Christiansen, Lizet B. and Iturrino, Gerardo J. (2007): Core-scale permeability of an actively venting, felsic-hosted hydrothermal system; the PACMANUS hydrothermal field

ODP 193


Christiansen, Lizet B.
U. S. Geological Survey, Menlo Park, CA, United States

Iturrino, Gerardo J.
CSIRO, Australia

Core-scale permeability of an actively venting, felsic-hosted hydrothermal system; the PACMANUS hydrothermal field
In: Barriga, Fernando J. A. S., Binns, Raymond A., Miller, D. Jay, Asada, Ryuji, Bach, Wolfgang, Bartetzko, Anne C. M., Benning, Liane G., Bjerkgard, Terje, Christiansen, Lizet B., Elswick, Erika R., Findlay, Robert, Iturrino, Gerardo J., Kimura, Hiroyuki, Kulange, John B., Lackschewitz, Klas S., Lee, Sang-Mook, Masta, Andrew, Paulick, Holger, Pinto, Alvaro M., Roberts, Stephen, Scott, Steven D., Vanko, David A., Warden, Ian, Yeats, Christopher J., Proceedings of the Ocean Drilling Program; scientific results; anatomy of an active felsic-hosted hydrothermal system, eastern Manus Basin; covering Leg 193 of the cruises of the drilling vessel JOIDES Resolution; Apra Harbor, Guam, to Townsville, Australia; Sites 1188-1191; 7 November 2000-3 January 2001
Texas A&M University, Ocean Drilling Program, College Station, TX, United States
Permeability of the ocean crust is one of the most crucial parameters for constraining submarine fluid flow systems. Active hydrothermal fields are dynamic areas where fluid flow strongly affects the geochemistry and biology of the surrounding environment. There have been few permeability measurements in these regions, especially in felsic-hosted hydrothermal systems. We present a data set of 38 permeability and porosity measurements from the PACMANUS hydrothermal field, an actively venting, felsic hydrothermal field in the eastern Manus Basin. Permeability was measured using a complex transient method on 2.54-cm minicores. Permeability varies greatly between the samples, spanning over five orders of magnitude. Permeability decreases with both depth and decreasing porosity. When the alteration intensity of individual samples is considered, relationships between depth and porosity and permeability become more clearly defined. For incompletely altered samples (defined as >5% fresh rock), permeability and porosity are constant with depth. For completely altered samples (defined as <5% fresh rock), permeability and porosity decrease with depth. On average, the permeability values from the PACMANUS hydrothermal field are greater than those in other submarine environments using similar core-scale laboratory measurements; the average permeability, 4.5 x 10-16 m (super 2) , is two to four orders of magnitude greater than in other areas. Although the core-scale permeability is higher than in other seafloor environments, it is still too low to obtain the fluid velocities observed in the PACMANUS hydrothermal field based on simplified analytical calculations. It is likely that core-scale permeability measurements are not representative of bulk rock permeability of the hydrothermal system overall, and that the latter is predominantly fracture controlled.
Coverage:Geographic coordinates:
West:151.4000East: 151.4100

Oceanography; Bismarck Sea; cores; crust; experimental studies; felsic composition; fluid dynamics; hydrothermal conditions; hydrothermal vents; igneous rocks; laboratory studies; Leg 193; Manus Basin; measurement; Ocean Drilling Program; ocean floors; oceanic crust; Pacific Ocean; PACMANUS hydrothermal field; permeability; physical properties; porosity; sea water; South Pacific; Southwest Pacific; thermal waters; volcanic rocks; water-rock interaction; West Pacific;