Mapping the Earth's mantle in 4D using the proton microprobe

Abstract

The CSIRO proton microprobe is used to study the trace element chemistry of garnet and chromite grains recovered from kimberlites and other volcanic rocks, both to develop new diamond exploration methods and to further understanding of the makeup and evolution of the earth's upper mantle. Analysis of the partitioning of trace and major elements between garnet and chromite and their coexisting phases in mantle rocks has led to the development of two single-mineral thermometers and a barometer. Trace Ni in Cr-pyrope garnet is used to determine the equilibration temperature (TNi) of each garnet grain. This is the temperature of the garnet in its source rock before it was entrained in the erupti..