Features and origin of mafic microgranular inclusions in the Mishuling intrusion in the West Qinling

The host rocks of the Mishuling intrusion consists of a grayish white porphyritic monzogranite-granodiorite-quartz diorite,in which mafic microgranular inclusions are well developed.The in clusions are close-spaced and occur in swarms and zones.They are highly varied in size and display preferred orienta-tion.Some of them have fine-grained rims and chilled borders.The inclusions commonly exhibit grada-tional contact relationships with their host rocks in respect to the composition,color index and fabrics,the boundaries being vague.Acicular apatite,K-feldspar megacrysts(xenocrysts),rimmed structure as well as abnormal zoning of plagioclase can be observed in most of the inclusions.These features suggest that the Mishulin g intrusion formed by mixing of basic magma and acid magma.This offers important evidence for the determination of the regional tectonic boundary and tectonic units and also furnishes new information for the study of Mesozoic crust-mantle mixing and crustal accretion in the study area.