Abstract

Xa Yu granitoid is isometric shape, with the exposure of 7.5 km2 area. The petrographical component consists of medium – coarse to small grained biotite granite. The vein rocks are incusive of aplite, pegmatoid,…The main mineral components are plagioclase, potassium felspate, quartz, biotite, and little horblende. The common accessory mineral components are zircon, orthite and apatite. Chemical components of rocks are: SiO2: 65.96 –76.50, Na2O: 1.85 –3.30, K2O: 3.60 – 5.27, K2O+Na2O: 5.45 –7.18; K2O/Na2O: 1.23 – 1,95. The content of Ba, Sr is low but Rb is higher, variability Rb/Sr: 0.552 –10.526; Ba/Sr: 0.379 – 1.816, Ba/Rb: 0.055 – 3.092; K/Rb: 235.3 – 246.9, Type I-S-granite.