Mineralization Of Gold Deposits In Jiao-Liao Massif

Jiao-Liao Massif is located in the the eastern area of North China craton,and east of Tancheng-Lujiang Fault.This area contains two important gold deposit concentration areas in China.Many large and super-large gold deposits has been found in this area,such as Jiaojia,Linglong,wulong,Maoling,and so on.The large number and reserves of gold make this place become the key place for geologists.The Jiao-Liao Massif locats in the intersection of the North China plate,Yangtze plate and Pacific plate.The North China plate in turn interacted with the Yangtze plate and the Pacific plate intensively since the unified double crystalline basement formed.And then the large-scale tectonic-thermal events initiated.These events resulted in mineralization.Special ore-forming geological conditions,various types of ore deposits and complex mineralization are remarkable characteristics of gold mineralization in this area,which are also one of the hottest and most difficult issues in geology.On the basis of former study,the metallgonenic geological setting,classifing metallogenic system,mineralization and dynamic model for mineralization of Jiaodong and Liaodong area were researched by field reconnaissance,sample collection,analysis,and so on.The main results are at list:(1)The Jiaodong and Liaodong areas have the similar tectonic evolution history.According to the relationship between tectonic evolution and mineralization,both regional gold mineralization can be divided into four periods:the formation of Precambrian crystalline basement and source bed,the Paleozoic stable caprock development and gold mineralization intermittent period,Mesozoic craton activation and gold metallogenic explosion,and Cenozoic tectonic reformation.However,the ore-controlling factors of these two areas are different.The gold deposits in eastern Liaoning are controlled by Liaohe group and basement structure.Enriched elements such as As,Bi and so on,show inheritance of Liaohe group.The gold deposits in eastern Shandong are controlled by fracture tectonic system and intrusive body.The orebodies locate in the superimposed position of granite body and fracture structure.(2)The metallogenic geological characteristics typical gold deposits are analyzed and compared.Based on the differences in ore-forming geological characteristics,the gold deposits in this area can be divided into metamorphic rock area mineralization system and intrusive rock area mineralization system.The metamorphic rock area mineralization system hosts in early Proterozoic metamorphic strata,and orebody location is controlled by basement structure.This system can be divided into altered mylonite type gold deposits,silicification altered rock type gold deposit and silicon kalium altered rock type gold deposit.The intrusive rock area mineralization system developes inside or on the edge of granite body.And orebody location is controlled by fracture structure system.The intrusive rock area mineralization system can be divided into altered breccia type gold deposits,fissure filling type of gold deposit and the fracture zone altered rock type gold deposit.(3)The time and space distribution of gold deposits is characteristic of explosive mineralization in time,gathering output in space.Main ore-forming period of Jiaoliao massif mainly concentrats in the Mesozoic era.And there are two large gold ore-forming events happened in the Jurassic and early cretaceous.Metamorphic rock area gold mineralization system and intrusive rock area mineralization system form respectively.The locating of gold deposit is controlled by early nearly east-west basement tectonics and Mesozoic north eastern fracture structure.The gold deposits distributes in the northwestern and eastern Jiaodong,and the northern and southern Liaodong.The metamorphic rock area mineralization system distributes in northern and southern Liaodong.The intrusive rock area mineralization system distributes in the northwestern and eastern Jiaodong,Wulong area in southern Liaodong.The deposits stand in row in the direction of east-west and look like a line in the direction of north-south.Gold deposits in Jiaodong area concentrated on the northwest and east,and gethered in the north and south gold metallogenic belt in Liaodong area.(4)The gold deposit geochemical test data show that the sources of ore-forming materials of different gold deposits are differenc,exhibited multi source and difference characters.Metallogenic material of metamorphic rock area mineralization system mainly comes from the Precambrian metamorphic basement and the granite of the same period.And intrusive rock area mineralization system has more mantle source materials in mineralization.The characteristics of fluid inclusions and hydrogen and oxygen isotope of gold deposits show that the ore-forming fluid in the main metallogenic stage of two metallogenic system is NaCl-H2O-CO2 system.The ore-forming fluid is characteristics of rich H2O and CO2,medium temperature and low salinity,low density,mainly weak acid and weak reductive metallogenic environment condition.Source of ore-forming fluid mainly comes from magmatic hydrothermal,and mixing with multifocal fluid.During the high temperature main ore-forming phase,the fluid is mainly magmatic water,and then gradually turned into atmospheric precipitation.(5)According to the researching of coupling relation between diagenesis,mineralization and geotectonic evolution,the gold mineralization in Jiao-Liao Massif is proposed to controlled by the subduction of paleo-Pacific Plate to Eurasian Plate,and lithospheric extension and thinning of North China Craton.The gold deposits are the product of large scale tectonic-magmatic activity.In different geological conditions,the different types of gold deposits develop.