Abstract: Jiling pluton is Caledonian magmatic rock in Longshoushan uranium ore belt. Diorite is one of the main rock types of Jiling pluton, which emplaced in the Early Caledonian. Diorite is mainly distributed in Xinshuijing and Jiling area;the early diorite is graydark gray mediumgrained; while the later one is dark gray finegrained.This investigation obtains (4856±14) Ma as the age of the mediumgrained diorite by LAICPMS zircon UPb dating. The research shows that the diorite plays an important role in later uranium metallogeny. The altered diorites provide the Ubearing hydrothermal fluids for unloading space. There are albite, chlorite, calcite, and hematite in altered diorite. With increasing of U content, SiO2 content is a bit increasing while Na2O increasing obviously; the K2O,FeO and P2O5 contents are obviously decreasing; and CO2 content increases at first and decreases when U content is much higher, but it is slightly increasing overall. By comprehensively studying and analyzing, the diorite is regarded as a favorable host rock to sodium metasomatic uranium, and the contact belt of diorite and granite provides a physicochemically sharply changing setting as a physicochemical barrier for the uranium enrichment.

Key words: Jiling pluton, altered diorite, uranium ore deposit, geochemical barrier