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摘要
stable isotopes of o, h and s were used to investigate the origin of magmatic rocks of the jauru and the pontes e lacerda terrains, sw portion of the amazonian craton, mato grosso state, brazil. granitic rocks of the alto jauru greenstone belt and cachoeirinha suite, jauru terrain, present 汛18o values between +9.0ˋ and +6.3ˋ, indicative of derivation from juvenile magmas. the rio branco intrusive suite basic and felsic rocks%26apos; 汛18o values fall, respectively, within +5.4ˋ to +5.8ˋ and +8.7ˋ to +9.0ˋ ranges; the intermediate rocks present 汛18o between +7.3ˋ and +8.3ˋ. the lower values of 汛18o, obtained from basic rocks, are compatible with a mantle source, however the felsic rocks present 汛18o values indicative of crustal source. the stable isotopes of hydrogen yielded 汛d values between - 83ˋ and - 92ˋ, different from the 汛d signatures of metamorphic rocks and rain water. sulphur isotopes in sulfides from basic and intermediate rocks of the rio branco suite presented 汛34s values coherent with a mantle source (between + 0.7ˋ and +3.8ˋ), whereas 汛34s values between + 5.2ˋ and + 6.1ˋ, obtained from the felsic rocks, suggest crustal participation in their genesis. for the santa helena suite (pontes e lacerda terrain) the 汛18o values fall between +4.4ˋ and +8.9ˋ. the present study confirms the advantages of using stable isotopes to understand magmatic processes and crustal evolution.
