PETROGRAPHY AND GENESIS OF THE DARK MICROGRANULAR ENCLAVES IN THE MACHANGQING INTRUSIVE BODY, WESTERN YUNNAN PROVINCE

A detailed petrographic study on the dark microgranular enclaves found in the Machangqing intrusive rock body shows that, the enclaves are mostly dark black or grayish black in color, round or sub-round in shape, with apparent plastic rheological characteristics. The enclaves are in micro-fine granular texture, containing acicular apatites, K-feldspar and quartz phenocrysts from the host rocks. These characteristics suggest the magma mixing origin of the enclaves, indicating that the Machangqing intrusive rock may be the production of mixing of crust-derived and mantle-derived magma. The injection of mantle-derived magma is a key factor to the mineralization of such magma.