Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Tirkine

stripes

Occurrence number: 
105-00-002
Country: 
Mali
Location: 
Longitude: 0.08, Latitude: 20.72
Carbonatite: 
No

Tirkine is a nepheline syenite intrusion surrounded by sand that obscures outer contacts. It consists of an outer nepheline syenite ring displaying igneous lamination with a central nepheline syenite intrusion with no apparent directional fabric. The syenite of the ring is a biotite-hastingsite-albite-nepheline syenite within which nepheline-rich and nepheline-poor facies have been distinguished (Liegeois et al., 1991). It is cut in the southwest by an intrusion of sodalite-bearing nepheline syenite. The central intrusion is a medium- to coarse-grained titanite-biotite-hastingsite-nepheline syenite that contains enclaves of a mesocratic, coarse-grained nepheline syenite rich in kaersutite and titanite, which also occurs as a separate intrusion in the southeast. In the centre of the complex is a small body of magmatic breccia consisting of porphyritic mesocratic biotite-diopside-kaersutite malignite with inclusions of a melanocratic malignite. A neck of phonolite is present near the centre of the complex and three outcrops, one 0.5 km across, of nordmarkite occur 4 km to the north.

Age: 
A Rb-Sr isochron, based on eight whole rock determinations, yielded an age of 215±11 Ma (Liegeois et al., 1991).
References: 

LIEGOIS, J.P., SAUVAGE, J.F. and BLACK, R. 1991. The Permo-Jurassic alkaline province of Tadhak, Mali: geology, geochronology and tectonic significance. Lithos, 27: 95-105.

Map: 
Fig. 3_163 The distribution of alkaline intrusions in the Tadhak Province, which lies to the northwest of the Iforas intrusions. The most northwesterly of the Iforas occurrences (Tessalit, No. 10) is shown.
Location: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith