Quantifying the Contribution and Mobility of In Situ-Produced Helium in He-Retentive Minerals: A Case Study of the Salla-Kuolajarvi Metasomatic Rocks (Russia)
2024
Maria Andreevna Gannibal | Andrey Evgenievich Gannibal | Arkadii Avenirovich Kalinin | Tatiana Vladimirovna Kaulina | Vitalii Valentinovich Kolobov
An alternative approach to separating trapped and radiogenic helium, and assessing the mobility of the latter in He-retentive minerals implemented in the present work, has been developed on the basis of helium extraction patterns obtained via incremental heating of mineral samples. We used these data both to estimate helium mobility in concentrates of various ore minerals (pyrite, magnetite, and hematite) and to assess the contribution of in situ-produced 4He in the total helium budget. The rocks of uranium-ore and gold mineralization of the Salla-Kuolajarvi belt (northern Karelia, Fennoscandian Shield) were used as test materials for the new approach. The method allowed such parameters as diffusivity, activation energy, closure temperature, and the contribution of the trapped helium to be obtained for all samples. The latter was used for the correction of apparent U-Th-He bulk ages. The interpretation of the calculated values was performed taking into account the closure temperatures of the U-Th-He system, as well as the peculiarities of each individual sample.
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