Genesis Of The Yanghuidongzi Copper Deposit In Dongning County, Heilongjiang Province

The Yanghuidongzi copper deposit, located in the Dongning county,Heilongjiang province was found in recent years. I took part in related designand field work of the project when I was in Non-ferrous Metal GeologicalExploration702team, Heilongjiang province. Based on collected andorganized previous data, I have studied the deposit according to field workabout two years. The author mainly studied on characteristics of ore-bearingquartz-hosted fluid inclusion and S, Pb isotope from ore mineral of theYanghuidongzi copper deposit, and discussed source of metallogenic material,migration and evolution of ore-forming fluid, and metallogenesis. Finally, theauthor determined the genetic type of Yanghuidongzi copper deposit, anddraw the following conclusions according to research in this paper:(1) The Yanghuidongzi copper deposit is located in the northeast part ofMesozoic circum Pacific metallogenic belt, east China, the southeastHeilongjing of Wandashan-Taipingling gold, copper polymetallic metallogenicbelt, east of Dunhua-Mishan fault. The exposed stratum mainly are theNeo-proterozoic Huangsong complex Yangmu group and Yanwangdian group,Paleozoic Lower Triassic Shuangqiaozi group and less Mesozoic LowerJurassic Suifenghe group, as well as Cenozoic Chuandishan basalt. Themagmatism in the area is intensity and mainly on mesogene granite. Thegranite can be classified into three periods: Zhangguangcailing epoch, LateIndo-Chinese epoch and Late Yanshanian. The rock type is mainly ongranodiorite, monzonite granite, granite porphyry, porphyritic granodiorite and porphyritic rhyolite.(2) The ore mineralogy is dominated by chalcopyrite, pyrite, arsenopyrite,with minor molybdenite, sphalerite, galena, pyrrhotite. Wall-rock alterationassociated with mineralization consists of biotite development, silicificationand sericitization. Four stages of mineralization have been identified usingmineral paragenetic relationships:(I) a quartz–pyrite stage,(II) aquartz–sulfide stage,(III) a polymetallic sulfide stage, and (IV) a carbonatitestage.(3) The fluid inclusions from the Yanghuidongzi copper deposit isdominated by gas–liquid inclusion and minor colorless pure gaseous or pureliquid inclusions. The fluid inclusions are relatively small and focus on4μm–10μm. The ratio of gas and liquid focus on10%–20%,＞20%and＞80%. The homogenization temperature vary from130℃to420℃with fourstages of metallogenic characteristic: a quartz–pyrite stage (I) withmetallogenic temperature of380℃–420℃, a middle quartz–sulfide stage (II)with metallogenic temperature of330℃–370℃, and this stage is one of mainmetallogenic stages. The middle–late polymetallic sulfide stage (III) withmetallogenic temperature of190℃–290℃, and this stage is mainmetallogenic stage. The late a carbonatite stage (IV) with metallogenictemperature of130℃–180℃and granulate pyrite was observed in geode.The salinity of ore–forming fluid is range from0.87%to13.55wt%NaCl andmean value is5.57wt%NaCl. The mid–value is range from4.0%to8.0wt%NaCl. The density of ore–forming fluid is range from0.56g/cm~3to0.98g/cm~3and mean value is0.84g/cm~3. The mid–value is range from0.70g/cm~3to0.90g/cm~3. The pressure for gas–liquid inclusion is range from9.69MPa to32.82MPa. The depth for metallogenesis is range from0.36km to1.22kmand mean value is0.77km. In conclusion, the ore–forming fluid for theYanghuidongzi copper deposit is characterized by medium-high temperature,low salinity, low pressure and low metallogenic depth.(4) The zircons from porphyritic granodiorite, which is closely related tometallogenesis yielded U–Pb age of194.8±1.9Ma, and inferred thatmetallogenic epoch is the Early Jurassic. The process of metallogenesis isdiscussed following: The intruded upward of the Earlyl Jurassic porphyriticgranodiorite provided heat and minor magmatic hydrothermal, which drived formation water from the Yanwangdian group phylite migrated along tectonicfissure. Meanwhile, magmatic hydrothermal leached stratum (theNeo-proterozoic Yanwangdian group phylite) and intrusion rock, which madeore–forming elements activated, migrated and enriched. Then theore–forming elements deposited in structural fracture zone and formed copperdeposit with changing of physical and chemical conditions of metallogenicmaterials, such as temperature, PH value.(5) Based on research into geologic characteristic, material source,evolution of fluids and petrologenesis and metallogenesis, we preliminaryconfirmed that the Yanghuidongzi copper deposit is a medium-hightemperature pyrometasomatic deposit formed in the Early Jurassic.