Differentiating hydrous and anhydrous carbonaceous chondrites by secondary ion mass spectrometry

Abstract

An accurate identification of hydrous and anhydrous chondrites is the first step towards a comprehensive study of the hydration processes on meteorite parent bodies. The accurate differentiation between hydrous and anhydrous carbonaceous chondrites is of interest and two approaches are proposed. The first approach is the identification of phyllosilicate species using secondary ion mass spectrometry together with principal component analysis. The species of Si₂O₅⁻ and Si₂O₅H⁻ are spectrally determined as phyllosilicate fragments and both are described by the first two principal components. The Si₂O₅⁻ fragment variance is described up to 60%, and the Si₂O₅H⁻ to 30% by the first component, providing differentiation significance. The second approach is an evaluation of the same spectra by using a convolutional neural network. Two data reduction procedures are proposed, achieving an accuracy from 78 to 100%. The first approach is based on the chemical identification of phyllosilicate species in spectra, while the second approach is more general and does not require any knowledge of hydration processes. In both approaches, the spectra represent a qualitative surface analysis, which itself is fast and almost non-destructive. Both approaches unambiguously differentiate the spectra of meteorites with various degrees of hydration. The only requirement for successful identification of the degree of hydration for an unknown sample is a comprehensive data set of known meteorites loaded in the principal component analysis or learned by the convolutional neural network.

Graphical abstract