Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: -28.07, Latitude: 68.05

Lilloise is an oval-shaped intrusion of about 10x5 km which cuts Tertiary tholeiitic basalts and post-dates the regional dyke swarm of this area. It comprises a layered sequence passing upwards from peridotites into olivine gabbros which is cut by a plexus of veins and syenitic dykes up to 10 m thick. The syenite comprises perthite, aegirine-augite, biotite and accessories including analcime. Some rock and mineral analyses are available and a hydrogen and oxygen isotope study (Sheppard et al., 1977) indicated that meteoric water had little effect on the intrusion.

Fission-track ages on zircon and apatite gave 52.5±1.2 and 51.0±1.2 Ma (Gleadow and Brooks, 1979, Table 4).
BROWN, P.E. 1973. A layered plutonic complex of alkali basalt parentage: the Lilloise intrusion, East Greenland. Journal of the Geological Society of London, 129: 405-18. GLEADOW, A.J.W. and BROOKS, C.K. 1979. Fission track dating, thermal histories and tectonics of igneous intrusions in East Greenland. Contributions to Mineralogy and Petrology, 71: 45-60. SHEPPARD, S.M.F., BROWN, P.E. and CHAMBERS, A.D. 1977. The Lilloise intrusion, East Greenland: hydrogen isotope evidence for the efflux of magmatic water into the contact metamorphic aureole. Contributions to Mineralogy and Petrology, 63: 129-47
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