Abstract
No requirement for non-peridotite sources for Snaefellsnes off-axis lavas, Iceland
Abstracts with programs - Geological Society of America, Vol.45(7), p.762
Geological Society of America, 2013 annual meeting & exposition
2013
Abstract
Compositional heterogeneity in the Icelandic mantle can be broadly described as a mixture of a 'depleted' component (high (super 143) Nd/ (super 144) Nd; low (super 206) Pb/ (super 204) Pb), sampled by high-degree melts at the rift zones, and more fusible 'enriched' components (low (super 143) Nd/ (super 144) Nd; high (super 206) Pb/ (super 204) Pb), best expressed in low-degree melts in the off-axis zones. The HIMU-like trace element and isotopic features of the dominant 'enriched' component is generally attributed to recycled oceanic crust, but the lithology is less well-constrained. Two recent studies of rift zone lavas led to divergent opinions: a positive correlation between (super 187) Os/ (super 188) Os and Ni-enrichment in olivines suggested a pyroxenite component, while modelling of major element compositions could be explained just through melting of variably fertile peridotite. This study focuses on post-glacial lavas from the Snaefellsness off-axis zone that represent the 'enriched' extreme of Icelandic compositions, dominated by a mantle component with (super 206) Pb/ (super 204) Pb>19 and (super 143) Nd/ (super 144) Nd<0.5129. The relative abundances of first-row transitional metals in mafic lavas can preserve a signal of lithological heterogeneities in mantle sources, and element ratios can be chosen (e.g. Fe/Mn, Zn/Fe, Co, Fe) that show limited fractionation during peridotite melting but are sensitive to melting of non-peridotite lithologies. Preliminary whole rock Fe/Mn data on representative samples from the Snaefellsnes off-axis zone and the main rift zones have been acquired using a collision-cell ICP-MS method. Variations of Fe/Mn and (super 187) Os/ (super 188) Os with (super 143) Nd/ (super 144) Nd are similar, with the Snaefellsnes off-axis lavas extending to slightly lower Fe/Mn and (super 187) Os/ (super 188) Os than the 'depleted' lavas in the main rift zones. The low Fe/Mn (54-59) of Snaefellsnes lavas indicate a peridotite source (Fe/Mn<64). PRIMELT-2 modelling of major element compositions is also consistent with a peridotite mantle source. Data on other transition metal ratios (Zn/Fe, Co/Fe) will be determined to confirm this conclusion. In contrast, lavas with the highest Fe/Mn and (super 187) Os/ (super 188) Os values, indicative of non-peridotite sources, are volumetrically minor and only found in lavas with intermediate (super 143) Nd/ (super 144) Nd. These data are revealing how the isotopic diversity of the Icelandic mantle is linked to its lithological diversity.
Details
- Title: Subtitle
- No requirement for non-peridotite sources for Snaefellsnes off-axis lavas, Iceland
- Creators
- David W Peate - University of Iowa, Department of Earth & Environmental Sciences Iowa City, IA USA United States
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.45(7), p.762
- Conference
- Geological Society of America, 2013 annual meeting & exposition
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2013 annual meeting & exposition
- Language
- English
- Date published
- 2013
- Academic Unit
- Earth and Environmental Sciences; Honors Program
- Record Identifier
- 9984240909802771
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