ИСТИНА

Carbonates of Anyui-Chukotka fold belt are widespread in Devonian – Carboniferous and Permian age. For Carboniferous Unit they are represents by Visean to Moscovian – Kasimovian Ages. Carbonates of different tectonic structure were investigated. We examine limestones from: i) South-Anyui Suture (Polarny Creek); Alarmaut uplift, iii) Kibera Cape and iv) Wrangel Island. Limestones of i) Polarny Creek contain fragments of fauna and they occur with basalt-chert rocks [1, 2]. Sedimentation was not far from bioherm reef. ii) Carbonates of Alarmaut uplift have clastic materials and are associated with schists. Carbonate rocks contain grains of quartz, mica and volcanic rock fragments. They were accumulating in the shallow marine environment, in active hydrodynamics conditions.iii) Carboniferous rocks of Kibera Cape consist of sandstones, gravels and conglomerates in the lower part. In the upper part they replaced by limestones and dolostones. All carbonate rocks contain lenses and interlayer of cherts. Sedimentation of carbonates was in shallow-marine shelf of carbonate platform. iv) Limestones and dolostones of Wrangel Island are presented by two types of outcrops: one is widespread in the Central zone of Island; another – in the South zone. Lower part of Carboniferous rocks in Central zone show conglomerates and gravels, limestones are present in the Upper part of outcrop. Carbonates of South zone consists of intercalation of limestones, dolostones, evaporates and other rocks. REE proxies have been considered problematic particularly with regard to diagenetic alteration. We use following geochemical criteria – HREE/LREE, Ce and Eu anomalies, δO18 and δC13 isotopes. We have demonstrated the different paleogeographic environments for Chukotka’s carbonates. Limestones of Polarny Creek may be a part of a carbonate sequence formed on a volcanic atoll. Sedimentological, geochemical and isotopic data indicate shallow-marine and lagunal environnments of carbonate platform for limestones of Alarmaut uplift, Kibera Cape and Wrangel Island with more marine from North to South