HR: 0800h
AN: V21B-0612    [Abstracts]
TI: Compositional Comparison of Iceland Rift Zones and Adjacent Portions of the Mid-Atlantic Ridge.
AU: * Kelley, D
EM: kelley.196@osu.edu
AF: Division of Earth and Planetary Dynamics, School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory 125 South Oval Mall, Columbus, OH 43202, United States
AU: Barton, M
EM: barton.2@osu.edu
AF: Division of Earth and Planetary Dynamics, School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory 125 South Oval Mall, Columbus, OH 43202, United States
AB: Iceland is a portion of the Mid-Atlantic Ridge (MAR) that has been built by anomalous crustal production throughout the 55ma spreading history of the opening of the Atlantic Ocean. The anomalously thick crust of Iceland contains the subaerial traces of the MAR which are the volcanically active rift zones. From the south, the Reykjanes Ridge (RR) continues on land as the Western Volcanic Zone (WVZ). In the north, the Northern Volcanic Zone (NVZ) traces into the sea where it offset from the Kolbeinsey Ridge (KR) by the Tjornnes Fracture Zone (TVZ). We report the results of petrologic comparison of the WVZ, the EVZ, and the NVZ of Iceland and the adjacent portions of the MAR – the RR and the KR. The EVZ, WVZ, and NVZ have been shown to have similar crustal structures with ~20 km thick crust thickening toward the hotspot in central Iceland with magma chambers located at the base of the crust and at some depth in the upper crust. Likewise, the KR and RR have melt chambers at the base of and within the crust. Melt compositions have been compared using a filtered database of 588 glass analyses from 29 localities throughout the rift zones, 57 glass analyses from the KR, and 521 glass analyses from the RR. This is the first such study carried out with such an extensive data set. Compositions are similar between the NVZ and WVZ with SiO₂ wt.% of 49.0, and 48.6, MgO wt.% of 7.9, and 7.5, and FeOT wt.% of 10.9, and 11.7 respectively. The EVZ which is considered to be a propagating rift is a bit different with SiO₂ wt.% of 49.4, MgO wt.% of 5.9, and FeOT wt.% of 13.8. The NVZ and WVZ have also been compared with their respectively adjacent ridge segments, the KR (SiO₂ 50.3 wt.%, MgO 6.9 wt.%, and FeOT 12.0 wt.%), and the RR (SiO₂ 50.8 wt.%, MgO 6.9 wt.%, and FeOT 12.3 wt.%). Mg#s for the NVZ and the WVZ are 0.56, and .053 respectively while the Mg# for both the KR and RR is 0.50. For further comparison, a database of 9035 glass analyses from mid-ocean ridge basalts worldwide gives average SiO₂ wt.% of 50.7, MgO wt.% of 7.3, FeOT wt.% of 10.3, and Mg# of 0.56.
DE: 1021 Composition of the oceanic crust
DE: 1032 Mid-oceanic ridge processes (3614, 8416)
DE: 3035 Midocean ridge processes
DE: 3614 Mid-oceanic ridge processes (1032, 8416)
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting