Fast identification of mineral inclusions in diamondat GSECARS using synchrotron X-ray microtomography, radiography and diffraction.

Michelle D Wenz,Margo Regier,Steven D Jacobsen,Steven B Shirey,Mark Rivers,Hannah J Bausch,Dongzhou Zhang,Przemyslaw K Dera,Peter Eng,D Graham Pearson

doi:10.1107/s1600577519006854

Abstract

Mineral inclusions in natural diamond are widely studied for the insight that they provide into the geochemistry and dynamics of the Earth's interior. A major challenge in achieving thorough yet high rates of analysis of mineral inclusions in diamond derives from the micrometre-scale of most inclusions, often requiring synchrotron radiation sources for diffraction. Centering microinclusions for diffraction with a highly focused synchrotron beam cannot be achieved optically because of the very high index of refraction of diamond. A fast, high-throughput method for identification of micromineral inclusions in diamond has been developed at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS), Advanced Photon Source, Argonne National Laboratory, USA. Diamonds and their inclusions are imaged using synchrotron 3D computed X-ray microtomography on beamline 13-BM-D of GSECARS. The location of every inclusion is then pinpointed onto the coordinate system of the six-circle goniometer of the single-crystal diffractometer on beamline 13-BM-C. Because the bending magnet branch 13-BM is divided and delivered into 13-BM-C and 13-BM-D stations simultaneously, numerous diamonds can be examined during coordinated runs. The fast, high-throughput capability of the methodology is demonstrated by collecting 3D diffraction data on 53 diamond inclusions from Juína, Brazil, within a total of about 72 h of beam time.

Highlights

Most diamonds are thought to crystalize in the mantle roots of the continental lithosphere (Stachel & Harris, 2008), whereas so-called super-deep diamonds and their inclusions are believed to crystalize in the convecting upper mantle, transition zone and even lower mantle (Nestola et al, 2018; Palot et al, 2016; Pearson et al, 2014, 2003; Shirey et al, 2013; Stachel et al, 2005)
Provided that the host diamonds are not cracked, minerals included within them are essentially encapsulated in an inert preservation vessel during eruption to the surface in kimberlitic magmas
We describe a fast, high-throughput and nondestructive methodology for identifying microinclusions in diamond as small as 10–20 mm in the maximum dimension by combining synchrotron microtomography with a newly developed radiography system installed on the singlecrystal diffraction beamline of the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS), Advanced Photon Source (APS), USA

Summary

Introduction

Most diamonds are thought to crystalize in the mantle roots of the continental lithosphere (Stachel & Harris, 2008), whereas so-called super-deep diamonds and their inclusions are believed to crystalize in the convecting upper mantle, transition zone and even lower mantle (Nestola et al, 2018; Palot et al, 2016; Pearson et al, 2014, 2003; Shirey et al, 2013; Stachel et al, 2005). We describe a fast, high-throughput and nondestructive methodology for identifying microinclusions in diamond as small as 10–20 mm in the maximum dimension by combining synchrotron microtomography with a newly developed radiography system installed on the singlecrystal diffraction beamline of the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS), Advanced Photon Source (APS), USA. Such a fast yet thorough method allows for all inclusions within the full volume of each diamond to be identified, allowing for a better relative modal proportion of inclusions to be obtained as smaller inclusions, which would be missed if only utilizing optical methods are not overlooked. 1764 Michelle Wenz et al Fast identification of mineral inclusions in diamond at GSECARS

Synchrotron X-ray diffraction

Results

Funding information