Alkaline Rocks and Carbonatites of the World

Funded by HiTech AlkCarb - New geomodels to explore deeper for Hi-Tech critical raw materials in Alkaline rocks and Carbonatites



Occurrence number: 
Longitude: 8.98, Latitude: 18.82

This, the smallest of the Air complexes, is circular and about 800 m in diameter. It comprises a central depression 550 m across encircled by a ridge. The central area consists predominantly of early, coarse-grained basic rocks including monzo-anorthosite and leucogabbro, which are cut by granitic dykes. These rocks are enveloped on all but the western side by peralkaline granite and quartz monzonite (Moreau et al., 1987). The basic rocks grade from an outer ring of anorthositic gabbro into gabbroic anorthosite with increase of plagioclase and decrease of olivine and clinopyroxene. The centre is occupied by monzo-anorthosite which contains only minor clinopyroxene and olivine but a little amphibole, quartz and some 14% alkali feldspar. The peralkaline granite of the outer ring comprises orthoclase perthite, quartz, sodic amphibole, biotite and opaques. The quartz monzonites of the outer ring consist of microcline perthite, with plagioclase cores, quartz and rare amphibole, biotite and opaques. Mineralogical, modal and chemical data, including REE for the basic rocks, are given by Moreau et al. (1987).

HUSCH, J.M. and MOREAU, C. 1982. Geology and major element geochemistry of anorthositic rocks associated with Paleozoic hypabyssal ring complexes, Air massif, Niger, West Africa. Journal of Volcanology and Geothermal Research, 14: 47-66.MOREAU, C., BROWN, W.L. and KARCHE, J.-P. 1987. Monzo-anorthosite from the Taguei ring-complex, Air, Niger: a hybrid rock with cumulus plagioclase and an infiltrated granitic intercumulus liquid? Contributions to Mineralogy and Petrology, 95:32-43.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith