Development Of TOF-SIMS For Geochemical Trace Elements Analysis

In-situ analysis of trace elements plays an important role in geochemistry and cosmochemistry.It is an effective technique to reveal the source of ore-forming material,to establish ore-forming conditions and ore genesis,and is also an important method to study the composition of the moon and other planets.However,for geological material it usually requires high resolution in order to resolve the complex structure and chemical composition in micro-scale earth and cosmic samples.At present,trace elements analysis is mostly carried out by ID-TIMS,LA-ICP-MS and magnetic SIMS.The first two are destructive and semi-destructive methods,and the last technique is also semi-destructive with the increasing of analytic elements.The current techniques often do not meet the requirement of in-situ analysis of trace elements in precious or complex micro-samples.TOF-SIMS is one of the most effective surface analytical techniques that can achieve high sensitivity in-situ analysis without damage and can determine almost all isotopes by single measurement consuming only 10-1 to 10-5 of the sample required by SHRIMP or IMS1280 methods.It is therefore suitable for in-situ analysis of trace elements on a small scale in geological samples.This paper outlines the overall design of a TOF-SIMS instrument for trace elements analysis in response to new demand for small-scale in-situ SIMS analysis in the earth sciences.An ion source and primary ion optics system,combined with a high-resolution TOF mass analyzer and a neutral particle femtosecond laser post-ionization system have been developed.The performance of this instrument is as follows:Mass resolution: R = 21720(FWHM)(m/z = 228)Spatial resolution: 5 ?mMass range: 1-350 amuMass accuracy: better than 100 ppmLong-term mass stability: better than 10 ppmDetection limit: better than 0.2 ppmAccuracy for REE analysis(NIST610): better than 10 %We have carried out accurate in-situ TOF-SIMS analyses of Ti and REE in zircon and obtained good Ti-in-zircon results for thermometry.The results show that the new TOFSIMS instrument is able to perform near-nondestructive,high spatial resolution,high sensitivity in-situ analysis of geological samples and provides a new technique for the analysis of precious and/or complex material.