Geology and petrography of the Pingyang gneissic trondhjemite, Fuping, Hebei

Abstract: The Pingyang gneissic trondhjemite is located in the vicinity of Pingyang Township, Fuping County, Hebei Province. Its country rocks are supracrustal rocks including migmatites and gneisses, stratigraphically equivalent to the lower part of the Fuping Group. The high-grade metamorphism, migmatization and anatexis have close spatial relationships in the Pingyang area, showing the ‘trinity’; thus the change from metamorphic rocks to granites show the gradational features with respect to systematic petrology, petrography and occurrence relationships. The metamorphosed supracrustal rocks and some inclusions in granites can not only be correlated with their equivalents in the surrounding areas but also show signs of modification by anatexis. Ample evidence indicates that the Pingyang gneissic trondhjemite is generally autochthonous anatectic trondhjemite, which has been displaced to some extent locally. The anatexis of metamorphosed supracrustal rocks in the Pingyang area progressed through the early stage characterized mainly by dissolution and recrystallization of minerals and the late stage when melting of some minerals predominated. The formation of the Pingyang gneissic trondhjemite represents the higher evolutionary stage of anatexis of metamorphosed supracrustal rocks of the Fuping Group-complex, which has great significance for the objective understanding of the composition and geological evolution of the Fuping Group-complex.