Age of the Deccan traps using 187Re-187Os systematics

A suite of basaltic rocks sampled over a vast exposure and stratigraphic thickness in the Deccan traps has been investigated for Os isotopic systematics. The results plot on a very well defined Re-Os isochron corresponding to an age of 65.6 +/- 0.3 Ma (2 sigma uncertainty). This age is in excellent agreement with previous K-Ar and Ar-Ar data. Os data also imply a short duration of volcanism, which should have important implications on mantle geodynamics. The Os-187/Os-188 initial ratio is typically chondritic: 0.12843 +/- 0.00047 (2 sigma) and indicates that metasomatism and crustal contamination played only a very minor role in the Re-Os budget during formation of the Deccan traps. (C) 1999 Elsevier Science B.V. All rights reserved.