Abstract
Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time.
Highlights
This paper focuses only on the pyrites and chalcopyrites which are the two most common Au-bearing sulphides of the Golpu and Nambonga North porphyry deposits
The Main Golpu porphyry had 39 pyrite analyses where 13 of them were below the detection limit (
The porphyry-related alteration and mineralisation are centred at the Golpu Porphyries and Nambonga North Porphyry, which are separate porphyry systems but cooling intrusions responsible for supplying magmatic-hydrothermal fluids may be sourced from the same, larger magma chamber at depth
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Papua New Guinea’s unique geological heritage and its striking natural resources result from its location in the Southwest Pacific along the famous ‘Pacific Ring of Fire’. Porphyry Cu-Au and epithermal Au deposits are common [1,2,3] along the major magmatic arcs of the northward-moving Indo-Australian plate and the westward-moving Pacific plate [4,5,6]. The northwest trending collisional zone in the interior of mainland PNG defines the New Guinea Orogenic Belt and hosts several porphyry and epithermal deposits such as
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