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Granite is found in large plutons on the continents, in areas where the Eart crust has been deeply eroded. This makes sense, because granite must solidify very slowly at deeply buried locations to make such large mineral grains. Plutons smaller than 100 square kilometers in area are called stocks, and larger ones are called batholiths.

Lavas erupt all over the Earth, but lava with the same composition as granite quot httpgeology.about.comonly erupts on the continents. That means that granite must form by the melting of continental rocks, which happens for two reasons, adding heat and adding volatiles (water or carbon dioxide or both).

Continents are relatively hot because they contain most of the planet

uranium and potassium, which heat up their surroundings through radioactive decay. Anywhere that the crust is thickened tends to get hot inside (for instance in the

 

What Granite Means

Students of granites classify them in three or four categories. I-type (igneous) granites appear to arise from the melting of preexisting igneous rocks, S-type (sedimentary) granites from melted sedimentary rocks (or their metamorphic equivalents in both cases). M-type (mantle) granites are rarer and are thought to have evolved directly from deeper melts in the mantle. A-type (anorogenic) granites now appear to be a special variety of I-type granites. The evidence is intricate and subtle, and the experts have been arguing for a long time, but that is the gist of where things stand now.

The immediate cause of granite collecting and rising in huge stocks and batholiths is thought to be the stretching apart, or extension, of a continent during plate tectonics. This explains how such large volumes of granite can enter the upper crust without exploding, shoving or melting their way upward. And it explains why the activity at the edges of plutons appears to be generally gentle and why their cooling is so slow.

On the grandest scale, granite represents the way the continents maintain themselves. The minerals in granitic rocks


and are carried to the sea. Plate tectonics returns these materials through seafloor spreading and subduction, sweeping them beneath the edges of the continents. There they are rendered back into feldspar and quartz, ready to rise again when and where the conditions are right.

Granite is found in large plutons on the continents, in areas where the Earthcrust has been deeply eroded. This makes sense, because granite must solidify very slowly at deeply buried locations to make such large mineral grains. Plutons smaller than 100 square kilometers in area are called stocks, and larger ones are called batholiths.

Lavas erupt all over the Earth, but lava with the same composition as granite  only erupts on the continents. That means that granite must form by the melting of continental rocks, which happens for two reasons, adding heat and adding volatiles (water or carbon dioxide or both).

Continents are relatively hot because they contain most of the plane uranium and potassium, which heat up their surroundings through radioactive decay. Anywhere that the crust is thickened tends to get hot inside (for instance in the

 

What Granite Means

Students of granites classify them in three or four categories. I-type (igneous) granites appear to arise from the melting of preexisting igneous rocks, S-type (sedimentary) granites from melted sedimentary rocks (or their metamorphic equivalents in both cases). M-type (mantle) granites are rarer and are thought to have evolved directly from deeper melts in the mantle. A-type (anorogenic) granites now appear to be a special variety of I-type granites. The evidence is intricate and subtle, and the experts have been arguing for a long time, but that is the gist of where things stand now.

The immediate cause of granite collecting and rising in huge stocks and batholiths is thought to be the stretching apart, or extension, of a continent during plate tectonics. This explains how such large volumes of granite can enter the upper crust without exploding, shoving or melting their way upward. And it explains why the activity at the edges of plutons appears to be generally gentle and why their cooling is so slow.

On the grandest scale, granite represents the way the continents maintain themselves. The minerals in granitic rocks


and are carried to the sea. Plate tectonics returns these materials through seafloor spreading and subduction, sweeping them beneath the edges of the continents. There they are rendered back into feldspar and quartz, ready to rise again when and where the conditions are right.

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