Early Paleozoic geodynamic evolution of the Eastern Central Asian Orogenic
Belt: Insights from granitoids in the Xing’an and Songnen blocks
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Abstract
The early Paleozoic tectonic framework and evolutionary history of the eastern Central Asian Orogenic Belt
(CAOB) is poorly understood. Here we present zircon U–Pb geochronology, whole rock geochemistry, and Sr-Nd-
Hf isotope data of the early Paleozoic granitoids in eastern CAOB to investigate the petrogenesis and geodynamic
implications.
The early Paleozoic granitoids from the Songnen Block yield zircon U–Pb ages of 523–490 Ma, negative εNd(t)
values of –6.7 to –0.8, and εHf(t) values of –8.6 to 7.1, indicating they were generated by partial melting of ancient
crustal materials with various degrees of mantle contribution. They generally show affinities to A-type granites,
implying their generation from an extensional environment after the collision between the Songnen and Jiamusi
blocks. In comparison, the early Paleozoic granitoids from the Xing’an Block have zircon U–Pb ages of 480–465
Ma, εNd(t) values of –5.4 to 5.4, and εHf(t) values of –2.2 to 12.9, indicating a dominated juvenile crustal source
with some input of ancient crustal components. They belong to I-type granites and were likely related to subduction
of the Paleo-Asian Ocean. The statistics of TDM2 Hf model ages of the granitoids indicate that the Erguna
and Jiamusi blocks contain a significant proportion of Mesoproterozoic crystalline basement, while the Xing’an
Block is dominated by a Neoproterozoic basement.
Based on these observations, the early Paleozoic evolutionary history of eastern CAOB can be divided into four
stages: (1) before 540 Ma, the Erguna, Xing’an, Songnen, and Jiamusi blocks were discrete microcontinents
separated by different branches of the Paleo-Asian Ocean; (2) 540–523 Ma, the Jiamusi Block collided with the
Songnen Block along the Mudanjiang suture; (3) ca. 500 Ma, the Erguna Block accreted onto the Xing’an Block
along the Xinlin–Xiguitu suture; (4) ca. 480 Ma, the Paleo-Asian Ocean started a double-side subduction beneath
the united Erguna–Xing’an and Songnen–Jiamusi blocks.
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