Geological Characteristics And Metallogenic Regularity Of Gold Deposits From Naozhi To Duhuangling In Wangqing County, Jilin Province

Naozhi-Duhuangling area is an important region of gold mineralization of Yanbian areain Wangqing county, Jilin province. On the basis of field geological investigation and research,the author conducted the study of rock geochemistry, fluid inclusions analysis, andcomprehensive comparison to analyse five gold deposits (ore spots) in Naozhi-Duhuanglingarea on the deposit geological characteristics, ascertained the metallogenic geologicalconditions and indicators of prospecting, summarized the metallogenic regularities, and thencarried out the metallogenic prediction of this area.The study of ore deposit geology shows that these five gold deposits (ore spots) inresearch area are medium-high temperature hypabyssal magmatic hydrothermal gold deposits.Based on the ore-controlling structures and attitude of ore bodies, these are further dividedinto two: the hypabyssal hydrothermal vein type gold deposits (including Miantian-Naozhicopper-gold deposit, Shajingou gold spot) and cryptoexplosive breccia type gold deposits(including Duhuangling copper-gold deposit, Xingou-Shajingou gold spot, Qingjingou goldspot).The hypabyssal hydrothermal vein type gold deposits in study area are controlled byfaults in the form of veins and hosted in granodiorite intrusions or subvolcanic rocks. The oreminerals of this type of deposits mainly consist of pyrite, chalcopyrite, sphalerite, galena,chalcocite, magnetite, bornite, and native gold; the wall rock alteration from ore body to wallrock with evident zoning varies from beresitization, to intermedium silicification andpropylitization, to potash alteration. The study of fluid inclusions shows that the mainore-forming temperatures of Miantian-Naozhi deposit range from200℃to320℃, with the ore-forming depth of0.8-1.5km, while Shajingou deposit has the ore-forming temperaturesof280-360℃，with the ore-forming depth of1.1-2.1km.For cryptoexplosive breccia type gold deposits, the ore bodies are controlled bycryptoexplosive breccia pipes and fracture structures around them occurring in the forms offine veins and stockwork veins and hosted in the neutral volcanic rocks and intermediateacidic small intrusive bodies; the metal minerals are mainly pyrite, chalcopyrite, sphalerite,galena, marcasite, bornite, native gold and so on; the wall rock alteration of unconspicurouszoning are mainly beresitization, silicification, carbonatation, chloritization. From the study offluid inclusions, the main ore-forming temperatures of Duhuangling deposit range from280to340℃, with the ore-forming depth ranging from0.7to1.4km, corresponding theore-forming temperatures and depth of300-360℃and0.8-1.9km in Xingou-Shajingou orespot, moreover, the main ore-forming temperatures of Qingjingou gold ore spot range from260to380℃, with the ore-forming depth of0.8-2.4km.The study of ore-forming geological conditions indicates that the Au mineralization isclosely associated with the regional structure, specifically, the EW striking deep fault ofDunhua-Chunhua, together with NW, NE and NS trending secondary faults controlling thedistribution of the ore deposits. The relationship of volcano-volcanic magmatism andmineralization is showed that the gold deposits were formed at the late period of thevolcanic-volcanic magmatism activities, magmatic activities provided metallogenic materialand heat and volcanic apparatus controlled the attitude and type of the orebodies. The rockassemblage of volcanic-subvolcanic rock formation closely associated with mineralization ismainly diorite porphyry—andesite porphyry—diorite and andesite—(quartz) diorite porphyry—quartz diorite—granite porphyry—syenite porphyry.Two types of ore deposits have different regularities in the combination and distributionof elements in this area. In the hypabyssal hydrothermal vein type gold deposits, Au issignificantly related to As, whereas is separated from Ag. However, in the cryptoexplosivebreccia type gold deposits, Au was significantly related to Bi and has a symbiotic relationshipwith Ag, never separated from Ag. The relativity between Au and Cu in most of gold depositsin this area is not evident, except for Miantian gold deposit, in which Au is significantlyrelated to Cu, with the possibility of copper mineralization. The rocks in most of mining districts in research area are rich in such elements as Au, Ag, Cu, As, Sb, Bi, W, Mo, Pb, andso on, but are depleted Sn in the hypabyssal hydrothermal vein type gold deposits, while aredepleted Zn in composite gold deposits. The axial zoning calculation for Miantian andQingjingou deposits shows the characteristic of inverse zoning, suggesting the occurrence ofblind orebodies in the deep, indicating that mineralization not only occurred on the surface,but underground in the deep.Considering that the gold deposits in this area are controlled by the regional deep faults,the gold deposits show nearly east-west distribution. Metallogenic epoch is older in the westpart of this area than that in the east part, with the metallogenic epoch of100-140Ma. Theore-forming materials of gold deposits result from the upper mantle, with the source ofore-forming fluid showing the characteristics of combinations of magmatic water andatmospheric water.Summarizing the metallogenic regularities of gold deposits in Naozhi-Duhuangling area,combined with regional geological, geophysical, geochemical and remote sensing imageinformation, the auther blocked out six metallogenic prediction area includingLongyan-Miantian-Yongchang, Jiusangou-Xingou-Shajingou, Duhuangzibeigou metallogenicprediction area, and so on.