Ngualla

Mount Ngualla, often referred to simply as Ngualla, is a collapsed volcano located in the remote south west of Tanzania. It is approximately 200 km north of the Mbeya township.

Ngualla is a Proterozoic carbonatite estimated to be about 1,000 million years old and is a plug-like intrusive carbonatite with a diameter of approximately 3 km, made up of various successive carbonatite phases.

Ngualla is intrusive into Precambrian gneisses, quartzites and rhyolite-dacite volcanics. It is a carbonatite-fenite complex of oval outline with a longer axis orientated approximately north-south.

Over a north-south trending central ridge and an area of the north-western side of the complex carbonatite outcrops are found, surrounded by red soil. This is in turn surrounded by a ring of low-hills that are predominantly covered by fenites. The fenite zone is up to 1 km wide with a breccia zone adjacent to the carbonatite.

The carbonatite is broadly of three types:

Dolomitic and ankeritic veins are widespread throughout the complex as are calcite-quartz veins with minor galena, baryte and chalcopyrite.

The name 'Ngualla' comes from the Swahili word for 'bald head', which reflects the appearance of a large piece of the mostly bare land in which there is no habitation, agriculture and very little wild life.

The carbonatite has important resources of rare earth elements and is currently managed by ASX-listed Peak Resources. It gained widespread attention in 2010 after it was first reported to contain quantities of rare earths oxides.

...
Wikipedia