This study presents new geochemical,zircon U-Pb and Lu-Hf isotopic data for the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group in eastern Guangxi.Geochemical data show that the meta-sedimentary rocks of the Yingyangguan Group have moderate composition maturity and weathering extent,and their rare earth element(REE)patterns are similar to that of the Post-Archaean Australian Shale(PAAS),with moderate Eu negative anomalies.The trace element distributions diagram shows that some samples are depleted in U,with higher Co and Ni contents compared with those of the meta-sedimentary rocks in the Nanling range,suggesting that the provenance was mostly intermediate to mafic rocks.The matrix of the Yingyangguan tectonic mélange contains a component of meta-sedimentary rocks.The detrital zircon U-Pb dating results give a maximum depositional age(660 Ma)of the matrix part of the tectonic mélange.Combined with previous results,we suggest that the Yingyangguan tectonic mélange was formed in the Middle-Late Neoproterozoic,and resulted from reworking by the Early Mesozoic thermal events.Provenance analysis reveals that the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group are mainly of felsic components,combined with zircon cathodoluminescence image characteristics,zircon U-Pb geochronological characteristics,Hf model age of the second stage(TDM2)and relevant regional geological data,we suggest that the intermediate to mafic provenance in the meta-sedimentary rocks mainly originated from the Yingyangguan area or the adjacent terranes,suggesting a close affinity of the Yingyangguan Group with the Cathaysia Block.Combined with the characteristics of regional tectonic evolution,it is inferred that the Neoproterozoic meta-sedimentary rocks of the Yingyangguan Group were deposited in a post-orogenic extension rift basin.
关键词
变质沉积岩/锆石U-Pb年龄/Lu-Hf同位素/新元古代/桂东鹰扬关群
Key words
meta-sedimentary rocks/zircon U-Pb ages/Lu-Hf isotopes/the Neoproterozoic/the Yingyangguan Group in eastern Guangxi
维普
万方数据