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 [Na 2 Ca(CO 3) 2 ] and gregoryite [(Na 2,K 2,Ca)CO 3 ]. 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 ∼120 Ma carbonatite complex of Oka (Canada). Melt inclusions are hosted by magnetite (Fe 3 O 4), 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:	Refereed Article
Keywords:	Earth sciences, Geology and geophysics
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Igneous and metamorphic petrology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the earth sciences
UTAS Author:	Kamenetsky, VS (Professor Vadim Kamenetsky)
ID Code:	87966
Year Published:	2013
Funding Support:	Australian Research Council (DP130100257)
Web of Science® Times Cited:	50
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	2013-12-20
Last Modified:	2014-06-10
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