40Ar-39Ar dating and geochemical characteristics of the potassic lamprophyre in Linxiang area, northeastern Hunan

Abstract：Isotopic age and geochemical characteristics of the potassic lamprophyre in Linxiang area of northeast Hunan were analyzed in this paper. Its whole-rock 40Ar/39Ar plateau age is (119.5±2.2)Ma, indicating a product of Early Cretaceous. The lamprophyre belongs to the alkaline series and is of potassic-superpotassic nature, with rich large-ion lithophile elements (LILE) and high field-strength elements (HFSE), right oblique chondrite-normalized REE pattern, clear low TDMⅡ value of 1.5Ga and low εNd（t）value of -7.3. These characteristics suggest that the lamprophyre was derived from anomalous (metasomatic enriched) mantle, and was formed in a post-orogenic tectonic setting characterized by lithospheric extension and thinning.