Single-shot laser ablation split stream (SS-LASS) petrochronology deciphers multiple, short-duration metamorphic events

•SS-LASS capable of dating zircon rims < 1 μm (or rims with composite age structure) to within 106 yr, for Cenozoic rocks•High spatial and temporal resolution of SS-LASS offers great promise for study of short-duration metamorphic phenomena.•SS-LASS able to decipher four zircon growth events at 33.0, 28.3, 23.0 and 18.2 Ma in the Cordillera de la Costa, Venezuela•(Hydro)thermal activity at 33.0, 28.3, 23.0 and 18.2 Ma mark episodes of tectonism affecting South American plate margin

Single-shot laser ablation split stream (SS-LASS) petrochronology offers spatial resolution of < 1 μm per (surface) analysis. This enables the technique to interrogate metamorphic zircon overgrowths that are very thin, or that preserve a composite age structure. To demonstrate the advantages of SS-LASS, the technique was applied to metamorphic zircon overgrowths in five rocks from the Cordillera de la Costa, Venezuela. In these rocks, SS-LASS was able to decipher discrete, short-duration (< 106 yr) zircon growth events at c. 33.0, c. 28.3, c. 23.0 and c. 18.2 Ma. Comparison with existing geo-/thermochronology suggests that the SS-LASS dates represent (hydro)thermal events that mark distinct episodes of tectonism affecting the northern margin of South America.With an external error of 5% incorporated into isotope ratios (as required to achieve satisfactory analytical precision), SS-LASS dates for reference materials were accurate to within 1.5% of published values. The SS-LASS technique is thus, in favorable cases, capable of providing < 106 yr resolution for Cenozoic rocks. Methods in 'geospeedometry'-which employ forward models to reproduce observed diffusion length scales-have obtained anomalously short time scales of 104-106 yr for metamorphism. The high spatial and temporal resolution of SS-LASS offers tremendous promise for investigating the veracity of these claims.