The ultramafic–intermediate Riwaka Complex, New Zealand: summary of the petrology, geochemistry and related Ni–Cu–PGE mineralisation

The geotectonic setting, age and mineral deposit inventory of global layered intrusions

“…New Zealand hosts several arc-related Triassic layered intrusions (e.g., Riwaka, Otu, Pahia, Greenhills, Knobs, and Lone Stag) that tend to contain amphibole as a primary cumulate phase and thus appear to have crystallised from a relatively hydrous basaltic magma (~ 11-13 wt.% MgO) of calc-alkaline affinity (Spandler et al 2005). The Riwaka Complex consists of out-of-sequence intrusive sheets characterised by sharp and crosscutting boundaries, with subordinate evidence for crystal accumulation and modal layering (Turnbull et al 2017). The intrusion contains Ni-Cu-PGE sulphides that occur predominantly in hornblende-bearing clinopyroxenite (2.2% Ni, 2.1% Cu, and 1 g/t PGE from grab samples; Turnbull et al 2017).…”

“…The Riwaka Complex consists of out-of-sequence intrusive sheets characterised by sharp and crosscutting boundaries, with subordinate evidence for crystal accumulation and modal layering (Turnbull et al 2017). The intrusion contains Ni-Cu-PGE sulphides that occur predominantly in hornblende-bearing clinopyroxenite (2.2% Ni, 2.1% Cu, and 1 g/t PGE from grab samples; Turnbull et al 2017). Localised enrichments in PGE have also been reported in the lower units of the Greenhills (Spandler et al 2000) and Pahia (Ashley et al 2012) intrusions.…”