Metamorphic zone

Schematic map of a terrane with an increasing metamorphic grade. There are two folded lithologies: quartzite (originally sandy sediment) and pelite (originally clayey sediment). The index minerals can only grow in the pelite. The highest indicated isograd is the solidus of hydrated granite, at higher metamorphic grade partial melting occurred in the quartzite.
Metamorphic zones in Scottish Highlands, the region where they were first recognized by geologist George Barrow in 1912. Most of the region has Barrow zones, but an area north of Aberdeen has Buchan zones (andalusite and biotite).

In geology, a metamorphic zone is an area where, as a result of metamorphism, the same combination of minerals occur in the bedrock. These zones occur because most metamorphic minerals are only stable in certain intervals of temperature and pressure.[1]

  1. ^ See for example Best (2003), pp 431-436 for a good summary