Field and Geochemical Studies of the Melilite-Bearing Arydzhangsky Suite, and an Overall Perspective on the Siberian Alkaline-Ultramafic Flood-Volcanic Rocks

This paper presents the first comprehensive geologic, petrographic, geochemical, and Sr- and Nd-isotopic study of the 350 m thick Arydzhangsky lava suite, the last suite in the entire north Siberian, flood-volcanic sequence to require study by modern methods. Within this sequence, only the Arydzhangsky Suite includes melilite-bearing lavas; it is composed of melanephelinites to limburgites (both melilite-bearing and melilite-free), with rare melilitites and picrites. The lavas contain from 0 to 60 vol% melilite, with MgO contents ranging from 5.7 to 29.5 wt%. Nonetheless, these compositionally diverse lavas are all quite similar in incompatible-element geochemistry. They are distinct from all other Siberian alkaline-ultramafic lavas and, among these lavas, show the most resemblance to the Yakutian kimberlites. With this contribution, all of the north Siberian, alkaline-ultramafic lavas will have received equal geochemical and isotopic characterization. Five rock groups have been identified among them on t...