Chapter 4- Metamorphism Flashcards
isochemical
no elements are added or removed
granoblastic
texture of metamorphic rocks that contain interlocking equidimensional crystals
foliation
texture found in metamorphic rocks, formed by preferred alignment of flat, platy minerals
slaty cleavage
texture in fine grained rocks formed by low grade regional metamorphism. Platy crystals recrystalise perpendicular to direction of stress so the rock splits into thin sheets
cataclasis
brittle fracturing and grinding down of existing rock, usually in fault zones
Porphyroblasts
large crystals that have grown during recrystalisation in a metamorphic rocks and are surrounded by a finer grained crystal groundmass
Schistosity
the texture in medium and coarse grained metamorphic rocks formed by the preferred alignment of flat/tabular minerals. alignment is perpendicular to direction of stress and no traces of the original bedding remains
gneissose banding
seperation of light and dark coloured minerals into layers/bands, mm-cm thick. light band is typically granoblastic and the dark band normally shows schistosity
Contact Metamorphism
Metamorphism due to heat but not pressure, occurring adjacent to igneous intrusions, no foliation but change to chemical composition
Dynamic Metamorphism
occurs in fault zones, directional stress leads to recrystalisation
Regional metamorphism
occurs over large areas with high/low temps/pressures, at convergent plate margins. minerals show preferred alignment
mylonite
forms at depth where ductile deformation oeads to recrystalisation producing a fine grained and highly deformed rock
Metamorphic rock produced by limestone
marble
metamorphic rock produced by sandstones high in quartz content/orthoquartzite
metaquartzite
Metamorphic rock produced by shale
slate, phyllite, schist, gneiss
