RESUMEN
The results of Micro-FTIR spectra analysis of the euhedral faceted polycrystalline diamonds (EFPCDs) from the Western Yangtze Craton show that the EFPCDs are mostly IaAB type, the concentration of nitrogen.varies greatly from 25. 70- 358.35 µg x g(-1). Different nitrogen content distributes in different diamond grains or position in same sample. The C Center was not found in the samples and the conversion from A center to B center is incomplete, in the meanwhile, B% value concentrated in 40%. Thus, polycrystalline diamonds are not formed in the stage of nucleation but gathered together after formation of the individual diamond grains during the residence time in the mantle. And its formation environment is. more complex than the euhedral faceted polycrystalline diamonds from Mengyin kimberlite, the Eastern of North China Craton. The diamonds extremely possibly originated in the deep mantle from 160 to 180 km, reaching the depth of the core of the Yangtze Craton, at the same time it is close to the bottom of the lithosphere. The C-H bond of sp2 hybridization are conducive to the formation of platelets in diamonds. Meanwhile, its concentrations are generally higher than the C-H bond of sp3 hybridization in the samples.
RESUMEN
The FTIR and Raman spectra of 10 diamonds from Yuanshui, Hunan province show that the alluvial diamonds from this area are mostly IaAB type, with a significant character that the A-center is enriched relatively; the nitrogen concentration in the diamonds is between 38.20 and 840.67 microg x g(-1), which has a tremendous distinction in different crystal. The residence time of the diamonds in the mantle are between 0.043 and 3.315 Ga, which is also has a great difference in different diamond grains. The remotest residence time (3.315 Ga) of one diamond is older than the most aged rock (3.285 Ga) in Xiang-E-Qian-Gui contiguous zone. A remarkable environment change had took place during the process of diamonds formation. The formation depth of dodecahedral diamonds is deeper than that of the octahedral ones.
RESUMEN
The results of FTIR spectra study of OH in olivines from Mengyin kimberlite show that there are more than 60 OH absorption peaks in the range of 3800-3000 cm(-1). We identified four major spectral features in the OH absorption bands of kimberlitic olivines. One is with nuOH in the range of 3800-3700 cm(-1), which is caused by the vapour of the room circumstance, and can not be regarded as intrinsic or non-intrinsic nuOH of the olivines. Another one is with nuOH in the range of 3710-3620 cm(-1), which belongs to three "water"-bearing minerals including serpentine, talc and Mg-bearing amphiboles, which is the non-intrinsic nuOH of the olivines. There is the possibility that H in hydrous minerals mainly entered into olivines during post-emplacement processes of the kimberlite magma. The third one is with nuOH in the range of 3620-3425 cm(-1), which originated from H occupying the Si-defect in the olivine structure, forming humite-like defects, and/or the defects that H occupies (Mg,Fe)-depletion, which is certainly attributed to the intrinsic nuOH of the olivines. In this case, H possibly entered into olivines following its immersion in the high temperature and rich fluid kimberlite magma in the mantle circumstance. The last one is with nuOH in the range of 3425-3000 cm(-1). In this area, nuOH is assigned to fluid inclusions of the olivines, and is the non-intrinsic nuOH of olivines. Fluid inclusions can enter into the olivines either during post-emplacement processes of the kimberlite magma or during the periods that olivines were formed in the mantle.