Geological Features And Metallogenic Regularity Of SuiShiZi Gold Deposit In LiZiYuan, TianShui

Western Qinling is one of the important gold deposit areas of China.The spatial distribution of mineral resources in the area has the characteristics of distribution into groups and belts segmentally. And SuiShiZi gold deposit in LiZiYuan was found in north metallogenic belt of western Qinling. In this paper, the author takes SuiShiZi gold deposit in LiZiYuan,TianShui as the research object. During the field investigation, geological surveies in mining area have been operated in detial, and the ore body to deliver the characteristic as well as with the stratum, the structure, the magmatic rock spatial relations have been Studied. At the same time,the auther took the thin section under the light microscope, chemical analyses and tests of major elements and trace elements, determination of fluid inclusions, stable isotope analysis, zircon SHRIMP U-Pb dating, K-Ar dating of mineralized altered sericite, etc indoors. The regional geological features and metallogenic regularities were studied in detail, preliminary cognitions have been acquired as follows:1.LiZiYuan gold deposit which occurs in secondary falt structural belt in the south of Western Qinling Shang-Dan suture zone, is located near the Tianzishan monzonitic granite,Kuangou granite porphyry and diorite porphyrite, and controlled by north-west uolcanic fractured zones,Suishizi gold deposit,located in the intel of Tianzishan rock mass,is associated with diorite porphyrite.2.Test on isotope age showed that the diagenetic age of Tianzishan monzonitic granite is 236.1 Ma, while that of granite porphyry,Suishizi diorite porphyrite are respectively 212.2 Ma and 213.9 Ma. Tianzishan rock mass was formed during the collision period of Qinling orogenic belt, while Kuangou porphyry granite,Suishizi diorite porphyrite were formed during regime switching in late orogenesis.3.Suishizi gold deposits mainly occur in the diorite porphyrite and breakage crushed belt near the diorite porphyrite,and are controlled by breakage crushed belt and diorite porphyrite dike, the mineral types are diorite porphyrite mineral and crushed zone alteration mineral.4.The gold-carrying minerals of the deposit are pyrite, with the contributions of chalcopyrite and galena. Gold and silver-bearing minerals, which are mainly disseminated and vein-disseminated,mostly show fine granulars and fine veins, filling in the cracks and gaps of pyrite, or disseminating in the interface between pyrite and other sulfide minerals or gangue minerals.5.The deposit is a middle-low temperature(metallogenic temperature is 100～300℃)and salinity(2.0 to 10.8 wt% for NaCl eqv).Ore-forming fluids are charactered by a mixed resource of magma water(mainly), metamorphic water and air water.Mineralizing materials have the characteristics of deep source.6. Combining the diagenetic age of diorite porphyrite is 212.2 Ma,the K-Ar isotopic age of sericite in altered diorite porphyrite is 206 Ma, representing the forming age of the gold deposit, indicates the close relationship between mineralization of gold and diorite porphyrite.This deposit isthe metallogenic model of gold deposit which is related with diorite porphyrite,and it formed during tne spread stage of the later of Qinling orogenesis.7.Based on the above studies, the metallogenic model of SuiShiZi gold deposit in LiZiYuan has been preliminary established,providing certain references for the geological research and the development of the ore-prospecting work in the region.