STUDIES ON Si4+ ION, Al3+ ION AND H2O (+) IN VOLCANIC GLASSES BY MEANS OF INFRARED ABSORPTION AND OTHER METHODS

Abstract

The nature of volcanic glassed in andesitic to rhyolitic rocks have been studied by means of infrared absorption and other several methods. The main results are as follows: (1) The atomic distance of Si-O bond in volcanic glasses becomes random with the increase of contents of intermediate and modifying ions. (2) The network structure of volcanic glasses expands with the increase of contents of intermediate and modifying ions. (3) The network structure of volcanic glasses expands with the increase of contents of intermediate and modifying ions. (4) In the structure of volcanic glasses, most of Al3+ ions substitute for Si4+ ions, and are tetrahedrally coordinated. (5) In the structure of pumiceous glass and obsidian glass, H2O(+) presents mainly as monomeric hydroxyl and minorly as hydrogen-bonded hydroxyl. On the contrary, in perlitic glass, H2O(+) presents as hydrogen-bonded water and monomeric hydroxyl.