The Doriri Creek Ni-PGE occurrence, Papua New Guinea: mineralogy and geochemistry of the ore and host rock alteration halo

[摘要] The Doriri Creek (DC) prospect is located in the Papuan Ultramafic Belt in the Mt Suckling area in PNG, 3 km from the contact of the Australian and Woodlark (South PNG) tectonic plates. The Doriri Creek prospect is the result of episodic hydrothermal fluids flowing through the Doriri fault (orientation ~330/70-80E) that resulted in Ni concentration (grades up to 1.55 wt% nickel, up to ~15 m width and ~500 m long) during the alteration of an ultramafic unit of peridotites/pyroxenites within a Mg-rich gabbronorite envelope. Ni is concentrated in chlorite and serpentine group minerals and in Fe oxides, with a minor amount in pentlandite in locally sulfidic samples. The ore mineralogy is also associated with a high concentration of phosphorous in the form of apatite that concentrates LREE (Light Rare Earth Elements). Palladium concentrations correlate with Te-Se and Ni content in the ore samples, which are enriched in Pd up to 0.37 ppm. Platinum is present in concentrations up to 0.06 ppm.There is a rock host unit (dunite, D42) in the North of the Doriri Creek nickel prospect that displays primary platinum group element enrichment not associated to hydrothermal activity (Ir ~23 ppb; Pd ~65; Pt 320; Rh ~30; and Ru ~54 ppb).The Doriri Creek alteration halo is narrow, ~100 m in width, and more pronounced to the West than to the East, and is characterized by enrichments of U, K and W over background values, as well as a local magnetite concentration of up to ~35 % of the rock sample, which is very pronounced in a locally sulfide rich area of the system. The top part of the DC system is overprinted by tropical weathering, which displays REE fractionation, characterized by LREE enrichment and positive Ce anomalies.Exploration criteria for DC type prospects in the area are: background enrichments of U, K, W and P, in combination with magnetic positive anomalies (magnetite content), associated with faults in the proximity of the Mt Suckling intrusion. Based on the previous criteria and a combination of magnetic and radiometric geophysical surveys supplied by PPM, and the geological/geochemical data presented in this study, an area to the NE of the DC prospect has been identified as highly prospective for hydrothermal Ni mineralization.

[发布机构] CSIRO

[效力级别] Geochemistry not elsewhere classified [学科分类] 地球科学(综合)