Abstract

Concordant radiocarbon and cosmogenic 3He dates of 3 and 11 ka on basalt flows and associated scoria deposits from the Zuni-Bandera volcanic field in New Mexico further substantiate published production rates and latitudinal and altitudinal corrections for 3He. Identical 3He concentrations in coexisting olivine and clinopyroxene confirm that these two minerals have very similar production rates. A cosmogenic 3He date of 57 ka on another flow is concordant with a U-series date and is younger than two K-Ar dates, suggesting that this flow contains excess 40Ar. This excess 40Ar is also evident in gases released by vacuum crushing of olivine-clinopyroxene fractions from all three flows.

First Page Preview

First page PDF preview
You do not currently have access to this article.