Kimberlite eruptions bring exotic rock fragments and minerals, including di
amonds, from deep within the mantle up to the surface. Such fragments are r
apidly absorbed into the kimberlite magma so their appearance at the surfac
e implies rapid transport from depth. High spatial resolution Ar-Ar age dat
a on phlogopite grains in xenoliths from Malaita in the Solomon Islands, so
uthwest Pacific, and Elovy Island in the Kola Peninsula, Russia, indicate t
ransport times of hours to days depending upon the magma temperature. In ad
dition, the data show that the phlogopite grains preserve Ar-Ar ages record
ed at high temperature in the mantle, 700 degrees C above the conventional
closure temperature.