thumbnail

New method for the measurement of osmium isotopes applied to a New Zealand Cretaceous/Tertiary boundary shale

Nature

By:
, , , , ,
DOI: 10.1038/322816a0

Links

Abstract

The determination of osmium content and isotopic abundances in geological materials has received increasing attention in recent years following the proposal of Alvarez et al.1 that mass extinctions at the end of the Cretaceous period were caused by the impact of a large (???10km) meteorite which left anomalously high iridium levels as a geochemical signature in the boundary shales. Here we report a new and simple method for measuring osmium in geological materials, involving fusion of the sample with sodium peroxide, distillation of the osmium as the tetroxide using perchloric acid, extraction into chloroform, and absorption of the chloroform extract onto graphite powder before instrumental neutron activation analysis. In a variant of this technique, the chloroform extract is back-extracted into an aqueous phase and the osmium isotopes are determined by plasma-source mass spectrometry (ICPMS). We have used this method on the Woodside Creek (New Zealand) Cretaceous/Tertiary boundary clay and have obtained the first osmium content (6g ng g-1) for this material. The 187Os/186Os ratio is 1.12??0.16, showing a typical non-crustal signature. This combined distillation-extraction- ICPMS method will prove to be useful for measuring osmium isotopes in other geological materials. ?? 1986 Nature Publishing Group.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
New method for the measurement of osmium isotopes applied to a New Zealand Cretaceous/Tertiary boundary shale
Series title:
Nature
DOI:
10.1038/322816a0
Volume
322
Issue:
6082
Year Published:
1986
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
816
Last page:
817
Number of Pages:
2