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Geochemical Constraints on Mantle Sources for Volcanic Rocks from Mt.Melbourne and the Western Ross Sea, Antarctica

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Title
Geochemical Constraints on Mantle Sources for Volcanic Rocks from Mt.Melbourne and the Western Ross Sea, Antarctica
Authors
Lee, Mi Jung
Lee, Jong Ik
Kim, Taehoon
Nagao, Keisuke
Keywords
International Symposium on Polar Sciences
Issue Date
2015
Citation
Lee, Mi Jung, et al. 2015. Geochemical Constraints on Mantle Sources for Volcanic Rocks from Mt.Melbourne and the Western Ross Sea, Antarctica. The 21st International Symposium on Polar Sciences. Incheon. 2015.05.19-20.
Abstract
We report geochemical and isotope data (Sr, Nd, Pb) of submarine samples from the Terror Rift Region and subaerial lavas from Mt. Melbourne Volcanic Field (MMVF) in the western Ross Sea. The MMVF samples can be subdivided into Groups A and B based on their temporal and spatial distribution. All samples are alkaline, ranging from basanite to trachybasalt, and exhibit an HIMU-like isotopic signature (206Pb/204Pb = 18.510-19.683, 87Sr/86Sr = 0.70300-0.70398, 143Nd/144Nd = 0.51284-0.51297) and trace element affinities (Ce/Pb = 25-35, Nb/U = 45-60, Ba/Nb = 5-13, La/Nb = 0.5-0.9). The Terror Rift submarine lavas (0.46-0.57 Ma) display a distinct trend, with more primitive geochemical characteristics (higher MgO (7.2-9.8 wt.%) and CaO (9.9-11.9 wt%) and stronger HIMU signature than those of MMVF basalts. Results from a rare earth element (REE) model suggest that the Terror Rift submarine lavas are derived from small degrees (1-2%) of partial melting of an amphibole-bearing garnet peridotite mantle source. Incompatible trace element ratios (e.g., Ba/Nb = 6.4-13.2, La/YbN = 14.4-23.2, Dy/Yb = 2.2-3.0) and isotopic compositions of the MMVF Group A and B volcanics suggest derivation from higher degrees (2-5%) of partial melting of a garnet peridotite source and strong influence of an EMI-type mantle source. The stronger HIMU signature of the Terror Rift submarine lavas appears to be related to smaller degrees of partial melting, suggesting preferential sampling of the HIMU component in the less partially melted rocks from the Cenozoic NVL magmatism. In contrast, the higher degree of MMVF A and B magmas can be explained by greater interaction with heterogeneous lithospheric mantle, resulting in a diluted HIMU signature compared with that of the Terror Rift submarine lavas.
Conference Name
The 21st International Symposium on Polar Sciences
Conference Place
Incheon
Conference Date
2015.05.19-20
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