Métamorphique

Métamorphique is a term originating from the Greek words 'meta' meaning change and 'morphe' meaning form. It is primarily used in geology to describe rocks that have undergone transformation from their original form. This transformation, known as metamorphism, occurs when existing rocks are subjected to changes in temperature, pressure, or chemical environment, without melting. The original rocks, called protoliths, can be igneous, sedimentary, or even other metamorphic rocks.

The process of metamorphism causes changes in the mineralogy, texture, and chemical composition of the protolith. For instance, heat can cause minerals to recrystallize or new minerals to form. Intense pressure can lead to the alignment of minerals, creating a foliated texture, as seen in slate or schist. The depth at which metamorphism occurs, the proximity to magma intrusions, and the presence of fluids all influence the type and extent of the transformation.

Metamorphic rocks are classified based on their texture and mineral content. Foliated rocks, such as gneiss, schist, and slate, exhibit a layered or banded appearance due to the parallel arrangement of minerals. Non-foliated metamorphic rocks, like marble and quartzite, do not show this layering. These rocks are significant indicators of geological processes and provide valuable insights into Earth's history and tectonic activity.