F2 - Surface and Internal Processes of the Rock Cycle - Key Idea 2 Flashcards
Metamorphic minerals
- Quartz
- Orthoclase feldspar
- Muscovite mica
- Biotite mica
- Hornblende
- Augite
- Chiastolite/Andalusite
- Garnet
- Calcite
- Clay minerals (low grade)
Size
Measurements - um, mm, cm
Description - fine, medium, coarse
Shape
Euhedral - perfect shape - can be phenocrysts - longer cooling
Subhedral - in between - only phenocrysts
Anhedral - no shape - shorter cooling
Colour
Dark - Mafic
Medium - Intermediate
Light - Silicic
Composition
What minerals are in the rock and what percentage of the rock do they make up
Texture
- Interlocking crystals - rate of cooling/crystallisation
Equicrystalline - all crystals are a similar size, formed at the same rate
Vesicular - gas bubbles in lava flows, measure size of vesicles, can be flow oriented
Porphyritic - more than one crystal size, coarser crystals in a finer ground mass, phenocrysts
Fragmental - volcanic material from explosive volcanoes
Glassy - looks like glass
Crystalline - all igneous rock other than fragmental rocks
Vesicular
Gas is dissolved in magna at depth due to high pressure
Magma erupts onto the surface (lava), the pressure is lower and the gas exsolves (comes out of solution)
Fragmental
Fine - Tuff
Medium - ???
Coarse - Agglomerate
Granite
Size - Coarse 2mm-2cm
Shape - Anhedral
Colour - Light
Composition - Quartz 30%, Biotite 20%, Orthoclase 40%, Muscovite 10%
Texture - Equicrystalline, crystalline
Gabbro
Size - Coarse 5mm
Shape - Anhedral
Colour - Dark
Composition - Plagioclase 40%, Hornblende + Augite 60%
Texture - Equicrystalline, crystalline
Dolerite
Size - Medium
Shape - Medium
Colour - Dark
Composition - Plagioclase 30%, Hornblende + Augite 70%
Texture - Equicrystalline, Crystalline
Peridotite
Size - Coarse 1-2mm
Shape - Anhedral
Colour - Dark
Composition - Olivine 50%, Augite 50%
Texture - Equicrystalline, Crystalline
Major intrusions
