Dike Complexes of the Gromadnen–Vurguveem Ophiolite Massif, West Chukotka: Composition and Geodynamic Setting

Abstract

The Middle (?) to Late Paleozoic ophiolite association of West Chukotka comprises the large Aluchin, Atamanov, and Gromadnen–Vurguveem mafic–ultramafic massifs, which are spatially associated with Late Paleozoic volcanic rocks of the Yarakvaam terrane. This paper is devoted to the dikes of the Gromadnen–Vurguveem massif, which form two spatially isolated complexes: “dikes 1” and “dikes 2.” Both complexes intrude the plutonic gabbroids of the massif. The “dikes 1” complex forms a dike body nappe structurally linked with Paleozoic island-arc volcanics. The rocks of the complex are differentiated from basalts to dacites and chemically correspond to island-arc tholeiites. The “dikes 2” complex consists of separate basaltic dikes, some of which are similar to the “dike 1” rocks. The Ar/Ar dating of these samples gave 264–266 Ma. The other part of the rocks of this complex shows mixed signatures of island-arc tholeiites and N-MORB. It was concluded that the studied dike complexes, together with the earlier studied dikes of the Aluchin massif, marks the early (Late Permian) stage of the back-arc basin evolution. The Late Triassic dikes of the Atamanov massif reflect a more mature stage in the evolution of this basin.