Development of a Double Vacuum Furnace Tube and Its Application in Gas Composition Determination during Rock Heating Degassing

Abstract

BACKGROUND The analysis of gas chemical composition in rock and mineral can provide important information and constraints for the study of different geochemical processes of lithospheric mantle, redox environment in the earth, and water circulation in the deep earth. Heating rock and ore samples to remove gas is a common experimental method. A single quartz glass tube is used as the sample tube. Irregular voids in quartz glass structure make gas easy to diffuse and permeate at high temperature. The double vacuum furnace tubes consisting of molybdenum and tantalum crucibles are generally used for the analysis of rare gas isotope composition, but seldom used for the analysis of gas chemical composition. The device has a complex structure, is not easy to assemble and disassemble, and is easily damaged. OBJECTIVES To solve the problems contained in the sample-filling tube proposed in the background research. METHODS A double vacuum sampling furnace tube composed of quartz glass and metal parts had been developed. The furnace tube had the characteristics of small size, easy assembly, disassembly and movement. Under the same experimental conditions, the result was compared with that of a single quartz glass tube. RESULTS H2 concentration measured by the double vacuum sampling tube was higher than that measured by the single quartz glass tube under the same experimental conditions, no matter which type of sample was heated to degas at 500℃ or 950℃. CONCLUSIONS The closure of the double vacuum furnace tube is better than that of the single quartz glass tube, which is conducive to obtain more real gas chemical composition in the sample.

Keywords

• double vacuum furnace tube
• single quartz glass tube
• gas chromatography
• gas-released from rock