Geological characteristics and zircon SHRIMP U-Pb data of Jinchangzi dioritic porphyrite dykes in Zhongwei City, Ningxia

Abstract：Jinchangzi dioritic porphyrite dykes widely distributed in the study area are spatially closely associated with the mineralized zone. These dykes were probably of the same source with the regional concealed acid intermediate-acid rocks and formed simultaneously with these rocks. These concealed acid rocks in the study area might have been the source and center of polymetallic mineralization, and hence a study of their formation epoch is of great significance for the ore-prospecting work in the study area. SHRIMP zircon U-Pb dating of the diorite yielded an age of （147.2±2.3）Ma （MSWD=1.6）, indicating Late Jurassic of Yanshanian period. The confirmation of Yanshanian acid activity has provided an important basis for understanding the evolution of the Mesozoic lithosphere in western China, its tectonic setting and its constraints for Weiningbeishan granite and mineralization.