Magmatism And Resource Prospects Of Getiaowan Mine Section Of Yangshan Gold Belt,Wenxian,Gansu

The Western Qinling Range is an important geographical boundary in China,and has extremely complicated tectonic evolution.It is an important mineral concentration area of noble metals,nonferrous and ferrous metals in China.Gold is hosted as dominant mineral species.The Yangshan Gold Ore Belt is located in southern subzone of the West Qinling Orogenic Belt,within the Mianlue suture zone between the South Qinling Microcontinent and the Bikou Block.From the west to the east,the gold ore belt is successively distributed with such ore sections as Nishan,Getiaowan,Anba,Gaoloushan,Yangshan and Zhangjiashan.The main exposure strata in the Getiaowan ore section are the Qiaotou（Dq）and Tunzhai（Dt）Formation of Lower Devonian Series.Among them,Qiaotou Formation（Dq）is the main host strata.The Getiaowan section is located in the Anchanghe-Guanyinba fault zone,where the rock is intensity deformation and the structure is complex.Dominated by fault and developed a large number of small folds.The fault in the Getiaowan section is mainly the secondary faults of the Anchanghe-Guanyinba fault zone,such as F1,F2 and F3.The fold in the Getiaowan section mainly consists of Caopingliang-Getiaowan anticlinorium.The magmatism in the Getiaowan section is relatively weak,and only some acid dikes are exposed,mainly plagioclase granite porphyry and granite aplite.The morphology of the plagioclase granite porphyry in the Getiaowan section is strictly controlled by the fault zone.The plagioclase granite porphyry is mostly produced in the shape of lenticle and crumb structure in the structure fracture zone.Composite plagioclase granite porphyry dikes are commonly found in the field.The plagioclase granite porphyry dikes are affected by the later tectonic activities.The plagioclase granite porphyry occurs dislocation and the continuity is generally poor.The magmatism in the Getiaowan section mainly formed plagioclase granite porphyry and granite aplite.The zircon U-Pb age of the plagioclase granite porphyry are 216.5±2.4 Ma and 214.8±1.2 Ma,which should be the result of late Indo-Chinese（Triassic）magmatism.There are still Late Archean,Paleoproterozoic,and Neoproterozoic that capture or inherit zircon.The zircon U-Pb age of granite aplite is 177.7±2.9Ma,which may formed in the early Yanshanian period,and the49.5±1.8Ma age data may be the the metallogenic age of Himalayan epoch.The aluminum saturation index A/CNK of the plagioclase granite porphyry in the Getiaowan section is 1.17～5.45,and the A/NK is 1.59～5.99,greater than 1.1.It has the characteristics of S-type granite and is peraluminous rock.The differentiation index（DI）of the plagioclase granite porphyry is 75.34～83.77,and the variation range is small,indicating that the degree of crystallization of the rock is similar and the degree of differentiation is high,which is beneficial to the formation of industrial ore bodies.In the composition of trace elements,the plagioclase granite porphyry is rich in light rare earth and large ion lithophilic elements,but deficient in heavy rare earth and high field strength elements.The total range of rare earth is 10.28×10^-6～11.92×10^-6,the average content is 11.22×10^-6,the content is low.Light and heavy rare earth fractionation is more obvious（La/Yb=18.11～26.40）,the overall is weakly negative europium anomaly,δCe is 0.97～1.03.The standardized pattern diagram of rare earth element chondrites presents a weak negative Eu anomaly and a light right rare earth-enriched gentle rightward spectral pattern.When the material in the source area of the plagioclase granite porphyry is partially melted,a large amount of plagioclase with low total rare earth and high fractionation ratio of light and heavy rare earth enters the source area,and the magma is formed in the deep crust.The plagiogranite porphyry was formed in the post-collision tectonic environment and has the characteristics of crust source.Based on the grade,scale,distribution,and gold ore body characteristics of the gold veins in the Getiaowan ore section,using structure superposition halo prediction blind mining method to analyze elemental anomalies of collected samples from 4exploration line in the ore section,such as the 30,22,14 and 06 lines.A total of 11elements such as As,Sb,Hg,Ag,Cu,Pb,Zn,Bi,Mn,Mo,Co were analyzed.Prediction of No.311 vein and No.325（327）vein in the mine section,circled 2 target region predicting and 6 predicted target positions（No.311 vein 2 predicted target positions;No.325 vein 4 predicted target positions）.The amount of gold metal predicted for target area 1 is 1522 kg,and the amount of gold metal predicted for target area 2 is 8477 kg,a total of 9999 kg.China’s proven gold reserves and production temporarily disproportionate to national demand.The resource prospect forecast of the Getiaowan mining section not only provided the estimated reserves of gold resources,but also provided a basis for the subsequent mining and development of the mining section.