The Constraints And Metallogenic Prognosis Of The Jinchanggou Copper-molybdenum Deposit In The Jidong City, Heilongjiang Province

The Jinchanggou copper-molybdenum deposit is located 50 kilometer southeast of the the Jidong City, and it contains an area of about 7.3 km2 and is at a longitude of 131°01′00″～131°03′00″E and an latitudes of 44°52′30″～44°54′15″N.The copper-molybdenum deposit lies at the northern end of a polymetallic metallogenic belt in the Taipingling uplift in the Khanka-Bureyan block and it is adjacent to a regional sinistral strike-slip fault belt called the Dun-Mi fault belt to the southwest. The faults related to the Dun-Mi fault belt in the studied area apparently had an effect on the magmatic activities and controlled the metallogenesis in the area.The deposit under study is controlled both by several NNE-trending faults (F1～F2) and by hypabyssal, sub-hypabyssal breccia pipes which are thought to be related to the hypabyssal intrusions exposed in the area. The Ore-controlling breccia pipes are unique and major characteristics of the copper-molybdenum deposit.According to the vertical zoning of the breccia pipes proposed by Baker(1985),we consider that the denuation of the No. I,Ⅳbreccia pipes are weak and they are well-preserved; other pipes could have reached their middle portion. So, based on study of these breccia pipes, we think that the deposit is potential at deep levels.Based on the research on the Mesozoic intrusions in the area, it is found that the ore bodies are spatially controlled both by the granodiorite porphyry and by the faults. The formation of the copper-molybdenum deposit is closely related to granodiorite porphyry in both time-space and derivation of the ore-components. Late magmatic hydrothermal fluids are responsible for the main source of the ore-forming fluids.Major ore minerals include chalcopyrite, molybedenite, pyrite and so on. The ore structure is characterized by development of veinlet, breccia and veinlet–disseminated structures. The Ore texture includes corrosion, metasomatic texture, platy and hypautomorphic granular ones. The ores averaged at about 0.274% of Mo, 0.62% of Cu and 3.93g/t of Au. The geological and geochemical studies of the Jinchanggou copper-molybdenum deposit indicate that three types of mineralizations, breccia-, veinlet- and veinlet disseminated-are frequently met and the first type is most extensively exposed in the deposit.By compiling data from the previous researches, and based on the study on the ore fabric and the mineral assemblages of the deposit, we have classify the evolution of the deposit into four metallogenic stages. The metallogenic model of the Jinchanggou copper-molybdenum deposit is set up based on the detailed summary on the geological features, the ore-forming constraints and on the spatial distribution of the ore bodies.By comprehensive analysis and summary of the geological, and geochemical and geophysical information of the deposit, the indicators for searching the new and blind ore bodies are listed as the followings: 1)both the NNE-trending and the NW-trending faults controlled the distribution of the diorite porphyrite and granodiorite porphyry and the intersection parts of the two differently oriented faults and granodiorite porphyry body controlled the distribution of breccia pipes; 2)The breccia pipes are the favorable sites for the existence of the Mo(Cu) ore-bodies; 3) granodiorite porphyry are the main host for the breccia pipes and for the Mo(Cu) ore-bodies; 4) alteration to malachite, covelline, pyrite and chalcopyrite and silicification, are the main proximal alteration of the host rocks. In anomalous concentrations of elements maps of soil samples at 1:10000 scale, high anomalous concentration and apparent element concentration centers are thought to be the direct indicators for Mo(Cu) minerlizations in the deposit. Higher polarizability(Fa>5.0%), low resistivity(ρ<400Ωm) are important indirect indicators of the conceal ore bodies in the studied area.Based on the metallogenic model and ore constraints of the deposit, combined with the ore indictors summarized, the paper has made some target prediction. 2 first rank, and 4 second rank, of the ore body targets have been defined, and among them one is most promising.