鄂西黄陵基底石墨矿物学、地球化学特征及其对石墨成因的指示OA

[Objective]The Huangling Basement is an important production area of crystalline graphite in China,where the graphite is characterized by high grade,large flake size,and excellent beneficiation performance.However,the understanding on the carbon source and mineralization processes of these graphite deposits is insufficient and further relevant research is needed.[Methods]In this study,Petrographic observation,Raman spectroscopy and carbon isotope analysis were performed in three typical graphite ore districts including Dongchonghe,Sanchaya and Tanjiagou.[Results]The results indicate that the ore-hosting rocks are predominantly graphite schist,biotite plagiogneiss,and mica schist of the Paleoproterozoic Huanglianghe Formation,with protoliths interpreted as organic-rich metapelites The δ13C values of organic carbon in graphite range from -26.90 ‰ to -9.33 ‰,indicating that the carbonaceous material was mainly derived from microbial organic matter such as cyanobacteria.In contrast,the δ13C values of inorganic carbon in marble are concentrated between 6.11 ‰ and 9.78 ‰,corresponding to the Paleoproterozoic Lomagundi-Jatuli positive carbon isotope excursion.Raman thermometry of carbonaceous material(CM)yields graphite metamorphic temperatures of 400-730℃,suggesting that the peak metamorphism reached granulite facies.[Conclusions]Collectively,these results suggest that graphite mineralization in the Huangling area is closely linked to Paleoproterozoic orogenesis of the Yangtze Craton.Carbon-bearing sediments deposited along the continental margin prior to～2.05 Ga provided the primary material source,whereas regional metamorphism and associated magmatic activity during the 2.05～1.95 Ga collisional orogeny supplied the critical thermal and tectonic drivers.These processes facilitated the recrystallization of carbonaceous material,ultimately leading to the formation of crystalline graphite deposits.This study provides new insights into the Paleoproterozoic carbon cycle of the Yangtze Craton and the genesis of regional metamorphic graphite deposits.