Alumoåkermanite, (Ca,Na)2(AI,Mg,Fe2+)(Si2O7), a new mineral from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, northern Tanzania

A supposed s6vite from Oldoinyo Lengai, Tanzania" result of extreme alteration of alkali carbonatite lava

A calcite-rich block in nephelinitic agglomerate at Oldoinyo Lengai comprises Sr-calcite, apatite, fluorite, a Ba-Mn oxide akin to romanrchite, and a distinctive Mn-Fe spinel. Formerly reported as sC3vite, on textural, mineralogical and stable isotope grounds it is now re-interpreted as a highly-altered natrocarbonatite lava. An implication of this study is that natrocarbonatite is not just a m...

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

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 car...

Magnetic properties of some carbonatites from Tanzania, East Africa

The magnetization of fresh natrocarbonatite lavas from Oldoinyo Lengai in Tanzania is dominated by small amounts of singleor pseudo-single-domain grains of a spinel in the solid solution series jacobsite (MnFe204)-magnetite (Fe304). Although this phase may acquire TRM before carbonatite lava crust has ceased being mobile, the Oldoinyo Lengai samples are good palaeomagnetic recorders of the fiel...

An Unusual Lava Cave from Ol Doinyo Lengai, Tanzania

Metasomatism and Partial Melting in Upper-Mantle Peridotite Xenoliths from the Lashaine Volcano, Northern Tanzania

REE (LREE) into the glass with respect to clinopyroxene, but the A group of chrome-spinel peridotite upper-mantle xenoliths from the reverse for Sr and Y, in both mica-bearing and mica-free parageneses. Lashaine volcano, northern Tanzania, differs from other xenoliths In a mica-bearing melt pocket, Rb and Ba partition preferentially at this locality in containing glassy melt pockets. Modal, min...