Question: what types of rocks are in the canadian shield
[{'answer': 'Precambrian', 'provenance': [{'wikipedia_id': '6230', 'title': 'Canadian Shield', 'start_paragraph_id': 1, 'start_character': 100, 'end_paragraph_id': 1, 'end_character': 111, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'igneous', 'provenance': [{'wikipedia_id': '6230', 'title': 'Canadian Shield', 'start_paragraph_id': 1, 'start_character': 112, 'end_paragraph_id': 1, 'end_character': 119, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'high - grade metamorphic', 'provenance': [{'wikipedia_id': '6230', 'title': 'Canadian Shield', 'start_paragraph_id': 1, 'start_character': 124, 'end_paragraph_id': 1, 'end_character': 152, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '6230', 'title': 'Canadian Shield', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 725, 'bleu_score': 0.9530446225172671, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4619429967665754413}, 'section': 'Section::::Abstract.'}]}]