Imagine you are analyzing a metamorphic rock and find that it contains beta quartz and andalusite. Under which of the following temperature and pressure conditions could this metamorphic rock have been formed?

2-9 kilobar and 450-700 degrees Celsius

Explanation:

Metamorphic rocks are commonly formed at temperatures greater than 200 degrees Celsius and pressures greater than 3kiloBar. This temperature and pressures can only be achieved deep beneath the earth surface where the temperature is high and and the pressure is great. It is natural for metamorphic rocks to contain quartz because it is an inherited mineral. But on the other hand, the grade of metamorphism also determines the kind of mineral that can be found in a metamorphic rock. There is high grade metamorphism(high temperature, high pressure). An example of such mineral is sillimanite. We also have medium grade and low grade metamorphism according to their respective temperature and pressure. Andalusite mineral falls under the medium grade metamorphism. A medium grade metamorphism occurs around 450-700 degrees of temperature and pressure of 2-9 kilobar.

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