Geological Characteristics And Genesis Of Qilishan Gold Deposit, Zhaoyuan, Shandong Province

After plate movement, Jiaodong region undergo a long geological processes, whichenriched the variety of mineral resources such as gold, iron, coal, diamonds etc, being oneof the most important mineral resources region in our country. Gold as a national strategicreserve of resources is significant. Qilishan gold deposit is one of the representativesamong gold deposits in Jiaodong, and after two decades it has been closured. Comparingwith other1000m depth big gold deposits, Qilishan gold deposit only mine400m depth.So this mining area has great prospecting.The Qilishan gold deposit is located in the southern Zhaolai gold ore belt in thenorthwestern Jiaodong region, strictly controlled by Lingbei fault. The main wall rock isLinglong granite which has a strong alteration and is typical alteration rock type of goldmineralization.Its ore bodies with veined or irregular shape occur within the structural alterationzone. The ore bodies are NE trending and SE dipping. NoⅠ a nd Ⅲorebody are the majororebodies in Qilishan dold deposit, with the character of equidistant pinchout andreproduction.The minerals of the ores mainly include pyrite, chalcopyrite, native gold, electrum,argentite, matildite, hematite, quartz and calcite. The ores are characterized bymetasomatic dissolution structure, as well as veined and brecciated structures.Qilishan gold deposit suffer a strong alterated process. From the inside to out, there issilicification, phyllitization, potassium alteration and carbonatization. Unlike the potassium alteration and carbonatization, silicification and phyllitization have a strongrelationship with gold mineralization.Comparing with the same analogy gold isotopes in the gold ore field, Qilishan golddeposit source of minerals should be a mixture of both mantle and crustal material usefulcomponents; ore forming fluids is mainly the mantle derived fluid and accompanied by asmall amount of magmatic fluids with a little atmospheric precipitation joined.Study on fluid inclusion shows that the deposit is composed of two phase aqueousinclusions (type I) and three phase CO2bearing inclusions (type II), and that the former isdominant. The homogenization temperature is152.2～412℃; the salinity of three phaseCO2bearing inclusions is2.62～12.11%(NaCl); the salinity of two phase aqueousinclusions is2.73～11.84%(NaCl); and the estimated ore forming pressure is86MPa.According to the nonlinear relationship between the depth and pressure of the fluid in thefracture zone, the ore forming depth of the Qilishan gold deposit is calculated as7.60km.In conclusion, Qilishan gold deposit is a meszonal mesothermal gold deposit. Itforms in Yanshanian (120Ma).