摘要
The Late Triassic Yanzhiba Pluton located in the Northern margin of the Mianxian—Lüeyang Suture, central China. This paper presented the data of occurrence, petrography, zircon U-Pb chronology and geochemistry ,and genesis of the pluton. The pluton mainly consisted by biotite granite. Zircon LA-ICP-MS U-Pb dating for the biotite granite yields a weighted mean age of 200±4 Ma. They have high SiO2 (70.09%~73.35%), alkalis (Na2O +K2O=7.49%~8.59%), Rb, Th, U, K contents and high CaO/Na2O ratios (>0.3), their A/CNK=1.01~1.08 ,σ=2.07~2.62, depletion of Nb, Ta, Ba, Sr, P and Ti. The ∑REE ranges from 129.98×10-6 to 189.97×10-6, slight enrichment of LREE (LREE/HREE=8.00~10.73, (La/Yb)N=8.62~15.68), and significant negative Eu anomalies (δEu =0.41~0.50). In combination with regional geological settings, the authors suggest that the biotite was formed by partial melting of metasedimentary crust, which was induced by fluids from the lower crust or mantle lithosphere.