Geological and Geochemical Evidence for Discriminating Anatectic and Subsolidus Migmatites in the Dabieshan Complex,Northeastern Hubei Province

Based on the geological and geochemical information about migmatites,the following lines of evidence have been proposed for discriminating the anatectic leucosome in the Dabieshan Complex:(1)its width is larger than that derived from the subsolidus genesis,cutting across regional foliation,thus giving rise to complicated folds and wider selvages;(2)it is composed of melanic and accessory minerals in addition to quartz and feldspars;(3)the significant dfference in anorthites of plagioclase between paleosome and leucosome;(4)temperature and pressure(P/T) conditions revealed by the mineral compositions and assemblages are over those for the onset of anatexis;and (5)it is enriched in the major elements(e.g.Al2O3.Fe2O3and TiO2)and immobile and incompatible elements(e.g.LREE,Th,Hf and Zr).Finally,by combining the geological and geochemical features with the statistical data for the spatial distribution of minerals and mass-balance in the migatites,it is concluded that anatexis is the cardinal mechanism of migmatization in the Dabieshan Complex.

Geological and geochemical evidence for discriminating anatectic and subsolidus migmatites in the Dabieshan Complex, northeastern Hubei Province

Based on the geological and geochemical information about migmatites, the following lines of evidence have been proposed for discriminating the anatectic leucosome in the Dabieshan Complex: (1) its width is larger than that derived from the subsolidus genesis, cutting across regional foliation, thus giving rise to complicated folds and wider selvages; (2) it is composed of melanic and accessory minerals in addition to quartz and feldspars; (3) the significant difference in anorthites of plagioclase between paleosome and leucosome; (4) temperature and pressure (P/T) conditions revealed by the mineral compositions and assemblages are over those for the onset of anatexis; and (5) it is enriched in the major elements (e.g. Al₂O₃, Fe₂O₃ and TiO₂) and immobile and incompatible elements (e.g. LREE, Th, Hf and Zr). Finally, by combining the geological and geochemical features with the statistical data for the spatial distribution of minerals and mass-balance in the migmatites, it is concluded that anatexis is the cardinal mechanism of migmatization in the Dabieshan Complex. This subject was jointly supported by the National Natural Science Foundation of China (NSFC Grant No. 49333030 and No. 49472134) and the President Funds of the Chinese Academy of Sciences.