Open AccessEffects of variable magma supply on mid‐ocean ridge eruptions: Constraints from mapped lava flow fields along the Galápagos Spreading Center
Author(s) -
Colman Alice,
Sinton John M.,
White Scott M.,
McClinton J. Timothy,
Bowles Julie A.,
Rubin Kenneth H.,
Behn Mark D.,
Cushman Buffy,
Eason Deborah E.,
Gregg Tracy K. P.,
Grönvold Karl,
Hidalgo Silvana,
Howell Julia,
Neill Owen,
Russo Chris
Publication year - 2012
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2012gc004163
Subject(s) - geology , lava , magma chamber , volcano , magma , ridge , petrology , volcanology , bathymetry , lateral eruption , geochemistry , explosive eruption , paleontology , oceanography
Mapping and sampling of 18 eruptive units in two study areas along the Galápagos Spreading Center (GSC) provide insight into how magma supply affects mid‐ocean ridge (MOR) volcanic eruptions. The two study areas have similar spreading rates (53 versus 55 mm/yr), but differ by 30% in the time‐averaged rate of magma supply (0.3 × 10 6 versus 0.4 × 10 6 m 3 /yr/km). Detailed geologic maps of each study area incorporate observations of flow contacts and sediment thickness, in addition to sample petrology, geomagnetic paleointensity, and inferences from high‐resolution bathymetry data. At the lower‐magma‐supply study area, eruptions typically produce irregularly shaped clusters of pillow mounds with total eruptive volumes ranging from 0.09 to 1.3 km 3 . At the higher‐magma‐supply study area, lava morphologies characteristic of higher effusion rates are more common, eruptions typically occur along elongated fissures, and eruptive volumes are an order of magnitude smaller (0.002–0.13 km 3 ). At this site, glass MgO contents (2.7–8.4 wt. %) and corresponding liquidus temperatures are lower on average, and more variable, than those at the lower‐magma‐supply study area (6.2–9.1 wt. % MgO). The differences in eruptive volume, lava temperature, morphology, and inferred eruption rates observed between the two areas along the GSC are similar to those that have previously been related to variable spreading rates on the global MOR system. Importantly, the documentation of multiple sequences of eruptions at each study area, representing hundreds to thousands of years, provides constraints on the variability in eruptive style at a given magma supply and spreading rate.