Geochemistry Of The Granite From The Haobugao Skarn Zn-Pb Deposit In Inner Mongolia,and Its Geological Significance

Haobugao deposit is a typical skarn Zn-Pb polymetallic deposit located in the south of Daxing’an ridge,Northeast China.The ore bodies occur in the carbonate strata of the upper Permian,the skarn minerals include garnet,pyroxene,wollastonite,andalusite,and actinolite,the ore minerals include sphalerite,magnetite,galena,chalcopyrite and pyrite,and a small amount of cassiterite is developed in the ore body,but whether the Haobugao deposit has the prospect of tin ore is still uncertain,this paper will discuss.The SiO₂-Fe₂O₃/（FeO+Fe₂O₃）diagram shows that the samples of Haobugao are all located near the Zn skarn rock body with high oxidation,which indicates that the rock body forming Haobugao deposit has high oxidation.The calculation results of zircon oxygen fugacity show that the sample oxygen fugacity of Haobugao deposit is higher than that of damogutu Sn Fe deposit and dashishan Sn-Pb-Zn deposit in the adjacent area in log（fo₂）-T diagram.The latter two samples are formed in the relatively original environment and are related to the mineralization of Sn polymetallic deposit.Haobugao rock body is not conducive to the formation of Sn ore.The high ratio of zircon Eu/Eu^*in Haobugao ore body indicates the relatively high oxidation of Haobugao ore body.It is proved that the redox environment of Haobugao ore-forming body is quite different from that of Sn ore-forming body,so it has no potential to form Sn ore.The REE analysis results of biotite granite in Haobugao ore body show that the∑REE content is lower than the world average granite(273×10^-6),indicating that the evolution degree of the rock body is relatively low and the differentiation degree is not high,which is inconsistent with the typical skarn Sn ore.The average age of Haobugao ore-forming body is 140.9±0.8 Ma,indicating that the mineralization occurred in the early Cretaceous.The age is 140Ma,which is in the stage of subduction and retreat of the ancient Pacific Ocean,and it is generally continental arc environment,while Sn skarn related rock mass occurs in the continental plate,so the Haobugao related rock mass does not have the tectonic environment to form Sn ore.Based on the analysis of oxygen fugacity of zircon,it can be concluded from the evolution degree of the rock mass and the tectonic environment that the Haobugao rock body does not have the potential to form Sn ore.The results of this study may be used to guide the exploration of ore deposits.