CHARACTERISTICS,CRYSTALLIZATION CONDITIONS AND EMPLACEMENT DEPTHS OF QUARTZ MONZONITES FROM DASHUI AREA,GANSU PROVINCE

Study of petrology of quartz monzonites from Dashui area suggests that the Zhonggezhala,Zhongqu and Ge'erkuohe bodies are derived from a comagmatic region.Although their crystallization temperature of about 700℃~800℃ is exactly alike,the emplacement depth among them is very different,from 20km~22km of Zhonggezhala through 16km of Zhongqu to 8km~11km of Ge'erkuohe towards the east.Moreover,the later two bodies show a signature of subvolcanic rock.This implies that hypabyssal magma is beneficial to the gold mineralization in the Dashui area.This is why the large-scale gold deposit was defined in the vicinity of Ge'erkuohe and Zhongqu bodies,but only ore spot was found nearby Zhonggezhala body.