List of top Geology Questions on Igneous Petrology

A mafic magma with 'Sr' concentration of 400 ppm has undergone 60% fractional crystallization. If 'Sr' is incompatible in the mineral assemblage that crystallizes from the magma with a bulk distribution coefficient of 0.2, the concentration of 'Sr' in the residual liquid is ppm (rounded off to nearest integer).
The ternary diagram given below shows phase relations for the Anorthite-Diopside-Forsterite system at 1 bar pressure. Broken lines represent isotherms with temperature in °C. If 'P' is the initial melt composition, which one of the following is the CORRECT sequence of crystallization assuming equilibrium between crystal and melt?
The given table shows modal volume percentage of quartz, alkali feldspar and plagioclase in coarse-grained rocks, X and Y. Which of the following rock names of X and Y are CORRECT according to the IUGS classification?
MineralX (volume %)Y (volume %)
Quartz1525
Plagioclase2060
Alkali feldspar6515
Which one of the following is NOT a volcanic igneous rock?