Study On Metallogenesis Of Mesozoic Endogenetic Metal Deposits In The Eastern Patr Of Jilin Province

Based on detailed field survey, analysis and synthetical researches in the eastern partof Jinlin Province, the author deepened the Mesozoic metallogenic tectonic settings andmetallogenesis. It was thought that the eastern part of Jilin province underwent the latePaleozoic-early Mesozoic superposition, late Indosinian-early Yanshanian transition ofbetween two tectonic domain, middle Jurassic-early Cretaceous large scale thrust and lateYanshanian lithosphere detachment and thinning. The late Indosinian light alkaline granite(216±3Ma)and Hongqiling magmatic liquation-type Cu-Ni sulfide deposits(232.75±0.95Ma)represent the end of Paleo-Asian tectonic domain. Since that time, the studyingregion came into the period of circum-Pacific tectonic domain. Early Yanshanian largescale mineralizations were related to subduction of Pacific plate, which formed a series ofcalc-alkaline granite like Daheishan granodiorite porphyrite (170±3Ma) and Badaohezigranite porphyrite (174.4±0.59Ma). Then network-type Mo deposit like Fu'anpu,Jidetun, Badaohezi related to plutonic monzonite and porphyry Mo deposit like Daheishanfomed, respectively. The hydrothermal mineralizations reach to the climax. These types ofdeposits develop commonly in the eastern part of China, whose geodynamic settings aredifferent from those of porphyry Mo deposits related with alkaline, calc-alkaline granites.The ore deposits in eastern part of Jilin province formed in compressional structural-magmatic system, in deeper locality close to subduction zone, which belong to low-gradeMo deposits. While the deposits in the western part of USA formed in post-subductionextensional structural-magmatic system and in shallower locality far away fromsubduction zone, which belong to high-grade Mo deposits. In the late Yanshanian, theeastern part of Jilin province belongs to the south part of Xiao hinggan ling-Zhangguangcailing huge metallogenic belt. Because of large-scale lithosphere detachmentin the region and East China, A series of gold endogenetic deposits includingXiaoxinancha Cu-Au, Yangjingou W, Shanmen Ag, Ciweigou Au, Wufeng Au andWuxingshan Au deposits formed in extensional system. It is represent anothermetallogenic climax in the eastern part of Jilin province. It was the first time to propose that there exist large-scale nappe structure in Mesozoicin Jilin province. The author determines the dynamic sources, active time, and geologicalrecords of it. Because of later strong uplift, the nappe structure is characterized by a seriesof alone klippe in cluding those in Siping-Changchun and even in Changping in Liaoningprovince, and some thrust faults and klippes in Ji'an-Baishan-Huinan. It was thought thatthe forming time is190-130Ma, and dynamic source derived from strong subduction ofpacific plate toward Euroasia continent. It was the product of the tranversion period thatEuroasia continental margin in the western Pacific transferred from passive margin toactive one.According to LA-ICP-MS high precision zircon U-Pb dating and molybdenite Re-Osdating, the author got diagenetic and metallogenic ages as follows: There are two groupsof LA-ICP-MS zircon U-Pb ages for gneissic granites in Erdaodianzi gold deposit. Theweighted mean age for the first group is242.0±1.8Ma, the concordant age is242.6±0.84Ma; the concordant age for second group (5zircons) is241.7±1.6Ma, whichmatch well with the first one. There are still two zircons has the concordant age of299.2±4.1Ma, which represent the cores derived from Hercynian inherited zircons. Thereare other three zircons with concordant age of254.1±1Ma, which may be late Hercynianinherited zircons. Seven zircons from the ore-bearing granite have the concordant age of245.2±2.0Ma, and there are other two zircons from it have the concordant age of499.8±4.0Ma, which are also represent the cores derived from Caledonian zircons.According LA-ICP-MS zircon U-Pb dating and molybdenite Re-Os dating for BadaoheziMo deposit, the weighted mean age of zircons U-Pb dating for granite porphyry is177.3±1.2Ma, concordant age is177.4±0.59Ma, so the177Ma±can represent the intrusiveage of granite porphyry. The molybdenite Re-Os isochron age is178.3±4.4Ma, and itsweighted mean age is176.9±1.4Ma that is close to the diagenetic age of rock bodies. Themolybdenite Re-Os isochron ages for Daheishan and Fu'anpu are168.2±3.2Ma and166.9±6.7Ma, respectively, and the LA-ICP-MS zircon U-Pb weighted mean age is232.75±0.95Ma for ore-bearing pyroxenite in Sandaogang deposit in Hongqiling Nideposit. Such ages characterized different periods of intrusive rocks and conrrespondingmineral deposits. They are affluent in diagenetic and metallogenic data, and are importantreference for geodynamic settings.According to fluid inclusions researches, it was shown that ore fluid from Haigougold deposit is characterized