The dolomitic mudstone from the lower of the Leikoupo Formation in the northwestern margin of Sichuan Basin which is grayish-yellow and lacking siliceous pisolite, had been different from the sedimentary volcanic tuff（locally called “green-bean rock”）in South China region during the Early-Middle Traissic. The dolomitic mudstone has been studied with methods of LA-ICP-MS U-Pb isotope dating, geochemical analysis and X-ray diffraction. The detrital zircon age data yield a wide range, varying from 2 635 Ma to 236 Ma with the population groups of 473～236 Ma, 750～972 Ma, 1 436～1 114 Ma, 1 983～1 628 Ma and 2 635～ 2 253 Ma. The results of U-Pb isotope dating are similar to the stratum of Middle-Upper Triassic in Sichuan in addition to the eastern area, indicating the dolomitic mudstone from the lower of the Leikoupo Formation were mainly derived from Qinling Mountains, the westhern of Yangtze Craton, probably little influenced by the volcanic activity in South China. The feature of X-ray diffraction and major elements shows that the dolomitic mudstone contains dolomite and the clay minerals are illite. Diagrams of Co/Th-La/Sc and La/Th-Hf show that the provenance of the dolomitic mudstone is felsic rocks. The dolomitic mudstone from the Leikoupo Formation and the stratum of the western Sichuan Middle-Upper Triassic have similar chondrite-normalized REE patterns, which showing they have the same provenance, but had a greater distinction in “green-bean rock”.
Deng Yulin Lang Xinghai Yang Zongyao Qi Jing Wang Xuhui Lou Yuming Han Peng Cui Zhiwei. Detrital zircon U-Pb geochronology, geochemistry and implication for provenance of the dolomitic mudstone in the northwestern margin of Sichuan Basin in the Early-Middle Traissic, SW China[J]. Chinese Journal of Geology, 2018, 53(2): 638-660.