prograde metamorphism
Quick Summary
Prograde metamorphism refers to the changes in a rock's mineral composition and assemblage that occur as it is subjected to increasing temperature and pressure, typically during burial deep within the Earth's crust. These changes are driven by heat flow from the Earth's mantle, radioactive decay within the crust, and tectonic processes.12
Key factors influencing prograde metamorphism include:
* Temperature: Ranges from about 150°C to 1100°C, depending on the rock's composition.2
* Pressure: Primarily caused by the weight of overlying rocks, increasing with depth. Pressures can range from a few hundred bars to over 20 kilobars in continental crust.3
* Rock Composition: The original chemical makeup of the rock (e.g., pelitic, calcareous, felsic, mafic) dictates the types of minerals that can form.4
During prograde metamorphism, minerals that are stable at lower temperatures and pressures break down and recrystallize into new minerals stable under the higher-grade conditions. This process can lead to significant changes in the rock's texture and appearance.1
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