by CO₂rich water. The homogenization temperatures of fluidare258.2³31.3℃, salinity are7.44⁸.94wt%NaCl,density are0.75⁰.88g/cm-3, andcalculated depth are8.7¹0.1km,so it was thought that Haigou gold deposit belongs tomesozonal orogenic gold deposit. The fluid from Erdaodianzi gold deposit is characterizedby two-phase aqueous fluid. The homogenization temperatures of fluid are141.2²96.7℃, salinities are1.22⁴.79wt%NaCl,densities are0.74⁰.94g/cm3, and calculated depths are1.04².33km,so it was thought that Erdaodianzi gold deposit belongs to mesozonal toepizonal orogenic gold deposit. The fluid from Shanmen Ag deposit in Siping city is alsocharacterized by two-phase aqueous fluid. The homogenization temperatures of fluid are143.5³06.7℃with peaks from160to190℃,salinities are0.87⁶.14wt%NaCl,densitiesare0.71⁰.96g/cm3, and calculated depths are1.03².65km,so it was thought thatShanmen Ag deposit belong to epithermal Ag deposit. The fluid from Bdaohezi Modeposit is also characterized by two-phase aqueous fluid. The homogenizationtemperatures of fluid are154.1³37.2℃with peaks from140to240℃, salinities are0.35⁵.99%NaCl,densities are0.71⁰.95g/cm3, and calculated depths are1.01².64km.The above data improve the research degree of typical deposits in the eastern Jilinprovince and are reliable data.Among metallogenesis in Jilin province, the author researches the porphyry andfine-network-type Mo deposits in the east part of Jilin province and compares them tothose abroad. It was concluded that the parent rock belongs to calc-alkaline granitoidrocks in compressional settings. They can be divided into two sub-classes, i.e. stock type(e.g. Daheishan) and plutonic rock type (e.g. Jidetun, fu'anpu) similar to those in theNorth American. The parent rocks of some fine-network-type Mo deposits in USA (e.g.Climax) are alkaline and calc-alkaline intrusions in extensional tectonic environment.According to researches to14typical deposits, the author ascertains major genetictypes of endogenetic metal deposits in the Mesozoic in the eastern part of Jilin province.Hongqiling, Chaqianling, Sandaogang, Piaohechuan magmatic liquation-type Cu-Nisulfide deposits formed in the late Indosinian, and different depths of Jiapigou, Haigou,Erdaodianzi gold deposits and Yinggou Sb-Au deposits, then Lanjia skarn-type Au (Fe)deposit, Tianbaoshan skarn-type Pb-Zn-Cu-polymetal deposit, Daheishan Mo, Ermi Cu,Xiaoxi'nancha Au and Badaohezi Mo porphyry deposits in the early Yanshanian. In XiaoHinggan Liing-Zhangguangcailing metallogenic belt, Sandaowanzi, Dong'an and Wulagagold deposits in Heilongjiang province formed in the late of Yanshanian. And Ciweigougold and Wufeng-Wuxingshan gold and Shanmen Ag epithermal deposits, Yangjingoularge-scale scheelite deposit and Shanmen large-scale Ag deposit and Yangjingoularge-scale mesothermal quartz-vein-type W deposit formed in the eastern part of Jilinprovince in the same late Yanshanian.There is exclusive metallogenic species with magmatic rocks. Mo deposits in theeastern part of China including eastern part of Jilin province are related with calc-alkalineseries of intrusive rocks, while those Mo deposits in North American are related withalkaline or calc-alkaline intrusive rocks. The intrusive rocks in eastern part of Jilinprovince show exclusive metallogenic species with granites series of magnetite and ilmenite, which denote different oxidative-reductive conditions during diagenesis.Magnetite series of granites have high oxygen fugacity, which represent oxidativediagenetic environment, low temperature and shallow depth. They control forming of Au,Ag, Cu, Mo, Pb, Zn deposits. On the contrary, Ilmenite series of granites have low oxygenfugacity, which represent reductive diagenetic environment, high temperature and deepdepth. They control forming of W and Sn deposits.According to inherent relationship of metallogenesis, the author built regionalmetallogenic series. Three different endogenetic metallogenic series that consist ofdifferent ore species and genetic types formed in the late Inosinian of216-232Ma, earlyYanshanian of200-160Ma, and late of Yanshanian of130-100Ma in the Mesozoic in theeastern part of Jilin province, respectively. Such metallogenic series include the lateIndosinian magmatic liquation-type Cu-Ni sulfide deposits, early Yanshanian orogenic,skarn-type, porphyry, network Au, W, Mo, Fe, Cu, Pb, Zn, Sb, polymetal deposits and lateYanshanian epithermal, porphyry, mesothermal vein-type Cu, Au, Ag, W deposits. Basedon researches to metallogenic series, the author summarized the spatio-temporalregularities for Mesozoic endogenetic metal deposits in eastern part of Jilin province. Thelate Indosinian metallogenic series of magmatic liquation Cu-Ni sulfide deposits arelocated in the Ji-Hei orogenic belt close to the north margin of North China plate, and theother two metallogenic series are all distributed among whole eastern part of Jilinprovince.