Structural control of hydrothermal flow: A comparison between RIDGE2000 sites and Iceland spreading centers

D. Curewitz¹* & J.A. Karson¹

Corresponding author: dcurewit@syr.edu
¹Syracuse University, Department of Earth Sciences, Syracuse, NY, 13244

Abstracts:
The distribution of permeable conduits in the shallow crust is thought to control the spatial relationships between hydrothermal vents at the surface and deeper structural and magmatic components of spreading/rifting systems. By mapping local structures and surficial deposits with respect to current vent locations and characteristics (i.e. temperature, flow rate, chemistry), we gain a first-order understanding of the structural influence on outflow sites. Earthquake locations and the identified boundaries of shallow crustal magma bodies will further enhance our understanding of the current tectonic context of hydrothermal flow. We hypothesize that local tectonic or magmatic activity, such as eruptions or intrusions with associated fault slip and seismic activity will cause systematic changes in vent location and/or behavior as a result of changes in the geometry, connectivity, and permeability of shallow, fracture-controlled conduits.

Hydrothermal outflow style over time (i.e. transitions from focused to diffuse flow; changing location of ephemeral vents; changes in flow rate, temperature or chemistry of long-lived vents) is expected to vary as a function of changes in local structural geology (changes in fault distribution or population characteristics at the surface); geology (new lava flows, fissures, or eruptive features); and the geometry, depth, or behavior of deeper structures such as magma bodies or faults in the subsurface. By quantifying changes in location and/or behavior of outflow sites over time with respect to the structural geology and shallow crustal architecture of the area, we can infer the impact of tectonic and magmatic events on the maintenance of permeable conduits over the period of time between repeated surveys of well-mapped hydrothermal sites along Ridge2000 focus sites and in Iceland.

Variations in short-term hydrothermal systematics will be expressed in the geological record. After mapping the short-term temporal relationships between structural, magmatic, and hydrothermal components of these systems, we can develop testable hypotheses regarding the distribution and relative age of hydrothermal deposits, alteration products, and vein-filling materials.

Contributions to Integration and Synthesis:
The work described above will entail collaboration with researchers focused on sonar and mapping investigations East Pacific Rise, Lau Basin, Juan de Fuca, and Mid-Atlantic Ridge spreading systems. This will include data and results sharing with workers investigating similar phenomena. We anticipate collaboration with investigators focusing on hydrothermal vent systematics (chemistry, temperature, flow rate, and etc). Collection and compilation of structural and hydrothermal data from mid-ocean ridge spreading centers and Iceland will provide a point of comparison for future analyses. Data collected and analyzed will be presented as a series of maps constructed from available bathymetric and deep-tow sonar investigations, with special focus on locations that have been surveyed multiple times. Surficial structural and geological maps will be constructed for each survey conducted. Vent locations will be integrated with these maps, and (if available) vent characteristics in terms of temperatures, flow rates, and chemistry will be depicted on each map. All results will be freely shared via the RIDGE2000 database in both digital data and in map form. The results of this investigation will provide a comprehensive visual and digital catalogue of changes in the structural, hydrothermal, and geophysical characteristics of representative mid-ocean ridge segments and along the Iceland rift zone. These data will primarily be collected from existing databases and surveys, and as such will be the result of close cooperation and ongoing exchange with researchers across, as well as outside the RIDGE community.