Hydrothermal circulation in the upper part of the igneous (volcanic) seafloor feeds submarine hot springs that support vigorous biological communities and causes an exchange of chemical elements between the rocks and sea water the affects the chemistry of the oceans in important ways, yet understanding these hydrothermal systems has been hampered by the difficulty of measuring heat flow and fluid flow. Heat flow blankets developed by one of the proponents of this projects are designed for deployment on bare rock, and thus hold the potential of providing improved and more detailed heat flow values. This deployment of heat flow blankets in combination with magnetic gradiometer and high-resolution bathymetry data seeks to characterize hydrothermal circulation at the RAVEN in detail. In additional to developing a heat flow method and contribution important new data to the field, broader impacts of this work include student participation, and outreach through teaching and public lectures.
Importance of the Study: Hydrothermal circulation transfers heat from newly formed oceanic crust into the overlying ocean, removing more than 88% of the total heat of formation from crust younger than 1 million years. The resulting interaction during this transfer of fluid and heat influences the chemical composition of the ocean crust and seawater and establishes an environment for unique chemosynthetic biological communities. Hydrothermal circulation within oceanic igneous basement is a fundamental process at mid-ocean ridge spreading centers responsible for the physical and chemical evolution of the crustal rocks, the deposition of metal rich, economically valuable minerals, and for the colonization by unique biological communities. The magnitude, pathways, and extent of subsurface fluid circulation are difficult to constrain at an active mid-ocean ridge, especially where sediment cover is minimal and direct conductive heat flux measurements are not possible with conventional heat flow probes. Moreover, it has also been difficult to determine the conductive heat flux in and around vent sites at the resolution required for the sub-100 m scale of hydrothermal vent fields. Insight into the geometry of subsurface hydrothermal circulation related to vent sites has been previously provided from newly developed technology and, in this program, applied to a major question regarding the formation of ocean crust. Primary Results of this Research Program: A systematic geophysical survey using thermal blankets, near bottom magnetic anomalies and high resolution video images within the Endeavour segment of the Juan de Fuca Ridge axial valley provided a quantitative estimate of the magnitude and distribution of heat within the thermal environment at a mid-ocean ridge. The primary goal was the testing current models of hydrothermal circulation present within newly formed oceanic crust. The program was unusually successful, resulting in 3 major scientific publications that developed a new model of shallow fluid circulation cells that is present in the uppermost 600 meters of oceanic crust. We anticipate that this new fluid circulation model will have a profound impact on on-going studies of the biology, chemistry and geology associated with the formation of new oceanic crust.
