Metallogeneses And Tectonic Setting Analysis Of Shaling Gold Deposit In Jiaodong

The geotectonics in Jiaodong area is located in the southeast margin of North China Craton and the northeastern end of Qinling-Dabie-Sulu orogenic belt.It is the famous gold deposit concentration area in China.Shaling gold deposit which is controlled by the Jiaojia main fault and located in the Jiaodong Jiaojia gold field,is a large deposit discovered in recent years.The ore types of Shaling gold deposit can be divided into three types:pyrite sericite clastic rock type,pyrite sericite granitic clastic rock and pyrite sericite granitic granite.Most of the orebodies occur in the tectonic altered rock beltand pyrite is the main gold-bearing gold deposit.The occurrence state of gold minerals is mainly interstitial gold,a small amount of inclusion gold and fractured gold.This paper comprehensively studies the geological characteristics of the Shaling gold deposit,on the basis of detailed field geological survey,mineralogy and petrography,divided into ore-forming stages and periods,the trace elements,S isotopes and H-O isotopes of gold-bearing pyrite and quartz of No.1main orebody were tested,and the temperature measurement and analysis of fluid inclusions in quartz were carried out,on the basis of which the genesis of the deposit was discussed.The study of trace elements in pyrite shows that As,Te,Sb,Bi,Se,Cu,Pb,Co and Ni are obviously enriched,and the ratio of Co/Ni is between 0.01 and 26.16,with an average of 2.30,the variation range of the ratio is large.The results show that there may be metasomatism or superposition of multi-stage hydrothermal activities,which is close to the characteristics of hydrothermal genesis.The sulfur isotope composition of the pyrite in Shaling gold deposit shows that the?³⁴S of the deposit is between 7.71‰and 11.69‰.The?³⁴S decreases from shallow to deep shallow,suggesting that the ore-forming materials may have originated from the deep mantle and contaminated the crustal materials in the process of migration.The?D and?¹⁸O values range from-83.68‰?-116.95‰and 12.04‰?16.28‰.In?D-?¹⁸O diagram,the input point of H-O isotope composition of Shaling gold deposit shows that the ore-forming fluid has the characteristics of mixed source,dominated by magmatic water and mixed with atmospheric water in the later stage.The study of fluid inclusions shows that fluid inclusions can be divided into H₂O inclusions,H₂O-CO₂two-phase inclusions and H₂O-CO₂three-phase inclusions.The homogenization temperature is 113??372?and the salinity is 1.22%?13.38%,indicating that the ore-forming fluid in the main metallogenic period of the Shaling gold deposit is a H₂O-CO₂-Na Cl fluid system with medium-high temperature,low salinity.It is also found that there is the coexistence of H₂O-CO₂three-phase inclusions and H₂O inclusions at the same homogenization temperature,indicating that the ore-forming fluid is immiscible or boiling during the main metallogenic period.The transition of Mesozoic tectonic system is the key to the formation of Jiaodong gold deposit.In the early Cretaceous,the Jiaodong area experienced strong magmatic activity,with the thinning of the lithosphere and the interaction between crust and mantle,mantle fluid flows up and mixes with crustal fluid to form crust-mantle mixed fluid.In the process of rising,the fluid constantly extracts the ore-forming elements from the surrounding rock to form gold-bearing hydrothermal fluid.Due to the connectivity of fault structures near the surface,meteoric water is mixed in the fluid,the physicochemical conditions of the metallogenic system have been changed,the fluid is immiscible or phase separated,and the ore-forming materials are unloaded and finally enriched and mineralized.