What processes are related to metamorphism

Metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids.

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Which is most likely why many scientists reject the cold fusion theory?

The original results have not been replicated consistently and reliably. Martin Fleischmann and Stanley Pons were the first scientists to have conducted this but when replicated, gave lacking results.