TY - JOUR

T1 - EVIDENCE OF EXTREME REDOX VARIATIONS IN SUBDUCTION-ZONE DIAMOND

AU - Shatsky, V.s.

AU - Ragozin, A.l.

AU - Kupriyanov, I.n.

AU - Kalinina, V.v.

PY - 2024/10/19

Y1 - 2024/10/19

N2 - The article presents new data on multiphase inclusions in two diamonds sampled from placers in the northeastern Siberian craton. Diamond HLS-4 is a round variety V crystal containing a multiphase mineral inclusion with more or less strongly oxidized iron carbides and moissanite in one part and calcite and iron oxides in another part. Another sample, HI-180, is a partly dissolved yellow cuboid that hosts a multiphase inclusion and numerous submicrometer inclusions delineating the crystal zoning. Sample HI-180 is deformed, with cracks and cavities up to 200 mu m in size exposed in a polished section. The submicrometer inclusions plot in the field of microinclusions in fibrous diamonds from the world database, mostly near the silicic corner. They must have a hydrous composition, judging by the water-carbonate ratio of H2O/(H2O + CO2) = 0.80-0.82 estimated from FTIR data. The multiphase inclusion consists of quartz, Fe-armalcolite, anatase, and diamond grains in an amorphous matrix, as well as moissanite and calcite detected by SEM-EDS, FTIR and Raman spectroscopy. One diamond grain in the inclusion, in turn, encloses moissanite. The coexistence of calcite and moissanite in multiphase inclusions is evidence that cracks were fully healed up under extreme redox variations, possibly, during diamond growth in a subduction setting.

AB - The article presents new data on multiphase inclusions in two diamonds sampled from placers in the northeastern Siberian craton. Diamond HLS-4 is a round variety V crystal containing a multiphase mineral inclusion with more or less strongly oxidized iron carbides and moissanite in one part and calcite and iron oxides in another part. Another sample, HI-180, is a partly dissolved yellow cuboid that hosts a multiphase inclusion and numerous submicrometer inclusions delineating the crystal zoning. Sample HI-180 is deformed, with cracks and cavities up to 200 mu m in size exposed in a polished section. The submicrometer inclusions plot in the field of microinclusions in fibrous diamonds from the world database, mostly near the silicic corner. They must have a hydrous composition, judging by the water-carbonate ratio of H2O/(H2O + CO2) = 0.80-0.82 estimated from FTIR data. The multiphase inclusion consists of quartz, Fe-armalcolite, anatase, and diamond grains in an amorphous matrix, as well as moissanite and calcite detected by SEM-EDS, FTIR and Raman spectroscopy. One diamond grain in the inclusion, in turn, encloses moissanite. The coexistence of calcite and moissanite in multiphase inclusions is evidence that cracks were fully healed up under extreme redox variations, possibly, during diamond growth in a subduction setting.

UR - https://www.webofscience.com/wos/woscc/full-record/WOS:001331563400001

U2 - 10.2113/RGG20244767

DO - 10.2113/RGG20244767

M3 - Article

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

ER -