关键词: 华北南缘；中元古界兵马沟组；泥质岩；地球化学特征；沉积环境；物源

Abstract:

The Paleao-Mesoproterozoic tectonic and sedimentary evolution of southern North China craton has been debating for long
time, with controversies focusing on whether it is a subduction or cracking rift. As the first sedimentary layer formed after Xiong’er
Group, the Mesoproterozoic Bingmagou Formation is important to address this issue. Based on the analysis of geochemical
characteristics of REE and trace element of argillaceous rocks in Bingmagou Formation, the sedimentary environment and properties of
provenance and their tectonic significance were discussed in this study. The results showed that Chondrite normalized REE and trace
elements have a high differention between LREE and HREE, which showed anomaly negativeδ Eu, anomaly insignificantδ Ce, and enrich
Rb, Th, La, Ce, Nd, Zr, Hf, etc. Compared with the average upper crust, it was enriched in Sc, V, Cr , Co, Ni, Rb. Also we found that
Ceanom index and V/V+Ni ratio reflected a reduction argillaceous sedimentary environment, and Sr/Ba and B/Ga ratios indicate its

transitional environment from continent to marine. In addition, Cr/Zr, Th/U and other elements ratios prove its provenance is not deep
material, and La/Yb-Ce, Co/Th-La/Sc diagrams indicate the provenance is middle-acidic volcanic rocks. Furthermore, Th-Sc-Zr/10,
Th-Co-Zr/10 illustrations indicate its provenance is mainly from continental volcanic arc. Taken these results and regional geological
information together, it can be concluded that Bingmagou Formation in Yichuan was formed in an extensional back-arc basin, Xiong’er
Group was an arc islan

Key words: southern North China craton, Mesoproterozoic Bingmagou Formation, argillaceous rock, geochemical characteristic, sedi?
mentary environment, provenance