The First Finding of Carbonatite Tuffs in Cenozoic Basaltic Volcano of Southeastern Primorye

摘要

The origin of carbonatites and carbonatite-type rocks remains a debatable petrologic problem. Therefore, any information on findings of these rocks is valuable for the better understanding of key mechanisms of their formation. We found carbonatite tuffs among eruption products of the early Neogene Amba Volcano in southwestern Primorye (Fig. 1). The volcanic edifice occupies an area of ～20 km~2 in the middle reaches of the Amba River at a distance of 28 km from Amur Bay. The basalts of the stratovolcano base overlie the Permian carbonate and volcanosedimentary rocks and the Triassic arkose sandstones. The basalts are, in turn, overlapped by the upper Miocene volcanosedimentary rocks of the Ust-Suifun Formation and basalts of the Shufan Plateau. The central vent of the Amba Volcano is filled with explosion breccia and basaltic lavas. Pyroclastic rocks, including layers of carbonatite tuffs, compose the peripheral facies of the volcano.