Volcanic diamond production
25 May 2012 by Evoluted New Media
Scientists from the University of Southampton have discovered a previously unrecognised volcanic process – similar to one used in chocolate manufacture – which produces diamonds. The process– fluidised spray granulation – offers new insights into the dynamics of volcanic eruptions.
The scientists studied pelletal lapilli, well-rounded particles containing fragments from the Earth’s mantle – notably diamonds. They consist of an inner seed particle with a complex rim, thought to represent quenched juvenile magma. Gas jets are produced by intensive degassing and the seed particles are fluidised and coated by low-viscosity melt simultaneously.
[caption id="attachment_28328" align="alignright" width="200" caption="New best friend – pelletal lapilli"]
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The process is similar to the gas injection and spraying process used to form smooth coatings on confectionary, and layered and delayed-release coatings in the manufacture of pharmaceuticals and fertilisers.
“The origin of pelletal lapilli is important for understanding how magmatic pyroclasts are transported to the surface during explosive eruptions, offering fundamental new insights into eruption dynamics and constraints on vent conditions, notably gas velocity,” said Thomas Gernon, a lecturer in Earth Science.
“The ability to tightly constrain gas velocities is significant as it enables estimation of the maximum diamond size transported in the flow. Gas fluidisation and magma-coating processes are also likely to affect the diamond surface properties.
The occurrence of pelletal lapilli is linked to diamond grade, size, and quality, and in Lesotho – one of the world’s largest diamond mines – petal lapillia have been found in association with concentrations of large diamonds, up to 215 carat. Knowledge of flow dynamics will inform models of mineral transport, and ultimately could improve resource assessment.
