Study on the Cause of Jurassic Granodiorite and its Dioritic Enclaves in Baoantun Region of Jilin Province
In this paper,detailed geological survey and systematic studies on petrogeochemistry and zircon U-Pb dating were carried out on the Baoantun granodiorite and its dioritic enclaves in the southern section of Xiaoxinganling-Zhangguangcailing magmatic arc.The studies show that the magmas of the granodiorite and its dioritic enclaves have different origins.the host granodiorite has an affinity to crustal origin,whereas the dioritic enclaves display some signatures of mantle.In addition,the formation temperature and pressure of the enclaves are higher than those of the host granodiorite.Both the lithologies are enriched in light rare earth elements and depleted in heavy rare earth elements.Compared with the granodiorite,the dioritic enclaves show obvious nagative Eu anomaly in the chondrite-normalized diagram.Zircon U-Pb dating reveal that the dioritic enclaves formed at 182.0±1.3Ma,whereas the host granodiorite formed at 168.1±1.6Ma～172.1±1.2Ma.The distinct differences in the geochemistry and formation ages suggest that the dioritic enclaves were captured from the wall-rock during the granodioritic magma ascending.Therefore,the dioritic enclaves are belonged to tiny xenoliths within the host granodiorite.Indirectly,there are at least two types of dark xenoliths widely developed in Jurassic granite in the Southern Zhangguangcai Range,one is xenoliths,the other is cause of magma mixing.
万方数据
维普
