Romanikha

The largest intrusion on the western bank of the Meimecha River, Romanikha was discovered by Ya.I. Polkin and studied by Butakova and Egorov (1962). The country rocks are upper Cambrian and Ordovician limestones. The intrusion has a symmetrical form, occupies an area of 4 km2, and has a concentric, zonal structure. The approximately circular nucleus to the intrusion is 1.5 km in diameter and composed of jacupirangite and melteigite containing 50-90% of clinopyroxene (augite and titanaugite), 10-50% of titanomagnetite, nepheline, biotite and accessory titanite, perovskite, olivine, aegirine-augite, apatite, K-feldspar and phlogopite. The nucleus is surrounded by a broad ring-dyke of melanite ijolite, composed of nepheline, pyroxene, melanite, up to 10% titanomagnetite, biotite-phlogopite and accessory perovskite, titanite, apatite and calcite. These rocks contain, and in many cases contaminate, small xenoliths of melilite rocks which comprise melilite, nepheline, pyroxene and olivine. Melilitolite is also found in a small plug a kilometre east of the main intrusion. There are lens-like bodies, up to 100x500 m, of coarse-grained diopsidites which grade into typical phoscorites, the main minerals of which are carbonate, apatite and forsterite.