skip to main content

Microstructure sections:


Microstructures of Metamorphic Rocks

Feedback mechanisms

Most size distributions show a peak at intermediate grain size, with fewer grains in small size classes. Various feedback mechanisms potentially affect the nucleation rate in the later stages of reaction and account for the left-hand tail of the size distribution:

We believe that multivariant reaction is the most important factor.

Here are two further examples of measured size distributions with their possible interpretations.

Very small left tail suggests andalusite formed by discontinuous reaction, small b parameter (compared to other andalusites) indicates slow heating.

Long left tail suggests cordierite formed by multivariant reaction, larger b parameter (compared to andalusite in same rock) suggests easier nucleation or slower reaction.

<< Previous page      ^ Back to Index     Next page >>