Radiogenic isotopes in syngenetic inclusions in diamond indicate a very ancient origin for those belonging to the peridotitic paragenesis (3.2-3.3 Ga), whereas eclogitic diamonds have genesis ages ranging between 1.67 and 0.99 Ga. These ages are distinctly older than those of the volcanic rocks which brought diamonds to the surface. Most diamonds form at depths of about 150 km, but the presence of rare majorite and magnesiowustite inclusions extends this depth of origin to between 150-450 km and up to 670 km respectively. With the deeper diamonds, convective forces or magma plumes in the mobile asthenosphere probably provide the initial transportation to the shallower levels.
|Number of pages||5|
|Journal||Diamond and Related Materials|
|Issue number||2 -4 pt 1|
|Publication status||Published - 1 Jan 1993|