Alkaline Rocks and Carbonatites of the World

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Egalah (Agalak)

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Occurrence number: 
121-00-012
Country: 
Niger
Region: 
Timia
Location: 
Longitude: 8.7, Latitude: 18.17

This is a circular intrusion 15 km in diameter composed of a central biotite granite around which is a coarse-grained amphibole-biotite granite. The latter rock consists of perthite, quartz, sometimes in micrographic intergrowth, ferrohastingsite and/or riebeckite, biotite and accessory fluorite, magnetite and zircon.

Age: 
A Rb-Sr whole-rock isochron gave 435(8 Ma (Karche and Vachette, 1978).
References: 
BLACK, R., JAUJOU, M. and PELLATON, C. 1967. Notice explicative sur la carte geologique de l'Air à l'échelle du 1/500 000. Direction des Mines et de la Geologie. Republique du Niger, 1-57.KARCHE, J.-P. and VACHETTE, M. 1978. Age et migration de l'activité magmatique dans les complexes paléozoïques du Niger. Consequences. Bulletin de la Société Géologique de France, 20: 941-53.
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