On the basis of zircon U-Pb dating and rock total analysis of Laoshanzhai rock mass, the authors hold that chemical components of Laoshanzhai rock mass have ultra-acid, alkali-rich and peraluminous characteristics, thus belonging to ultra-acid, alkali-rich and high-K calc-alkali series. The data indicate that Laoshanzhai rock mass is characterized by enrichment of LILE (Rb, K), HFSE (Hf, Th, U,) and LREE, and depletion of HREE, with moderate negative Eu anomaly. Rare earth element distribution curve is higher on the right side and flat on the left side, exhibiting light REE enrichment. Major trace elements show that magma of rock mass was mainly from lower crust source, and was probably mixed with a small amount of mantle materials. Zircon LA-ICP-MS U-Pb dating shows that ²⁰⁶Pb/²³⁸U weighted average age value of rock mass is 133±2 Ma (n=21, MSWD=3.1), which represents the emplacement age of Laoshanzhai rock mass as the product of magmatic activities of Early Cretaceous period. Laoshanzhai rock mass was formed by tectonic regime transition and the extension mechanism of Qinling-Dabie orogenic belt in Mesozoic, during which the lower crust had not yet been delaminated, the lower crust of high pressure granulite that contained plagioclase, pyroxene, hornblende and garnet was subjected to partial melting, and experienced upward migration along deep faults, then experienced consolidation diagenesis in the shallow crust.