Study on the mineralogical characteristics of crystalline graphite from Xiangshan graphite deposit in Huaining County, Anhui Province

In this paper, the researchers have employed a variety of analytical testing methods and research techniques to conduct the first study on the crystalline graphite mineralogical characteristics of Xiangshan graphite deposit in Huaining County, Anhui Province. The crystalline graphite of the Xiangshan deposit has a relatively complete crystal form and appears as flake aggregates. Energy spectrum analysis shows that the content of C atom in the crystalline graphite ranges from 91.99% to 92.74%. Laser Raman spectroscopy shows that graphite has a high degree of crystallinity and an orderly complete carbon atomic structure. Its laser Raman characteristic spectrum lacks D₁ and D₂ peaks, similar to the Raman spectroscopy in graphene. Powder X-ray diffraction (XRD) reveals that the crystalline graphite exhibits characteristics of 2H type graphite, with an axis length a=0.246 1～0.246 6 nm, c=0.669 3～0.670 0 nm, and a unit cell volume V=0.035 1～0.035 29 nm³. The thickness of graphite flake varies from 37.1～43.3 nm, the degree of graphitization 82～96, the estimated metamorphic temperature 542.4～587.2 ℃, the content of 3R polymorphism 9.03%～10.37% and δ¹³C value −29.223‰～−26.926‰. These findings all suggest that the graphite carbon derived from bio-organic carbon deposited in the strata, which is closer to the level of peat and modern organic matter. Besides, there is no evidence of carbon-containing fluid brought in by magma and inorganic carbon resulting from carbonate rock decomposition.