Interpretation and modeling of aeromagnetic data from helicopter surveys of the Morobe goldfield, Papua New Guinea

Abstract

We interpreted and modelled aeromagnetic data from helicopter surveys of the Morobe goldfield, Papua New Guinea, by comparing gridded magnetic data with mapped surface geology. In some cases, geologic units may be recognized and distinguished based on contrasts in magnetic intensity and texture, including the Morobe Granodiorite, Kaindi Metamorphics, Bulolo Volcanics, and Langimar Beds. Magnetic anomalies occur due to intrusions of Edie Porphyry and related igneous rocks that are associated with gold mineralization. Numerous faults control the size and shape of the intrusions. Magnetic anomalies of interest were identified in gridded data from high-resolution surveys and modelled using flight line data. Two-dimensional magnetic models included dipping slabs with thicknesses of 100-400 m. Three-dimensional models were prepared, including a dipping tabular body and a dipping cylinder. A 2008 survey of the Papuan peninsula sponsored by the European Union (EU) provided continuous coverage of the Morobe goldfield area and helped resolve regional features that were only partially covered by previous smaller surveys. In particular, the EU survey covers the full length of the Sunshine Fault and greatly extends coverage of outcrops of the Morobe Granodiorite and Langimar Beds. The EU survey contains isolated anomalies south-west of Wau that may correspond to intrusions of Edie Porphyry, Morobe Granodiorite.