The peroxide here serves as a radical chain initiator. In the field of chemistry the radical initiatives are those substances that are used in industrial processes like polymer synthesis. These initiatives have weak bonds generally and they're mostly used to create free radicals. These radicals are atoms that have odd numbers of electrons. Peroxide is an example of such.
It allows a scientist to understand the history of metamorphic rock by estimating the temperature, depth, and pressure at which a rock undergoes metamorphism.
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