Section 5.2 Flashcards
Compare the colour, content, and give examples of felsic and mafic rocks.
Felsic: Colour- light-coloured Content- high silica contents; contain Quartz and the feldspar orthoclase and plagioclase Example- granite Mafic: Colour- dark-coloured Content- lower silica contents and are rich in iron and magnesium. Contain plagioclase, biotite, amphibole, pyroxene, and olivine. Example- gabbro
What are ultramafic rocks? How are they formed (two theories)?
Ultra mafic rocks are formed by the fractional crystallization of olivine and pyroxene as the minerals may have been separated from magma and did not convert to another mineral upon reaching a different temperature. Others believe that ultra mafic rocks represent pieces of the upper mantle that have been brought to Earth’s surface.
What is the composition of ultramafic rocks?
The composition of these rocks is that they have low silica contents and very high levels of iron and magnesium.
How do different cooling rates contribute to the variety of grain sizes seen in igneous rock?
When lava flows on Earth’ surface and is exposed to air and moisture, if it cools quickly there is not enough time for large crystals to form and if it cools slowly beneath Earth’s surface there is sufficient time for large crystals to form.
Are there visible mineral grains in extrusive igneous rocks and intrusive igneous rocks?
Extrusive igneous rocks- no visible mineral grains
Intrusive igneous rocks- visible mineral grains
What is porphyrite texture characterized by?
Large, well-formed crystals surrounded by finer-grained crystals of the same mineral or different minerals. It occurs when a slowly cooling magma suddenly begins cooling rapidly.
What is an important igneous rocks that is used in construction? Why?
Granite because it is among the most durable of the igneous rocks due to the interlocking grain textures and resistance to weathering.
What are metallic elements that are not incorporated into the common igneous minerals and are released at the end of magma crystallization and solidified into veins?
Gold, silver, lead, and copper
What are the elements that are found in the veins of pegmatites?
Lithium and beryllium
What are the valuable minerals that are found in kimberlite? How are they formed?
The valuable minerals that are found in kimberlite are diamonds. They are formed deep in Earth’s crust at depths of 150-300 km because diamonds and other minerals found in kimberlite a can only form under very high pressure.
