Isotopic Dating of Diamonds
The desire to obtain crystallization ages for diamonds is driven by both economic criteria and scientific curiosity. Geologists have endeavored to answer a number of questions concerning diamond formation. Perhaps the most fundamental question that has been addressed in diamond-dating studies is whether diamonds are much older xenocrysts, simply transported by their predominant host magma, kimberlite, or whether they in some way related to the kimberlite-forming event itself. Progressing from this is the matter of whether diamonds have formed continuously throughout Earth’s history or during discrete episodes. At a more detailed level, a desire to know what diamond formation can tell us about Earth’s evolution, tectonics, and volatile outgassing drives the quest to know whether diamond-forming events can be related to geologic events or phenomena observable on the earth’s surface. In addition to this, one of the great values in knowing diamond crystallization ages is in driving potential exploration strategies. Determination of diamond ages can be instrumental both in identifying new target areas for primary sources and also in constraining the sources of alluvial diamonds, thus supporting paleogeographical reconstructions useful for further exploration.
Since no natural terrestrial diamonds of which we are aware are young enough to take advantage of the cosmogenic 14C chronometer, and the diamond lattice contains no other useful radioisotope in significant quantities, it has not been possible to date diamonds directly by isotopic methods.