LA-ICP-MS Zircon U-Pb Ages, Geochemical Characteristics of the Silurian Basic Dykes in the Hengshi Area, Southern Jiangxi, and Their Geological Significances, and the diagenetic models and source characteristics are preliminarily discussed. The geochemical Characteristics indicate that the mafic dykes are pertain to the tholeiite series and calc alkaline series, and also belong to the sodium rich rock type. Especialy the TiO2 values are in the average of 1%, attributes to the basic rocks enrich of titanium . A/CNK values are less than 1%, shows that it belongs to the meta aluminous basic rocks, and displaying it s mantle derived magmatic characteristic. LA-ICP-MS U-Pb isotopic dating of zircons separated from the mafic dykes yields average 206Pb/238U ages of (422.8±1.8) Ma and (421.7±2.2) Ma, respectively, indicate that the mafic dykes belong to the Late Silurian, suggesting that the mafic dykes are later Caledonian orogenesis period in the tension (stretch) settings. At the same time, exposing two kind of acidic granite of the Caledonian orogenic and post orogenic period in this area， Which generally reflects this area has experienced the construction process from the extrusion type acidic magmatic emplacement gradually converted to tension mafic magma emplacement.