Study On Tectonic Characteristics And Tectonic Metallogenesis Of Laochang Lead-zinc Ore Field,GuangXi

The Laochang lead-zinc deposit in Guangxi is located on the northeastern sag of the Nanhua platform,the outer side of the southern margin of the Jiangnan paleo continent.It is part of the western part of Nanling nonferrous metals metallogenic belt.This article will combine the previous research results and data from the aspects of regional geological features,ore geological features,ore field tectonic features,and geochemical characteristics of ore deposits and so on.And it mainly studied The ore field structure of the Lao Chang lead and zinc deposit,structure metallization and and the relationship between metallogenic structure and lead-zinc mineralization.The main understandings are as follows:The overall tectonic framework of the lead-zinc deposit is controlled by two deep faults-facing North East and near North and south direction and Northwestern folds.The basement of laochang dome developed NorthWest fold and a series of North East extensional fracture belts in the region play a key role in the formation of lead-zinc deposits in this area.The extensional faults in Caledonian mining area are trending NE,SW and perpendicular to the fold axis of NW,SE.The formation of folds is the result of horizontal squeezing forces.The main compressive stress trajectory in the mining area is NorthEast,SouthWwst direction,and the stress trajectory is northwest-southeast.The Hercynian-Indosinian folds are axially NNW,SSE,and the fault zone is further transformed,but the overall trend is unchanged.The formation of folds is the result of vertical extrusion force.There are two kinds of veins and lamellar ore bodies in the area.The vein-shaped ore body is mostly in the Cambrian strata in the form of lenticular veins.The occurrence is consistent with the fault zone;the stratified ore body is mainly composed of Cambrian white clouds.In rock,its occurrence is consistent with the formation.The analysis of the geochemical characteristics of the vein ore shows that the enrichment of Fe,Ti,Co and other pro magmatic elements in the ore and surr ounding rock,along with the same characters of Co/Ni ratio in both the ore and surrou nding rock and pyrite caused by magmatic hydrothermal indicate that the ore body ma y undergo the transformation by the magmatic hydrothermal fluid;the total amount of the rare earth element is high and the light rare earth is enriched,and the europium is negative abnormality and the cerium is positive anomaly,similar to the acid vein in th e mining area;the isotopic characteristics of sulfur and lead indicate that one part of the was derived from the strata and one part was derived from the magma,therefore w e can speculate the metallogenic material of the vein ore body is partly originate from strata,mainly derived from magma.The analysis of the geochemical characteristics of the lamellar ore shows that the sample sites all fall within the hot-water sedimentary rock area in the Al-Fe-Mn triangle map.The projection points of rock and ore samples on the Y-P205 relation map are below the hot water sediment trend line and the concentrated area.The lamellar ore may be related to the hydrothermal sedimentary environment.The total amount of rare earth elements is low,and the light rare-earth is enriched,and the europium is positive anomaly,while the cerium is characterized by a weak negative anomaly.It is presumed that the formation of the lamellar ore may be formed by hot water deposition.Through lamellar ore formed by Caledonian submarine jet deposition,it is concluded that syngenetic syngenetic basin structure controlled the the metallogenic structure.And the lamellar ore mayalso be damaged or deformed by later fold defomatiaon;The formationofvein orecontrolledbylattice frame and a series of mineral izationfracture,it formedin Hercynian-Indosinian period.As the same time,along with magmatichy drotherm alactivities and ore-bearing fluidactivities,migrated along with the fault rises and enriches,forming vein orebody.