Fluid kinematics, fluid residence times, and rock degassing oceanic crust determined from noble gas contents of Deep Sea Drilling Project pore waters

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doi: 10.1029/JB092iB12p12491
Author(s): Barnes, Ross O.; Clarke, W. Brian
Author Affiliation(s): Primary:
Univ. Wash., Sch. Oceanogr., Seattle, WA, United States
Other:
McMaster Univ., United States
Volume Title: Special section on Helium studies in geology
Source: Special section on Helium studies in geology. Journal of Geophysical Research, 92(B12), p.12,491-12,506. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 60 refs.; illus. incl. 5 tables
Summary: The 3He, 4He, Ne, and Ar in sedimentary pore fluids, extracted in situ, were measured on samples from Deep Sea Drilling Project (DSDP) sites 398, 410, 419, 420, 424, 436, and 438. Earlier results from DSDP leg 15 are also discussed. Where regional sediment cover prevents direct penetration of seawater into basement rocks at sites 149, 436, and 438, He concentration profiles indicate slow vertical and/or horizontal advection of sedimentary pore fluids, suggesting that fluids can ventilate through the sediment cover either in diffuse, bulk flow or in "aquifers" confined to regions of relatively high permeability such as ash beds, sand/silt layers, or fracture channels in lithified sediments. At site 410, where basement outcrops are prevalent, no advection was detectable in the sediments; however, the basement was well flushed by seawater. On <2 m.y. crust near the East Pacific Rise and the Galapagos Spreading Center, the collection of only one sample per hole precluded Calculation of sedimentary fluid velocities. However, most juvenile helium is degassed from the crust in <6 × 105 years, except for the deep crust or upper mantle, where juvenile helium may be released locally to fluids advecting in deep fissures or faults. Fluid residence times in upper basement rocks increased from ∼5 × 103 years in 10 m.y. crust open to direct seawater penetration to ∼105-106 years in Cretaceous basement sealed by hundreds of meters of sediment, to >1-5 × 108 years (apparent age) in sediments on the active continental margin off NE Japan.
Year of Publication: 1987
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; Crust; DSDP Site 398; DSDP Site 410; DSDP Site 419; DSDP Site 420; DSDP Site 424; DSDP Site 436; DSDP Site 438; Deep Sea Drilling Project; Degassing; Fluid phase; Geochemistry; Helium; IPOD; Leg 15; Leg 47; Leg 49; Leg 54; Leg 56; Leg 57; Marine sediments; Noble gases; Oceanic crust; Pacific Ocean; Pore water; Sea water; Sediments
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Record ID: 1988010440
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