Controlling factors and metallogenic belts of coal-based graphite in the South-western Fujian Province

Graphite is recognized as one of national strategic mineral resources. Coal-based graphite,a kind of microcrystalline graphite,is formed by the metamorphism of coal seams. The South-western Fujian Province locating at the circum Pacific magmatic-tectonic activity belt has favorable metallogenic conditions for coal-based graphite. Based on the study of microstructural characteristics of meta-anthracite and coal-based graphite from southwestern Fujian,the decrease of aromatic interlayer spacing and the elimination of structural defects do not change linearly during the evolution from coal to graphite. Thus,two indices of interlayer spacing d002 and Raman parameter R2 were proposed to classify different rank meta-anthracite and coal-based graphite into four types:meta-anthracite (Ⅳ),graphitized anthracite(Ⅲ),coal-based semi-graphite (Ⅱ1 and Ⅱ2 ) and coal-based graphite (I). The classification template of coal-based graphite was also presented. The formation and distribution of coal-based graphite was restricted to tectonic and igneous activities. Yanshanian intrusions provided thermal energy for graphitization,and the Zhenghe-dapu fault and Yongan-jinjiang fault were two major ore controlling faults. A series of nappe,gliding faults and folds combined with magma intrusion,providing tectonic-thermal conditions as open type,semi-open and semi-closed type and closed type for graphitization and causing the divergence of distribution and types of coal-based graphite. On the basis of the distribution of different types of coal-based graphite and influencing factors,Datian-Zhangping (Ⅰ1 ) and Yongan-Anxi (Ⅰ2 )metallogenic belts of coal-based graphite were divided in the south-western Fujian Province,including Kekeng-Wukeng(Ⅱ1 ),Yongan-Datian (Ⅱ2 ),Changao (Ⅱ3 ) and Anxi (Ⅱ4 ) metallogenic sub-zones.