Aqueous Volatile Concentrations and Isotopic Composition, pH, and Alkalinity in Mariana forearc borehole fluids

Aqueous Volatile Concentrations and Isotopic Composition, pH, and Alkalinity in Mariana forearc borehole fluids Project Name: Collaborative Research: Collaborative Research: Characterization of Subduction Channel Processes, Borehole Sampling at Active Serpentinite Mud Volcanoes on the Mariana Funding: NSF-OCE-1921654 Susan Lang, Woods Hole Oceanographic InstitutionForearc NSF-OCE-1922671 Geoff Wheat, University of Alaska Fairbanks NSF-OCE-1921361 Jeff Seewald, Woods Hole Oceanographic Institution Permits: Mariana Trench National Wildlife Refuge, U.S. Fish & Wildlife Service, Department of the Interior Permit Number: 12541-22009 Project goals: The overarching goal of the project was to understand the reaction processes that occur at depth during subduction. Boreholes drilled during the recent International Ocean Discovery Program Expedition 366 were targeted to collect pristine fluids. The specific goals of the project were to (1) determine the water-rock reactions that control the chemical composition of deep-sourced fluids ascending from atop a subducting slap (2) identify the processes that regulate the nonbiological formation of methane, and assess its potential metabolic impact (3) characterize the origin and abundance of organic carbon molecules to constrain redox and pH conditions within the subduction channel and shallow subsurface environment and (4) relate the permeability of fluid pathways to seamount structure Samples were collected during a 25 day expedition with a deep-sea submersible. A CORK-Lite was be deployed at three newly cased boreholes: U1492D (Yinazao), U1497D (Fantangisña), and U1496C (Asùt Tesoru). Fluids discharging from these three new boreholes, and a fourth already cased borehole (U1200C, South Chamorro), were collected for inorganic and organic geochemical analysis. Dataset Description: Alkalinity, pH, and concentrations and carbon isotopic composition of aqueous volatiles in fluids collected with isobaric gas-tight (IGT) fluid samplers from boreholes at the Marianna forearc during research crsuie KM22-14 aboard the RV Kilo Moana