Zircon SHRIMP U-Pb Age and Petrogeochemical Features of the Lanjiagou Granite in Western Liaoning Province

Abstract

Lanjiagou molybdenum deposit is located in western Liaoning province,and orebodies mostly occur in the Lanjiagou fine-grained granite with minor in the contact zone of-grained and coarse-grained granite.Lithoglical and geochemical analysis of the Lanjiagou granites shows that they are rich in Si(ω(SiO2)=73.65%~77.88%),alkalis(ω(K2O)+ω(Na2O)=5.92%~9.14%),metaluminous(A/CNK=0.99~1.07).The chondrite-normalized REE patterns are characterized by LREE enrichment and medium negative Eu anomalies(δEu=0.52~0.66).The primitive mantle-normalized spidergrams show that they are depleted in Ba,Sr,P,Ti and Nb.In the SiO2-P2O5 diagram,the P2O5 content dereases with increasing SiO2 content.These geochemical characteristics suggest that the Lanjiagou granite had undergone to some extent fractional crystallization processes and belongs to differential I-type composite granite.The fine-grained granite and coarse-grained granite were the results of the congnate evolutional series.The zircon SHRIMP U-Pb dating for the fine-grained granite yields concordant ages ranging from 184.7 to196.4 Ma,with a weighted mean age of(188.9±1.2)Ma.The granite emplaced in Early Jurassic,and that is corresponding to Mo mineralization,suggesting that the mineralization in this area may be genetically associated with the granite.Base on regional geology data,it can be concluded that the emplacement of the Lanjiagou granite and the mineralization timing of the molybdenum deposit occurred in the Yan-liao area during the compressional deformation period in Early Jurassic.