Altered former alkalic carbonatite lava from Oldoinyo Lengai, Tanzania: Inferences for calcite carbonatite lavas

摘要: The active volcano Oldoinyo Lengai, Tanzania, is well known for its extrusions of alkalic carbonatite lava, first witnessed in 1960. An older flow from the was originally also rich Na and K, but replacement nyerereite by pirssonite as a result leaching these elements (together with soluble components such SO 3 , Cl, Rb) addition Ca has resulted rock intermediate bulk composition between unique 1960 Lengai lavas calcite-rich flows reported other localities. Further could theoretically pure calcite rock, we suggest that partially altered lava described here “missing link” are now calcitic which had high alkali content when extruded. suggested link carbonate precursors present-day calcium “lavas” explains apparent paradox existence “flows” experimental evidence denies possibility hot, liquid carbonate.