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What does Porphyritic mean ?

Porphyritic is commonly applied to igneous rocks and relates to their bi-modal grain size distribution; meaning 2 main grain sizes usually one larger than the other. The occurrence of this is down to the dif...
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Answered by Michael H. • Geology tutor
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Describe the formation of mineral deposits at hydrothermal vents

Hydrothermal vents form where cold seawater percolates down into the Earth's oceanic crust, and is superheated by the geothermal gradient. Under the confining pressure of the surrounding rock and the overlyi...
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Answered by Chris B. • Geology tutor
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What are the three broad classifications of rock type? How is each produced?

The three main classifications of rock are igneous, sedimentary and metamorphic. Igneous rocks are produced by volcanic eruptions and form via the solidification of lava. Sedimentary rocks form via the erosi...
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Answered by Benjamin R. • Geology tutor
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Explain 2 features of a pluton/surrounding country rock that may influence the width of themetamorphic aureoles

When a pluton (essentially a large pocket of magma) intrudes into rock, the heat from the pluton 'bakes' the surrounding rock- remember that heating a rock to high temperatures will initiate contact metamorp...
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Answered by Demi S. • Geology tutor
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How can you tell the environment a sedimentary rock is deposited in?

The first stage in the formation of a sedimentary rock is the deposition of sediment. The size, shape and type of sediment can tell you lots about the depositional environment. In a high energy environment, ...
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Answered by Holly U. • Geology tutor
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