| Summary: | The Panzhihua intrusion in southwest China is part of the Emeishan large igneous province and host of a large Fe-Ti-V ore deposit. In previous interpretations it was considered to be a layered, differentiated sill with the ore deposits at its base. New structural and petrological data suggest instead that the intrusion has an open S-shape, with two near-concordant segments joined by a discordant dyke-like segment. During emplacement of the main intrusion, multiple generations of mafic dykes invaded carbonate wall rocks, producing a large contact aureole. In the central segment, magmatic layering is oriented oblique to the walls of the intrusion. This layering cannot have formed by crystal settling or in-situ growth on the floor of the intrusion; instead we propose that it resulted from inward solidification of multiple, individually operating, convection cells. Ore formation was triggered by interaction of magma with carbonate wall rocks.
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