Refers to a type of contact metamorphism caused by intense, unusually high temperatures at very low pressures. This alteration happens rapidly when country rock comes into direct contact with flowing lava, shallow magma intrusions, or natural underground coal fires. The resulting rocks often exhibit glass-like textures or high-temperature mineral assemblages.
Heard on the job
The sandstone adjacent to the basalt dike shows a distinct pyrometamorphic halo where the quartz grains fused.