Graphites are widely generated in geological processes of magmatism

metamorphism and hydrothermal alteration & metasomatism

and considered to be an indicative mineral for these geological processes. Xiuyan nephrite jades (locally named Laoyu)

especially gravel nephrite jades

in Liaoning province

commonly contain graphite as internal enclaves. The study of these graphites will contribute to understand the formation of their host nephrite jades and the relationship between graphite enclaves and their host nephrite jades. In this paper

microscopic observation

Raman spectra and X-ray single-crystal diffraction are used to study graphites in host nephrite jades from Xiuyan

Liaoning

and the genetic relationship between graphites and their host nephrite jades. The results show that crystalline graphites commonly occurred in three clustered patterns of stripped

star-like and nebulous

in their host nephrite jades

and contained 19.52%～23.00% graphites in rhombohedral polymorph. The crystallinity indexes of graphites range between 0.562～0.644

and calculated forming temperatures range between 454～623 ℃. The temperatures are identical to those for amphibolite facies

obviously higher than previously reported data of nephrite jades. These results infer that graphites and their host nephrite jades probably formed in different geological processes or periods. Combining field investigation

we think that graphites in Xiuyan gravel nephrite jades were probably the remnant minerals of primary regional metamorphism prior to their host nephrite jades-formation

and Xiuyan nephrite jades formed through multi-stage or multi-period metamorphic and hydrothermal metasomatism processes from Liaohe group primary strata such as graphite & calcite-containing marble

graphite-containing tremolite granulite

or tremolite marble.