Geochemical characterisation and protolith restoration of metamorphic rocks at Lazishao graphite mine, Sichuan.

This study determined the deposit characteristics and geochemical features of metamorphic rocks from the Lazishao graphite deposit in order to reconstruct the metamorphic protoliths and palaeo-sedimentary environment. The results show that the SiO2 content of the metamorphic rocks is high (55.60% to 77.94%), while Na2O is 0.22% to 1.85%, K2O is 1.87% to 3.45%, K2O > Na2O, and K2O/Na2O + K2O > 0.5. The fractionation degree of light rare earth elements (LREEs) is greater than that of heavy rare earth elements (HREEs), with LREE/HREE ratios of 3.09 to 8.77; LaN/YbN is 2.72 to 10.75, with a mean value of 9.69. The rocks have moderate negative Eu anomalies (δEu = 0.50 to 0.89, mean = 0.64). Ionic lithophile elements (e.g., Rb, Ba, and K) are relatively enriched, but Sr is relatively depleted. The graphite-bearing metamorphic rocks in the study area originated from sedimentary rocks, mainly mudstone and greywacke. The palaeo-sedimentary environment was a low-salinity terrestrial freshwater body in a cold or moderately cold climatic zone. [ABSTRACT FROM AUTHOR]