Research cruise SO299 ‘DYNAMET’ investigated the New Ireland Basin in the vicinity of Lihir, Papua New Guinea, in June and July 2023. The area is known for the world-class porphyry-epithermal Ladolam Au deposit on land as well as epithermal-style mineralization at Conical Seamount. The main goal of SO299 was to study the geodynamic controls on alkaline magmatism and fluid flow on a regional scale by combining targeted rock, fluid and gas sampling with a wide range of geophysical methods.
During SO299, the first active deep sea vent site in the area was discovered in ~1330 meters below sealevel at the western flank of Conical Seamount. Currently, the vent field emits low-temperature (<50°C) fluids and methane-rich gases. Associated mineral precipitates include framboidal pyrite and marcasite, As-rich sulfides and native S. However, the polymetallic and Au-rich character of the mineralization provides evidence for an earlier phase of high temperature venting possibly reaching 340°C. Two other sites of seepage/venting in the area are known: the so-called Mussel Cliff and Edison Seamount. Both are characterized by diffuse fluid flow without any significant temperature anomalies or free gas and Mussel Cliff can be regarded as a ‘classic’ cold seep site.
In my talk, I will present direct observations from the seafloor and initial results from rock, fluid and gas chemistry. First results point towards differences in the formation and migration of hydrocarbons as well as their relation to hydrothermal venting between Karambusel and other comparable sites such as the Guayamas Basin or the Calypso Vents offshore New Zealand.
