Figure 4. Binary immobile-element plots for rhyolite A. Altered samples are also included. Mass changes caused by alteration result in the formation of near-linear trends. Linear regression equations the are given in the first three plots. The fourth plot (Y vs. Zr) shows that rhyolite A is calc-alkaline. Plots such as these can be set up for each rock type and then used to readily identify rocks samples once they have been analyzed.