Question: what is any process that changes a rock's chemical composition
[{'answer': 'metamorphism', 'provenance': [{'wikipedia_id': '44424', 'title': 'Metamorphic rock', 'start_paragraph_id': 1, 'start_character': 92, 'end_paragraph_id': 1, 'end_character': 104, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '44424', 'title': 'Metamorphic rock', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 373, 'bleu_score': 0.873294914575339, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13902334420472514866}, 'section': 'Section::::Abstract.'}]}]