187Re-187Os Calibration of Molybdenite from Henderson, Colorado: A New NIST Reference Material

Colorado State University, Fort Collins CO

Investigators

Abstract

0111876 Stein Use of the geochronometer based on the decay of rhenium (Re) to osmium (Os) is rapidly expanding, and there are no reference materials certified by the National Institute of Standards and Technology (NIST) for inter-laboratory comparison. Advances in chemical and mass spectrometric procedures permit high precision determination of Re and Os, even on low-ppt level samples. Molybdenite (MoS2) is uniquely suited for the Re-Os chronometer because it commonly contains high concentrations of the parent Re and essentially no initial daughter Os. Thus, the decay of 187Re to 187Os yields precise ages, even in very young samples, without correction for initial Os. With increasing demand for Re-Os dating, particularly of molybdenite, the need for an accepted reference material for inter-laboratory comparison has become crucial. We propose to calibrate a Re-Os molybdenite reference material, working together with University of Alberta and NIST. The proposed Re-Os reference molybdenite is from Henderson, Colorado, the location of a well-studied molybdenum deposit. NIST will physically mix, split, and bottle the Henderson molybdenite powder. Statistically representative sets of samples will be analyzed by the AIRIE Lab at Colorado State University and by the isotope lab at the University of Alberta. The distribution of the reference material will be fully handled by NIST, and the cost for the molybdenite reference material will reflect only the costs incurred by NIST for their part of the work. ***