Subalkaline picrobasalts and plateau basalts from the Putorana plateau (Siberian continental flood basalt province): I. Mineral compositions and geochemistry of major and trace elements

In this article, we report on the results of the investigation of trace and major element contents and compositions of minerals for the representative collection of subalkaline picritic basalts from the Putorana plateau and f or tholeiitic plateau basalts sampled from the same locality. Subalkaline p icritic basalts (SAPB) are characterized by a significant enrichment in hig hly incompatible trace elements and steep LREE enriched rare earth element patterns, whereas tholeiitic flood basalts (TFB) show only a mild enrichmen t in incompatible elements and flatter REE patterns. High levels of incompa tible elements in SAPB are reflected in the abundance of accessory apatite, baddeleyite, and altered zirconolite in them. Minerals of the armalcolite- pseudobrookite series are present in solidified melt inclusions in olivine phenocrysts. Olivine phenocrysts in SAPB contain crystalline inclusions of Ti-rich chrome spinel with a significant fraction of the magnetite componen t, which points to the high values of oxygen fugacities. Certain geochemica l features of SAPB (high values of Ti/Na and Luna ratios, negative K and P anomalies on BSE normalized diagrams) show that their primary magmas formed at very high pressures. The TFB lack these high pressure characteristics, but are characterized by distinct Nh and Ta negative anomalies, which imply a certain level of crustal contamination, whereas, in MgO-rich SAPB, Nh an d Ta anomalies are absent.