Permeability-porosity relationships in seafloor vent deposits : dependence on pore evolution processes
Tivey, Margaret K.
Craddock, Paul R.
MetadataShow full item record
Systematic laboratory measurements of permeability and porosity were conducted on three large vent structures from the Mothra Hydrothermal vent field on the Endeavor segment of the Juan de Fuca Ridge. Geometric means of permeability values obtained from a probe permeameter are 5.9 × 10−15 m2 for Phang, a tall sulfide-dominated spire that was not actively venting when sampled; 1.4 × 10−14 m2 for Roane, a lower-temperature spire with dense macrofaunal communities growing on its sides that was venting diffuse fluid of <300°C; and 1.6 × 10−14 m2 for Finn, an active black smoker with a well-defined inner conduit that was venting 302°C fluids prior to recovery. Twenty-three cylindrical cores were then taken from these vent structures. Permeability and porosity of the drill cores were determined on the basis of Darcy's law and Boyle's law, respectively. Permeability values range from ∼10−15 to 10−13 m2 for core samples from Phang, from ∼10−15 to 10−12 m2 for cores from Roane, and from ∼10−15 to 3 × 10−13 m2 for cores from Finn, in good agreement with the probe permeability measurements. Permeability and porosity relationships are best described by two different power law relationships with exponents of ∼9 (group I) and ∼3 (group II). Microstructural analyses reveal that the difference in the two permeability-porosity relationships reflects different mineral precipitation processes as pore space evolves within different parts of the vent structures, either with angular sulfide grains depositing as aggregates that block fluid paths very efficiently (group I), or by late stage amorphous silica that coats existing grains and reduces fluid paths more gradually (group II). The results suggest that quantification of permeability and porosity relationships leads to a better understanding of pore evolution processes. Correctly identifying permeability and porosity relationships is an important first step toward accurately estimating fluid distribution, flow rate, and environmental conditions within seafloor vent deposits, which has important consequences for chimney growth and biological communities that reside within and on vent structures.
Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): B05208, doi:10.1029/2006JB004716.
Showing items related by title, author, creator and subject.
Anisotropy in seafloor flange, slab, and crust samples from measurements of permeability and porosity : implications for fluid flow and deposit evolution Gribbin, Jill L.; Zhu, Wenlu; Tivey, Margaret K. (American Geophysical Union, 2012-03-21)Seafloor hydrothermal vents accommodate the convective transfer of fluids from subsurface environments to the oceans. In addition to black smoker chimneys, a variety of other deposit-types form. Flanges protrude from the ...
Anomalous porosity preservation and preferential accumulation of gas hydrate in the Andaman accretionary wedge, NGHP-01 site 17A Rose, Kelly K.; Johnson, Joel E.; Torres, Marta E.; Hong, Wei-Li; Giosan, Liviu; Solomon, Evan A.; Kastner, Miriam; Cawthern, Thomas; Long, Philip E.; Schaef, H. Todd (Elsevier, 2014-06-06)In addition to well established properties that control the presence or absence of the hydrate stability zone, such as pressure, temperature, and salinity, additional parameters appear to influence the concentration of gas ...
Comparison of the physical and geotechnical properties of gas-hydrate-bearing sediments from offshore India and other gas-hydrate-reservoir systems Winters, William J.; Wilcox-Cline, R. W.; Long, Philip E.; Dewri, S. K.; Kumar, P.; Stern, Laura A.; Kerr, Louis M. (Elsevier, 2014-09-09)The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom ...