Geochemistry of metasediments from the Precambrian Hapschan Series, eastern Anabar Shield, Siberia

The Precambrian Hapschan Series in the Anabar Shield in northern Siberia is composed of garnet paragneisses (pelitic graywackes), marbles, calciphyres, and calc-silicate rocks (carbonates and carbonate-rich clastic sediments), and a minor amount of enderbite and mafic granulite. Trace element distributions in the paragneisses (especially REE patterns and low Cr and Ni) suggest felsic sources for the graywacke protoliths. With exception of Mn, Pb, and Sr trace elements in Hapschan carbonates and calc-silicates are housed chiefly in chiefly silicate contaminant phases. When normalized to Al₂O₃ to partially compensate for trace elements contained in Al-silicates, most trace elements are depleted in Hapschan carbonates relative to average Phanerozoic marine limestone (PML). Rb, Cr, Ni and Ti are strikingly depleted in Hapschan as well as other Precambrian high-grade carbonates relative to PML. The element depletions in Hapschan marbles may be explained by some combination of loss during granulite-facies metamorphism or by removal in another depository such as BIF. Geologic and geochemical data are consistent with deposition of the Hapschan Series in a cratonic or passive continental margin setting, during the Early Proterozoic. Basement to this series may be the high-grade rocks of the Daldyn and Upper Anabar Series from which a zircon U ion probe age of 3.3 Ga has been reported.