Shallow magma diversions during explosive diatreme-forming eruptions

Nicolas Le Corvec, James D Muirhead, and James D L White

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Received: 18th October 17

Maar-diatremes are inverted conical structures formed by subterranean excavation and remobilization of country and volcanic rocks during explosive eruptions. These processes alter the local crustal stress state and geometries of magmatic intrusions, however feedbacks between maar-diatreme formation and intrusive processes have not been considered previously, despite their importance for understanding evolving hazards during explosive volcanic eruptions. We apply innovative numerical modeling to test the impacts of excavation and infilling of diatreme structures on stress states during eruptions. Results suggest that explosive excavation and infilling of diatremes fundamentally affects dynamics of syn-eruptive, intrusive activity and mechanisms of diatreme formation. Rapid unloading during excavation generates horizontal compressive stress states beneath diatremes, allowing magma to divert laterally as saucer-shaped sills and circumferential dikes. Diatreme infilling generates extensional stresses within the infill’s base, favoring magma ascent in the lower half of the structure, whereas volumetrically large infill creates compressive stress in the upper half, inhibiting magma ascent to the surface and promoting intra-diatreme explosions and host rock mixing. We demonstrate novel mechanisms explaining evolving locations of explosive fragmentation during maar-diatreme volcanism, and magma diversions into saucer-shaped sills. Similar mechanisms can be inferred to act at other, monitored, volcanic vents producing crater-forming eruptions.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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