They decrease in age, structurally, downward." This decrease in age is an effect of a phenomenon called inverted metamorphism ...

The degree of crystallization of the graphite correlates with the rocks' metamorphism, indicating that metamorphism affects the preservation and change of carbon-based materials. More information ...

Primary minerals form at elevated temperatures from cooling magma during the original solidification of rock or during metamorphism, and they are usually derived from igneous and metamorphic rocks ...