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Explaining Anomalously High Magma Flux at Volcanic Centers on the Northern Kolbeinsey and Southern Mohns Ridges using Bathymetry and Basalt Geochemistry

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dc.contributor.advisor Elkins, Lynne Davis, Rachel Joy 2013-11-14T15:13:23Z 2013-11-14T15:13:23Z 2013
dc.description.abstract The slow-spreading Northern Kolbeinsey Ridge (NKR) and Southern Mohns Ridge (SMR) segments immediately adjacent to the Jan Mayen Fracture Zone exhibit similar types of volcanism along their spreading axes. Each segment has small, flat-­topped cones and hummocky pillow basalt flows typical of slow-­spreading ridges as well as an unusually large volcanic edifice, indicating a focused zone of high magma flux to the ridge. The NKR has parallel axial valleys, an active fault line that is not parallel to the axial valleys, and monogenetic cones on the northern and southern parts of the NKR in addition to the large volcanic crater at the center. I compared the bathymetry (crustal thickness, ridge features) and mid-­ocean ridge basalt geochemistry of these two ridge segments to better understand oceanic crust formation at slow-spreading mid-­ocean ridges with anomalously high magma supply. These processes constrain melting dynamics beneath the two segments by fingerprinting the source of the unusually focused magmatism suggested by the large cones and locally thick crust. Trace element geochemistry (ICP-­‐MS) and bathymetric analyses indicate high degrees of melting and mantle source enrichment at the SMR similar to that observed for Jan Mayen Island (SMR La/SmN=3.139 to 3.710, Sm/YbN=2.107 to 2.674). The ratios indicate a residual garnet signature near Jan Mayen Island further suggesting a deep onset of melting. The NKR basalts are relatively depleted in light rare earth elements (La/SmN=1.427 to 2.152, Sm/YbN=0.826 to 1.026,), with the least enrichment in the western axial valley of the NKR (La/SmN=0.886, Sm/YbN=0.729). The extensive normal faulting in the eastern axial valley of the NKR in addition to hummocky terrain, non-­parallel faults, immature fault boundary near the central Kolbeinsey Ridge and relative enrichment of the NKR basalts from the eastern axial valley indicates a tectonically active axis that is likely being pulled eastward by a hotspot source. The large volcanoes, distinct changes in eruption, a shallow axis and enriched geochemical signature are evidence for a long-­lived mantle plume source in the area of the NKR and SMR ridge segments that has contributed to source enrichment and high magma supply.
dc.description.sponsorship Bryn Mawr College. Department of Geology
dc.language.iso eng
dc.subject.lcsh Magmas -- Iceland -- Kolbeinsey (Island)
dc.subject.lcsh Magmas -- Mohns Ridge
dc.title Explaining Anomalously High Magma Flux at Volcanic Centers on the Northern Kolbeinsey and Southern Mohns Ridges using Bathymetry and Basalt Geochemistry
dc.type Thesis
dc.rights.access Haverford users only

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