Beitrag
The silicate lavas of Oldoinyo Lengai, Tanzania
Donaldson, C. H.; Dawson, J. B.; Kanaris-Sotiriou, R.; Batchelor, R. A.; Walsh, J. N.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 156 Heft 3 (1987), p. 247 - 279
45 Literaturangaben
veröffentlicht: May 7, 1987
DOI: 10.1127/njma/156/1987/247
ArtNo. ESP154015603002, Preis: 29.00 €
Abstract
Olivine-free nephelinite-phonolite tuffs and lavas comprise > 99% of this carbonatite volcano. The lavas are peralkaline, rich in phenocrysts (principally nepheline) and were multiply saturated on eruption. Mineral chemistry and major- and trace-element whole-rock chemistry display regular changes in a suite of the lavas. However, the bulk compositions cannot be related to one another by computations modelling fractionation of the observed phenocrysts. Additional processes, including palagonitization and interaction of magmas with wall rocks have dispersed the rock compositions.
Schlagworte
Nephelinite-phonolite tuffs • peralkaline lavas • major- and trace-element chemistry • mineral chemistry • nephelinite volcano • Oldoinyo Lengai • Tanzania