In the inky depths off Papua New Guinea, a remotely operated robot has revealed a rare deep-sea environment where superheated volcanic fluids and cold, methane-rich gases escape the seafloor side by side—something never documented before.
The discovery, made during a June–July 2023 expedition led by German researchers aboard the RV Sonne, centers on the western flank of Conical Seamount, near Lihir Island. There, at 1,300 meters below the surface, scientists located a novel hydrothermal field now named Karambusel, where geologic forces combine two typically separate phenomena: hydrothermal venting and hydrocarbon seepage.
This fusion of chemical extremes has fostered a vibrant and possibly unique deep-ocean ecosystem, with dense colonies of mussels, tube worms, shrimp, and other species clustered around gas and fluid vents just centimeters apart.
Heat Meets Methane on the Seafloor
Karambusel is the first known deep-sea vent system globally where hot hydrothermal fluids (up to 51 °C) emerge just a few centimeters from cool methane seeps, which range between 3 °C and 20 °C. In one case, a 41.9 °C vent was observed just 30–40 centimeters from a 10.2 °C gas bubbling site.
The gases emitted include methane in concentrations exceeding 80%, a level far higher than in any other known hydrothermal field. Gas analysis confirmed a thermogenic origin, likely formed from buried organic matter heated by magmatic activity. This methane is accompanied by higher-chain hydrocarbons and volatile trace elements like arsenic, mercury, thallium, and antimony, indicating a complex fluid history involving both magmatic vapor and sediment-hosted gas.
Field researchers used GEOMAR’s Kiel 6000 deep-sea robot to sample fluids, gases, and rocks. Unlike many vent sites that form chimney-like sulfide structures, Karambusel features shimmering flows without chimneys, discharging directly from fissures in volcanic rock.
The research also revealed that the venting site formed during a separate volcanic episode roughly 89,000 years ago—distinct from the older main edifice of Conical Seamount—suggesting it’s geologically younger but chemically more active. Full site parameters and geochemical interpretations can be reviewed in the Scientific Reports published research.
Biodiversity Hotspot Under Industrial Threat
Beyond its geological novelty, Karambusel supports a rich and highly specialized deep-sea ecosystem. The vent field spans roughly 300 by 300 meters and includes mussel beds, lamellibrachid and escarpiid tube worms, deep-sea crabs (Shinkaia crosnieri), stalked barnacles, and microbial mats. Many of these species are only found at chemosynthetic vent habitats and may be endemic to the TLTF island chain, a poorly studied region.
The expedition identified 23 vent-endemic taxa, some observed only at Karambusel. These faunal assemblages differ markedly from those at nearby sites like Edison Seamount and Mussel Cliff, where venting and seepage also occur but lack the same diversity and density. The nature of this co-located vent-seep interface likely creates a unique chemical niche supporting specialized life forms.
Despite its isolation, Karambusel lies just offshore from the Ladolam gold mine, one of the world’s largest open-pit mining operations. The region is under active offshore exploration licenses for mineral and hydrocarbon extraction. The proximity raises concerns about seafloor mining impacts on fragile ecosystems that may not exist elsewhere.
The research team, in a public report via Discover Wildlife, emphasized the urgency of protecting the site. “We have discovered an unexpected treasure trove of biodiversity… that needs to be protected before economic interests destroy it,” said the team’s principal investigator, Dr. Philipp Brandl of the GEOMAR Helmholtz Centre.
Hidden Ore System Beneath the Seafloor
Geological sampling of the site revealed evidence of fossil epithermal mineralization, with gold, silver, and a suite of sulfide-rich minerals present in altered volcanic rocks. These findings suggest Karambusel once hosted a high-temperature ore-forming system akin to those mined at nearby Lihir.
Minerals like chalcopyrite, sphalerite, and galena were found in brecciated veins—clear signatures of ancient hydrothermal boiling episodes. Isotopic analysis indicates that the fossil ore stage was triggered by the same magmatic system now driving the lower-temperature venting observed today.
The study authors propose a multi-phase mineralization model, where earlier gold-rich fluids were overprinted by a second stage of low-temperature, volatile-rich venting, transporting metals such as arsenic and mercury. This kind of bimodal system is rare and offers insights into the genesis of seafloor metal deposits and the role of magmatic heat in metal transport through sediments.