Distribution of He and Ar isotopes in amphibole from quartz-felspar vein in the contact zone of the Panov massif (Kola Peninsula)
Skiba V. I., Kamensky I.L., Gannibal M. A., Pakhomovsky Ya. A.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 4. P. 96-107
https://doi.org/10.30695/zrmo/2018.1474.07
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Language: Russian
Abstract
Inventory and distribution of helium and argon isotopes were investigated in the natural amphibole samples via noble gas mass-spectrometry. According to the electron microscopic study the amphibole is presented mostly by riebeckite and contain ca. 1 % admixture of accessory minerals such as quartz, microcline, rutile, and fergusonite. Thermal analysis (differential scanning calorimetry and thermogravimetry methods) of riebekite in the inert atmosphere (argon) has shown that the oxidation of Fe2+ does not take place up to the temperature of riebekite dehydration endothermic event. Gas extraction was carried out by both thermal (stepwise heating, thermal analysis) and mechanical (crushing) methods. It was shown that within amphibole grains helium and argon may occupy several positions in the mineral structure, fluid microinclusions and microminerals. It was found out that along with diffusion from the mineral lattice and decrepitation of fluid inclusions there is another mechanism («decrepitation» of solid-state inclusions) to stimulate gas release in the course of sample heating, which results in peak on the helium release curves.
Key words: amphibole, thermal analysis, helium, argon, isotopes, mass-spectrometry.
