stripes
Atyrdyakh was discovered in 1958 by Egorov and Surina (1961). It has an oval shape, an area of 0.5-0.6 km2 and is emplaced in upper Cambrian and Ordovician limestones. It is composed, like Changit (No 17), of jacupirangite, melteigite and olivine melanephelinite of variable texture and mineralogy. The main minerals are augite and titanaugite (30-90%), nepheline (up to 35%), biotite, titanomagnetite, olivine and minor titanite, perovskite, aegirine-augite, apatite, K-feldspar and phlogopite. Towards the margin of the intrusion these rocks grade into a porphyritic facies of melanephelinite, olivine melanephelinite, nepheline picrite and augitite.
BUTAKOVA, E.L. and EGOROV, L.S. 1962. The Meimecha-Kotui complex of formations of alkaline and ultrabasic rocks. In Petrography of Eastern Siberia. 1: 417-589. Izd-vo AN SSSR, Moscow.
EGOROV, L.S. 1969. The melilite rocks of the Maimecha-Kotui province. Nedra, Leningrad. 247 pp.
EGOROV, L.S. and SURINA, N.P. 1961. The carbonatites of the Changit intrusive at the north of the Siberian platform. Trudy Nauchno-Issledovatel'skogo Instituta Geologii Arktiki, Leningrad, 125: 160-78.