Stochastic analysis of exit fluid temperature records from the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°N) : 1. Modes of variability and implications for subsurface flow
Sohn, Robert A.
MetadataShow full item record
Yearlong time series records of exit fluid temperature from the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°N) reveal a complex space-time pattern of flow variability within the mineral deposit. Exit fluid temperatures were measured every 8–10 min from 17 sites distributed across the upper terrace of the mound from June 2003 to June 2004. High-temperature records were obtained using Deep Sea Power and Light SeaLogger® probes deployed in fractures discharging ∼360°C black smoker fluids, and low-temperature records were obtained using VEMCO Ltd. Minilog probes deployed in cracks discharging ∼20°C diffuse flow fluids. The temperature records are considerably more variable than those acquired from vent fields on the fast spreading East Pacific Rise and exhibit a complex mix of both episodic and periodic variability. The diffuse flow records alternate between periods of discharge and periods of what I infer to be recharge when fluid temperatures are equal to background water column levels (∼2.7°C) as ambient seawater is drawn into the seafloor. The space-time patterns of these episodic variations suggest that they represent reorganizations of the secondary circulation system driving diffuse discharge on the upper terrace of the mound on timescales from a few hours to a few days, most likely in response to permeability perturbations. Harmonic temperature oscillations were observed over a range of periods, with the principal lunar semidiurnal tidal period (M2) being most dominant. During certain times, exit fluid temperatures at diffuse sites pulse at diurnal and semidiurnal tidal periods when they are hovering near background water column levels, which I interpret as flow reversals associated with the vertical displacement of a fluid boundary layer at the seafloor interface when the local net flux is near zero. The pulsing behavior is predicted by poroelastic models of tidal loading but is not consistent with effects from tidal currents, which demonstrates that poroelastic effects from tidal loading modulate shallow subsurface flow at the active TAG mound.
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): B07101, doi:10.1029/2006JB004435.
Showing items related by title, author, creator and subject.
Friedman, Carrie T. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1998-02)Stable sulfur isotopes (δ34S) and trace Co are analyzed in sulfide and sulfate minerals from six sample types collected from the TAG active mound, 26°N Mid-Atlantic Ridge. δ34S values range from 2.7 to 2O.9%, with sulfate ...
Stochastic analysis of exit fluid temperature records from the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°N) : 2. Hidden Markov models of flow episodes Sohn, Robert A. (American Geophysical Union, 2007-09-12)I develop a stochastic signal model for episodic modes of variability in hydrothermal flow records using probabilistic functions of Markov processes (i.e., hidden Markov models, HMMs) and fit the model to exit fluid ...
Cemented mounds and hydrothermal sediments on the detachment surface at Kane Megamullion : a new manifestation of hydrothermal venting Tucholke, Brian E.; Humphris, Susan E.; Dick, Henry J. B. (John Wiley & Sons, 2013-09-03)Long-lived detachment faults are now known to be important in tectonic evolution of slow-spreading mid-ocean ridges, and there is increasing evidence that fluid flow plays a critical role in development of detachment ...