Mineral inclusions in lithospheric diamonds

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Marco E. Ciriotti
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Mineral inclusions in lithospheric diamonds

Messaggio da Marco E. Ciriotti » mar 31 gen, 2023 10:04

Referenza:
▪ Stachel, T., Aulbach, S., Harris, J.W. (2022): Mineral Inclusions in Lithospheric Diamonds. Reviews in Mineralogy & Geochemistry, 88, 307-392.

Abstract:
Initially, it may seem extremely daunting to be sitting in front of several thousand carats of small diamonds, knowing that the likelihood of finding a diamond with a meaningful inclusion is about 1% of that parcel. Like other events in life, however, the joy of finding such material soon outweighs the perceived hardship. Mineral inclusions in diamond provide unique and pristine information about inner Earth, from depths of about 120 to just over 800 km and over 3.5 to 0.1 billion years of Earth history. Such is the scope and importance of inclusion research.
Once the inclusion-bearing diamonds have been collected, hopefully from a known source, an intricate set of procedures falls into place. A microscopic description of the physical features of the diamond and its valuable cargo are needed, a preliminary paragenesis is assigned based on inclusion color, and both diamond and inclusion are photographed in detail. Then comes the release of the µm-sized inclusion by crushing of the diamond host, the hope being that the mineral is recovered in one piece, an infrequent event. The next stage is mounting in epoxy and polishing, minimizing rounding of the inclusion surface en route to quarter μm perfection. When this stage is complete, the researcher can afford to relax as modern-day analytical techniques are non-destructive (electron microprobe) or dig only small holes in the perfect inclusion surface (ion microprobe and to a lesser degree, laser ablation-based micro-sampling). In this chapter, we present results of the above procedures for minerals included in diamonds that originate in the lithospheric mantle. A comprehensive review of the mineral chemistry of inclusions, based on an already largely saturated database of almost 5000 inclusion analyses, was previously presented by Stachel and Harris (2008) and is not repeated here. Instead, the two main sections of the review focus on detailed comparisons of the major and trace element compositions of peridotitic and eclogitic suite inclusions with the equivalent minerals in cratonic xenoliths.
Marco E. Ciriotti

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