Genesis Of The Yuerya Gold Deposit,Hebei Province

The Yuerya gold deposit is located in the eastern part of the Hebei Province,on the northern margin of the North China Craton.The stratums of the deposit area can be divided into two parts.The lower part is Archean metamorphic rocks.The upper part is Mesoproterozoic carbonate rocks.The deposit is spatially associated with the Yuerya granite,and a group of NE-and NNE-trending faults.The ore bodies occur as quartz vein and quartz veinlet.Pyrite is the dominant ore mineral,along with small amount of chalcopyrite,sphalerite,galena,pentlandite and so on.Gangue minerals mainly include quartz,feldspar,sericite,chlorite,calcite.Gold occurs in the fissure of sulfides or as inclusions in sulfides,and a little in quartz.The alterations are mainly silicification,pyritization,sericitization,choritization.The stages of mineralization recognized are as follows:(stage1)white quartz with coarse-grained pyrite;(stage2)smoky gray quartz with polymetallic sulfides;(stage3)fine-grained quartz with pyrite;(stage4)vein-like calcite.Stage 2 and 3 are the main stages of mineralization.The ?D and ?18O values for the water in the ore quartz fluid inclusion samples are-66‰~-112‰,5.4‰~7.2‰,respectively.The ?D and ?18O values for the water in the granite quartz fluid inclusion samples are-63‰~-104‰,3.3‰~5.8‰,respectively.The ?13CPDB values of calcite in ores are-3.7‰~-6.8 ‰.The ?34S of pyrite in ores are 2.5‰ ~4.5‰.All of the isotope data indicate that the ore-forming fluids and materials were mainly derived from a magmatic source.Pb isotope data indicate that the metallogenic material mainly originated from the lower crust.The rare earth element distribution patterns of the ores indicate that the mineralization is closely related to the Yuerya granite.The Yuerya granite is characterized by enriched Si(SiO2: 74.34%~75.78%)and Al(A12O3: 13.22%~14.68%),and high content of alkali(K2O+Na2O: 7.79%~9.25%).The A/CNK values of the granite are 0.98~1.06,with an average of 1.02,which shows the characteristic of peraluminous.The w(TFe2O3)/w(MgO)values are 3.26~7.36,with an average of 5.66.The granite is relatively enriched in Rb,Th,U,K,La,Ce and depleted in P,Ti.The granite exhibit LREE-enriched with right-inclined REE distribution patterns.A synthesis of all these characteristics indicate that the Yuerya granite was probably derived from anatexis of the lower crust.It is concluded that the ore-forming fluids and materials were mainly derived from the Yuerya granite which mainly formed by the anatexis of the lower crust.The deposit is a typical magmatic hydrothermal gold deposit.