Recent volcanic events and the distribution of hydrothermal venting at the Lucky Strike hydrothermal field, Mid‐Atlantic Ridge

Abstract

[1] We present new high-resolution bathymetry and backscatter data acquired in 2006 with the ROV Victor 6000 over the Lucky Strike hydrothermal field, Mid-Atlantic Ridge. As long-term monitoring of the Lucky Strike area (MoMAR project) is being implemented, these new high-resolution data offer an unprecedented view of the distribution of hydrothermal edifices, eruptive facies, and small-scale tectonic features in the Lucky Strike vent field. We show that vents located in the NW and NE correspond with wide expanses of lumpy seafloor which we interpret as primarily made of broken chimneys and sulfide edifices. They are found above scarps with relief >50 m or on associated mass wasting deposits. By contrast, the SE and SW vents correspond with small expanses of lumpy seafloor and are located near smaller scarps which we interpret as more recent faults. Hydrothermal edifices in the SW venting area appear very recent, postdating the emplacement and faulting of the most recent lava. We propose that this difference in the age of hydrothermal edifices does not mean that hydrothermal venting itself is more recent in the southern part of the Lucky Strike field because preexisting sulfide deposits there may have been buried by recent volcanic deposits. Instead, the older edifices in the northern part of the hydrothermal field may have been allowed more time to grow because they are set above the level of recent lava flows. The formation of a lava lake is the most recent eruptive event detected at Lucky Strike. Lava drainback is evidenced by benches and lava pillars, suggesting a close connection with an underlying magma reservoir, which probably corresponds to the melt body imaged by Singh et al. (2006). We have found no evidence that this lake was active for months to decades, as lava lakes at terrestrial volcanoes. It may instead have formed as a lava pond, with successive lava flows covering the eruptive vents, as proposed for similar features at the EPR. The horizontal surface of the lake is deformed only near its southwestern shore, along a NNEtrending set of faults and fissures, which appear to control the distribution of hydrothermal chimneys.

Picturing thermal niches and biomass of hydrothermal vent species

“…More than 20 sulphide edifices are distributed around a large central lava lake (Ondréas et al, 2009) with a magmatic chamber located at 3 km depth (Singh et al, 2006). The hydrothermal fluids of LS are strongly controlled by geological settings in four areas (north-western, north-eastern, south-western and south-eastern areas), with the source of the south-eastern region being different from the three others (Barreyre et al, 2012).…”

Permeability of the Lucky Strike deep-sea hydrothermal system: Constraints from the poroelastic response to ocean tidal loading

“…For this study we use the eight best-quality, high-temperature (T > 200 • C) exit- Barreyre et al, 2014) to estimate the phase lag, ϕ T , between discharge temperature and bottom pressure at tidal periods. We estimate coherency and phase lag by applying multi-taper (Thomson, 1982) cross-spectral methods with adaptive weighting (Percival and Walden, 1993) to yearlong temperature and pressure records sampled either at 90 s or 24 min intervals. Uncertainties in the phase lag parameter are calculated by jackknifing the independent phase estimates obtained for each of the orthogonal tapers (values are given in Table 1, estimated for all the semi-diurnal tidal constituents).…”

Community dynamics over 14 years at the Eiffel Tower hydrothermal edifice on the Mid‐Atlantic Ridge

“…Statistics-Nonmetric multidimensional scaling (NMDS) and cluster analyses were performed with the Vegan package (Oksanen et al 2008) in R (version 2.8, R Development Core Team 2008), while correlations and significance tests were carried out in Statistica 6 (StatSoft 2001). We used NMDS because, in addition to its robustness, it can find nonlinear and nonmetric relationships.…”