Matangkaka manganese deposit, Ambitle Island, Feni Island Group, Papua New Guinea: a Quaternary epithermal stratabound manganese oxide deposit

The Matangkaka manganese deposit is an unusual Quaternary epithermal stratabound oxide from Ambitle Island in the Feni Group, New Ireland Province, Papua Guinea. a small volcanic island that has undergone explosive and effusive activity. Oldest rocks on consist of mafic–intermediate lavas epiclastic Pleistocene Volcano (Waramung Volcanics). These rest unconformably Oligocene calcilutites Basin. summit now modified as semi-circular topographic rim around Nanum Valley, known Valley Crater. This crater formed during gravity induced failure (or sector collapse) southwest flanks Volcano. Crater resurgent Pleistocene–Holocene located within Deposits volcanism include block ash deposits, lavas, trachyte tephra lacustrine sediments (Babamis Two new members are described Babamis Volcanics (Nanmikit Trachyte Member Danmagal Tephra Member). member youngest Plio-Pleistocene Tabar–Lihir–Tanga–Feni alkalic arc. Three intrusive units (Kabang Syenite, Monzonite Saddle Monzonite). hydrothermal system (new name) active geothermal system, elongated along arc-parallel northwest-trending Niffin structural zone. occurrence classified Mn–Fe–Cu–Mo deposit. Active structures northeast-trending faults allowed sea water to circulate depth, leach metals basement overlying volcaniclastic ascend shallow levels. Manganese mineralisation was deposited marine conditions, focussed porous permeable forming 3–4 m-thick bedded deposits. Circulating neutral chloride waters played key role deposition units. Mineralising fluids were probably ≤120 °C. KEY POINTSThe arc, Guinea.Ambitle fractures have convect levels.Manganese by waters, ≤120°C. Y/Ho ratios indicate there component mineralising fluids. deposit.Manganese units,