| Summary: | New evidence exist that micro diamonds do not only form at high pressure and under high
temperature conditions in the diamond window, but can also be synthesized by
polycondensation of light carbon-bearing molecules at medium to low pressure conditions
under favourable thermodynamic, stoichiometric and kinetic circumstances. This process
may even occur close to the Earth´s surface. The studied eclogites contain OH, CO2, CO,
CH4, CH2O and CH3OH. These C:O:H-bearing volatiles can be found around totally
embedded micro cracks in nominally anhydrous minerals (NAMS). Micro cracks act like
monomineralic and interphase grain boundaries, and can also be interpreted as two
dimensional defect structures.
High-resolution synchrotron based FT-IR was used in the study to detect C:O:H-bearing
volatiles around two-dimensional defect structures in NAMS; for example garnet. A
correlation between the different C:O:H-bearing volatiles is visible in the micro diamond
bearing defect structures, whereas in inclusion free defect structures, no correlation of the
different C:O:H containing volatiles can be recognized. The findings from the study shows
that the C:O:H-bearing volatiles, and their distribution pattern around the studied micro
cracks, are indicators for the formation of micro diamonds in natural eclogites. The outcomes
confirm the results from experimental studies on the growth and synthesis of diamond
crystals as a consequence of polycondensation of light carbon molecules.
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