Seawater recharge into oceanic crust; IODP Exp 327 Site U1363 Grizzly Bare outcrop

Online Access: Get full text
doi: 10.1002/ggge.20131
Author(s): Wheat, C. Geoffrey; Hulme, Samuel M.; Fisher, Andrew T.; Orcutt, Beth N.; Becker, Keir
Author Affiliation(s): Primary:
University of Alaska at Fairbanks, Global Undersea Research Unit, Fairbanks, AK, United States
Moss Landing Marine Laboratory, United States
University of California at Santa Cruz, United States
Aarhus University, Denmark
University of Miami, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 14(6), p.1957-1972. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 55 refs.; illus., incl. 3 tables, sketch map
Summary: Systematic differences in sediment thermal and pore water chemical profiles from Integrated Ocean Drilling Program Site U1363 document mixing and reaction within the basaltic crust adjacent to Grizzly Bare outcrop, a site of hydrothermal recharge into 3.6 My-old basaltic crust. A transect of seven holes was drilled ∼50 m to ∼750 m away from the base of the outcrop. Temperatures at the sediment-basement interface increase from ∼6°C to >30°C with increasing distance from the outcrop, and heat flow is suppressed within several hundred meters from the outcrop. Calculated fluid compositions at the sediment-basement interface are generally explained by mixing between bottom seawater and altered crustal basement fluids, with a composition similar but not identical to fluids from seeps at Baby Bare outcrop, located ∼45 km to the northeast. Reactions within upper basement and overlying sediment affect a variety of ions (Mn, Fe, Mo, Si, PO43-, V, and U) and δ13DIC, indicating a diagenetic influence and diffusive exchange with overlying sediment pore waters. The apparent 14C age of basal pore fluids is much older than bottom seawater. Collectively, these results are consistent with seawater recharge at Grizzly Bare outcrop; however, there are strong gradients in fluid composition within 50 m of the outcrop, providing evidence for complex flow paths and vigorous mixing of young, recently recharged seawater with much older, more reacted basement fluid. The proximity of these altered fluids to the edge of the outcrop raises the possibility for fluid seepage from the outcrop in addition to seawater recharge. Abstract Copyright (2013), American Geophysical Union. All Rights Reserved.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Actinides; Basalts; Bottom water; C-13/C-12; Carbon; Crust; East Pacific; Expedition 327; Fluid phase; Grizzly Bare Outcrop; Ground water; Hydrothermal vents; IODP Site U1363; Igneous rocks; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Juan de Fuca Ridge; Low temperature; Marine sediments; Metals; Mixing; North Pacific; Northeast Pacific; Ocean floors; Oceanic crust; Pacific Ocean; Phosphate ion; Pore water; Recharge; Sea water; Sediments; Seepage; Stable isotopes; Temperature; Uranium; Vanadium; Volcanic rocks
Coordinates: N471719 N471736 W1280145 W1280210
Record ID: 2014029597
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union