Mid-north Region Of The Silurian Law Of Lead And Zinc Mineralization And Prospecting Direction,

In recent years, a series of lead-zinc deposits were explored in Silurian strata in the north area of Xunyang County. Through summarize the geological and geochemical characteristics of these lead-zinc deposits, The paper mainly research it's metallogenic regularity and propose the exploration direction in this area in the future.From north to south, the Silurian lead-zinc deposits in this area can be divided into 3 mineralized zones, they are Sirengou-Nanshagou lead-zinc mineralized zone, Hongtupo-Hanshigou-Xiaogou lead-zinc mineralized zone and Xiying-Huangshiban lead-zinc mineralized zone.These lead-zinc deposits locate in some fine detrital stones, the ore bodies are beded and pod-like, they have the same occurrence and fold curve with there country rocks.Most of ore is zinc ore, then is lead-zinc ore, and the lead-ore can be found very rarely. The main mineral composition of the ore is zinc blende and lead glance. The ore have disseminated structure, stratified structure, stipped structure, lamellar structure, vein structure and brecciated structure. The alteration types of the country rocks are silicification, chloritization, sericitization and pyritization. Usually the country rock alteration of the floor and the roof of the ore body are not same, it has the character that the floor of the ore body has strong country rock alteration.The rocks such as albitite and silicalite are hydrothermal sediment rocks, they have the same character with the lead-zinc ore deposits in the geochemistry, such as the microelement, the sulfur isotope, the hydrogen and oxygen isotope, the lead isotope , the rare earth element composition, and so on, so they are different from the sedimentary rocks.The genesis of these lead-zinc deposits are hydrothermal sedimentation-reformation type, the ore-forming metals come from the basement under the basin, the sulfur come from the sulfate in seawater, and the mineralization fluid was the seawater which come into the basement under the basin. The metallogenic model was: the hydrothermal ore-forming solution convection under the basin, they come into the sea through thesynsedimentary faults and formed lead-zinc ore beds, at late the tectonic movement and hydrothermal solution reform the lead-zinc ore beds.The paper analysed the metallogenic regularity of Silurian lead-zinc deposits in the north area of Xunyang County, and consider the strata, synchronous faults, the basement before Cambrian system and the third class sedimentary basin were the main factor who cortrol the forming and the distributing of the lead-zinc minerallized zones. The geochemical interface, such as environment break interface, fluid evolution interface, fluid environment interaction interface, tectonic movement and hydrothermal solution actvation interface were the interspaces which the ore bodies formed in. The syndeposition potholes, the interfaces between sandrock and mudrock, the interlayer faults and hydrothermal alteration belts enriched these lead-zinc deposits. The hydrothermal solution and tectonic movements after the mineralizing process reformed and enriched these lead-zinc deposits. At the same time, the author point out that there are space-time marginal metallogenesis system in the research area, the north margin of YangZi plate cortrolled the mineralized zones of South Qinling area, the margin of the third class basin and synsedimentary fault cortrolled the lead-zinc mineralization in the area of Xunyang county, the boundaries between different strata and the anticlines cortrolled the forming of the lead-zinc deposits, the lead-zinc ore bodies formed in the interfaces of different rocks.In the end, the author summarize the indicator about the Silirian lead-zinc deposits, and consider in the south area of Hanjiang river, the area of Shuanghe in Xunyang county, the west area of Huangshiban in Baihe county and the area near by Ankang city have great foreground in ore rearch in the future.