Precambrian terrane within the Songnen–Zhangguangcai Range Massif, NE China: Evidence from U–Pb ages of detrital zircons from the Dongfengshan and Tadong groups

Abstract

The Central Asian Orogenic Belt (CAOB) is a natural laboratory of the Phanerozoic accretionary orogen. The eastern section of the CAOB contains several microcontinental massifs, and it is unknown whether these massifs carry Precambrian basement. Here we present the results of U–Pb dating of detrital zircons from the Dongfengshan and Tadong groups in the eastern margin of the Songnen–Zhangguangcai Range Massif. The Dongfengshan and Tadong groups are subdivided, from bottom to top, into the Liangzihe, Huapigou, and Honglin formations, and the Lalagou and Zhudundian formations, respectively. Zircons from a two-mica quartz schist (sample HCM4-2) in the Liangzihe Formation yielded eight age populations, from 821 to 1802Ma, whereas zircons from a two-mica quartz schist (sample 12HCM3-2) in the Huapigou Formation yielded four age populations (752, 803, 821, and 851Ma). Zircons from a two-mica schist in the Lalagou Formation of the Tadong Group yielded two age populations (450 and 485Ma), and zircons from a biotite-bearing plagioclase gneiss in the lower part of the Zhudundian Formation yielded five main age populations, from 551 to 1815Ma. Samples 11NNA5-1 and 11HNA10-1 from the upper layer of the Zhudundian Formation yielded six main age groups, from 749 to 948Ma. These data, together with the ages of zircons within a tonalite that intrudes the Tadong Group and the overlying Chenming Formation, indicate the presence of a Precambrian terrane associated with sedimentation at various times during the Neoproterozoic, including at ~821–752, ~752–560, and ~750–516Ma, on the eastern margin of the Songnen–Zhangguangcai Range Massif. The Dongfengshan and Tadong groups were previously thought to be Proterozoic, but our study reveals that they constitute a Neoproterozoic–Late Paleozoic tectonic mélange. In addition, the widespread occurrence of detrital zircons with ages of 0.75–0.95, 1.5–1.6, 1.8, and 2.4–2.5Ga provides evidence of a Neoproterozoic magmatic event and the presence of remnant ancient basement material within the Songnen–Zhangguangcai Range Massif.