What the Syllabus says, and the Details
You need to be able to identify three metamorphic rocks; slate, schist and marble from their diagnostic properties:
As shown in the pictures below; the rocks have different identifying characteristics: -
Marble (the white rock) shows no foliation (lining up) of its crystals,
Slate (in the middle) has foliated crystals that show as layers of rock that split apart easily - this is referred to as a slaty cleavage.
Schist on the right) has its crystals arranged in layers - this type of foliation is called schistosity.
There are two types of metamorphism that you need to know about...
Contact Metamorphism is the result of the high temperatures caused by nearby magma intrusions making minerals in pre-existing rocks recrystallise. Marble is made in this way from the 'cooking' of limestone. The area area around the magma where contact metamorphism occurs is called the metamorphic aureole. This idea is shown by the diagram below.
Regional Metamorphism is the result of pressure on pre-existing rocks causing recrystallisation of the pre-existing material to form new minerals. Slates and Schists are formed in this way. Regional metamorphism is normally caused by plate collisions so vast, long, thin regions of metamorphism are produced such as the rocks of the Alps or Himalayas.
You need to be able to use the characteristics of metamorphic rocks [texture, acid reaction] as seen in hand specimens, diagrams/photographs and analysis of simple geological maps and cross sections to interpret their contrasting modes of formation
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