Shallow magma diversions during explosive diatreme-forming eruptions

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

doi:10.1038/s41467-018-03865-x

Abstract

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. Magma diversion is known to occur during explosive volcanic eruptions generating subterranean excavation and remobilization of country and volcanic rocks. However, feedbacks between explosive crater formation and intrusion processes have not been considered previously, despite their importance for understanding evolving hazards during volcanic eruptions. Here, we apply numerical modeling to test the impacts of excavation and subsequent infilling of diatreme structures on stress states and intrusion geometries during the formation of maar–diatreme complexes. Explosive excavation and infilling of diatremes affects local stress states which inhibits magma ascent and drives lateral diversion at various depths, which are expected to promote intra-diatreme explosions, host rock mixing, and vent migration. Our models demonstrate novel mechanisms explaining the generation of saucer-shaped sills, linked with magma diversion and enhanced intra-diatreme explosive fragmentation during maar-diatreme volcanism. Similar mechanisms will occur at other volcanic vents producing crater-forming eruptions.

Highlights

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent
This allows us to test how local stress fields, and magma propagation, respond to the mechanical changes produced by excavation of maar-diatreme structures that are common in mafic and kimberlite volcanic fields (Fig. 1a)
We conclude that stress fields generated from maar-diatreme volcanism can cause magma diversions, with diverted magma producing intrusions with a variety of geometries, which will affect the location of magma fragmentation sites and surface eruptions

Summary

Introduction

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. We observe differential tectonic stresses down to −80 MPa in areas of horizontal compression, and up to 10 MPa in areas of horizontal extension in the country rock surrounding excavated diatremes with no infilling (Supplementary Fig. 1). Horizontal extension occurs near the contact between the diatreme wall and the infill, with differential tectonic stress values up to 10 MPa (Fig. 3b).

Results

Conclusion