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TitleFocused fluid flow and methane venting along the Queen Charlotte fault, offshore Alaska (USA) and British Columbia (Canada)
AuthorProuty, N G; Brothers, D S; Kluesner, J W; Barrie, J VORCID logo; Andrews, B D; Lauer, R M; Greene, H G; Conrad, J E; Lorenson, T D; Law, M D; Sahy, D; Conway, K; McGann, M L; Dartnell, P
SourceGeosphere vol. 16, issue 6, 2020 p. 1336-1357, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200624
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf; html
ProvinceBritish Columbia
AreaAlaska; United States of America; Canada
Lat/Long WENS-139.2500 -128.0000 59.1667 50.5833
Subjectsgeochemistry; Science and Technology; carbonates; methane; volcanoes; Queen Charlotte fault
Illustrationslocation maps; tables; diagrams; seismic reflection profiles; cross-plots
Released2020 11 02
AbstractFluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ~850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic plates offshore southeastern Alaska (USA) and western British Columbia (Canada). Indications for fluid seepage along the QCF margin include gas bubbles originating from the seafloor and imaged in the water column, chemosynthetic communities, precipitates of authigenic carbonates, mud volcanoes, and changes in the acoustic character of seismic reflection data. Cold seeps sampled in this study preferentially occur along the crests of ridgelines associated with uplift and folding and between submarine canyons that incise the continental slope strata. With carbonate stable carbon isotope (8"C) values ranging from -46%o to -3%, there is evidence of both microbial and thermal degradation of organic matter of continental-margin sediments along the QCF. Both active and dormant venting on ridge crests indicate that the development of anticlines is a key feature along the QCF that facilitates both trapping and focused fluid flow. Geochemical analyses of methane-derived authigenic carbonates are evidence of fluid seepage along the QCF since the Last Glacial Maximum. These cold seeps sustain vibrant chemosynthetic communities such as clams and bacterial mats, providing further evidence of venting of reduced chemical fluids such as methane and sulfide along the QCF.

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