Abstract
In the El Vapor creek (Puerto Berrio-Antioquia), mylonitic rocks were identified. The geochemical data for the mylonites revea] high SiO2 content (65.7 to 80.9 wt %) and a peraluminous character. A Rb-Sr isochron for these mylonites yielded an age of 894 ± 36 Ma, with an initial 87Sr/86Sr ratio of ca. 0.71785. This date is interpreted here as a metamorphic resetting age in response to the Grenvillian orogeny. The high initial ratio suggests a long crustal residence period. This interpretation is confirmed with TDM model a ges of 1757 and 1829 Ma and zircon evaporation age of 1.1 Ga.
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References
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