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Evidence for the alkaline nature of parental carbonatite melts at Oka complex in Canada


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Chen, W and Kamenetsky, VS and Simonetti, A (2013) Evidence for the alkaline nature of parental carbonatite melts at Oka complex in Canada. Nature Communications, 4 (Articl).

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The Earth’s sole active carbonatite volcano, Oldoinyo Lengai (Tanzania), is presently erupting unique natrocarbonatite lavas that are characterized by Na- and K-bearing magmatic carbonates of nyerereite [Na2Ca(CO3)2] and gregoryite [(Na2,K2,Ca)CO3]. Contrarily, the vast majority of older, plutonic carbonatite occurrences worldwide are dominated by Ca-(calcite) or Mg-(dolomite)-rich magmatic carbonates. Consequently, this leads to the conundrum as to the composition of primary, mantle-derived carbonatite liquids. Here we report a detailed chemical investigation of melt inclusions associated with intrusive (plutonic) calcite-rich carbonatites from the B120Ma carbonatite complex of Oka (Canada). Melt inclusions are hosted by magnetite (Fe3O4), which crystallizes through a significant period of carbonatite melt solidification. Our results indicate mineral assemblages within the melt inclusions that are consistent with those documented in natrocarbonatite lavas. We propose therefore that derivation of alkali-enriched parental carbonatite melts has been more prevalent than that preserved in the geological record.

Item Type: Article
Journal or Publication Title: Nature Communications
Identification Number - DOI: 10.1038/ncomms3687
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Copyright 2013 Macmillan

Date Deposited: 04 Nov 2013 03:48
Last Modified: 18 Nov 2014 04:56
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