Publication Date:
2022-05-25
Description:
© The Author(s), 2015. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 121 (2015): 8-16, doi:10.1016/j.dsr2.2015.02.015.
Description:
Over the last ten years, geophysical studies have revealed that the Trans-Atlantic
Geotraverse (TAG) hydrothermal field (26°08’N on the Mid-Atlantic Ridge) is located
on the hanging wall of an active detachment fault. This is particularly important in light
of the recognition that detachment faulting accounts for crustal accretion/extension along
a significant portion of the Mid-Atlantic Ridge, and that the majority of confirmed vent
sites on this slow-spreading ridge are hosted on detachment faults. The TAG
hydrothermal field is one of the largest sites of high-temperature hydrothermal activity
and mineralization found to date on the seafloor, and is comprised of active and relict
deposits in different stages of evolution. The episodic nature of hydrothermal activity
over the last 140 ka provides strong evidence that the complex shape and geological
structure of the active detachment fault system exerts first order, but poorly understood,
influences on the hydrothermal circulation patterns, fluid chemistry, and mineral
deposition. While hydrothermal circulation extracts heat from a deep source region, the
location of the source region at TAG is unknown. Hydrothermal upflow is likely focused
along the relatively permeable detachment fault interface at depth, and then the high
temperature fluids leave the low-angle portion of the detachment fault and rise vertically
through the highly fissured hanging wall to the seafloor. The presence of abundant
anhydrite in the cone on the summit of the TAG active mound and in veins in the crust
beneath provides evidence for a fluid circulation system that entrains significant amounts
of seawater into the shallow parts of the mound and stockwork. Given the importance of
detachment faulting for crustal extension at slow spreading ridges, the fundamental
question that still needs to be addressed is: How do detachment fault systems, and the
structure at depth associated with these systems (e.g., presence of plutons and/or high
permeability zones) influence the pattern of hydrothermal circulation, mineral deposition,
and fluid chemistry, both in space and time, within slowly accreted ocean crust?
Description:
We acknowledge the National Science Foundation which has supported our research at the
TAG hydrothermal field through many awards for cruises, technological advancement of
equipment, analytical, and modeling work.
Description:
2016-02-23
Keywords:
Hydrothermal fields
;
Mid-ocean ridges
;
Faults
;
Sulfide deposits
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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