Abstract
Detrital zircon grains preserved within clasts and the matrix of a basal diamictite sequence directly overlying the Carrapateena IOCG deposit in the Gawler Craton, South Australia are shown here to preserve U–Pb ages and geochemical signatures that can be related to underlying mineralisation. The zircon geochemical signature is characterised by elevated heavy rare-earth element fractionation values (GdN/YbN ≥ 0.15) and high Eu ratios (Eu/Eu* ≥ 0.6). This geochemical signature has previously been recognised within zircon derived from within the Carrapateena orebody and can be used to distinguish zircon associated with IOCG mineralisation from background zircon preserved within stratigraphically equivalent regionally unaltered and altered samples. The results demonstrate that zircon chemistry is preserved through processes of weathering, erosion, transport, and incorporation into cover sequence materials and, therefore, may be dispersed within the cover sequence, effectively increasing the geochemical footprint of the IOCG mineralisation. The zircon geochemical criteria have potential to be applied to whole-rock geochemical data for the cover sequence diamictite in the Carrapateena area; however, this requires understanding of the presence of minerals that may influence the HREE fractionation (GdN/YbN) and/or Eu/Eu* results (e.g., xenotime, feldspar).
Highlights
Assessment of the heavy rare-earth element (HREE) fractionation content and Eu/Eu* ratios of whole-rock geochemistry data for the cover sequence samples used in this study shows that samples display geochemical characteristics that can be compared to zircon criteria (Figures 7 and 8)
Given that this study demonstrated that the zircon geochemical exploration criteria could be applied using whole-rock geochemistry, new handheld technologies may allow for faster application of the criteria
The cover sequence basal diamictite lying directly at the basement–cover unconformity over the Carrapateena iron oxide–copper–gold (IOCG) deposit contains rounded to angular clasts of variable lithology that are primarily ~1850 Ma, suggesting they have been derived from the underlying
Summary
Introduction published maps and institutional affilMineral exploration is becoming increasingly challenging as the exploration for ore deposits moves into terranes that are buried and overlain by extensive cover sequences [1,2].Cover sequences are commonly considered a hindrance in exploration; in the last~20 years, research has increasingly focused on how the geochemical signatures of mineral systems can be translated into overlying cover sequences and aid exploration [3,4,5,6,7].Geochemical signatures can be transported into the overlying cover through chemical [3,8]and mechanical [5,6,7,9] processes, and are commonly preserved in resistate phases (e.g., zircon, monazite, rutile [6,10,11,12]). From a barren basal diamictite overlying the Carrapateena IOCG deposit is assessed to gold (IOCG) provinces and hosts several large deposits including Olympic Dam, Promidetermine if there is any similarity with that of zircon grains from the underlying minernent Hill, and Carrapateena [13,18] (Figure 1a). This metallogenic province hosts numeralised basement rocks. Copper–gold mineralisation is extend the geochemical signature of an IOCG deposit in cover sequences, and be widely regarded as predominantly forming during a major tectonothermal and magmatic a useful tool for IOCG exploration in areas of thick cover. Copper–gold mineralisation is widely regarded as predominantly forming during a major tectonothermal and magmatic event at
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