Location, chemical content, and origin of Loveringite from Paleoproterozoic layered intrusions of the Fennoscandian Shield: The Syöte block of the Koillismaa, Finland, and the Nyud of the Monchegorsk pluton, Russia

We present the results of a study of loveringite found in two Paleoproterozoic layered intrusions of the Fennoscandian Shield: the Syöte block, Koillismaa intrusion, Finland, and the Nyud intrusion of the Monchegorsk pluton (Monchepluton), Russia. Loveringite is found in various rock types: 1) in non-cumulative gabbronorite (NcG) of a later phase from the middle zone of the Syöte block of the Koillismaa intrusion and 2) in orthopyroxene orthocumulates from lower zone of the Nyud intrusion. The loveringite morphology is diverse. It occurs as euhedral, anhedral, and corroded grains. Loveringite from the Syöte block, in contrast to that of the Nyud intrusion, is characterized by increased contents of Ti, Ca, V, and Zr, the presence of U and Th, and also reduced contents of REE. The loveringite composition is not strictly controlled by the stratigraphy of the layered intrusions, but is related the composition of residual liquid. The ilmenite reaction rims with baddeleyite and chrome-spinel are constantly present around the loveringite. Thinnest rims are observed around euhedral loveringite, whereas the thickest rims are observed around corroded grains, which indicates that the rim formation is due to reaction of the grain with residual liquid. Loveringites were formed at the late magmatic stage, after crystallization of cumulus orthopyroxene in the Nyud intrusion and pyroxene-plagioclase assemblage in the Syöte block. The presence of incompatible elements (Zr, U, Th, and REE) in the loveringite composition indicates crustal contamination for its genesis.