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زمینشناسی و معدن::
سنگ گوشته
As shown in Figure 4.18, when a typical geothermal gradient is compared to the melting point curve for the mantle rock peridotite, the temperature at which peridotite melts is higher than the geothermal gradient.
However, tectonic processes trigger melting though various means, including reducing the melting point (temperature) of mantle rock.
Decompression melting occurs wherever hot, solid mantle rock ascends, thereby moving into regions of lower pressure.
Below the ridge crest, hot mantle rock rises and melts, generating a magma that replaces the material that shifted horizontally away from the ridge axis.
At a depth of about 100 kilometers (60 miles) the wedge of mantle rock is sufficiently hot that the addition of water leads to some melting.
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