Variability factors of 40K radionuclide origin in meteorites

Abstract

This study confirms the theory of the variability of the origin of radioactive potassium in various meteorite classes, generated from the dynamic nucleosynthesis (primordial) process, and other processes induced by the solar/cosmic-radiation activation or fractionation caused by the impact vaporization mechanism. Highprecision radioactive 40K analysis confirms the differences between various types of meteorites. The concentrations of potassium change from 0.50 ±0.02 Bq/kg (NWA 15015, mesosiderite) to 26.2 ±1.2 Bq/kg (Chelyabinsk, LL chondrite) i.e. three orders of magnitude. All radiometric measurements have been made using a lowbackground gamma spectrometry system. Additionally, a set of common minerals – Fa (fayalite in olivine), Fs (ferrosilite), and Wo (wollastonite in pyroxenes) – was applied (MetBase n.d.). For the radionuclides factor variability, the principal component analysis (PCA) for the chemometric analysis has been applied. Two factors of the 40K variability have been identified, described, and explained. In this study, PCA was applied for the interpretation of the 40K potassium origin sources in 32 meteorite specimens, represent various groups and classes of meteorites. Two significant PCA factors of variability have been identified, PC1 (51.04%) and PC2 (30.68%), assigned as an activation process by cosmic radiation exposure and a nucleosynthesis mechanism (primordial), respectively.