Revisit and comparative analysis of the typical graphite deposits in the Paleoproterozoic khondalite series, western North China Craton: Implications for genesis, depositional environment and prospecting potential

Abstract

The phaneritic graphite deposits in the western North China Craton can be delineated into an E-W trending belt, which is consistent with the Paleoproterozoic khondalite series. To interpret why graphite is not ubiquitous among the Paleoproterozoic supracrustal rocks, we revisit and comparatively analyze the typical graphite deposits in the Paleoproterozoic khondalite series employing sequence stratigraphy, chronology, tectonic deformation and metamorphism for the khondalite series and carbon isotope analysis for graphite. Our renewed profile of the western graphite belt (WGB) reveals the following: 1) A greater abundance of organic matter was trapped within the lower part of the khondalite series than in the middle and upper parts; consequently, all the known deposits are restricted to the lower part of the khondalite series. 2) As the protolithic basin evolved from a passive continental margin into an active continental margin, subduction-related magmatism provided the influx of heat needed to transform the organic matter into amorphous graphite. 3) Continental collision-induced high-grade metamorphism and associated magmatism finally reworked the original amorphous graphite into the present-day phaneritic graphite deposits.