Diamond dating site

16 Oct

This phase diagram depicts the stability fields of graphite and diamond in relation to the convecting mantle (asthenosphere) and the lithospheric mantle.The graphite/diamond transition was recently revised to lower pressures (Day, 2012), providing for even greater storage of diamonds at shallower levels in the cratonic keel.It is hoped that this article will give the gemologist a ready way to convey how nature first created the rough diamonds.For the reader who is unfamiliar with geologic terms, a glossary is presented at the end of the article.

Diamonds are stable under the high pressure and temperature conditions that are only met at great depth in the earth’s mantle.

Archean cratons in South Africa have yielded gem diamonds such as these specimens from the GIA Museum’s Oppenheimer Student Collection. Since then, there have been significant advances in the analysis of diamonds and their mineral inclusions, in the understanding of diamond-forming fluids in the mantle, and in the relationship of diamonds to the deep geology of the continents and the convecting mantle.

It has been more than two decades since diamond ages have proven to be up to billions of years older than their host magmas of kimberlite or lamproite.

This article reviews currently accepted areas of knowledge, along with topics that are still the subject of ongoing research, where science does not yet have all the answers.

This basic subject was discussed more than two decades ago in (Kirkley et al., 1991); since then, there have been major advances in our understanding of diamond geology.