Genesis of dioritic inclusions in Late Ordovician granitic rocks in the Yichun area

Abstract: A compositional evolutionary series of Late Ordovician granite bodies is developed in the vicinity of the Xiaoshanhe Tree Farm in the Yichun area, Heilongjiang Province. Through systematic 1:50000 regional survey, the series has been studied and classified in detail and the hierarchical mapping units of the Beiying Tree Farm have been established. Dioritic inclusions are common in fine-to medium-grained, porphyritic hornblende-bearing biotite monzogranite of the Xiaoshanhe unit. Most of these inclusions occur as elliptical grains of varying size at the edges of the granite intrusions. Intensive petrological, mineralogical and rock geochemical studies of the granitic rocks and dioritic inclusions indicate that the rocks and inclusions are genetically related and have an affinity in evolution. The dioritic inclusions are immiscible ones and resulted from the evolution of the felsic magma during its liquation.