Secondary fluid recharge and circulation in the Middle Valley hydrothermal system

Author(s): Inderbitzen, Katherine E.
Author Affiliation(s): Primary:
, Marina, CA, United States
Volume Title: Geological Society of America, 2017 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 49(6); Geological Society of America, 2017 annual meeting & exposition, Seattle, WA, Oct. 22-25, 2017. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: Currently, fluid circulation patterns and the evolution of rock/fluid compositions as circulation occurs in subseafloor hydrothermal systems are poorly constrained. Sedimented spreading centers provide a unique opportunity to study subsurface flow because sediment acts as an insulating blanket that traps heat from the cooling magma body and limits: (a) potential flow paths for seawater to recharge the aquifer in permeable upper basaltic basement and (b) points of altered fluid egress. This also allows for a range of thermal and geochemical gradients to exist near the sediment-water interface. Models of fluid circulation patterns in this type of hydrologic setting have been generated (eg. Stein and Fisher, 2001), but our recent work has also incorporated fluid chemistry datasets to test the viability of the model. We accomplished this by integrating the existing circulation model with fluid compositional data collected from sediment pore waters and high temperature hydrothermal vents located in Middle Valley on the Juan de Fuca Ridge. Middle Valley hosts a variety of hydrologic regimes: including areas of primary fluid recharge into basement (Site 855), active high temperature venting (Site 858/1036; Dead Dog vent field), recent venting (Site 856/1035; Bent Hill Massive Sulfide Deposit) and a section of heavily sedimented basement located between recharge and discharge sites (Site 857). We will present results based on thermal, mineralogical, and geochemical data from the area of active venting (Sites 858 and 1036) that was collected during Ocean Drilling Program Legs 139 and 169 and a subsequent heat flow/gravity coring effort. These results illuminate fine scale controls on secondary recharge and fluid flow within the sediment section at Site 858/1036.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 21 Hydrogeology and Hydrology; Aquifers; Discharge; East Pacific; Ground water; Hydrothermal vents; Juan de Fuca Ridge; Middle Valley; North Pacific; Northeast Pacific; ODP Site 856; ODP Site 857; ODP Site 858; Ocean Drilling Program; Pacific Ocean; Recharge
Coordinates: N482600 N482631 W1284048 W1284248
Record ID: 2018059047
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States