Pelites

- derived from pelitic sediments (mudstones)

- characterised by high Al₂O₃ & K₂O contents, which result in abundant micas produced during metamorphism

•   Muscovite - common in low temperature pelites
•   Biotite - common in higher temperature pelites

Pelites often display a well developed schistosity, defined by parallel alignment of micas - Micaschists

Also present in pelite one will have minerals rich in Al, e.g.,

•   Al₂SiO₅, kyanite, andalusite, sillimanite
•   Staurolite Fe₂Al₉O₆(SiO₄)₄(OH)₂
•   Cordierite Mg₂Al₃(AlSi)₅O₁₈
•   Garnet (Fe,Mg)₃Al₂(SiO₄)₃
  

Basic Rocks (Metabasites)

Equivalent to basaltic rocks with 50 wt % SiO₂. Basalts are often included in sedimentary piles within orogenic belts, thus mineral assemblages in metabasites can be correlated with assemblages in associated pelites as both formed under similar pressure and temperature conditions.

Basic rocks rich in MgO, FeO, CaO, & Al₂O₃, metamorphic minerals produced include:

- Chlorite, actinolite, epidote, at low temp greenschist

- Hornblende, plagioclase in amphibolite

- Hornblende, plag & garnet, opx & cpx in granulite