Alkaline Rocks and Carbonatites of the World

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In Tifinar And Tidjerazraze


Occurrence number: 
Longitude: 0.33, Latitude: 20.8

The In Tifinar and Tidjerazraze centres comprise numerous volcanic plugs with some plutonic rocks extending in a north-south line over some 30 km with to the east a northeasterly orientated dyke swarm (Liegeois et al., 1991 and J.F. Sauvage, pers. comm., 1985). The more southerly Tidjerazraze complex comprises nepheline syenites covering 12 km2 that invaded phonolites. Three phases of nepheline syenite define a concentric structure and comprise an outer sodalite-biotite-diopside-aegirine-augite-hastingsite-nepheline syenite that is separated by an arcuate intrusion of sodalite-analcime-hedenbergite-aegirine-hastingsite-arfvedsonite-nepheline syenite from a central stock of aenigmatite-arfvedsonite-aegirine-nepheline syenite. The more agpaitic nepheline syenites and their pegmatites contain eudialyte, catapleiite, wohlerite and mosandrite as important accessory minerals. The phonolites include both miaskitic and agpaitic types. No detailed information on the In Tifinar centre has been found except that it includes nepheline syenite.

Rb-Sr determinations on seven rocks yielded an isochron age of 161(5 Ma (Liegeois et al., 1991).
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.J.F. Sauvage, pers. comm. 1985).
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