U-Pb AGES AND Hf ISOTOPIC COMPOSITION OF CRYSTALLINE ZIRCONS FROM IGNEOUS ROCKS OF THE CHANGJIANG DRAINAGE BASIN AND THEIR IMPLICATIONS FOR PROVENANCE

High-resolution provenance study has been an important target for application of single-grain microanalysis technique. It is vital to carry out high-resoulation provenance study in the Changjiang drainage to set up detail crystalline-zircon microanalysis database including U-Pb age because of its vast catchment area, complex composition and distribution of parent rocks. The data of crystalline-zircon U-Pb age and Hf isotope in the catchment were therefore systematically collected from the recent decadal publications, and analyzed together with the update geologic investigation results of parent rock lithology, age and outcropped areas. It was indicated that only a few zircon grains can be traced to their separate sources directly by their typical ages, including those of <50 Ma, 250~270 Ma and >3 000 Ma, which are discriminated to the sources of the Changdu Block or the Jinshajiang Suture zone in the upper reach of the catchment,the Emeishan Basalt province in the Western Yangtze Block, and the Kongling Complex in the Three Gorges region, respectively. The effectiveness of provenance discrimination can be much highly improved through combined ananlyses of zircon U-Pb age and εHf(t) value. It is worthy noting that input of recycled detrital zircons will make the source discrimation more complicated.