Aeromagnetic Interpretation of Wau-Bulolo Region, Papua New Guinea

A geologic interpretation of the gold-bearing Wau-Bulolo region, Papua New Guinea, was prepared using data from three aeromagnetic surveys and existing geologic maps. Magnetic lineaments are consistent with many previously mapped contacts and faults, but help resolve discrepancies in others. The principal structural feature of the survey area is the centrally located Wau Graben. It is approximately 15 km wide by 40 km long, bounded to the east and west by the Wandumi and Watut Faults, and terminated to the north and south by the Snake and Kerimenge transfer structures. The most common rock type is the Miocene Morobe Granodiorite, which intrudes Mesozoic Kaindi metamorphics. Pliocene Bulolo Volcanics are common in the north of the study area. To the south, the auriferous Edie Porphyry and similar rocks occur in dacitic dikes and domes. Numerous faults control the size and shape of the intrusions. Mineralization is localized along faults and the margins of intrusives. Pliocene Otibanda sediments overlie the Edie Porphyry and older rocks. The northern end of the Wau Graben is terminated by the Snake Fault, which is clearly resolved in the magnetic data. A large extent of Kaindi Metamorphics in the survey area occurs in the south-central portion of the Wau Graben, and coincides with a magnetic low. The Wau Graben is bounded to the south and west by highly magnetic Morobe Granodiorite. Porphyritic intrusives appear to be associated with numerous small, high-intensity magnetic anomalies. The northern portion of the survey area shows medium to high magnetic anomalies resulting from the Bulolo Volcanics.