Kimberlite Volcanology: Transport, Ascent, and Eruption

Kimberlite rocks and deposits are the eruption products of volatile-rich, silica-poor ultrabasic magmas that originate as small-degree mantle melts at depths in excess of 200 km. Many kimberlites are emplaced as subsurface cylindrical-to-conical pipes and associated sills and dykes. Surficial volcanic deposits of kimberlite are rare. Although kimberlite magmas have distinctive chemical and physical properties, their eruption styles, intensities and durations are similar to conventional volcanoes. Rates of magma ascent and transport through the cratonic lithosphere are informed by mantle cargo entrained by kimberlite, by the geometries of kimberlite dykes exposed in diamond mines, and by laboratory-based studies of dyke mechanics. Outstanding questions concern the mechanisms that trigger and control the rates of kimberlite magmatism.

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Dynamic Magma Systems: Implications for Forecasting Volcanic Activity

Magma systems that supply volcanoes can extend throughout the crust and consist of mush (melt within a crystalline framework) together with ephemeral magma accumulations. Within a crystal-rich mush, slow processes of melt segregation and heat loss alternate with fast processes of destablisation and magma transport. Magma chambers form by two mechanisms: incremental magma intrusion into sub-solidus rocks or the segregation and rapid merging of melt-rich layers within mush regions. Three volcanic states reflect alternations of slow and fast processes: dormancy, unrest and eruption. Monitoring needs to detect processes of melt and fluid movements in the lower and middle crust during destabilisation to improve forecasting.

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