Abstract:

The Galale gold （copper） deposit is located in the west section of Bangong lakeNujiang suture zone in Tibet. It is a gold (of large scale) and copper (of small scale) skarn deposit. There are mainly huge porphyritic quartz diorite, middlefine grain granodiorite and diorite porphyrite in the mine area. The REE differential degree of rock sample in this ore deposit has a relatively higher value, and Eu negative anomaly is weak. The content of Al2O3 is 14.45%15.84%. The aluminum supersaturation index (A/CNK) ranges between 1.33 and 1.46, which is greater than 1, indicating its being Stype granite. According to the analysis of trace elements, the magmatic body belongs to MPG. The forming stage is close to the collision stage. The result of zircon LAICPMS dating indicates that the age of huge porphyritic quartz diorite is 131±17 Ma, that of the middlefine grain granodiorite is 86.52±0.41 Ma, and those of the two diorite porphyrites are 88.59±0.45 Ma and 88.09±0.41 Ma. Among them, the huge porphyritic quartz diorite is a nonmineralization magmatic body, and the dating data represents the lower limit of the mineralization age. The coppergold orebody was only produced in the contact zone of the middlefine grain granodiorite and the diorite porphyrite magmatic body with the limestone and the siltstone with silicalite. So it was mineralized in the stage of Yanshan. According to the result of dating, the evolutionary process of this ore deposit can be approximately divided into two stages: the invasion of nonmineralization magmatic bodyhuge porphyritic quartz diorite in the early cretaceous and the formation of mineralization magmatic body in the late Cretaceous. They occurred in the Cretaceous, the fourth stage of Prototethys tectonic evolution, i.e., the orogenesis stage of arccontinent collision.

Key words: Bangong lakeNujiang suture zone, Galale, LAICPMS, skarntype coppergold mine, mineralization in the stage of Yanshan