引用本文：康昱,陈刚,夏晓雨,任帅锋,张卫刚,师平平.2018.鄂尔多斯盆地南缘南曹德组与庄河沟组碎屑锆石年代学及其地质意义[J].地质学报,92(9):1829-1842. KANG Yu,CHEN Gang,XIA Xiaoyu,REN Shuaifeng,ZHANG Weigang,SHI Pingping.2018.Detrial Zircon U-Pb Geochronology and Its Geological Implication of the Nancaode and Zhuanghegou Formations in the Southern Margin Ordos Basin[J].Acta Geologica Sinica,92(9):1829-1842.
Abstract:The south Ordos basin (S-OB) is located at the west part of the South-sector of North China Block (S-NCB), involved in the multiple orogeny of the North Qinling Belt (NQB) that is composed of the S-NCB to the north and the north Qinling terrain (NQT) to the south. The pre-Ordovician tectonic correlation between the NQT and NCB, as well as the tectonic affinity of the NQT, is still controversial. Here, detrital zircon U-Pb dating analysis of 2-sample sandstones from the neritic-littoral deposits of Nancaode and Zhuanghegou Formations, outcropped in the S-OB, are carried out at the State Key Lab. of Continental Dynamics, China. All the concordant zircons (n=155) from sampled sandstones show broadly similar age patterns with a wide range of 825~2445 Ma. The largest population of zircons exhibits ages of 1659~1935 Ma (n=39) with a peak age at ca.1.86 Ga; and the subordinate populations display ages of 2017~2445 Ma (n=7), 1458~1650 Ma (n=24), 1223~1451 Ma (n=36), 1041~1203 Ma(n=23) and 825~995 Ma (n=13) with the peak ages of ca. 2.09 Ga, 1.59 Ga, 1.33 Ga, 1.12 Ga and 0.83 Ga, respectively. It indicates that the detritus of the the 2-formation deposites were mainly sourced from the metamorphic basement rocks of the NCB and subordinately from the complex and igneous rocks of the NQT. Also, the spectrum of the 2-sample zircon ages, with youngest peak age of 832Ma, is quite similar to that of interlayered sandstones of the late Neoproterozoic (Sinian) tillites exposed in the neighbor study areas of the southwest Ordos basin, but very different from that of sandstones of the Ordovician Pingliang formation outcropped in the S-OB, suggesting the deposit time of the analyzed sample host rocks to be late Neoproterozoic (Sinian) with no more than ca. 0.83 Ga. All of the above reveal that the sedimentary sources of late Neoproterozoic Nancaode and Zhuanghegou Formations are bidirectionally from the NCB and NQT, indicating the NQT was amalgamated to the NCB during the Grenvillian collision to late uplift process. So, it can be supported that the S-NCB amalgamated with NQT as an integrated continental margin developed an extensional sedimentary process after ca. 0.83 Ga, probably corresponding to the Rodinia break-up event.