Detrital Zircon U‐Pb Dating of Nanshuangyashan Formation in the Jiamusi Massif, NE China and its Tectonic Implications

Abstract

A suite of the fossil-rich marine-land interbedded strata (Nanshuangyashan Formation) is distributed at the eastern margin of the Jiamusi massif in the eastern Heilongjiang Province, NE China. The authors had recently discovered a suite of arkose beneath the marine-land interbedded strata, which overlays unconformably on the Permain granite in the eastern margin of the Jiamusi massif. The LA-ICP-MS zircon U-Pb dating indicate that all detrital zircons from the analysed four arkose samples show the four population ages of ＞800 Ma, 538-481 Ma, 269-250 Ma and 223-215 Ma. The former three population ages are widely recorded in the Jiamusi-Khanka massif and the Songnen massif. The later group is the minimal age population in the analyzed samples, limiting the sedimentation time of the arkoses occurred after the Late Triassic. At present, the minimal age population is not recorded in the Jiamusi massif, but the granites with the ages of 228-210 Ma are widely distributed in the Songnen-Zhangguangcai Range massif and the Khanka massif. The predominantly Permian zircons are characterized by oscillatory zoning and euhedral shapes, with variable zircon ε Hf (t) values (−5.5 to +11.2), indicating that they were derived from mixture sources, possibly mixed with components of the Songnen-Zhangguangcai Range massif and the Jiamusi-Khanka massif. These results, combined with regional analyses, indicate that the closing of Mudanjiang ocean and Panthalassa ocean possibly existed from Early Permian to Late Triassic.

Subduction of the Palaeo‐Pacific Plate beneath the Jiamusi Block: Constraints from the Late Triassic–Late Jurassic sedimentary records in the eastern Jiamusi Block

“…The Yunshan Formation section (Hulin County, Mishan City) is in the Jiamusi Block. The Late Triassic Nanshuangyashan Formation in the Sanjiang Basin of the Jiamusi Block is uncomfortable with underlying Hercynian alkali-feldspathic granites (Cui et al, 2019;Zhang et al, 2015) and in comfortable contact with the overlying Lower Jurassic Datushan Formation (Zhou, Wilde, et al, 2009). The longitude and latitude coordinates of the formation section are N46 04 0 and E132 36 0 , and the total thickness of the section is 154.89 m (Figure 2a).…”