| The area of Nimu-Qushui in Tibetan Plateau lies in Tethyan-Himalaya metallogenic belt, which is one of three main porphyry metallogenic belts. It is in the middle of marginal volcanic-magmatic arc of Gandise tectomagmatic belt. Multiphase and large-scale medium-acid intrusive and volcanic rocks have well developed in this area. Many Cu and Au mineralized spots have been discovered along Nimu-Qushui area. But large-scale Cu ore deposits have been found only in Tinggong area and there is no breakthrough in large primary Au ore deposit prospecting. It has been proved that large-area medium-acid magmatic rocks have well developed in this area and had close relation with some Au or Cu ore deposits and mineralized spots. But till now little research has been done for mineralization potentiality of medium-acid magmatic rocks, especially in the aspect of genetic mineralogy. In order to know the mineralization potentiality of medium-acid magmatic rocks in the area of Nimu-Qushui in Tibetan Plateau, this thesis focuses on the studies of genesis and prospecting potentiality of the intrusive rocks from the point of view of genetic mineralogy. This will provide some information for prospecting.The microscopical observation proves that the main types of granitoid rocks are granodiorite and quartz monzodiorite, and the enclave is mainly monzodiorite. The rock-forming minerals are mainly k-feldspar, plagioclase, amphiboie, biotite, quartz, magnetite, titanite, apatite, epidote, etc. The zonation of the feldspars is very popular. The dark-colored minerals, such as biotite and titanite, have been highly oxidized.The main element analysis of whole rocks, the REE analysis and the trace element analysis have been done for the granitoid samples in this area. The chemical composition analysis has been done for the amphiboie and biotite minerals. The EPMA and x-ray powdered crystal diffraction have been done for k-feldspar, plagioclase, amphiboie, biotite, quartz, magnetite, titanite. and apatite. By these analyses and comparison with general granite both in China and the world and with the granite in other Au or Cu belt in China, the characteristics of the granite in this area are concluded as follows. It belongs to magnetite-I or syntectic granite and has crust-mantle mixed characteristics; it was formed mainly by crystallization differentiation of melting magma and multiphase varied intrusion; the degree of differentiation evolvement is not high; the granite and its enclaves p.re congenetic; the range of temperature is about 500 -700 , the range of pressure is about 2.50 Gpa-4.35 Gpa,and the range of oxygen fugacity (lg fo2) is -15.53--14.00; most granite bodies formedbefore the collision of plates, and few formed after the collision of plates.Compared with the granite from other areas in mineralogy, petrology, and geochemistry, the granitoid in Nimu-Qushui has a high content of Fe, Mg and Ca. The value of Na2O/K2O is over 0.8, ANKC is under 1.10, and DI is under 88. Its Fm is 0.50-0.80, 5 Eu>0.3 and La/Yb > 10. The characteristics above mentioned are the signs profitable for formation of Au and Cu ore deposites.Comparing with the granitoid from Jiaodong Guojialing in mineralogy, the minerals in the granitoid in Nimu-Qushui granitoid crystallized in the environment of oxidization, the granitoid has a characteristic of rich volatile components and a high content of alkali, the rock-forming minerals and accessory minerals have a characteristic of I-type granite, and the granite shows a characteristic in favor of An and Cu ore formation.
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