Detrital Zircon Perspectives on Heavy Mineral Sand Systems, Eucla Basin, Australia

Abstract

Abstract Southern Australia’s Cenozoic Eucla basin contains world-class strandline heavy mineral deposits. This study links detrital zircon U-Pb geochronology and heavy mineral compositions from four mineral sand prospects, and a suite of published deposits, to bounding Archean to Neoproterozoic crustal areas. A variable number of distinct sediment sources is recorded from each prospect’s detrital zircon age spectrum. This variability in zircon ages, quantified using a Shannon-Weaver test, serves as a metric of source region heterogeneity. Greater zircon age heterogeneity correlates with heavy mineral enrichment. Enhanced heavy mineral yields reflect retention of resistate over labile minerals—a function of greater sediment transport, reworking, and upgrading processes that parallel those that result in detrital zircon age polymodality. In this case study, greater reworking in intermediate storage sites and transport by longshore processes, eastward along the ~1,000 km spanned by the study sites, corresponds to the direction of progressive heavy mineral enrichment identified in zircon ages and mineral compositions. This approach is a proxy for the duration minerals have spent in the sedimentary system and provides an important perspective for understanding heavy mineral sands.