Modification of Mantle Cargo by Turbulent Ascent of Kimberlite

Thomas J Jones,David Sasse,James K Russell

doi:10.3389/feart.2019.00134

Thomas J Jones, David Sasse + Show 1 more

Open Access

https://doi.org/10.3389/feart.2019.00134

Copy DOI

Abstract

Kimberlite magmas provide transport for cratonic mantle xenoliths and diamonds to the Earth's surface. However, the mechanisms supporting the successful and efficient ascent of these dense cargo-laden magmas remains enigmatic due to the absence of historic eruptions, uncertainties in melt composition, and questions concerning their rheology. Mantle-derived xenocrystic olivine is the most abundant component in kimberlite and is uniquely rounded and ellipsoidal in shape. Here, we present data from a series of novel attrition experiments designed to inform on the transport of low-viscosity melts through the mantle lithosphere. The experimental data suggest that the textural properties of the mantle-derived olivine are records of the flow regime, particle concentration, and transport duration of ascent for kimberlitic magmas. Specifically, our results provide evidence for the rapid and turbulent ascent of kimberlite during their transit through the lithosphere; this transport regime creates particle-particle interactions that continually modify the mantle cargo and facilitate mineral assimilation.

Highlights

Magmas erupt as a complex mixture of melt, solids, and volatile-rich fluid, the properties of these components, where preserved, inform on magma source, and ascent conditions
A stream of compressed gas fed into the vertical attrition tube system (Figure 1) fluidizes the particle bed of olivine of original height H0
The extent and nature of the fluidization varied as a function of experimental conditions (Table 1) and we identified two end member regimes corresponding to the experiments that use the highest (70 g) and lowest (10 g) initial particle feeds

Summary

Introduction

Magmas erupt as a complex mixture of melt, solids, and volatile-rich fluid, the properties of these components, where preserved, inform on magma source, and ascent conditions. Attrition has been shown to be a dominant and pervasive process in a variety of volcanic systems, including: within-conduit rounding of accessory lithics (Campbell et al, 2013); milling of pumice during conduit transport and pyroclastic flow (Dufek and Manga, 2008; Dufek et al, 2012; Kueppers et al, 2012; Jones et al, 2016); secondary production of fine ash (Engwell and Eychenne, 2016; Jones and Russell, 2017), and the transport of mantle xenoliths (Barton and Gerya, 2003; Arndt et al, 2010) These volcanological studies illustrate how the properties of the attritted cargo inform on the physical conditions attending transport, eruption and deposition—where attrition is linked to rapid, transitional to turbulent transport conditions

Methods

Results

Discussion

Conclusion