Publication Date:
2024-04-08
Description:
The formation and growth mechanisms of Mid-Ocean Ridges (MOR) are relatively well known, whereas
those of back-arc spreading ridges are comparatively less known because geophysical, geochemical, and
morphological data are scarce and of low density. Here we present a high-resolution bathymetry of the
Marsili Seamount (MS; 1Ma 3 ka), which represents the inflated spreading ridge of the 2Ma old Marsili
back-arc basin associated to the subduction of the Ionian Sea below the Calabrian Arc and Tyrrhenian Sea.
MS is 70 km long, 30 km wide, and its height reaches about 3000 m from surrounding seafloor. Our new
digital bathymetric model has a 5 m grid cell size resolution and covers the MS bathymetry from 1670
mbsl to the top at 491 mbsl. We conduct morphometric and morphological analyses of the bathymetry
and recognize landforms due to volcanic, tectonic, hydrothermal and gravity processes. MS consists of
volcanoes related to fissural and central-type activity, this latter located at the northern and southern tips
of the main dike swarms. Dike swarms represent the surface expression of different ridge segments
whose strikes are controlled by the larger scale back-arc spreading processes and by the local occurrence
of an active hydrothermal field. This latter develops in a flat area between two partly overlapping ridge
segments where historical volcanism and extensional processes concentrate. Such ridges represent the
embryonic stage of the formation of transform-like faults. Central volcanoes, the northern of which is
characterized by a caldera, form at the tips of MS because the decrease in width of the major volcanic
fissures promotes vent localization associated with the formation of sill-like reservoirs from which
central-type vents may develop. Gravity processes affecting the MS flanks are due to shallow seafloor
sliding. Caldera collapses affecting the northernmost central-type polygenic volcano must be included
in the evaluation of the hazard related to potential tsunami. Inward dipping faults characterize the MS
eastern flank suggesting a moderately asymmetric growth of the spreading ridge possibly associated with
the eastward opening of the Marsili back-arc.
The Marsili back-arc spreading rate is similar to those of MOR slow spreading ridges. However, the MS
morphology resembles that of fast spreading ridges. These two features also characterize more extended
back-arc spreading ridges (e.g. the Mariana in Western Pacific). We conclude that, independently from
the spatial scale, the increase in the ridge accretion rate is related to the progressive addition of a
subduction-related component to a pure spreading mantle source.
Description:
Published
Description:
101723
Description:
OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink