Capability of fs-LA-ICP-MS for sulfide analysis in comparison to ns-LA-ICP-MS: reduction of laser induced matrix effects?

Abstract

We applied three different LA systems (213 nm nanosecond solid state, 193 nm nanosecond excimer, and 200 nm femtosecond laser) coupled to a quadrupole ICP-MS or a sector field ICP-MS, respectively, for the analysis of different sulfide minerals (pyrrhotite, chalcopyrite, and sphalerite). Ablation craters were investigated via back-scattered electron (BSE) images to compare the amounts of melt produced, and fractionation factors were calculated to determine the degree of down-hole fractionation. Our results show significant differences in melting between the three LA systems. While samples show massive melting when using the ns systems, no melting has been observed utilizing the fs laser. Fractionation factors for a variety of elemental pairs indicate the absence of down-hole fractionation even at the highest melt production. The extent of melting of different sulfide specimens is independent of melting temperatures of these materials. Although no down-hole fractionation has been observed, Fe/S fractionation as calculated from sensitivities deviate among pyrrhotite and chalcopyrite when applying the 193 nm ns and 200 nm fs systems. Analyses of synthetic pyrrhotite with known PGE concentrations using the 200 nm fs LA system yielded moderately precise and accurate concentration data (3-4%; 4-14% 2SD) utilizing sulfide as the external reference material. Application of NIST610 as the reference material improved the precision to 1.4-2.4% 2SD and the deviation from reference values to 5-7%

Trace Element Analysis of Minerals in Magmatic-Hydrothermal Ores by Laser Ablation Inductively-Coupled Plasma Mass Spectrometry: Approaches and Opportunities

“…One factor considered to potentially influence data quality is heating and generation of melts or particles precipitated from aerosols and vaporized products of ablation (e.g., [23]) during laser ablation. If melts are generated, and these are inherently different, chemically to the reference material used for calibration, fractionation may be introduced that could lead to a reduction in precision [22].…”

“…These deviations were attributed to the composition and/or particle size distribution of aerosols formed over the sampling interval and could be corrected for by modifying fluence and spot size. Wohlgemuth-Ueberwasser and Jochum (2015) [22] compared the performance of nanosecond solid state and excimer lasers with a 200 nm femtosecond laser for analysis of common sulphide minerals. They report significant differences in the degrees of melting, with no melting observed utilizing the femtosecond laser.…”

Application of La-Icp-Ms Sulfide Analysis and Methodology For Deciphering Elemental Paragenesis and Associations In Addition To Multi-Stage Processes In Metamorphic Gold Settings

“…arsenopyrite, pyrite, pyrrhotite) and semi-quantitative in other phases (e.g., inclusions and/or surrounding material) and along fractures, etc. Despite differences in ablation between NIST610 (silicate glass) and sulphides contributing to melting and/or fractionation, similar measurements conducted by Wohlgemuth-Ueberwasser et al (2015) yielded concentrations within 20% of accepted values when calibrating sulphides with NIST610.…”

“…Unfortunately, there are no widely available sulphide reference materials that contain an appropriate suite of trace elements that can be used as an alternative at present. New reference materials may one day become available to alleviate this problem, but in the meantime, the use of fs-lasers could minimize the ablation differences between silicate glass and sulphides (Wohlgemuth-Ueberwasser et al, 2015).…”

Development of a Matrix‐Matched Sphalerite Reference Material (MUL‐ZnS‐1) for Calibration of In Situ Trace Element Measurements by Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry

“…The major element composition of MASS‐1 (S 27.6% m/m , Cu 13.4% m/m , Fe 15.6% m/m and Zn 21.0% m/m ) is far from the chemical composition of sphalerite. Additionally, fractionation effects have been observed during ablation due to melt formation, while sphalerite in contrast shows minor to no fractionation during ablation (Wohlgemuth‐Ueberwasser and Jochum ).…”