Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

Abstract

High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B.were merged to create a coregistered map of 71.7 km 2 of the Endeavour Segment of the Juan de Fuca Ridge.Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to 4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by 4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting 4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until 2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620-1760 yr BP and within the axial graben since 1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began 2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

Geology of the Alarcon Rise, Southern Gulf of California

“…Highly evolved mid‐ocean ridge lavas (andesites and dacites) occur preferentially near ridge segment ends (e.g., Wanless et al, and references therein) due to a “cold‐edge effect.” Not only do ridges vary along strike, but also across‐strike. Channelized lava flows, for example, are emplaced up to 3 km from the fast spreading East Pacific Rise (EPR; e.g., Soule et al, ), and ∼2 km at the intermediate‐spreading Endeavour segment of the Juan de Fuca Ridge (Clague et al, ), but a high‐resolution study at the intermediate‐spreading Galapagos Rise (Colman et al, ) did not find emplacement of long flows off axis. Off‐axis distribution of flows has important implications for how the ocean crust is constructed (e.g., Perfit & Chadwick, ), but the parameters, such as lava viscosity, that control flow distribution, are poorly understood.…”

Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records

“…Benthic foraminifera were used to date some cores due to insufficient planktic tests. The methods of calibration and R-factors used for calibrations are discussed in Clague et al (2013Clague et al ( , 2014. Presented ages refer to the peak probability ages.…”

A preliminary 1‐D model investigation of tidal variations of temperature and chlorinity at the Grotto mound, Endeavour Segment, Juan de Fuca Ridge

“…Based on pictures of the deployed wand (Figure 2b), $5 cm of the back end of the wand is exposed, suggesting $15 cm of penetration into the sulfide. Pictures taken 11 months after the deployment show the [Clague et al, 2008[Clague et al, , 2014. Geochemistry, Geophysics, Geosystems…”