Rapid dike emplacement leads to eruptions and hydrothermal plume release during seafloor spreading events

Abstract

The creation of ocean crust by rapid injection of magma at midocean ridges can lead to eruptions of lava onto the seafl oor and release of "event plumes," which are huge volumes of anomalously warm water enriched in reduced chemicals that rise up to 1 km above the seafl oor. Here, we use seismic data to show that seafl oor eruptions and the release of hydrothermal event plumes correspond to diking episodes with high injection velocities and rapid onset of magma emplacement within the rift zone. These attributes result from high excess magma pressure at the dike source, likely due to a new infl ux of melt from the mantle. These dynamic magmatic conditions can be detected remotely and may predict the likelihood of event plume release during future seafl oor spreading events.

Composition of the Oceanic Crust

“…Geologic mapping, 210 Pb/ 226 Ra dating (see Chapter 4.5), and paleomagnetic intensity dating suggest that several eruptions have occurred in the past 100 years in the superfast-spreading region near 17 30 0 S on the EPR (Bergmanis et al, 2007). Numerous eruptions have been detected seismically along spreading centers in the northeast Pacific (Dziak et al, 2007). At least three diking and eruption events occurred on the CoAxial Segment between 1981 and 1993, with the 1993 event being detected seismically (Embley et al, 2000).…”

Length and Timescales of Rift Faulting and Magma Intrusion: The Afar Rifting Cycle from 2005 to Present

“…Interferometric Synthetic Aperture Radar (e.g., Einarsson & Brandsdóttir 1980, Rubin & Gillard 1998, Dziak et al 2007). Unlike fault slip events, dike intrusion swarms lack a dominant, larger magnitude earthquake, and they have high event rates for much longer periods than those of comparable magnitude tectonic events (e.g., Tolstoy et al 2001, Dziak et al 2007).…”

“…Rifting episodes along the subaerial Mid-Atlantic Ridge in Iceland (1975Iceland ( -1984) (e.g., Bjornsson et al 1977, Sigmundsson 2006, the Gulf of Aden Ridge in Afar (1978-79) (Abdallah et al 1979), and submarine segments of the East Pacific Rise (2005-6) (e.g., Tolstoy et al 2006, Dziak et al 2009), Juan de Fuca Ridge (e.g., Fox et al 2001, Dziak et al 2007) and Mid-Atlantic Ridge (e.g., Tolstoy et al 2001, Dziak et al 2004) provide rare glimpses of magma intrusion and extrusion processes at mid-ocean ridges. Dike-involved rifting episodes also occur in continental rift zones with much thicker, colder lithosphere; faulting, dike intrusion, and a volcanic eruption occurred in the Natron basin, Tanzania from 2007 to 2008 (e.g., Calais et al 2008).…”

Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge

“…Earthquakes generated at MORs are relatively weak and are mostly missed by global seismic networks. Local arrays of ocean bottom seismometers (OBSs) and hydrophones , which have significantly higher sensitivity than the distant teleseismic networks on land, are needed to monitor these events such as the horizontal migration of earthquake swarms as a trace of intruding dykes [Dziak et al, 2007].…”

“…OBP data from the TAG field at the Mid-Atlantic Ridge (MAR, 26°N) revealed periodic pressure variations with spectral peaks between 22 min and 53 min and an amplitude of up to 13 mm water column equivalent (wce) which were interpreted as being caused by shallow subsurface pore pressure variations resulting in seafloor deformation [Sohn et al, 2009]. [5] The detection threshold of the teleseismic network for earthquakes in the oceans is typically at magnitudes of m b > 4 [Dziak et al, 2007]. Earthquakes generated at MORs are relatively weak and are mostly missed by global seismic networks.…”