HKDSE Geography/E1/Metamorphic Rocks
< HKDSE Geography | E1
There are two main types of metamorphism:
Dynamic and regional metamorphism
editFormation:
- Internal stress accumulates along a fault or fold
- High pressure forces the minerals to realign to form metamorphic rocks
- Rocks are flatted and the minerals are aligned towards the plane of flattening
- A foliated structure is formed
Conditions:
- Associated with large-scale mountain-building processes (the collision of two continental plates or the subduction of an oceanic plate)
- High temperature and pressure
Examples:
- Shale/Mudstone/Siltstone → Slate → Phyllite → Schist → Gneiss
- Granite → Gneiss
Contact/thermal metamorphism
edit- Rising magma intrudes into the rock strata
- Heat from magma intrusion creates high temperature, which melts and recrystallises the rock crystals into new rock
This is a localised process. The zone of contact between the existing rock and the intrusion - i.e. where the metamorphism takes place - is the aureole. The rocks do not have a foliated structure.
Conditions:
- High temperature
- Magma intrusion
Examples:
- Bituminous coal → Anthracite
- Sandstone → Quartzite
- Limestone → Marble