Petrology and Petrogenesis
Research group
Extrusive Carbonatites
- Carbonatite volcanoes are rare, with just one, at Oldoinyo Lengai in Tanzania, ever seen to erupt and about 40 more in the geological record. Extrusive carbonatites can give us new information on the nature of carbonate-bearing material brought to the Earth's surface from the mantle and the transport mechanisms that bring from the mantle to the crust and surface. Carbonatites form part of the global carbon cycle.
- We have been studying rocks from recently discovered new carbonatite localities in Italy and from the Le Bas Collection of material associated with classic locations in the African Rift Valley in western Kenya. They are all composed of pyroclastic material, confirming that carbonatite lava flows are very rare. They are also all calcite carbonatite rather than the natrocarbonatite observed at Oldoinyo Lengai. Mixed silicate - carbonate eruptions and disaggregated mantle material are common.
- Alan Woolley has preparing a review of extrusive carbonatites worldwide. - Woolley and Chruch (2005) to be published in Lithos.
- We are now seeking funding to continue work on localities in Transbaikalia which carry rare earth minerals and graphite carbonatites from explosive dykes and diatremes at Chagatai, Uzbekistan which carry diamonds.
- Anatoly Zaitsev has a Marie Curie Fellowship to study alteration of natrocarbonatite lavas at Oldoinyo Lengai, Tanzania. We will try to determine if it is unique in the geological record or if it is possible to find evidence of natrocarbonatite eruptions from other volcanoes.
New natrocarbonatite lava at Oldoinyo Lengai
Euhedral apatite, foidite glass shards and quenched calcite (d.grey), Oricola, Italy
We are working in particularly in collaboration with:
- Francesco Stoppa and Gianluigi Rosatelli, University G. d'Annunzio, Chieti, Italy
- Also Kathryn Moore, National University of Ireland, Galway, Ireland.
- Masha Sitnikova, University of St Petersburg, Russia.
- Anna Doroshkevich, Ulan Ude, Russia
- Farid Divaev, Uzbekistan
Contact Frances Wall for more information.