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The single-crystal diamond trap (SCDT) : a new method to determine the composition of high-P–T fluids

Title data

Abeykoon, Sumith ; Audétat, Andreas:
The single-crystal diamond trap (SCDT) : a new method to determine the composition of high-P–T fluids.
In: Contributions to Mineralogy and Petrology. Vol. 177 (2022) Issue 2 . - 24.
ISSN 1432-0967

Official URL: Volltext

Project information

Project financing: Deutsche Forschungsgemeinschaft

Abstract in another language

In view of recently reported discrepancies in mineral solubility results obtained with the classical diamond trap method, an alternative approach to quantify the composition of high P–T fluids was developed. In this approach the high P–T fluids are trapped in laser-drilled holes within single-crystal diamond plates and subsequently analyzed by LA–ICP–MS using the same pit size as the one that was used to drill the holes, which allows more rigorous testing of the data reproducibility than in the case of the classical diamond trap, where the fluid resides in a large, open network. To reduce the spikiness of the LA–ICP–MS signals and minimize element fractionation, the aqueous solution within the holes was allowed to evaporate, and the solid residue was melted to a glass. Because this results in the partial loss of the internal standard elements that are usually used for quantifying the LA–ICP–MS signals we developed a new quantification procedure that works without any internal standard in the fluid but instead uses the carbon signal produced by the epoxy that was filled into the holes after melting the precipitates. The new method was first tested on holes filled with epoxy resins doped with known amounts of chemicals, then on holes filled with known amounts of minerals that were subsequently melted, and finally on real high P–T mineral solubility experiments at 1.0 GPa and 700–900 °C in the quartz–H₂O and olivine–enstatite–H₂O systems, for which reliable reference data exist. In all 15 experiments the measured concentrations agree within 1–21% (avg. 13%) with the reference values. In contrast, four mineral solubility experiments that were performed at identical conditions with the classical diamond trap method returned concentrations that deviated by 7–56% (avg. 28%) from the reference value. Furthermore, a strong fractionation effect that has been observed during the ablation of albite + H₂O in a classical diamond trap is efficiently prevented in our single-crystal diamond trap (SCDT) approach. On the downside, we observe significant mobility of alkalies during the melting step in our approach.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: High P–T fluids; Mineral solubility; High P–T experiments; Single crystal diamond trap; LA–ICP–MS; Piston cylinder experiments
Institutions of the University: Research Institutions > Central research institutes > Bavarian Research Institute of Experimental Geochemistry and Geophysics - BGI
Research Institutions
Research Institutions > Central research institutes
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 550 Earth sciences, geology
Date Deposited: 10 Sep 2022 21:00
Last Modified: 12 Jul 2023 13:44