ABSTRACT
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.
ABSTRACT
The Guidong composite granite body (CGB) located in the north Guangdong Province consists of numerous rock bodies formed respectively in the early and late Jurassic and early Cretaceous. Analysis of the granites of different period with X-ray fluorescence spectroscopy and plasma mass spectrometry indicates: (1) From the top of a granite body downwards, the felsic components of rock decrease, while the mafic and sigmaREE, LREE/HREE, (La/Yb)N, as well as delta Eu value increase, suggesting the material differentiation in the in-situ melting of crustal rocks and crystallisation of magma; (2) From old to young of the different period granite-massifs in the Guidong CGB, the felsic compositions totally decrease, and the mafic components, sigmaEE, LREE/HREE, (La/Yb)N, and delta Eu value increase as well, implying multiple crustal melting (remelting) events in the Mesozoic in this area; and (3) Primitive mantle-normalized spider diagram for trace elements of Guidong CGB suggests high maturity of the crust involved in the in-situ melting.
ABSTRACT
Red pigment of continental red-bed is known originating from the fine-particle hematite in the rocks. Advance of researches on the origin of continental red-bed demonstrates that the red pigment of red-bed originated from its diagenetic but not depositional process. The high diagenetic temperature causes the dehydration of iron hydrate to form hematite, generating the red pigment. For examining the above hypothesis, the authors of this paper designed an experiment to approach the reddening process, i.e. formation of the red pigment of continental red-bed. Black ooze sampled from the Holocene sediments of the Pearl River Delta was heated in different ways. The diffuse reflectance spectroscopy (DRS) of those heated ooze samples were detected with Perkin-Elmer Lamdba 950 ultraviolet/visible/near-infrared spectrophotometer, and moreover, red-values of the samples were calculated for determining their coloring levels. Iron in black ooze sediment is predominantly in the form of goethite. Experimental results verified that initial dehydration-temperature of goethite is about 150 degrees C, either enhancing temperature or prolonging heating time is accompanied with decreasing goethite and increasing hematite, and a positive relationship exists between red-value of samples and peak-height of hematite. The experimental results strongly support the idea of thermal origin of continental red-bed.
