The evolution of deeply subducted carbonates and the formation of microdiamonds

点击翻译按钮获取中文摘要

Deeply subducted carbonate rocks from the Kokchetav Massif, Kazakhstan were investigated in terms of the following subjects.1. Extremely high concentration of microdiamond found in dolomite marble. The contents of microdiamond are largely different domain by domain of the dolomite marble. The highest concentration of diamond were measured as about 2800 carat/ton.2. One of the samples showed the close relations between chemical zonation of garnet and the diamond distribution.3. The microdiamonds in dolomite marbles were classified into three types, S-type, R-type and T-type by their morphology.4. Microscopic observation, micro-Laue diffraction, laser Raman spectroscopy and micro cathode luminescence showed that the microdiamond formed at two stages.5. Micro -aue diffraction clarified the orientation of the rim and the core of S-type microdiamond. The rim is very fine grained transparent crystals and overgrew on the core at the 2^<nd> stage. The core of S-type diamond is a single crystal.6. The results suggested that the microdiamond in dolomite marble formed from fluids during both prograde and retrograde stage of UHP metamorphism.