Abstract
Assimilation of lithospheric mantle melts by West Greenland tholeiitic magmas recorded by melt inclusions
Mineralogical magazine, Vol.75(3), p.1611
Goldschmidt 2011
2011
DOI: 10.1180/S0026461X00006502
Abstract
An issue in many flood basalt provinces is how to distinguish crustal assimilation from lithospheric mantle inputs. We have studied olivine-hosted melt inclusions in five high MgO samples (olivine separates from [1]) from the Paleocene picrite-dominated Vaigat Formation in West Greenland [2]. Melt inclusions can preserve a diversity of compositions that record petrogenetic processes taking place within the magmatic plumbing system. Inclusions were rehomogenized to glass in a 1-atm gas-mixing furnace prior to EPMA and LA-ICP-MS analysis. One sample (332788) has lower (super 143) Nd/ (super 144) Nd and higher (super 206) Pb/ (super 204) Pb than the other samples. Inclusions from the other four samples show limited compositional variability, limiting any role for crustal assimilation, and inclusions in rare high Fo% ( approximately 92) olivines are similar to inclusions in less forsteritic olivines in terms of incompatible element ratios, indicating that the high Fo% olivines are not xenocrystic. Whole rock data on more evolved flows [1] show isotopic evidence for assimilation by crust with low (super 143) Nd/ (super 144) Nd and low (super 206) Pb/ (super 204) Pb, different to the displacement trend of sample 332788. Inclusions in sample 332788 show significant compositional variability, with K/Ti varying from 0.14 to 0.33 (compared to 0.12 to 0.19 in inclusions from the other samples). Trace element data show that K/Ti in inclusions from sample 332788 correlates with incompatible element ratios such as Zr/Y and Zr/Nb but not with La/Nb and Ba/Nb that might have been expected for crustal assimilation. Small-volume, incompatible-element-enriched, alkali picrite flows, interpreted as melts of old metasomatized lithospheric mantle, are found at a similar stratigraphic level elsewhere in the province [3]. Their isotopic composition is consistent with the displacement of sample 332788 from the other samples, and their trace element composition can explain the variations in the inclusions. The presence of these melts near the surface suggests a shallow-level magma mixing model rather than assimilation during ascent through the lithosphere.
Details
- Title: Subtitle
- Assimilation of lithospheric mantle melts by West Greenland tholeiitic magmas recorded by melt inclusions
- Creators
- David W Peate - University of Iowa Iowa City, IA USA United StatesI Ukstins PeateA. J. R KentM. C Rowe
- Resource Type
- Abstract
- Publication Details
- Mineralogical magazine, Vol.75(3), p.1611
- Conference
- Goldschmidt 2011
- DOI
- 10.1180/S0026461X00006502
- ISSN
- 0026-461X
- eISSN
- 1471-8022
- Publisher
- Mineralogical Society
- Alternative title
- Goldschmidt 2011 abstract volume
- Language
- English
- Date published
- 2011
- Academic Unit
- Earth and Environmental Sciences; Honors Program
- Record Identifier
- 9984240785802771
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