40Ar/39Ar incremental-release age of biotite from a gabbro of the Shabogamo intrusive suite, southwestern Labrador

Abstract

Biotite from a gabbro sill of the Shabogamo intrusive suite in southwestern Labrador records a well defined 40Ar/39Ar plateau age of 1353 ± 17 Ma. This is similar to the 1375 ± 60 Ma dates recorded by Sm–Nd and Rb–Sr whole-rock isotopic systems of the suite. Together, recent radiometric results suggest that members of the suite were emplaced at approximately 1375 Ma and cooled quickly at shallow crustal levels.