Geology and Genesis of The Mayuan Lead-zinc Mineralization Belt in Shaanxi Province

The Mayuan lead-zinc mineralization belt is tectonically located on the southeastern marngin of the Beiba rise in the northern Yangtze platform.The belt is over 60km long and 10~200m wide and can be divided into the southern,eastern and northern zones,in which over 4% rebodies have been delineated. The southern Pb-Zn mineralization zone having 3% rebodies is more than 20 km long and 20~120m wide.The eastern zone with 7 orebodies is 30 km in length and 20~200m in width.The northern zone is over 10 km long and 10~100m wide. The length of orebodies in the area generally ranges from 100 m to~2 560m, thickness in between 0.80~10.01 m, Zn grade is 1.05%~10.82%,and Pb 0.55% and 7.54%. The major orebody is 2 560 m long,1.46~32.53 m thick (averaging 7.60m) and has 1.45%~11.42% Zn (averaging 4.47%).The mineralization belt mainly occurs in psephitic dolomitic breccias of the Sinian Dengying Formation,which is controlled by stratigraphy and structures. The study indicates that the Pb and Zn ore~forming elements probably come from the basement rocks;The initial Pb isotope could be derived from the crust-mantle mixing in the orogenic belt;sulfur isotope composition is enriched in heavy sulfur that may have come from the seawater sulfate in the synchronous sedimentation;the ore is characterized with REE enrichment,obvious fractionation of LREE and flat-pattern of HREE;ore-forming media is thermal brine fluid;both mineralization temperature and pressure are low;the metallogenic epoch is probably in late Dengying epoch of Sinian period.Integrate the geological characteristics and compare Mayuan lead-zinc mineralization belt with the MVT type Pb-Zn ore deposit abroad,we suggest that the mineralizatine type here is similar to the genesis of the MVT type Pb-Zn ore deposit with some differences. It is expected that favourable prospecting is in the areas of Beiba-Mayuan,Yunhe~Miaoba,Yangpingguan-Kuanchuanpu-Fuchuan,Sishang-Zhenba,Zhenping in Shaanxi province,and Zuxi,Shennongjia and Huanling in Hubei province.