Typecasting prospective Au-bearing sedimentary lithologies using sedimentary geochemistry and Nd isotopes in poorly exposed Proterozoic basins of the Tanami region, Northern Australia

Abstract

The development of a regional stratigraphy in Palaeoproterozoic basins within the Tanami region, Northern Australia has been hindered by the difficulty of discriminating sedimentary units and facies across this isolated and poorly exposed basin. A regional stratigraphy is important as it provides constraints on sedimentary basin evolution and assists in gold exploration. Gold is known to be more concentrated in certain rock formations. Based on Nd isotopes and whole-rock geochemistry, five main sedimentary events have been identified in the Tanami region. Some sedimentary units were derived from homogeneous local sources whereas others contain evidence of a well-mixed fine-grained remote provenance. Within the basins, major gold-bearing lithologies are characterised by mafic source indicators: (1) high Cr/Th ratios; (2) low Th/Sc ratios; (3) low (La/Yb) PAAS ratios relative to Post-Archaean Average Shale (Taylor and McLennan 1985); (4) Eu anomalies equal to ~1 and, (5) distinctive ranges in initial  Nd values. Potential future exploration target areas have been identified in the Tanami region at the Cashel and Sunline prospects using these geochemical parameters.

Proterozoic turbiditic depositional system (Tanami Group) in the Tanami region, northern Australia, and implications for gold mineralisation

“…These cores and outcrops are assigned to the Killi Killi Formation based on their whole-rock and trace-element geochemical and geochronological data (Cross & Crispe 2007;Lambeck et al 2008Lambeck et al , 2010). An additional drillcore, DBD 445 ( Figure 5), interpreted by Lambeck et al (2008) These surfaces were generated in Paradigm 2009 GOCAD 2.6.0 TM software to visualise the stratigraphic packages.…”

“…Regolith covers much of the region, making detailed lithostratigraphic correlation difficult (see Figure 4) and mapping the distribution of favourable host rocks for gold problematic. In this contribution, we combine the chemostratigraphic correlation proposed earlier (Lambeck et al 2008(Lambeck et al , 2010 with detailed core logs to establish depositional facies associations. We then combine these associations with seismic data (Goleby et al 2009) to construct a stratigraphic model for the evolution of the Tanami region.…”

“…The remainder of the region comprises siliciclastic sedimentary rocks deposited after ca 1865 Ma and intruded by post-1830 Ma granites, with both sedimentation and granite emplacement largely concluded by ca 1790 Ma Huston et al 2007;Lambeck et al 2008; Figure 3). (Lambeck et al 2008(Lambeck et al , 2010(Lambeck et al , 2011. The poorly outcropping Dead Bullock Formation contains mafic sediment that is iron-rich compared with felsic sediment of the overlying Killi Killi Formation (Lambeck et al 2008(Lambeck et al , 2011.…”

A Fragment of Columbia Supercontinent: Insight for Cathaysia Block Basement From Tectono‐Magmatic Evolution and Mantle Heterogeneity

“…Most of the felsic igneous rocks also plot in volcanic arc field in the Rb/30-Hf-Ta*3 diagram (Figure 1c). Data sources for north Australian craton are the following: Bagas et al (2009Bagas et al ( , 2010, Beyer et al (2012), Black and McCulloch (1984), Carson (2013), Champion (2013), Claoué-Long and Edgoose (2008), , Claoué-Long, , Compston (1994Compston ( , 1995, Cooper and Ding (1997), Crispe et al (2007), Cross and Crispe (2007), Donnellan (2013), Hoatson et al (2005), Hollis et al (2013), Iaccheri and Kemp (2018), Kositcin, Beyer, et al (2013), Kositcin, Carson, et al (2013), Lambeck et al (2008Lambeck et al ( , 2010, Li et al (2013Li et al ( , 2014, Maidment et al (2013), Nazaridehkordi et al (2017), Rösel et al (2014), Sivell and Mcculloch (1991), Smith (2001), Sun et al (1995), Thomas (2012), Wade et al (2008), Whelan, Beyer, et al (2014), Whelan, Woodhead, et al (2014), Windrim and McCulloch (1986), Windrim et al (1984), Zhao (1992Zhao ( , 1994, and Zhao and Mcculloch, (1995). However, compositions of granites essentially depend on the nature of their source rocks rather than the tectonic environment (Förster et al, 1997;…”

“…In Figure 2e, all these tholeiitic samples drop significantly above the DM curve. In GT terrane, the circa 1.86 Ga pillow basalts and sandstone from Dead Bullock Formation yield ε Nd (t) values up to +7.2 and +10.2, respectively, which is also much higher than the DM at that time and are interpreted to have been formed in a back-arc setting (Figure 2e; Bagas et al, 2008;Carson, 2013;Lambeck et al, 2010;Li et al, 2013). It is no coincidence that the two episodes of back-arc mafic magmatisms in Cathaysia block appear to be essentially synchronous with the BABB-like basaltic magmatism in Arunta and GT terranes, respectively.…”