The timing of sulfide mineralisation at the Reward, Rockface and Bellbird deposits, Jervois mineral field, Aileron Province

Abstract

Molybdenite and pyrite in five mineralised samples from the Jervois mineral field, northeastern Aileron Province, Central Australia were dated using the Re–Os (rhenium-osmium) method. Three samples with molybdenite were collected from the Reward polymetallic deposit and one from the Rockface Cu–Ag (copper-silver) deposit. One sample with pyrite was collected from the Bellbird polymetallic deposit. The molybdenite samples from the Reward deposit yielded ages of 1766 ± 8 Ma, 1763 ± 8Ma, and 1706 ± 7 Ma; the molybdenite sample from the Rockface deposit yielded an age of 1742 ± 8 Ma. Pyrite from the Bellbird deposit sample failed to yield a robust or geologically meaningful age.

Sulfides from the Reward deposit with an age of ca 1.77 Ga are directly associated with chalcopyrite (the main ore mineral at the Jervois deposits) and are therefore interpreted to provide an absolute age for the timing of this copper mineralisation. The other Reward deposit age of 1.76 Ga and the results of ca 1.74 Ga at the Rockface deposit and ca 1.71 Ga at the Reward deposit provide minimum ages for alteration or deformation of these samples, or remobilisation of pre-existing copper mineralisation.

In context with other regional data, all four new molybdenite ages suggest that hydrothermal activity related to mineralisation in the Jervois mineral field occurred during the Paleoproterozoic, contemporaneously with the intrusion of multiple pulses of silicate magma during a high-temperature and low-pressure tectonothermal cycle.