A novel purification technique for noble gas isotope analyses of authigenic minerals

Abstract

Noble and active gases are released from geological samples during gas extraction for noble gas isotope analyses. The active gases should be removed before inletting to mass spectrometers for the analyses. The normal noble gas preparation systems can clean up most geological samples. However, authigenic minerals from sedimentary rocks in oil/gas fields contain organic matter, which cannot be cleaned up by the normal preparation systems and thus influence the noble gas analyses. We introduce a novel gas purification system (PRC patent No. ZL201320117751.2), which includes several reversible purification pumps with different absorbing and degassing temperatures. It can well clean up water steam, carbon dioxide and organic gases. Mica minerals are often used for 40 Ar/ 39 Ar dating. A muscovite sample (2082MS) which could not be cleaned up by the normal preparation system with two SAES NP10 ® getters, becomes the test sample for a comparative experiment in this study. The experiment is assigned into 4 sections with the organic gas removal system (OGRS) "Closed/Opened" in turn. When the OGRS is closed only with two NP10 getters for purification, the 40 Ar intensities increase in curves with inlet time because of impurities, the 40 Ar/ 39 Ar dating results yield age errors about 2%-1% (2) . When the OGRS is opened for purification, in contrast, the 40 Ar intensities decrease linearly with inlet time. This indicates that the gases have been cleaned up effectively, and the 40 Ar/ 39 Ar results yield ages with errors in 0.4%. The OGRS is very helpful to obtain high-quality analysis data.

40Ar/39Ar Dating and In Situ Trace Element Geochemistry of Quartz and Mica in the Weilasituo Deposit in Inner Mongolia, China: Implications for Li–Polymetallic Metallogenesis

“…The CO2 (IR, 10.4 µm) laser was used to heat the matrix grain step by step, and the heating time was 60 s. The released gas was purified with a newly designed gas purification system to remove moisture and other impurities [58][59][60]. Two SAES NP10 Zr/Al gasifiers were used to further purify the gas at approximately 400 °C and room temperature, respectively, to produce inert gas with sufficient purity for Ar isotope analysis in mass spectrometers.…”

Timing of Secondary Hydrothermal Alteration of the Luobusa Chromitites Constrained by Ar/Ar Dating of Chrome Chlorites

“…Around 12 mg of each aliquot was loaded into the laser chamber and heated for 12 total steps with increasing heating power of the laser. Gases extracted at each step were first passed through a cryotrap (−80 to −120 • C) to adsorb moisture, then further purified by two SAES NP 10 Zr-Al getters (one at~400 • C and the other at room temperature) [70]. Afterwards, pure noble gases were admitted into the mass spectrometer for argon isotope analyses.…”