Hydrothermal Exploration of the southern Chile Rise: Sediment-hosted
venting at the Chile Triple Junction.
Abstract
We report results from a hydrothermal plume survey along the
southernmost Chile Rise from the Guamblin Fracture Zone to the Chile
Triple Junction encompassing two segments (93km cumulative length) of
intermediate spreading-rate mid-ocean ridge axis. Our approach used
in situ water column sensing (CTD, optical clarity, redox
disequilibrium) coupled with sampling for shipboard and shore based
geochemical analyses (d3He, CH4, TDFe,
TDMn) to explore for evidence of seafloor hydrothermal venting. Across
the entire survey, the only location at which evidence for submarine
venting was detected was at the southernmost limit to the survey. There,
the source of a dispersing hydrothermal plume was located at 46°16.5’S,
75°47.9’W, coincident with the Chile Triple Junction itself. The plume
exhibits anomalies in both d3He and dissolved
CH4 but no enrichments in TDFe or TDMn beyond what can
be attributed to resuspension of sediments covering the seafloor where
the ridge intersects the Chile margin. From comparison with the Escanaba
Trough on the southern Gorda Ridge, we infer that the anomalies we
report here arise from sediment-hosted venting at the Chile Triple
Junction.