Structural Setting And Mineralization Model Of Dayaokeng Gold Deposit

The Dayaokeng gold deposit is located in Zhenghe County,Nanping City,Fujian Province,belong to the Jianou and Zhenghe metallogenic belt,and its geotectonic position lies in middle-west of Central Fujian rifting zone in eastern of South China fold system.Since the Paleo-Mesoproterozoic,the region has experienced the formation,splitting,splicing,passive continental margin and then evolved into an active continental margin.The complicated tectonic and magmatic activities in the area create favorable geological conditions for mineralization.Based on the study of geological characteristics,ore-controlling structure,geochemical characteristics and chronology of Dayaokeng gold deposit,the genesis and age of Dayaokeng gold deposit are determined,discusses the geological and tectonic environment of deposit and then establishes the metallogenic model.The main result are as follows:?1?The orebody of Dayaokeng gold deposit is controlled by fault structure and the occurrence of fault and fissure is basically consistent.The main metal minerals of the ore are sulfides and oxides.There are many mineralization types and the mineralization can be divided into five stages.?2?There are many types of veins in Dayaokeng gold deposit.The magma formation is related to the partial melting and crystallization of Mesozoic subduction plates in eastern China.The tectonic setting of veins formation is the local extension and uplift of plates in the late stage of collision and compression of active continental margin.The result of LA-ICP-MS zircon U-Pb dating show that the age of diorite porphyrite before mineralization is?176.5±4.0?Ma,the age of quartz syenite porphyry is?119.3±2.5?Ma and age of post mineralization veins is between?112.4±1.9?Ma and?99.4±1.4?Ma?3?The pyrite in Dayaokeng gold deposit is characterized by magmatic sulfur with a relatively small value of?³⁴S.The Pb isotope in the ore belongs to normal Pb,and its source should be orogenic belt,part of material comes from lower crust,the environment of ore formation should be Mesozoic back-arc rift orogenic environment.LREE is enricher and HREE is deficient in ore and?Eu obviously negative anomaly.The results of measurement and calculation of gas-liquid inclusions show that the ore forming fluids in Dayaokeng fold deposit are characterized by medium and high temperature,low salinity and low density.Two-phase ore-forming fluid is the main ore-forming fluid and there are few three-phase ore-forming fluid which enrich in CO2.The main source of metallogenic fluid in Dayaokeng gold deposit is magmatic water.?4?The ore-controlling faults can be divided into NE,EW and NW according to strike in Dayaokeng gold deposit,and the NE fault is the main ore-controlling structure.The ore-controlling tectonic system in Dayaokeng gold deposit can be divided into two subsystems.First is the NE fault system closely related to the regional tectonic stress field activity,the early NW-SE compression tectonic stress field,the late sinistral strike-slip tectonic stress field which is the ore-controlling system;the second is the volcanic mechanism system superimposed on the regional tectonic stress field,which corresponds to the regional extension,tectonic uplift and fluid emplacement.?5?The type of Dayaokeng gold deposit should be high temperature epithermal gold deposit.The metallogenic age of Dayaokeng gold deposit is between?119.3±2.5?and?107.7±7.0?Ma according to the age of the diorite porphyrite before mineralization,quartz syenite porphyry and the post mineralization veins.