Abstract
A literature review about the Rb/Sr systematics in undertaken, as applied to granitoid rocks, poiting out potentials and interpretation limitations. Ages derived from Rb/Sr isochrons pinpoint either crystallization or post-crystallization homogenization events. Isochronic Sr/ 86 Sr initial ratios are a clue to the Sr evolution stage at the site of magma generation, and can evaluate the relative crustal-mantle contributions. Cogenetic granitoids, generated from isotopically homogeneous sources, show identical initial ratios: isochronic ages should pinpoint the true emplacement age, since magma cooling is generally thought to be a fast geologic process. Neverthless, supposed cogenetic granitoid often present real variations in initial ratios, a behavior which prcbably can be explained by several petrogenetic processes (e.g., mixing of magmas, crystal separation from magma mushes during protracted crystallization, assimilation of country rocks). Some of the cited mechanisms can be simulated using several Rb/Sr variation diagrams. Provided data dispersion is not linked to systematic errors of various kinds, it is clear thar anomalous Rb/Sr data reflect the influence of the cited genetic mechanisms, and may thus become valuable tool for petrogenetic interpretations. Rb/Sr data of selected Brazilian granitoid massifs show significant spread; a brief discussion of these and of the corresponding geological setting indicate that many discrepancies arise from analytical and/or interpretation errors, although it is clear that several ones are actually due to the influence of complications in the petrogenetic process, such as pointed out above.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
