Songwe Hill REE Project (Songwe Hill carbonatite), Phalombe, Southern Region, Malawii

Regional Level Types
Songwe Hill REE Project (Songwe Hill carbonatite)	Project
Phalombe	District
Southern Region	Region
Malawi	Country

Carbonatite deposit that lies on the north-facing slopes of Songwe Hill (990 m).

Located approximately 70 km from the former capital, Zomba.

Songwe Hill is interpreted as a volcanic vent that is expressed as a steep-sided hill approximately 800m in diameter. Information from surface mapping and drill core indicates that the vent complex consists of a multi-phase intrusion characterised by diverse carbonatites and breccias. The carbonatite is best exposed along the north-eastern slope of Songwe Hill. The vent complex cuts the western end of the large Mauze nepheline syenite intrusion, but the external contacts on the western and northwestern sides of the vent are hidden beneath recent surficial eluvial deposits.

The principal lithologies that comprise the Songwe Hill vent complex are carbonatite, fenite and breccia. The carbonatites are dominantly grey calcic carbonatites, although subordinate ferro-carbonatites are present. The fenites comprise dominantly K-feldspar rocks and appear to form an aureole around the carbonatite. They are interpreted to have formed through metasomatism related to the carbonatite intrusion. The breccias range from clearly abraded pebble-sized fragments (pebble dykes) to angular blocks that are metres in diameter and include significant volumes of breccia in which the fragments appear to have undergone little or no movement.

The principal zone of REE mineralisation outcrops along the northeastern slope of Songwe Hill. REE mineralisation is present in carbonatites, fenites and breccias, which are exposed intermittently over a surface area of approximately 350m by 100m. The REE mineralisation is untested to the northeast and southwest beyond the limits of the present drilling and below the deepest vertical intersection of approximately 350m below the surface of Songwe Hill and there is additional regional exploration potential in the Songwe and other carbonatites. The mineralised body is interpreted to be a carbonatite plug with essentially sub-vertical margins. In plan view, it is elongated in a northeast-southwest direction.

The dominant REE-bearing minerals are synchysite and apatite. The apatite is anomalously enriched in the HREO's compared to apatites in most carbonatite deposits. The REE mineralisation is closely associated with strontianite and baryte and is interpreted to have formed through sub-solidus hydrothermal alteration following the carbonatite intrusion.

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References