Study On The Genesis Of Ling Long Gold Deposit In Shandong Province

The Linglong gold deposit located in the Northwest of Shandong Peninsula inShandong Province, the junction of Zhaoyuan and Laizhou. The sructural position is innorthwest of uplift area which is in the Jiaoliao shield,the North China platform, and thewest is adjacent to Yi Mu large faults.The Strata of the area is exposed relatively simply,but the tectonic and magmatic activity are strong. In this paper, we discuss the genesis andmineralization mechanism on the basis of comprehension studying the regional geologicalbackground, geological features, geological congditions, physical and chemical conditionsand ore source.Linglong granites is the wall rock of Linglong gold deposits. Rock geochemicalanalyzes show that the average content of SiO2is about72.13%. K2O+Na2O=8.42%～10.1%, an average of8.96%; K2O/Na2O=0.75～1.30, an average of1.07.It belongs toPotassium-rich granites. A/CNK=0.72~1.04, an average of0.92; From above, it belongs tometaluminous to weakly peraluminous and S-type granites. Sr＞770μg/g, Y＜7.64μg/gand Yb＜0.5μg/g; The above REE patterns characteristics similar to the adakite.ZirconLA-ICP-MS U-Pb dating shows that the age of Linglong granites is about158.53±0.79Ma,MSWD=0.13, belongs to the late Jurassic. Linglong granites source-material comes fromthe Late-Archean and Paleoproterozoic crust.The granites burn from strong subduction ofthe Pacific plate caused continental arcextensional environment.The gold deposits are strictly controlled by the NE-NNE faults, and distributed in thesub-ductile-brittle shear zones. These veins were nearly parallel or echelon arrangement,and profile was conjugate-shaped output. The veins trend is generally35-70°and mainlyNW tendency. But the veinlets near the fractures are superficial to show the SE tendency,deep into the NW tendency. Between the veins group and the adjacent vein swarm, the veins was obvious interspersed intersection, branch, knot type and knot ring compoundphenomenon. Fault structure of the ore mineralization of the performance is L-pressuretorsion, mineralization of the performance characteristics is dextral transtensional. TheLinglong granites is the main ore-wall rock, from the deep mining area, it is possible tosee Guojialing granites.Mineral ores are mainly pyrite, chalcopyrite, galena, sphalerite, gold and silver ore,natural gold and a small amount of siderite. The wall rock alteration is mainlysericitization, silicification, pyrite phyllic, potassic, carbonate and chlorite and so, inwhich gold mineralization is closely related withpyrite phyllic alteration and silicification.Fluid inclusions containing CO2inclusions and gas-liquid two-phase inclusions, The gasphase composition are generally containing CO2, H2O and a small amount of N2. Theore-forming fluid has low salinity（0.83-5.247wt%NaCl）, low-density（0.69～0.92g/cm3）characteristics, The mineralization uniform temperature is about170-340℃. Ore-formingpressure is about58-128MPa, mineralization is about6.13-9.42km. The C、H、O isotopeanalysis of Linglong gold deposit shows that the main ore-forming fluid is mantle fluid,thelate metallogenic has got some atmospheric water to join.From the analysis of the Pbisotope of Linglong gold deposit、Jiaodong group and Mesozoic granites, we can speculatethat the forming materials are mostly derived from the mantle,lower crust provide part ofthe minerals.The strong subduction of early Yanshanian led to deep subduction zone away fromthetrench above the eastern part of the mainland side of the orogen strong stretchingandlithospheric thinning, and lead to large-scale underplating. It cause the Linglong granitesand subsequent Guojialing granites emplacement. Late Yanshanian, continued subductionof the Pacific plate makes the side of the continental arccontinuous stretch.The Linglong gold deposit is mainly mineralization of quarts-veins. The mainmetallic minerals are pyrite, chalcopyrite, galena, sphalerite and minor siderite, etc. Thereare many types of wall-rock alteration, such as K-fledspar phase, silicification,sericitization and Pyrite phyllic ect. This is typical of mesothermal-type deposits in thealteration assemblage. During100~120Ma, the lithospheric thinning to peak, it cause theoccurrence of large-scale mantle-derived magma and large-scale gold mineralization.Linglong gold deposit is the product of this tectonic activity. From above, we can determine that Linglong gold deposit is the typical type ofMesothermal vein-type gold deposits.