Transport of Trace Fe from the Mariana Arc and Hydrothermal Exploration of the Mariana Back Arc Basin

We will report on exploration of the Mariana back-arc basin for hydrothermal activity during a cruise in November to December 2015 aboard the Schmidt Ocean Institute’s RV Falkor. We intend to use CTD casts and tows and the AUV sentry to explore the ridge between 13° and 18.5°N, a section long enough to be representative of the back arc in general and short enough to be practical for a single cruise. Global patterns of the number of vent sites as a function of spreading rate suggest that there should be at least 5-10 undiscovered vent sites along this unexplored 600-km section of the Mariana back-arc. During CTD casts and AUV dives hydrothermal activity will be identified using temperature, optical back scatter, and oxidation reduction potential. Where practical, fine scale hydrothermal and mult-ibeam mapping will be conducted by Sentry. During CTD casts, samples will be collected for, carbonate system parameters, dissolved metals, particulate matter, hydrogen, methane, and helium isotopes.

We will take advantage of the cruise track to collect water in the upper 1000m using a Geotraces style rosette package and will analyze samples onboard for dissolved iron. Physical models of this region indicate transport is to the south and west at these latitudes. The Marina Arc lies to the east of the back-arc and past exploration of the arc has revealed hydrothermal activity from the near surface to more than 1000m at various sites along the arc.