Granitic magma primarily crystallizes into a variety of minerals as it cools. The specific minerals that crystallize from granitic magma at temperatures ranging from approximately 640°C to 930°C include:
- Quartz - typically crystallizes last as the magma cools further.
- Feldspar - both plagioclase (usually in the range of andesine to oligoclase) and alkali feldspar (such as orthoclase) crystallize at these temperatures.
- Muscovite - typically forms at temperatures above 600°C.
- Biotite - can also crystallize in this temperature range.
- Amphibole - specifically hornblende, may crystallize depending on the composition of the magma.
- Pyroxene - in some cases, augite may crystallize.
When granitic magma fully crystallizes, it will consist of these minerals in varying proportions, primarily resulting in a granite rock.
In terms of metamorphic facies, once a granitic body has crystallized, it would typically fall under the granulite facies if subjected to high temperatures and pressures after crystallization. However, if it remains in a cooler, less pressured environment, it could be part of the greenschist facies if there are significant metamorphic processes involved. Moreover, if the granite experiences conditions typical of contact metamorphism, it can also interact with high-grade metamorphic facies close to igneous intrusions.
In summary, the crystallizing minerals from granitic magma around 640°C-930°C are quartz, feldspar (both plagioclase and alkali), micas (muscovite and biotite), and possibly amphibole and pyroxene, and during metamorphism, it may relate to granulite or greenschist facies depending on specific geological conditions.
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