Constraints on the timing of sulfide breccia formation at the Grapple Cu-Au-Ag-Zn prospect, central Australia: in situ LA-ICP-MS monazite geochronology of a new Proterozoic greenfields discovery

Abstract

Monazite was dated in one sample of andalusite-biotite-muscovite schist from the Lander Rock Formation that hosts sulfide mineralisation at the Grapple Cu-Au-Ag-Zn-Pb-Co prospect, Willie (MOUNT RENNIE) in the Aileron Province, Northern Territory. Monazite dating was carried out in order to constrain the timing of mineralisation in this Proterozoic greenfields area. A single 207Pb/206Pb date of ca 1719 Ma obtained for monazite included in andalusite may relate to monazite growth prior to or during metamorphism. A 207Pb/206Pb age of 1668 +/- 7 Ma for monazite overprinting the main mylonite fabric is interpreted to be related to hydrothermal fluid flow during, or shortly after, mylonite formation in this sample. Based on cross-cutting relationships observed in drill core, this monazite age places a maximum timing constraint on sulfide breccia formation at the Grapple prospect, and suggests a likely mineralisation age. The age is similar to the emplacement age of ca 1640 Ma for the Andrew Young Igneous Complex, and other magmatism on MOUNT RENNIE, indicating a plausible genetic link between these igneous intrusions and the sulfide mineralisation.