Spatio-temporal framework and mineralization of the Yanshanian magmatic fluid systems in the Nyixung region, northern Xizang

The present paper deals, on the basis of field investigation and previous data, with the spatio-temporal framework of the Yanshanian magmatic fluid systems, and the relationship between the magmatic activity and mineral resources in the Nyixung region, northern Xizang. The Yanshanian magmatic fluid systems in the Nyixung region may be classified into two categories covering three subsystems. One of fluid systems is associated with the early Early Cretaceous intrusions, i. e. the arc granitic complexes caused by the closure of the Shiquanhe ocean. The fluid systems may further be subdivided, according to the ages of magmatic intrusion and features of fluid activity, into two subsystems, including the early fluid activity associated with the Nyixung iron deposit, and the later fluid activity associated with the southern Shasong iron deposit. The other is associated with granite porphyry dated about 90 Ma and closely related to the Ri'a porphyry copper deposit. The magmatic hydrothermal solution contains plenty of mineral elements in itself. The heat energy released by boiling magmas not only caused the formation water to be activiated, but also made the mineralization fluids to extract the mineral elements from the Xiala and Dibuco Formations, and thus resulting in the formation of rich contents of ores and larger sizes of ore bodies.