Publication Date:
2017-12-08
Description:
We studied the alteration of silicic volcanic glass of recent Towada ash in the different soil environments by means of electron-microprobe analysis. Two types of glass alteration (tentatively named [alpha] and [beta] types) were established and were distinguished on the basis of potassium and calcium contents of the glass samples.
The [alpha] type glass alteration was characterized by a very large gain of potassium and a large loss of sodium. This alteration was explained by the ion exchange reaction between Na+ and H+ plus K+ without significant change in the glass structure. The [beta] type alteration characteristically showed a significant loss of potassium and a large gain of calcium and some other elements. The behaviors of alkalies and alkaline earths in the [beta] type glass could not be interpreted by the stoichiometry of exchange processes of these elements. Changes of glass structure during weathering were suggested for the [beta] type glass.
There were close relationships between the mode of glass alteration, clay mineralogy of ash-derived soils, and soil environments. Only [alpha] type glass alteration was observed in the 2:1 mineral soils that showed the very low pH, very low contents of exchangeable bases, but relatively high content of exchangeable potassium. In contrast the [beta] type glass alteration was the most intense in the allophanic Ando soil, which showed a relatively high content of exchangeable bases and a high pH.
Type:
Article
,
PeerReviewed
Format:
text
