Petrography of Montserrat Volcanics

Several samples of dome rock were collected by the group from the flanks of the volcano. Thin sectons were cut and polished from these samples in the laboratories at the University of Ottawa. These transparent sections allowed for a detailed petrographic (microscopic) analysis to determine the composition of the volcanic rocks, and to note any relevant textures. It was found that the average dome rock composition was a fine-grained andesite. In the most general sense an andesite is medium grey in colour and contains large visible crystals, called phenocrysts, of plagioclase feldspar, amphibole, and pyroxene. To see more detailed descriptions of what was determined to be a typical dome rock, click on the adjacent thumbnails.

Geological significance

Photomicrograph of a volcanic rock

Etched plagioclase grain