February 2020
Volume 72    Issue 2

Rhenium in molybdenite: A database approach to identifying geochemical controls on the distribution of a critical element

Barton, Isabel F.; Rathkopf, Christian A.; Barton, Mark D.

ABSTRACT:

Rhenium (Re) is one of the rarest elements on earth and is a designated critical element in the United States and European Union for its uses in superalloys. Unusually among critical elements, Re is produced entirely as a byproduct of molybdenite (MoS2) mining, as pure Re minerals are extremely rare. However, Re concentration in natural molybdenites varies from a few parts per trillion to tens of percent. There are few known consistent patterns and no firmly established reason for this variation, making it difficult to use molybdenite Re content as a proxy for metal grades, a vector to high grades, a clue to the geological and geochemical nature of the ore deposit, a guide to overall Re resources or for any other of the applications that have been suggested for it over time. 

   In this paper and accompanying database, we have compiled more than 3,000 measurements of Re concentrations in molybdenite from more than 700 ore deposits and other hydrothermal systems. Using these data, we examined variations in molybdenite Re content with ore deposit type, metal grades, associated rock types and other geological characteristics. The results show that molybdenite Re concentration is largely uncorrelated with copper (Cu) grade, temperature and depth of ore formation, mantle influence or age of system. Molybdenite Re concentration shows positive correlations with intermediate igneous compositions and with relatively oxidized ore-forming systems, and negative correlation with Mo grades. These empirical trends indicate that the concentration of Re in molybdenite is controlled by the redox state and sulfide availability in the ore-forming systems. The analysis and accompanying database can be used in exploration as aides to evaluating deposits’ Re resource potential, redox history, and other geochemical characteristics. 

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