Constant 4He Concentration and 190Pt‐4He age of Detrital Pt‐Alloy Grains from the Santiago River, Ecuador: Potential as a 4He Mineral Reference Material

Abstract

Over the last few decades geo‐ and thermochronological techniques based on the accumulation of radiogenic 4He in minerals have gained popularity. Currently there is no mineral‐based 4He reference material that allows routine screening of gas extraction and measurement procedures. The commonly‐used mineral reference material for (U‐Th)/He thermochronology have variable U and Th contents which result in variable 4He concentrations. Here we demonstrate that native platinum grains (RS‐Pt) from placer deposits in the Santiago River, Ecuador, yield constant 4He contents and may be used as a reference material. Helium concentrations measured at the Scottish Universities Environmental Research Centre (n = 8) and Institute of Precambrian Geology and Geochronology RAS (n = 9) noble gas laboratories yield mean 4He concentrations that overlap at the 95% confidence level. The weighted mean 4He concentration is 215 ± 4 × 1011 at g‐1 (2s) and mean 190Pt‐4He age is 39.6 ± 0.7 Ma (2s). Samples of the Santiago River Pt concentrate are available on request from the SUERC laboratory.