The Characteristics And The Metallogenic Indicating Significance Of The Granite Porphyry,in The East Of Kaimuqi River Area,Golmud City,Qinghai Province

The eastern Kunlun region of Qinghai Province is a key area for the prospecting work in China in recent years.A number of porphyry copper,copper-molybdenum,silver and other polymetallic deposits have been discovered one after another.The east area of Kaimuqi River is located in the western section of the eastern Kunlun Mountains in Qinghai,and at the southern edge of the Qaidam Basin and is under the jurisdiction of Golmud City.A series of ore deposits,such as the Gounao Cu-Mo deposit of Lalinggaoli River and the Xiarihamu Cu-Ni deposit,have been discovered in the adjacent areas,while a number of typical granite porphyry bodies and dikes have been discovered in the area of the Kaimuqi River.Therefore,the study of granite porphyry in this area is of great significance to the porphyry-type metal prospecting work related to magmatic rocks in the eastern Kunlun area of Qinghai.In this paper,by sampling and analyzing a granite porphyry in the east of Kaimuqi River Area,it is found that the granite porphyry in this area includes two types of granite porphyry and granodiorite porphyry.All of them have undergone strong alterations,including the hightemperature stage of potassium mineralization alteration and biotite alteration,and the intermediate-low temperature stage of sericitization alteration,which show the typical characteristics of medium-high temperature alterations in porphyry deposits,furthermore pyrite and rutile were found in the samples.Through geochemical analysis,it was found that the content of SiO2 and K in granite porphyry in this area is relatively high,mainly in the high-K calc-alkaline series,the fractional distillation of light and heavy rare earth elements is obvious,the weak negative anomaly of Eu,the loss of high field strength elements,and large ions incompatible elements are relatively enriched,and elemental content of copper was abnormally high.These features are similar to the geochemical characteristics of the ore-bearing porphyry in the adjacent area,suggesting that the source may be the result of crust-mantle interaction.Through quantitative textural analysis method,it was found that the crystal size distribution and crystal spatial distribution characteristics of quartz phenocryst in granite porphyry all showed the characteristics of rapid rising emplacement during porphyry formation and magmatic-hydrothermal fluid interaction.The U-Pb age dating of zircon in the study area was 230.6±1.4 Ma and 228.0±1.6 Ma(Middle Triassic),which is a strong crustmantle interaction stage in the area that is conducive to mineralization.Therefore,We infer that the granite porphyry in the east of Kaimuqi River area was formed in the Middle Triassic.The magma was formed by a strong mixing of crust and mantle.After a period of cooling and crystallization in the deep,a large amount of hydrothermal fluid rose from the deep,and the consolidated magma chamber is reactivated,the magma is rising with amount of hydrothermal fluids.The unloading of copper and other metal minerals may occur during the ascent,forming porphyry copper polymetallic deposits.Due to the shielding effect of the superficial granodiorites,the magmatic eruptions are prevented and forms typical granite porphyry and porphyry alterations.Overall,regardless of the geochemical characteristics,chronological characteristics,or quantitative textural analysis characteristics,the granite porphyries in the east of Kaimuqi River area all show great mineralization potential.potential of porphyry copper polymetallic deposits.