Translithospheric mantle diapirism: geological evidence and numerical modelling of the Kondyor zoned ultramafic complex (Russian Far-East

We report new structural, microstructural, petrological, and major-and trace-element data on ultramafic rocks from the Kondyor zoned ultramafic complex in Far-East Russia. The ultramafic rocks are subdivided into three subconcentric lithologies, from core to rim: (1) a metasomatic domain where generally phlogopite-rich dykes perva-sively intrude dunite; (2) a main dunite core; (3) a pyroxenite rim. The ultramafic rocks have nearly vertical contacts with the sur-rounding Archaean basement (gneisses, quartzites and marbles) and hornfelsed Riphean sediments.The hornfelsed sediments show a relatively steep (4608), outward dipping layering, which rapidly flattens to horizontal away from the inner contact. Although the Riphean sediments define a dome-like structure, the inward, shallow dipping foliation of the dunites indicates a synformal structure. Detailed petro-structural investigations indicate that the Kondyor dunites were deformed by solid-state flow under asthenospheri