Leg 193 of the Ocean Drilling Program explored the subsurface of the active PACMANUS hydrothermal field situated on Pual Ridge, a felsic volcanic edifice rising above rifted early Tertiary arc crust in the eastern Manus backarc basin, Papua New Guinea (Binns and Scott, 1993; Binns et al., 2002; Binns, Barriga, Miller, et al., 2002). A major objective of the leg was to characterize an expected abundance of sulfide mineralization in the volcanic sequence below the seafloor and examine structural and geochemical processes that localize fields of chimneys at PACMANUS and explain their high contents of base and precious metals. However, although disseminated pyrite was found to be a widespread component in extensively altered volcanic rocks below the Snowcap (Site 1188) and Roman Ruins (Site 1189) hydrothermal sites, very few occurrences of significant sulfide mineralization were encountered, all at Site 1189. This was partly a consequence of poor core recovery, especially in an apparent stockwork zone in the upper part of Hole 1189B drilled at the crestal mound of Roman Ruins.
Although Holes 1189A and 1189B were collared 35 m apart at Roman Ruins, both beside sulfide chimneys, only three pieces of core classified as massive or semimassive sulfide (>75% and 25%–75% visually estimated abundance of sulfide minerals, respectively) were recovered (Binns, Barriga, Miller, et al., 2002). Despite the paucity of material, the aims of this study were to chemically characterize these samples and compare them with chimneys dredged from Roman Ruins (Moss and Scott, 2001; Binns et al., 2002).