages and disadvantages of mixed sample containers of different shape and size. Through making the experiments, I thought the cylinder mixed sample containers with the diameter of 30mm and height of 40mm had good functions which could make RSD of artificial synthesis international standard sample-NIST 610 stably up to 5%. And in the process of sample analysis, ICP-MS had the fast rate of receiving signal and high sensitivity.Using LA-ICP-MS at the laser plasma mass spectrometer laboratory of China University of Geosciences (Beijing) which was optimized by loading mixed sample containers, I did a testing between the Xinjiang Bachumazatage alkaline basic complex body gabbro-diorite igneous zircon and Xinjiang Yushugou granulite facies metamorphism granulite garnet second level typical metamorphism zircon in the ophiolite terrene, and then made a comparison of testing results about punctuate and linear ablation U-Pb age of two samples. It was showed that after loading the cylinder mixed sample containers with the diameter of 30mm and height of 40mm, the testing results of the punctuate and linear ablation sampling were consistent within the error and the testing results of Yushugou metamorphic zircon were consistent with the previous metamorphic zircon SHRIMP U-Pb age testing results carried out in the same samples within the error. Preliminary studies showed that the use of LA-ICP-MS optimized by loading containers, could detect simple linear ablation sampling of zircon U-Pb age and the abundance of trace elements. This kind of testing method will effectively expand the applications of LA-ICP-MS in earth science fine research, especially having significance in detecting metamorphic zircon U-Pb age and the abundance of trace elements.
Keywords/Search Tags:LA-ICP-MS, Zircons, Relative standard deviation, U-Pb dating, Mazhatage, Yushugou
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