Length Scales of Volcanic Deposition: A Comparison of the Fast-spreading East Pacific Rise and Slow-spreading Mid-Atlantic Ridge (Invited)
Abstract
The volcanic crust at mid-ocean ridges is built from a patchwork of individual eruptions that accumulate over time. The architecture of the volcanic crust reflects patterns of volcanic deposition that are controlled by a host of interrelated eruptive and environmental parameters including the size and frequency of eruptions, rates of eruption that influence whether deposition is localized or spreading, and pre-existing topography that may control the extent and direction of lava transport and thickness of deposits. In order to understand these collective processes, how they vary between and within ridge segments, and their impact on volcanic deposition it is useful to study individual eruptions and their products. Here we present a comparison of lava flow emplacement at the fast-spreading EPR at 9-10 degrees North and slow-spreading MAR at 37 degrees North. Key differences between these ridge segments include the spatial distribution and amount of available melt in the shallow crust and rates of tectonic deformation that influence ridge-crest morphology. We will present results of detailed near-bottom studies of individual eruptions and their relation to broader ridge-crest geology from sidescan sonar, seafloor photography, and lava sample geochemistry. From these data we identify three key parameters that provide primary controls on the across-axis length scales of volcanic deposition: eruption rate, amount of tectonic disruption, and position of eruptive vents (i.e., degree of focusing of magmatic intrusions). The interaction between theses processes may lead to very different characteristics of the volcanic crust. For example, high eruption rates lead to lava flows that spread laterally over significant distances, but their spatial extent may be limited where rates of tectonic disruption in the form of inward-facing normal faults are high. Low eruption rates lead to volcanic construction focused at or near the vent, but widespread eruptive vents can negate the effect of highly localized deposition. Variations in these parameters appear to correlate with spreading rate but these processes and their interactions are modulated by availability of and proximity to shallow crustal melt reservoirs, such that portions of the rift valley on slow spreading ridges may display patterns of volcanic deposition that are similar to those found at the axis of fast-spreading ridges.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.V12A..03S
- Keywords:
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- 3035 MARINE GEOLOGY AND GEOPHYSICS / Midocean ridge processes;
- 3045 MARINE GEOLOGY AND GEOPHYSICS / Seafloor morphology;
- geology;
- and geophysics;
- 8414 VOLCANOLOGY / Eruption mechanisms and flow emplacement;
- 8425 VOLCANOLOGY / Effusive volcanism