@article {parsons_hydrothermal_2024,
	title = {Hydrothermal Seepage of Altered Crustal Formation Water Seaward of the Middle America Trench, Offshore Costa Rica},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {25},
	number = {1},
	year = {2024},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023GC011246},
	month = {01/2024},
	pages = {e2023GC011246},
	abstract = {Chemical compositions of sediment pore waters are presented from 13 piston and gravity cores that were collected on \~{}24 Ma crust of the Cocos Plate seaward of the Middle America Trench and near the onset of crustal faulting from subduction. Cores were collected mainly within a 1.75 km2 area overlying a buried basement topographic high that supports an elevated heat flux, consistent with seawater transport within the upper volcanic crust. Systematic variations in pore water chemical profiles indicate upward seepage speeds (up to 1.7 cm yr-1 providing a net flux of 0.1 L s-1), constrain the chemical composition of the formation water within the underlying upper basaltic basement, and elucidate diagenetic reactions in the sediment. Relative to seawater, formation water has an elevated temperature (70{\textendash}80{\textdegree}C) and concentrations or values of Ca, chlorinity, Sr, Ba, Li, Fe, Mn, Si, Cs, D/H, and Mo, and lower concentrations or values of Mg, Na, sulfate, alkalinity, TCO2, K, B, F, phosphate, 87Sr/86Sr, δ13C, δ18O, U, and Rb. Although this site is located only 30 km from the trench axis, there is no chemical evidence for subduction-related hydrologic influences. Instead, the data are explained by a combination of seawater-basalt reactions within the upper basement and diffusive exchange with overlying sediment, as part of a shallow, ridge-flank hydrothermal system. It is unclear why this site has an elevated heat flux relative to neighboring crust, but this may result from variations in crustal properties or modification related to flexural faulting outboard of the trench.},
	keywords = {formation water, hydrogeology, hydrothermal, Middle American Trench, pore water, ridge flank},
	issn = {1525-2027},
	doi = {10.1029/2023GC011246},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023GC011246},
	author = {Parsons, Patrice K. F. and Wheat, C. Geoffrey and Fisher, Andrew T. and Silver, Eli A. and Hutnak, Michael}
}
@article {2615,
	title = {Microbial decomposition of marine dissolved organic matter in cool oceanic crust},
	journal = {Nature Geoscience},
	volume = {11},
	year = {2018},
	month = {Jan-05-2018},
	pages = {334 - 339},
	abstract = {Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling.
Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5\% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of {\textquoteright}aged{\textquoteright} and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in C-14 and C-13 into the deep ocean.},
	keywords = {carbon, community, deep-ocean, DISTINCT, extraction, fluid-flow, HEAT, MID-ATLANTIC RIDGE, SEAWATER, WESTERN FLANK},
	issn = {1752-0894},
	doi = {10.1038/s41561-018-0109-5},
	url = {http://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdfhttp://www.nature.com/articles/s41561-018-0109-5http://www.nature.com/articles/s41561-018-0109-5.pdf},
	author = {Shah Walter, Sunita R. and Jaekel, Ulrike and Osterholz, Helena and Fisher, Andrew T. and Huber, Julie A. and Pearson, Ann and Dittmar, Thorsten and Girguis, Peter R.}
}
