engleski

Spectroscopy of impact glasses: three methods compared.

The study of natural glasses which are the products of large asteroid impacts on the Earth demands knowledge on their chemical and mineral composition. These glasses are products of high-energy events which commonly exceed thermonuclear explosions and, though being relatively rare, represent very important evidence of major catastrophical events in Earth history. The study of chemical composition of these glasses from the islands of Krk and Rab was expected to provide data on the melted target rocks which might provide clue of the maximal age of the impact. Since the studeid matherial is natural and very rare, we have utilised three analytical procedures on the same samples ; PIXE, TXRF and ICP. The first method is undestructive, which is highy welcome, whereas the other two involved destruction of samples, and complete dissolution in the ICP MS age. These three methodes provided comparable results, but with notable variations. First, the PIXE analyses (performed at the Rudjer Bošković Institute in Zagreb, Croatia) was performed on diamond-cut samples with no preparation. The analysed sample was untreated and can be analysed again in the future. However, the analysed sample surface area is rather small, and does not record possible anysotropy of the matherial. The TXRF analyses were performed on crushed (but undissolved) sample. The fine-grained sample powder was suspended in ultra-clean water and applied on sample carrier surface. Possible inhomogeneities of the sample were equalized during the preparation process, but the original sample was destroyed. The ICP analyses were performed on completely dissolved sample, and each elemental analysis was calibrated after a standard.

PIXE ; TXRF ; ICP ; elemental composition

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