Geological characteristics of the deposit


The Caijiaying deposit located in the north of regional NEE tensional shear zone, the 10°~20°fault in the district controlled the extension of Pb-Zn-Ag ore body and there are NW post mineralizing faults cutting the ore body. There is exposed pyrogranite-porphyry (141Ma), quartz porphyry (119 Ma) (Rui Z Y) which has close relation with mineralization. There are ancient Proterozoic (Pt) stratum exposed in the ore district, they are composed of hornblende-biotite-plageclase granulite of Hongqiyingzi Group (1825Ma) (Wang L J, etc. 2003), but the others thought its age belong to new Archean based on the Sm-Nd isotope age (Wang Q C etc. 2004). There are acid tuff and tuff breccia of upper Jurassic covered on it uncomfortably. Lithology of all above stratum is sillimanite-plageclase granulite, hornblende granulite and hornblende- plageclase granulite, and there are marble and graphite light colour granulite, they belong to amphibolite facies.

Distribution of ore body

It is mainly composed of five ore belts and always with buried vein ore body and the Ag-Pb-Zn mineralizing are vary in the No. 2, 3, 5 ore belts and with large extension. The trending of the No.3 vein is NWW (280°~290°) and dipping S, dip angle 60°~65°,it occurred in the hornblende- plageclase granulite and biotite-plageclase granulite. The length of the ore body 1500m, widths 500~1500 m (exposed at 1000~1500m level) and the ore type is chlorite-sphalerite. The No.5 ore belt is composed of more than 20 ore bodies, with trending of the vein is 280°and dipping NWW , dip angle 65°,the thickness of the single ore body is 1~15m, extending to 1800m and extending depth 300~500m. The No.2 ore belt is composed of 3 ore bodies, with width 200m, extending to 400~500m and extending depth 1500~2000m.

Types of ore and mineralizing periods

The Caijiaying Pb-Zn-Ag ore deposit is duplex vein type and the main ore minerals as follows: marmatite, Fe-bearing sphalerite, sphalerite, galena, chalcopyrite and minor gold and silver-bearing minerals, etc. They can be divided into five mineralizing periods for the Caijiaying Pb-Zn-Ag deposit: (i) wall-rock metasomatism period: arsenopyrite; (ii) pyrite- kroeberite- sphalerite period; (iii) natural gold-galena- pyrite period; (iv) Ag-bearing galena- argentite-Ag-Cu-S-Sb mineral period; (v) natural silver-pyrite-calcite period.

Mechanism and resources of mineralization

The characteristics of quartz inclusions in each mineralizing period and homogeneous temperature results show that the ratio of gas to liquid was 25%~10% and the inclusion types from gas CO2 to liquid inclusion. The temperature results by inclusion homogeneous demonstrates that the temperature during mineralizing was 130~180°C.The liquid phase components of quartz inclusion and calculation of forming physical chemistry parameters show that F-,Cl-,SO42- and Na+ are riched in liquid components,and N2,CO2 and H2O are rich in gas phase components, the mineralizing physical chemistry parameters are pressure is 780 Pa, pH= 7.05~7.50, Eh=-0.69~-0.74 and salinity (NaCl) eq= 48.08% ~52.3%. There are two sorts of resources for the mineralizing matter based on the geological occurrence, the matter components of ore and the analysis results of Pb-Pb isotope; (1) the metamorphic medium-basic, medium-acidic volcanic rocks of Hongqiyingzi Group, ancient Proterozoic(Pt); (2) fluid came from lower crust-mantle. In summary, the Caijiaying Pb-Zn-Ag deposit is ancient eruption gas-hydrothermal sedimentary metamorphic-hydrothermal superimposed.