Spatial and temporal evolution of kimberlite magma at A154N, Diavik, Northwest Territories, Canada

Lastly, we estimate physical properties for the magmas that produced each deposit. The magma properties are combined with 3-D models for the geometry of the conduit at the time of eruption to constrain the mass flux and duration of each eruptive event. Steady-state assumptions for velocity and magma flux yield total eruption durations of minutes to hours. The diversity of textures and compositions recorded in pyroclastic kimberlite (PK1) and dykes of coherent kimberlite (CK1 and CK2) are a possible manifestation of separated three-phase flow involving kimberlite melt and crystals, and an ever-increasing proportion of exsolved CO2-H2O fluid. Specifically, we suggest that the early dykes (CK1), pyroclastic kimberlite (PK1), and late-stage dykes (CK2) are representative of three separate regimes of kimberlite magma created by the ascent of a vigorously degassing magma. We envisage this being composed of: (a) the gas-charged front of the magma created by decoupling the more buoyant gas phase from the silicate melt; (b) a transient, gas-rich body of magma in which later-stage exsolved fluids/gases are essentially coupled to the melt; and (c) a fluid-depleted tail of magma which remains buoyant within the lithosphere but ascends more slowly than the fluid and exsolving gas phases.