Fourteen K-Ar age values from the Santa Marta schists (Colombia), of greenschist and amphibolite metamorphic facies, indicate two metamorphic episodes: mid-Cretaceous (or older) and Paleocene. Argon retentivity of hornblende appears to be little affected by a large Eocene diorite batholith, except near the contact. Whole-rock phyllitesamples from the same terrain give mid-Tertiary age values, suggesting considerable argon loss.

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