Ore Controlling Factors And Geochemical Exploration Marks Of Jiaojia Type Gold Deposit In Northwest Jiaodong

The reserve of Jiaojia-type gold deposits has a total of 4,000 tons of proven gold,accounting for 72%of Shandong Province's gold reserve and 29%of the country's gold reserve,which has huge research and economic value.At present,the exploration depth of the main metallogenic belt of the Jiaojia-type gold deposits in the Jiaodong area have reached 2000 meters or even 3000 meters.A number of scientific research institutes and geological prospecting units have carried out a series of deep gold prospecting,which shows that there are still great metallogenic potentials in the ultra-deep parts of the Jiaojia fault zone,and Zhaoping fault zone.During the deep exploration period,the innovation of exploration technology and methods is the key factor for the breakthrough of deep gold exploration.However,as the buried depth of concealed mines increases and the geological environment becomes unclear,it is impossible to obtain direct prospecting information.Deep prospecting puts forward higher requirements on prospecting methods.In this study,two Jiaojia-type gold deposits are selected as typical deposits,the geochemical exploration signs of the deposits are sorted out,the geochemical anomaly patterns of the deposits are studied,and deep predictions are carried out on this basis.The Jiaojia-type gold deposit is controlled by regional structure which closely related to Linglong granite and Guojialing granite in space which has obvious alteration zoning characteristics.The ore body is mainly controlled by the pyrite sericite alteration zone with the characteristics of interfacial mineralization.The ore body is continuously formed in Linglong granite from the surface to the underground 5km.The alteration types and fluid characteristics of Jiaojia-type gold deposits are basically the same,while for a single ore body,there are differences from shallow to deep ore bodies.The ore bodies hosted in the Jiaojia fault zone mainly occur in the lower wall of the fault.From the top to the bottom,there symmetrically distributes potassium altered granite,sericite-quartz granite,sericite-quartz altered fractured granites,and(pyrite)-sericite-quartz altered tectonic fractured rocks in the hanging wall,and pyrite-sericite-quartz altered tectonic fractured rocks,pyrite-sericite-quartz altered fractured granites,sericite-quartz granite and potassium altered granite in the lower wall,respectively.The belt shows symmetric distribution of alteration and asymmetric distribution of structure,alteration strength,and chemical compositions.Generally,the structure of the bottom wall granite is more severely broken than that of the hanging wall.The content of pyrite is low in the hanging wall but high in the bottom wall,and gold mineralization occurs in the bottom wall.The ductile deformation of the Mesozoic granite is less well developed in the hanging wall of the fault,mainly brittle fracture.Au content,mineralizer element S,ore-forming related elements such as Ag,Pb,Zn,lithophile elements Ba,Sr and main elements Na₂O,Mg O also show asymmetric distribution in the alteration zone,indicating different ore-forming processes in the hanging and bottom walls of the main fault surface of the Jiaojia fault zone.The geochemical signatures of the bottom wall granites and tectonic alteration zones can be used as indicators to locate ore bodies and different alteration zones.Guided by the theory of multi-dimensional anomaly systems,the element distribution characteristics,enrichment and dilution rules and element migration rules in the altered rocks of the Jiaojia deep gold deposit and the Dayingezhuang gold deposit in the Northwestern Jiaowei ore concentration area have been identified,and the ore-bearing rules have been determined.Through the study of the change characteristics of variable zones,minerals,elements,etc.,the geochemical signs of ore-bearing geological bodies have been clarified,and the ore-induced anomaly patterns of typical gold deposits have been combed and summarized.On this basis,a geochemical exploration model for deep gold prospecting in the northwestern Jiaodong area was constructed.In this model,the geochemical exploration indicators are a few elements such as the mineralizer element S,the major element Na₂O,and the ore-forming element Au.The content of mineralizer element S is a typical indicator to measure the mineralization of geological bodies such as structural alteration zones;negative Na₂O anomalies indicate the intensity and range of influence of hydrothermal action;ore-forming elements such as Au indicate the ore-forming conditions of structural alteration zones.Conducted a 3000-meter-deep core drilled core in the Zhaoping fault zone to compare the vertical alteration zoning and elemental anomaly zoning,the location and scale of the Luanjiahe fault,Potouqing fault and Jiuqujiangjia fault in the northern section of the Zhaoping fault zone are calibrated using element anomalous characteristics.Combining fault properties and ore-controlling characteristics,the deep metallogenic potential is analyzed.Through the drilling rock survey of the deep hole ZK3401,the synergetic anomaly characteristics of 12 elements such as Au,Ag,Cu,Pb,Sb,S,Bi,and Na₂O in the altered zone are analyzed.It is concluded that the Luanjiahe fault is about-600 meters with an inclination of 80°;the fragmentation and alteration of the Potouqing fault is large,concentrated from-1700 meters to-2100 meters;the Jiuqu Jiangjia fault develops at about-2800 m,with a low degree of crushing alteration.The high value areas of Au and Ag generally correspond to the negative outlier areas of Na20,and the elemental synergy indicates the mineralization interval of the Potouqing fault with a range of 1700m-2100m.It shows that there is a prospecting space of 1.6km(estimated at an inclination angle of 30°)in the depth of-1700 to-2500meters on the southeast side of the Luanjiahe fault,and the target is the relatively shallow Potouqing fault zone.