TY - JOUR

T1 - A Practical Method for Accurate Measurement of Trace Level Fluorine in Mg- and Fe-Bearing Minerals and Glasses Using Electron Probe Microanalysis

AU - Zhang, Chao

AU - Koepke, Jürgen

AU - Wang, Lian Xun

AU - Wolff, Paul Eric

AU - Wilke, Sören

AU - Stechern, André

AU - Almeev, Renat

AU - Holtz, Francois

N1 - Funding Information: We thank Michael Marks (Universit?t T?bingen) for providing rock powders of AC-E, GS-N and DR-N, Martin Oeser for providing BCR-2G, and Tim M?ller and Anna-Maria Welsch for helpful discussions. Special thanks go to Julian Feige for his perfect preparation of thin sections. This paper benefited greatly from critical and constructive comments of two anonymous reviewers and the journal editors. This work was supported by a ?Wege in die Forschung? project (granted by Leibniz Universit?t Hannover to Chao Zhang), DFG projects KO 1723/17 and HO 1337/31. Requests for the newly synthesised AC-E, GS-N and DR-N glasses as microanalytical reference materials can be addressed to the corresponding author.

PY - 2016/9/3

Y1 - 2016/9/3

N2 - Fluorine plays an important role in magmatic and hydrothermal processes, but due to its low abundance in geological samples determining F is difficult by electron probe microanalysis. By using a W-Si multi-layered pseudocrystal as the diffraction crystal instead of thallium acid phthalate (TAP), count rates were considerably higher, which however introduced spectral interferences between FKα and FeLα and MgKβ lines when normal integral mode is applied. In this study, we developed a protocol using a W-Si multi-layered pseudocrystal for measuring accurately trace level F in both minerals and glasses. First, we used differential mode with an optimised PHA (pulse height analysis) setting in signal processing, instead of normal integral mode, which completely eliminated the second-order MgKβ line. Second, the overlap of the first-order FeLα on FKα peak, which cannot be filtered by modifying the PHA setting, was calibrated quantitatively using F-free minerals and silicate glasses. Applying this two-step method, F was determined in a number of reference glasses, as well as in glasses synthesised from powders of the rock reference materials AC-E, GS-N and DR-N. Our data are consistent within error with F concentrations determined by other methods, demonstrating the reliability of this method.

AB - Fluorine plays an important role in magmatic and hydrothermal processes, but due to its low abundance in geological samples determining F is difficult by electron probe microanalysis. By using a W-Si multi-layered pseudocrystal as the diffraction crystal instead of thallium acid phthalate (TAP), count rates were considerably higher, which however introduced spectral interferences between FKα and FeLα and MgKβ lines when normal integral mode is applied. In this study, we developed a protocol using a W-Si multi-layered pseudocrystal for measuring accurately trace level F in both minerals and glasses. First, we used differential mode with an optimised PHA (pulse height analysis) setting in signal processing, instead of normal integral mode, which completely eliminated the second-order MgKβ line. Second, the overlap of the first-order FeLα on FKα peak, which cannot be filtered by modifying the PHA setting, was calibrated quantitatively using F-free minerals and silicate glasses. Applying this two-step method, F was determined in a number of reference glasses, as well as in glasses synthesised from powders of the rock reference materials AC-E, GS-N and DR-N. Our data are consistent within error with F concentrations determined by other methods, demonstrating the reliability of this method.

KW - electron probe microanalysis

KW - in situ techniques

KW - microbeam techniques

KW - reference materials

KW - wavelength dispersive X-ray fluorescence spectrometry

UR - http://www.scopus.com/inward/record.url?scp=84955572337&partnerID=8YFLogxK

U2 - 10.1111/j.1751-908x.2015.00390.x

DO - 10.1111/j.1751-908x.2015.00390.x

M3 - Article

AN - SCOPUS:84955572337

VL - 40

SP - 351

EP - 363

JO - Geostandards and Geoanalytical Research

JF - Geostandards and Geoanalytical Research

SN - 1639-4488

IS - 3

ER -