Hydrothermal Systems in the Eastern Manus Basin: Fluid Chemistry and Magnetic Structure as Guides to Subseafloor Processes

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The PIs propose to conduct a high-resolution near-bottom bathymetric and magnetic survey and sampling program of the PACMANUS hydrothermal area and to collect and analyze fluid and solid samples and geophysical data from PACMANUS and Desmos hydrothermal systems in the eastern Manus Basin (EMB). Their goal is to integrate Leg 193 drill core data with comprehensive chemical, mineral, isotopic, and geophysical data to identify and constrain the key variables that influence crustal alteration, fluid chemistry, deposit composition and morphology, and the range of habitats available for biological communities in felsic-rock hosted systems. The idea is to study the entire system, including alteration assemblages at depth. Specific goals are to 1) delineate the tectonic and structural controls on hydrothermal activity within felsic crust of the EMB; 2) examine interaction of hydrothermal fluids with rocks of felsic composition (dacite to rhyodacite), which represent an endmember in the spectrum of basement compositions; 3) constrain geochemical processes responsible for ore formation; and 4) assess the role of magmatic fluids in EMB hydrothermal systems.