New massif of Archean alkaline syenites in the Murmansk domain of the Kola peninsula

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Alkaline magmatism typical of a mature continental crust is among the most important geodynamic markers in the Early Precambrian. The Late Archean alkaline rocks represented by alkali granites, alkali gabbros, syenites, nepheline syenites, and carbonatites are known at the ancient shields [1]. In the Kola Peninsula, such magmatism (with an age of 2.75‐2.61 Ga) in the form of alkali granite and alkali gabbro‐nepheline syenite complexes occurs in the Archean Keivy and Ingozero structures [2, 3]. No Precambrian alkaline complexes have been found yet in the Archean Murmansk domain of the Kola peninsula. The Late Archean Iokan’gskii intrusive complex of porphyritic lepidomelane‐ferrohstingsite granites was previously ascribed by Batieva [2] to the alkali granite complex. However, later studies [4] showed that it belongs to the complex of ancient rapakivilike granites of normal alkalinity. During recent studies of the granitoids from the Barents Sea shore of the Kola Peninsula in the area of Gremikha settlement and Mt. Ostrovnaya, the small Late Archean alkaline massif called Panejavr Massif after an nearby lake was discovered and studied. The Panejavr Massif is located within the Iokan’gskii block of the Murmansk domain, and its position is controlled by the junction of two faults (Fig. 1). The massif is contained among Late Archean migmatite‐granites and metabasite dikes that fill the NE-trending faults. The Panejavr Massif is a complex stock having an autonomous internal structure discordant to the host rocks (Fig. 1) and consisting of two chemically and mineralogically contrasting intrusive phases.